|Milli-Q® Integral Water Purification Systems|
|Systèmes de purification d'eau Milli-Q® Integral|
Licencias necesarias e Información técnica
Referencias bibliográficas | 97 Disponible | Ver todas las referencias
|Visión general referencias||Aplicación||Pub Med ID|
|The importance of ultrapure water for nano LC-MS applications |
M. Tarun, S. Mabic, D. Budac, M. Hayward
The Column (2011) 9 May, Issue 8, 12-17 2011
Nano-flow LC (nano-LC) has emerged as an important tool in proteomics research as well as quantitative measurement of low level biomarkers. A common problem facing users of this technique is emitter clogging. To avoid this, it is important not only to use robust nanobore columns and emitters, but also to make sure that the solvents and reagents are of the highest purity. This work presents a proof of concept that using freshly produced ultrapure water to prepare nano-LC eluent does not cause emitter clogging. This is demonstrated by comparing the mass chromatograms of peptides over numerous injections using the same emitter and using fresh ultrapure water in the eluent, as well as by physical examination of the used emitter under a light microscope.Artículo Texto completo
|Quantification of 2-hydrazinopyridine derivatized steroid hormones in fathead minnow (Pimephales promelas) blood plasma using LC-ESI+/MS/MS |
D. Hala, M.D. Overturf, L.H. Petersen, D.B. Huggett
J. Chromatogr. B 879 591–598 2011
Fathead minnows (Pimephales promelas) comprise a species-of-choice for the hazard assessments of various environmental contaminants, including compounds capable of disrupting endocrine function. Towards this end, the use of liquid chromatography coupled with mass spectrometry (LC–MS) and/or tandem mass spectrometry (MS/MS) is gaining common use for the quantification of steroid hormones as biomarkers of endocrine stress in small-fish toxicological studies. In this work, 2- hydrazinopyridine (2-HP) was used to derivatize and quantify the physiologically relevant steroid hormones of: 17 -hydroxypregnenolone, progesterone, 11-ketotestosterone, 11-deoxycortisol and 17 ,20 -dihydroxypregnenone, in the blood plasma of male and female fathead minnows. Liquid chromatographic separation was achieved using a WatersTM Sunfire C18 column (2.1mm×50mm with a 3.5 m particle size) and Milli-Q water:methanol (both with 0.1% formic acid) mobile phase over a gradient of 15 min. All mass analyses were conducted using electrospray ionization in the positive mode with tandem mass spectrometry (ESI+/MS/MS). This is the first such application of 2-HP derivatization for the quantifications of the structurally and functionally diverse C19 androgen of 11-ketotestosterone; C21 progestogens of 17 -hydroxypregnenolone, progesterone and17 ,20 -dihydroxypregnenone; and C21 corticosteroid of 11-deoxycortisol, in fathead minnow blood plasma. The limits of detection (LOD) were set to the lowest calibration standard that gave a signal-to-background response of ≥3, and were: 0.16 ng/ml for progesterone, 0.63 ng/ml for 17 -hydroxypregnenolone, 11-deoxycortisol and 17 ,20 - dihydroxypregnenone, and 1.25 ng/ml for 11-ketotestosterone. This study demonstrates the application of 2-HP derivatization for the analysis of a variety of steroid hormones representative of endocrine function in a species of fish commonly used in toxicological studies.
|Polishing Up On Water Quality |
C. Devaux, C. Monferran, M. Tarun, E. Riche, D. Darbouret
Laboratory Equipment – Chromatography Techniques (2010) Dec. 2010
Water plays a critical role in many analytical methods—particularly in the preparation of samples, standards, blanks, and eluents. It is crucial that water used for these applications does not introduce any impurities that could interfere with analytical results. As modern analytical instruments become capable of detecting ever increasingly low concentrations of analytes, ensuring the lowest level of background interference has become even more important—and more difficult. To meet this challenge, laboratory water purification systems have evolved accordingly. Current systems such as the Milli-Q Integral use a sophisticated combination of purification technologies to reduce ions, organics and other potentially background-causing contaminants to extremely low levels (i.e., 18.2 MΩ.cm resistivity and <5 µg/mL of TOC).Artículo Texto completo
|Endotoxin-Free Water for Tissue Culture |
E. Riché, J. Bôle and S. Mabic
Lab Manager Magazine (2010) May 2010
Water is a ubiquitous solvent used throughout cell isolation and culture. Therefore, water contamination may affect experimental outcomes. The use of ultrapure water is advisable for culturing of cells sensitive to environmental contaminants, such as endotoxins and bacteria. Cardiomycyte isolation experiments showed that using water contaminated with bacteria and endotoxins decreases cell viability, while using freshly produced ultrapure water dramatically increases it. Additionally, an ultrafiltration cartridge will efficiently remove large molecules that may be present in water.Artículo Texto completo
|Determining What's in Your Laboratory Water - "Emerging Contaminants" from the Tap Pose Subtle Threat to Experimental Data |
E. Riché, M. Tarun
GEN (2010), 30(12) 2010
When the Associated Press published results from a five-month study on the presence of pharmaceuticals in drinking water in 2008, the study made headlines across the country. In addition to pharmaceuticals, contaminants in drinking water such as perchlorates, pesticides, herbicides, endocrine disrupting chemicals, brominated flame retardants, and personal care products make for a steady stream of news about what is in the water supply. While such contaminants can be found in drinking water, should they be a concern for researchers? Are these contaminants making their way from the tap into the high-purity water used in the laboratory?Artículo Texto completo
|Designing a customized lab water system |
Laboratory Design newsletter (2010) 15 (10) 2010
Purified water is the most common reagent found in lab facilities, used throughout experimental protocols in virtually every type of application. Whether used for washing glassware, buffer preparation, cell culture or a highly sensitive analytical technique, the appropriate grade of water is essential to support research projects and maintain productivity. A well-designed lab water system can help ensure the success and integrity of research for all types of facilities, from the smallest academic labs to the largest research building. Designing a new lab water system or retrofitting an existing system requires a thorough understanding and working knowledge of common and emerging contaminants, purification technologies, industry standards, user requirements and water distribution options. This article describes key factors to be considered when designing a customized lab water system and outlines best practices for defining purity level and volume requirements. Options for water distribution design and equipment are also described.
|Designing a customized lab water system|
|Improving chromatographic performance by using freshly delivered ultrapure water in the mobile phase |
Vivek Joshi, PhD, Senior Scientist, Bioscience Business Unit and Estelle Riche, Senior Scientist, Lab Water Business Field, Merck Millipore
LCGC "The Peak" (2009), June, 7 - 14 2009
The purity of the solvent used for the mobile phase is one of many factors affecting the quality of chromatographic data obtained from high-performance liquid chromatography (HPLC). A typical reversed-phase HPLC gradient elution requires equilibration of the column to the initial conditions with several column volumes of the weak/aqueous solvent. Organic contaminants in the aqueous solvent will adsorb at the head of the column and can cause interferences in the succeeding chromatograms, such as massive baseline shifts and the appearance of extraneous peaks. This study illustrates how two different sources of water used as solvent in the gradient elution of a drug mixture affect chromatographic performance over time. The solvents being compared are commercially available HPLC-grade bottled water without total oxidizable carbon (TOC) specifications and freshly delivered ultrapure water with a TOC level of 5 ppb. Comparing the chromatograms of pre-concentrated water by analytical HPLC shows that bottled HPLC-grade water contains many more organic solutes than does freshly delivered ultrapure water, suggesting that these contaminating solutes may contribute to baseline variability and poor chromatographic performance when bottled water is used as a mobile phase in HPLC separations.Artículo Texto completo
|Trace Analysis of Perchlorate: Analytical Method and Removal Efficiency of Purification Technologies |
E. Castillo, E. Riché, I. Kano and S. Mabic
LCGC "The Peak" (2008) August, 21-30. 2008
Perchlorate recently has received attention as an environmental pollutant. Perchlorate may affect human health by interfering with iodide uptake by the thyroid gland and disrupting thyroid function. Perchlorate-free purified water is needed by laboratories analyzing samples for the presence of perchlorates. An ion chromatography method was developed to analyze perchlorate at the ng/L level in high purity water. The perchlorate-removal efficiency of various combinations of water purification technologies also was evaluated. Reverse osmosis alone removed 97 % of the perchlorate. Ion exchange resins and electrodeionization removed all the perchlorate present in water. Using a combination of purification technologies can provide perchlorate-free water suitable for ion chromatography analysis of perchlorate-contaminated samples.
|Trace Analysis of Perchlorate: Analytical Method and Removal Efficiency of Purification Technologies|
|Assessment of the acute toxicity of triclosan and methyl triclosan in wastewater based on the bioluminescence inhibition of Vibrio fischeri |
M. Farré, D. Asperger, L. Kantiani, S. González, M. Petrovic, D. Barceló
Anal Bioanal Chem 390 1999–2007 2008
In this work, the contributions of triclosan and its metabolite methyl triclosan to the overall acute toxicity of wastewater were studied using Vibrio fischeri. The protocol used in this paper involved various steps. First, the aquatic toxicities of triclosan and methyl triclosan were determined for standard substances, and the 50% effective concentrations (EC50) were determined for these compounds. Second, the toxic responses to different mixtures of triclosan, methyl triclosan, and surfactants were studied in different water matrices, i.e., Milli-Q water, groundwater and wastewater, in order to evaluate (i) the antagonistic or synergistic effects, and (ii) the influence of the water matrices. Finally, chemical analysis was used in conjunction with the toxicity results in order to assess the aquatic toxicities of triclosan and its derivative in wastewaters. In this study, the toxicities of 45 real samples corresponding to the influents and effluents from eight wastewater treatment works (WWTW) were analyzed. Thirty-one samples were from a wastewater treatment plant (WWTP) equipped with two pilot-scale membrane bioreactors (MBR), and the influent and the effluent samples after various treatments were characterized via different chromatographic approaches, including solid-phase extraction (SPE), liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS), and SPE coupled to gas chromatography–mass spectrometry (GC–MS). The toxicity was determined by measuring the bioluminescence inhibition of Vibrio fischeri. In order to complete the study and to extrapolate the results to different WWTPs, the toxicity to V. fischeri of samples from seven more plants was analyzed, as were their triclosan and methyl triclosan concentrations. Good agreement was established between the overall toxicity values and concentrations of the biocides, indicating that triclosan is one of the major toxic organic pollutants currently found in domestic wastewaters.
|Extraction of extracellular polymeric substances from extreme acidic microbial biofilms |
A. Aguilera, V. Souza-Egipsy, P. San Martín-Úriz, R. Amils
Appl Microbiol Biotechnol 78 1079–1088 2008
The efficiency of five extraction methods for extracellular polymeric substances (EPS) was compared on three benthic eukaryotic biofilms isolated from an extreme acidic river, Río Tinto (SW, Spain). Three chemical methods (MilliQ water, NaCl, and ethylenediamine tetraacetic acid [EDTA]) and two physical methods (Dowex 50.8 and Crown Ether cation exchange resins) were tested. The quality and quantity of the EPS extracted from acidic biofilms varied according to which EPS extraction protocol was used. Higher amounts were obtained when NaCl and Crown Ether resins were used as extractant agents, followed by EDTA, Dowex, and MilliQ. EPS amounts varied from approximately 155 to 478 mg g-1 of dry weight depending on the extraction method and biofilm analyzed. EPS were primarily composed of carbohydrate, heavy metals, and humic acid, plus small quantities of proteins and DNA. Neutral hexose concentrations corresponded to more than 90% of the total EPS dry weight. The proportions of each metals in the EPS extracted with EDTA are similar to the proportions present in the water from each locality where the biofilms were collected except for Al, Cu, Zn, and Pb. In this study, the extracellular matrix heavy metal sorption efficiencies of five methods for extracting EPS from eukaryotic acidic biofilms were compared.
|A General Method for Constructing Optically Active Supramolecular Assemblies from Intrinsically Achiral Water-Insoluble Free-Base Porphyrins |
Y. Zhang, P. Chen, M. Liu
Chem. Eur. 14 1793 – 1803 2008
We have developed a general method to construct optically active porphyrin supramolecular assemblies by using a simple air–water interfacial assembly process. The method involved the in situ diprotonation of the free-base porphyrins at the air–water interface and subsequent assembly under compression. We showed that two intrinsically achiral water-insoluble free-base porphyrin derivatives, 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine (H2OEP) and 5,10,15,20-tetra-p-tolyl-21H,23H-porphine (H2TPPMe), could be diprotonated when spread onto a 2.4?M hydrochloric acid solution surface, and the Langmuir–Schaefer (LS) films fabricated from the subphase exhibited strong circular dichroism (CD) absorption, whereas those fabricated from pure Milli-Q water subphase did not. The experimental data suggested that the helical stacking of the achiral porphyrin building blocks was responsible for the supramolecular chirality of the assemblies. Interestingly, such a method was successfully applied to a series of other intrinsically achiral free-base porphyrins such as 5,10,15,20-tetrakis(4-methoxyphenyl)-21H,23H-porphine (H2TPPOMe), 5,10,15,20-tetraphenyl-21H,23H-porphine (H2TPP), 5,10,15,20-tetrakis(4-(allyloxy)phenyl)-21H,23H-porphine (H2TPPOA), and 5,10,15,20-tetrakis(3,5-dimethoxyphenyl)-21H,23H-porphine (H2TPPDOMe). A possible mechanism has been proposed. The method provides a facile way to obtain optically active porphyrin supramolecular assemblies by using intrinsically achiral water-insoluble free-base porphyrin derivatives.
|LC/MS/MS structure elucidation of reaction intermediates formed during the TiO2 photocatalysis of microcystin-LR |
M. G. Antoniou, J. A. Shoemaker, A. A. de la Cruz, D. D. Dionysiou
Toxicon 51 1103–1118 2008
Microcystin-LR (MC-LR), a cyanotoxin and emerging drinking water contaminant, was treated with TiO2 photocatalysts immobilized on stainless steel plates as an alternative to nanoparticles in slurry. The reaction intermediates of MC-LR were identiﬁed with mass spectrometry (MS) at pH of Milli-Q water (pHsq = 5.7). Eleven new [M+H]+ were observed in the liquid chromatography mass spectrometry (LC/MS) chromatogram with some of them giving multiple peaks. Most of these reaction intermediates have not been reported from previous studies employing TiO2 nanoparticles at acidic conditions (pH = 4.0). Investigating the effects of pH (for 3.0
|Differential expression of chicken hepatic genes responsive to PFOA and PFOS |
L.W.Y. Yeung, K.S. Guruge, N. Yamanaka, S. Miyazaki, P.K.S. Lam
Toxicology 237 111–125 2007
The effects of PFOS and PFOA on the gene expression patterns of chickens that were exposed to either PFOS or PFOA at low doses were investigated with the use of microarray techniques. Twelve Genechip Chicken Genome Arrays were used to study hepatic gene expression in 6-week-old chickens (Gallus gallus) that were exposed to either PFOA (0.1, 0.5, or 5 mg/mL), PFOS (0.02 or 0.1 mg/mL), or a saline vehicle control (0.9% NaCl in Milli-Q water) via subcutaneous implantation of a 2 mL osmotic pump for 4 weeks or for 4 weeks with a further 4 weeks of depuration. Over 240 and 480 genes were significantly affected by PFOS after 4 weeks of exposure and after 4 weeks of exposure with a further 4 weeks of depuration, respectively and over 290 and 320 genes were significantly affected by PFOA, correspondingly. For PFOS, the genes that were affected after 4 weeks of exposure were mainly related to the transport of electrons and oxygen, and the metabolism of lipids and fatty acids; while the genes that were affected after 4 weeks of exposure with a further 4 weeks of depuration were mainly related to the transport of electrons and ions, and protein amino acid phosphorylation and proteolysis. For PFOA, the genes that were affected after 4 weeks of exposure were related to the transport of ions, lipids, and electrons and cytochromes; while the genes that were affected after 4 weeks of exposure with a further 4 weeks of depuration were related to protein amino acid phosphorylation and proteolysis, the transport of ions, and the metabolism of fatty acids and lipids. The results also showed that the gene expression patterns between chickens that were treated with PFOS and those that were treated with PFOA were different, which points to the importance of the separate evaluation of the toxicities of PFOS and PFOA. Specifically, the gene expressions of CYP8B and NOV were studied.
|Aligned Nanocables: Controlled Sheathing of CuO Nanowires by a Self-Assembled Tubular Glycolipid |
Y. Zhou, S. Kamiya, H. Minamikawa, T. Shimizu
Adv. Mater 19 4194–4197 2007
Aligned nanocables, consisting of CuO nanowire cores and lipid nanotube shells, are prepared by sheathing an aligned array of CuO nanowires with a self-assembled tubular glycolipid (see figure). The sheath thickness of the nanocable is tunable by changing the incubation temperature of the lipid on the CuO nanowire.
|Simultaneous determination of trace levels of ethylmercury and methylmercury in biological samples and vaccines using sodium tetra(n-propyl)borate as derivatizing agent |
D. Gibičar, M. Logar, N. Horvat, A. Marn-Pernat, R. Ponikvar, M. Horvat
Anal Bioanal Chem 388 329–340 2007
Because of increasing awareness of the potential neurotoxicity of even low levels of organomercury compounds, analytical techniques are required for determination of low concentrations of ethylmercury (EtHg) and methylmercury (MeHg) in biological samples. An accurate and sensitive method has been developed for simultaneous determination of methylmercury and ethylmercury in vaccines and biological samples. MeHg and EtHg were isolated by acid leaching (H2SO4–KBr–CuSO4), extraction of MeHg and EtHg bromides into an organic solvent (CH2Cl2), then back-extraction into Milli-Q water. MeHg and EtHg bromides were derivatized with sodium tetrapropylborate (NaBPr4), collected at room temperature on Tenax, separated by isothermal gas chromatography (GC), pyrolysed, and detected by cold-vapour atomic fluorescence spectrometry (CV AFS). The repeatability of results from the method was approximately 5–10% for EtHg and 5–15% for MeHg. Detection limits achieved were 0.01 ng g-1 for EtHg and MeHg in blood, saliva, and vaccines and 5 ng g-1 for EtHg and MeHg in hair. The method presented has been shown to be suitable for determination of background levels of these contaminants in biological samples and can be used in studies related to the health effects of mercury and its species in man. This work illustrates the possibility of using hair and blood as potential biomarkers of exposure to thiomersal.
|A thermo extraction–UV/Vis spectrophotometric method for total iodine quantification in soils and sediments |
B. S. Gilfedder, F. Althoff, M. Petri, H. Biester
Anal Bioanal Chem 389 2323–2329 2007
Iodine in soils and sediments is a difficult element to analyze due to its volatility in acidic conditions. Traditionally it has been quantified using neutron activation analysis techniques, which, unfortunately, requires access to a nuclear reactor. We present here a simple method for solid-phase iodine analysis by thermo extraction at 1000°C and quantification by UV/Vis photometry. Samples are combusted in an oxygen stream and trapped in Milli-Q water. The extracts are then quantified by an As3+–Ce4+ spectrometric method whereby iodide catalyzes the oxidation of As3+ to As5+ and reduction of Ce4+ to Ce3+. Three standard reference materials were analyzed with excellent recoveries (97–113%) and RSDs (<5%). Moreover, the detection limit was less than 50 ng absolute iodine with a confidence limit of 95%. When applied to carbonate-rich samples from sediment traps deployed in Lake Constance we found very low iodine levels (0.8–2 mg kg-1). Despite the low concentrations, the precision of the method was consistently better than 5% RSD. However, the method needed to be slightly modified for organic and iodine-rich sediments (20–30% organic carbon) from a lake in the Black Forest by increasing the oxygen flow rate and decreasing the combustion time. Using the modified method we were able to achieve RSDs lower than 5%.
|Ultraperformance Liquid Chromatography-Tandem Mass Spectrometry Analysis of Stimulatory Drugs of Abuse in Wastewater and Surface Waters |
M. Huerta-Fontela, M. Teresa Galceran, F. Ventura
Anal. Chem. 79 3821-3829 2007
Ultraperformance liquid chromatography coupled to electrospray tandem mass spectrometry was used for the rapid and simultaneous analysis of 15 stimulatory drugs in water. Cocaine, amphetamine-related compounds, LSD, ketamine, PCP, fentanyl, and metabolites, among the controlled drugs, and nicotine, caffeine, and their metabolites, among the noncontrolled drugs, were studied. Chromatographic separation was achieved in less than 4.5 min, with improved peak resolution and sensitivity. Identification and quantification of the compounds of interest was performed by selected reaction monitoring, using an electrospray ionization source. Isotope dilution (except for paraxanthine) was used for quantitation. Quality parameters of the method were established, and limits of quantification were obtained for controlled drugs in surface waters from 0.1 to 3.1 ng/L and in wastewaters from 0.2 to 4.0 ng/L. Run-to-run and day-to-day precisions were evaluated in different water matrixes (Milli-Q water, surface water, wastewater). To assess the presence of these drugs in real water samples, the optimized method was applied to the analysis of wastewater and surface river water. The analysis of several samples from wastewater treatment plants in northeast Spain revealed the presence of drugs such as cocaine and amphetamine-related compounds, in both influent and effluent samples. Cocaine metabolite and MDMA (ecstasy) were also found in surface waters while nicotine and caffeine were detected in all the analyzed samples. The results obtained demonstrate that the presence of these drugs in the aquatic media must be considered a matter of environmental concern.
|Feasibility of Pressurization To Speed Up Enzymatic Hydrolysis of Biological Materials for Multielement Determinations |
A. Moreda-Pineiro, A. Bermejo-Barrera, P. Bermejo-Barrera, J. Moreda-Pineiro
Anal. Chem. 79 1797-1805 2007
The feasibility of pressurized solvents (liquids at a high pressure and/or high temperature without the subcritical point being reached) has been newly investigated to accelerate enzymatic hydrolysis processes of mussel tissue for multielement determinations. The target elements (Al, As, Cd, Co, Cu, Fe, Hg, Li, Mn, Pb, Se, Sr, V, and Zn) were released from dried mussel tissue by action of two proteases (pepsin and pancreatin), and they have been evaluated by inductively coupled plasma optical emission spectrometry (ICP-OES). Variables inherent to the enzymatic activity (pH, ionic strength, temperature, and enzyme mass) and factors affecting pressurization (static time, pressure, and number of cycles) were simultaneously studied by applying a Plackett-Burman design (PBD) as the screening method. Results showed that pH, ionic strength, and temperature were the most statistically significant factors (confidence interval of 95%) under pressurized conditions for pepsin, while pH and ionic strength affected pancreatin activity. This means that metal extraction is mostly attributed to enzymatic activity. The static time (enzymatic hydrolysis time) was found statistically nonsignificant for most of the elements, meaning that the hydrolysis procedure can be finished within a 2-15 min range. For pepsin, optimized conditions (pH 1.0, temperature 40 °C, pressure 1500 psi, static time 2 min, and number of cycles 3) gave quantitative extractions for As, Cd, Co, Cu, Hg, Li, Mn, Pb, Se, Sr, V, and Zn. The pepsin mass was 0.05 g, and the solution was Milli-Q water at pH 1.0 (adjusted with hydrochloric acid). For pancreatin, quantitative recoveries were only reached for As, Cd, Cu, Li, Pb, and Sr at room temperature, at a pressure of 1500 psi, for a static time of 2 min and a number of cycles of 3. The extraction solution was a 0.3 M potassium dihydrogen phosphate/potassium hydrogen phosphate buffer at a pH of 7.5 working at room temperature. Around 0.5 g of diatomaceous earth was used as dispersing agent for hydrolyses with either enzyme. Analytical performances, such as limits of detection and quantification and repeatability of the overall procedure, have been established. Finally, accuracy of the methods was assessed by analyzing seafood certified reference materials (GBW-08571, DORM-2, DOLT-3, TORT-2), fatty tissues certified reference materials (BCR 185, NIST 1577b), and fibrous certified reference materials (BCR 62, GBW-08501).
|Determination of Quats in Beverages and Urine Samples by Capillary Zone Eletrophoresis |
J.S. Aulakh, A. Fekete, A.K. Malik, P. Schmitt-Kopplin, R.K Mahajan
Annali di Chimica 97 1157-1167 2007
Conditions have been developed for simultaneous determination of paraquat (PQ) and diquat (DQ) by capillary zone electrophoresis (CZE) with diode array detector (DAD) after their preconcentration by solid phase extraction using Megabond Elut C18 and Strata X 33 µm Polymeric sorbent cartridges. Conditions were optimised with reference to pH, EDTA concentration in sodium acetate acetic acid buffer of pH (3.8) with 3-8 % of methanol, ethanol and acetonitrile as organic modifier in the background electrolyte. UV detection with variable wavelength was used to determine each compound at its maximum absorption providing an excellent sensitivity. The recovery of these compounds from water samples spiked at different levels was more than 90 %. The limit of detection (S/N=3) obtained for milli-Q water when spiked with standards was 0.17 ppm for DQ and 0.19 ppm for PQ, in tap water samples it was found to be 0.27 ppm for DQ and 0.31 ppm for PQ, in cola beverages it was found to be 0.29 ppm for DQ and 0.35 ppm for PQ, and for the urine samples it was 0.36 ppm for diquat and 0.41 ppm for the PQ without preconcentration. After preconcentration using polymeric cartridge the detection limit was reduced to 2.5 ppb for DQand 3 ppb for PQ for the milli-Q water. These detection limits allows for the analysis of these compounds at the levels established by the US Environmental Protection agency.
|N40, a Novel Nonacidic Matrix Protein from Pearl Oyster Nacre, Facilitates Nucleation of Aragonite in Vitro |
Z. Yan, G. Jing, N. Gong, C. Li, Y. Zhou, L. Xie, R. Zhang
Biomacromolecules 8 3597-3601 2007
A novel nonacidic matrix protein from pearl oyster nacre has been purified by cation-exchange chromatography. It was designated N40 for the nacreous protein of approximately 40 kDa. On the basis of the extraction method (with Tris-buffered Milli-Q water) and amino acid compositions (Gly- and Ala-rich), N40 was inferred to be a conventional “insoluble matrix protein”. Crystallization experiments showed that N40 could facilitate the nucleation of aragonite drastically. So far, among the macromolecules that have been purified from the shell, N40 is an exclusive protein that can nucleate aragonite by itself, without the need for adsorption to a substrate. Thus, the present study has proposed the possibility that the nonacidic shell protein (maybe a conventional “insoluble framework protein”) can also directly participate in aragonite nucleation and even act as a nucleation site. It is a valuable supplement to the classic biomineralization theory, in which the soluble acidic proteins of the shell are generally believed to function as a nucleation site.
|Methylene Blue Dye Test for Rapid Qualitative Detection of Hydroxyl Radicals Formed in a Fenton’s Reaction Aqueous Solution |
AY Satoh, JE Trosko, SJ Masten
Environ. Sci. Technol 41 2881-2887 2007
|Filtration through nylon membranes negatively affects analysis of arsenic and phosphate by the molybdenum blue method |
A.C. Heimann, R. Jakobsen
Talanta 72 839–841 2007
Filtering synthetic arsenic- or phosphate-containing solutions (1.5–47.6 μmol/L) with nylon syringe filters significantly reduced absorbances (by 6–74%) when analyzed with the colorimetric molybdenum blue method. Filtering the same solutions with cellulose acetate syringe filters yielded no significant differences as compared to unfiltered controls. The detrimental effect of nylon membranes was also observed when pure Milli-Q water was filtered and subsequently spiked with arsenic(III) or phosphate suggesting that some compound(s) eluting from the filter membranes interfere with the color formation in the assay. Consequently, we caution against using nylon filters when filtering water samples for the determination of arsenic or phosphate with the molybdenum blue method.
|High-performance liquid chromatography and pharmacokinetics of aceclofenac in rats |
P. Musmade, G. Subramanian, K.K. Srinivasan
Analytica Chimica Acta 585 103–109 2007
A simple and sensitive high-performance liquid chromatographic (HPLC) method was developed for quantification of aceclofenac in rat plasma. Ibuprofen was used as an internal standard (IS). The present method used protein precipitation for extraction of aceclofenac from rat plasma. Separation was carried out on reversed-phase C18 column (250 mm × 4.6 mm, 5 µ) and the column effluent was monitored by UV detector at 282 nm. The mobile phase used was methanol-triethylamine (pH 7.0; 0.3% v/v in Milli-Q water) (60:40%, v/v) at a flow rate of 1.0 mL min-1. This method was linear over the range of 50.0–3500.0 ng mL-1 with regression coefficient greater than 0.99. The mean recovery of aceclofenac and IS were 84.62 ± 3.23 and 89.19 ± 1.57%, respectively and the method was found to be precise, accurate, and specific during the study. The method was successfully applied for pharmacokinetic study of aceclofenac in rats.
|Inﬂuence of the surface microlayer on atmospheric deposition of aerosols and polycyclic aromatic hydrocarbons |
S. del Vento, J. Dachs
Atmospheric Environment 41 4920–4930 2007
Atmospheric dry deposition is an important process for the introduction of aerosols and pollutants to aquatic environments. The objective of this paper is to assess, for the ﬁrst time, the inﬂuence that the aquatic surface microlayer plays as a modifying factor of the magnitude of dry aerosol deposition ﬂuxes. The occurrence of a low surface tension (ST) or a hydrophobic surface microlayer has been generated by spiking milli-Q water or pre-ﬁltered seawater with a surfactant or octanol, respectively. The results show that ﬁne mode (o2.7 mm) aerosol phase PAHs deposit with ﬂuxes 2–3 fold higher when there is a low ST aquatic surface due to enhanced sequestration of colliding particles at the surface. Conversely, for PAHs bound to coarse mode aerosols (42.7 mm), even though there is an enhanced deposition due to the surface microlayer for some sampling periods, the effect is not observed consistently. This is due to the importance of gravitational settling for large aerosols, rendering a lower inﬂuence of the aquatic surface on dry deposition ﬂuxes. ST (mN m-1)is identiﬁed as one of the key factor driving the magnitude of PAH dry deposition ﬂuxes (ng m-2d-1) by its inﬂuence on PAH concentrations in deposited aerosols and deposition velocities (d, cms-1). Indeed, d values are a function of ST as obtained by least square ﬁtting and given by Ln(d) = -1.77 Ln(ST)+5.74 (r 2= 0.95) under low wind speed (average 4ms-1) conditions.
|Optimisation of the separation of herbicides by linear gradient high performance liquid chromatography utilising artiﬁcial neural networks |
A.T.K. Tran, R.V. Hyne, F. Pablo, W.R. Day, P. Doble
Talanta 71 1268–1275 2007
An artiﬁcial neural network (ANN) was employed to model the chromatographic response surface for the linear gradient separation of 10 herbicides that are commonly detected in storm run-off water in agricultural catchments. The herbicides (dicamba, simazine, 2,4-D, MCPA, triclopyr, atrazine, diuron, clomazone, bensulfuron-methyl and metolachlor) were separated using reverse phase high performance liquid chromatography and detected with a photodiode array detector. The ANN was trained using the pH of the mobile phase and the slope of the acetonitrile/water gradient as input variables. A total of nine experiments were required to generate sufﬁcient data to train the ANN to accurately describe the retention times of each of the herbicides within a deﬁned experimental space of mobile phase pH range 3.0–4.8 and linear gradient slope 1–4% acetonitrile/min. The modelled chromatographic response surface was then used to determine the optimum separation within the experimental space. This approach allowed the rapid determination of experimental conditions for baseline resolution of all 10 herbicides. Illustrative examples of determination of these components in Milli-Q water, Sydney mains water and natural water samples spiked at 0.5–1µg/L are shown. Recoveries were over 70% for solid-phase extraction using Waters Oasis® HLB 6 cm3 cartridges.
|Behaviour of palladium(II), platinum(IV), and rhodium(III) in artificial and natural waters: Influence of reactor surface and geochemistry on metal recovery |
A. Cobelo-Garcia, A. Turner, G.E. Millward, F. Couceiro
Analytica Chimica Acta 585 202–210 2007
The recovery of dissolved platinum group elements (PGE: Pd(II), Pt(IV) and Rh(III)) added to Milli-Q® water, artificial freshwater and seawater and filtered natural waters has been studied, as a function of pH and PGE concentration, in containers of varying synthetic composition. The least adsorptive and/or precipitative loss was obtained for borosilicate glass under most of the conditions employed, whereas the greatest loss was obtained for low-density polyethylene. Of the polymeric materials tested, the adsorptive and/or precipitative loss of PGE was lowest for fluorinated ethylene propylene. The loss of Pd(II) in freshwater was significant due to its affinity for surface adsorption and its relatively low solubility. The presence of natural dissolved organic matter increases the recovery of Pd(II) but enhances the loss of Pt(IV). The loss of Rh(III) in seawater was significant and was mainly due to precipitation, whereas Pd(II) recovery was enhanced, compared to freshwater, because of its complexation with chloride. The results have important implications regarding protocols employed for sample preservation and controlled laboratory experiments used in the study of the speciation and biogeochemical behaviour of PGE.
|Comparative Pulmonary Toxicity Assessments of C60 Water Suspensions in Rats: Few Differences in Fullerene Toxicity in Vivo in Contrast to in Vitro Profiles |
C. M. Sayes, A. A. Marchione, K.L. Reed, D.B. Warheit
Nano Letters 7 2399-2406 2007
It has previously been reported that the in vitro cytotoxic effects of water-soluble fullerene species are a sensitive function of their surface derivatization status. In a recent study, it was reported that doses of an aggregated form of underivatized C60, termed nano-C60, were 3−4 orders of magnitude more toxic to human dermal fibroblasts, lung epithelial cells, and normal human astrocytes when compared to identical exposures of these cell types to a fully derivatized, highly water-soluble derivative, C60(OH)24. Accordingly, the aim of this study was to test and validate these in vitro findings by comparing the in vivo pulmonary toxicity effects in rats of intratracheally instilled nano-C60 and C60(OH)24. In two combined studies, groups of rats were instilled with doses of either 0.2, 0.4, 1.5, or 3.0 mg/kg of nano-C60, C60(OH)24, or α-quartz particle types using Milli-Q water as the vehicle. Subsequently, the lungs of vehicle and particle-exposed rats were assessed using bronchoalveolar lavage (BAL) fluid biomarkers, oxidant and glutathione endpoints, airway and lung parenchymal cell proliferation methods, and histopathological evaluation of lung tissue at 1 day, 1 week, 1 month, and 3 months postinstillation exposure. Exposures to both nano-C60 or water-soluble C60(OH)24 produced only transient inflammatory and cell injury effects at 1 day postexposure (pe) and were not different from water instilled controls at any other pe time periods. An increase in lipid peroxidation endpoints vs controls was measured in BAL fluids of rats exposed to 1.5 and 3 mg/kg of nano-C60 at 1 day and 3 month pe time points. In addition, no adverse lung tissue effects were measured at 3 months postinstillation exposures to the highest dose of the two types of fullerenes. In contrast, pulmonary exposures to quartz particles in rats produced dose-dependent lung inflammatory responses characterized by neutrophils and foamy lipid-containing alveolar macrophage accumulation as well as evidence of early lung tissue thickening consistent with the development of pulmonary fibrosis. The results demonstrated little or no difference in lung toxicity effects between the two fullerene samples when compared to controls, and these data are not consistent with the previously reported in vitro effects. The findings exemplify both the difficulty in interpreting and extrapolating in vitro toxicity measurements to in vivo effects and highlight the complexities associated with probing the relevant toxicological responses of fullerene nanoparticle systems.
|Development and validation of a high-performance liquid chromatography–tandem mass spectrometry for the determination of penciclovir in human plasma: Application to a bioequivalence study |
H. Lee, J. Seo, K. Lee
Journal of Chromatography B 852 852 382–388 2007
We developed and validated a simple high-performance liquid chromatography (HPLC) coupled with positive ion electrospray ionization tandem mass spectrometry (ESI-MS/MS) detection system for determining penciclovir (active metabolite of famciclovir) levels in human plasma using acyclovir as an internal standard (IS). Acquisition was performed in multiple reaction monitoring (MRM) mode by monitoring the transitions: m/z 254.00 > 152.09 for penciclovir and m/z 226.00 > 152.09 for IS. The analytes were chromatographed on a Capcellpak MGII C18 reversed-phase chromatographic column by isocratic elution using 30% methanol and 70% Milli-Q water containing 10 mM ammonium formate (adjusted to pH 3.1 with formic acid). Results were linear over the studied range (0.05–10 μg/ml) with r2 = 0.9999, and the total analysis time for each run was 2 min. Intra- and inter-assay precisions were 2.3–7.8 and 3.7–7.5%, respectively, and intra- and inter-assay relative errors (RE) were 2.0–8.4 and 1.9–9.1%, respectively. The lower limit of quantification (LLOQ) was 0.05 μg/ml. At this concentration mean intra- and inter-assay precisions were 7.8 and 7.5%, respectively, and mean intra- and inter-assay relative errors were 2.2 and 9.1%, respectively. Penciclovir was found to be stable in plasma samples under short-, long-term storage and processing conditions. The developed assay was successfully applied to a bioequivalence study of penciclovir administered as a single oral dose (500 mg as famciclovir) to healthy volunteers.
|Calcite dissolution: Effects of trace cations naturally present in Iceland spar calcites |
A.O. Harstad, S.L.S. Stipp
Geochimica et Cosmochimica Acta 71 56–70 2007
In situ dissolution experiments on a set of pure, optical quality Iceland spar calcite samples from four different localities showed etch pit step retreat rates to be inversely proportional to total inherent trace cation composition. Atomic absorption spectroscopy (AAS) revealed Fe2+, Mg2+, Mn2+ and Sr2+ in amounts varying from a few to hundreds of ppm. We used a very simple experimental set-up, with an Atomic Force Microscope (AFM) fluid cell and a droplet of MilliQ water. As the calcite dissolved and approached equilibrium with the solution, trace cations were released, which were then present for interaction with the dissolving surface. We monitored continuous free-drift dissolution, in situ, on fresh cleavage surfaces for up to 40 min. Dissolution produced one-layer-deep, rhombic etch pits that continually expanded as we collected images. The rhombohedral symmetry of calcite defines two obtuse and two acute edges on the cleavage surface of etch pits and these, as expected from previous work, had different dissolution rates. Despite identical experimental conditions for all samples, we observed lower step retreat rates for both obtuse and acute edges on calcite characterised by relatively high trace cation composition. Increased cation concentration, particularly Mn, was also correlated with rounding of obtuse–obtuse corners, resulting in obtuse step retreat rates similar to those for acute sides. Physcial limitations of the AFM technique were taken into account when measuring step rate retreat and results were collected only from single-layer etch pits, which represent crystalline calcite with minimal defects. Dissolution rates presented here are thus lower than previous reports for studies of deep etch pits and where the physical limitations of imaging may not have been considered. In addition to molecular-level proof that divalent cations inherent at ppm levels in the calcite affect the dissolution process, these results show that pure, optical quality Iceland spar calcite should not be considered pure in the chemical sense. The results imply that dissolution rates determined for ideal systems with pure, synthetic or natural, materials may be considered as the boundary condition for dissolution in real systems in nature, where cations are always present both in the solution and in the initial solid.
|Determining estrogenic steroids in Taipei waters and removal in drinking water treatment using high-flow solid-phase extraction and liquid chromatography/tandem mass spectrometry |
C. Chen, T. Wen, G. Wang, H. Cheng, Y. Lin, G. Lien
Science of the Total Environment 378 352–365 2007
River water and wastewater treatment plant (WWTP) effluents from metropolitan Taipei, Taiwan were tested for the presence of the pollutants estrone (E1), estriol (E3), 17β-estradiol (E2), and 17α-ethinylestradiol (EE2) using a new methodology that involves high-flow solid-phase extraction and liquid chromatography/tandem mass spectrometry. The method was also used to investigate the removal of the analytes by conventional drinking water treatment processes. Without adjusting the pH, we extracted 1-L samples with PolarPlus C18 Speedisks under a flow rate exceeding 100 mL/min, in which six samples could be done simultaneously using an extraction station. The adsorbent was washed with 40% methanol/60% water and then eluted by 50% methanol/50% dichloromethane. The eluate was concentrated until almost dry and was reconstituted by 20 μL of methanol. Quantitation was done by LC-MS/MS-negative electrospray ionization in the selected reaction monitoring mode with isotope-dilution techniques. The mobile phase was 10 mM N-methylmorpholine aqueous solution/acetonitrile with gradient elution. Mean recoveries of spiked Milli-Q water were 65–79% and precisions were within 2–20% of the tested concentrations (5.0–200 ng/L). The method was validated with spiked upstream river water; precisions were most within 10% of the tested concentrations (10–100 ng/L) with most RSDs < 10%. LODs of the environmental matrixes were 0.78–7.65 ng/L. A pre-filtration step before solid-phase extraction may significantly influence the measurement of E1 and EE2 concentrations; disk overloading by water matrix may also impact analyte recoveries along with ion suppression. In the Taipei water study, the four steroid estrogens were detected in river samples (ca. 15 ng/L for E2 and EE2 and 35−45 ng/L for E1 and E3). Average levels of 19–26 ng/L for E1, E2, and EE2 were detected in most wastewater effluents, while only a single effluent sample contained E3. The higher level in the river was likely caused by the discharge of untreated human and farming waste into the water. In the drinking water treatment simulations, coagulation removed 20–50% of the estrogens. An increased dose of aluminum sulfate did not improve the performance. Despite the reactive phenolic moiety in the analytes, the steroids were decreased only 20–44% of the initial concentrations in pre- or post-chlorination. Rapid filtration, with crushed anthracite playing a major role, took out more than 84% of the estrogens. Except for E3, the whole procedure successfully removed most of the estrogens even if the initial concentration reached levels as high as 500 ng/L.
|Basic Considerations for Laboratory Water |
E. Riché, S. Mabic
GEN (2006) 26 42-43 2006
Water is probably the most commonly used laboratory reagent. However, it is often taken for granted and its potential impact on experimental outcomes overlooked. It has been many years since deionized and distilled water were the only purified water choices available. Today, various combinations of purification technologies are used to remove contaminants efficiently. Therefore, matching the water quality with each application yields more consistent and reliable results. Understanding basic principles regarding laboratory water may help scientists avoid common pitfalls.Artículo Texto completo
|Comparative evaluation of Fe3+ and TiO2 photoassisted processes in solar photocatalytic disinfection of water |
A. Rincon, C. Pulgarin
Applied Catalysis B: Environmental 63 222–231 2006
A lost of culturability of bacteria Escherichia coli K12 was observed after exposition to a solar simulator (UV–vis) in a laboratory batch photoreactor. The bacterial inactivation reactions have been carried out using titanium dioxide (TiO2) P25 Degussa and FeCl3 as catalysts. At the starting of the treatment, the suspensions were at their “natural” pH. An increase in the efficiency in the water disinfection was obtained when some advanced oxidation processes such as UV–vis/TiO2, UV–vis/TiO2/H2O2, UV–vis/Fe3+/H2O2, UV–vis/H2O2 were applied. The presence of H2O2 accelerates the rate of disinfection via TiO2. The addition of Fe3+ (0.3 mg/l) to photocatalytic system decreases the time required for total disinfection (<1 CFU/ml), for TiO2 concentrations ranging between 0.05 and 0.5 g/l. At TiO2 concentrations higher than 0.5 g/l the addition of Fe3+ does not significantly increase the disinfection rate. The systems: Fenton (H2O2/Fe3+/dark), H2O2/dark, H2O2/TiO2/dark showed low disinfection rate. The effective disinfection time (EDT24) was reached after 60 and 30 min of illumination for the Fe3+ and TiO2 photoassisted systems, respectively. EDT24 was not reached for the system in the absence of catalyst (UV–vis). The effect on the bacterial inactivation of different mixture of chemical substance added to natural water was studied.
|Formation of iron-containing colloids by the weathering of phyllite |
H. Zanker, G. Huttig, T. Arnold, H. Nitsche
Aquat Geochem 12 299–325 2006
The formation of colloids during the weathering of phyllite was investigated by exposing ground phyllite to Milli-Q water. Secondary mineral colloids of 101–102 nm were detected in significant concentrations. At pH of about 8.5, the solution concentration of these colloids reached up to 10 mg/L (however, acidification to pH 4.0 prevented the formation of the colloids). The mineralogical composition of the secondary mineral colloids is assumed to be a mixture of ferrihydrite, manganese oxyhydroxides, aluminosilicates, amorphous Al(OH)3 and gibbsite with possible additions of iron silicates and?iron-alumino silicates. The colloids were stable over longer periods of time (at least several weeks), even in the presence of suspended ground rock. Direct formation of iron-containing secondary mineral colloids at the rock–water interface by the weathering of rock material is an alternative to the well-known mechanism of iron colloid formation in the bulk of water bodies by mixing of different waters or by aeration of anoxic waters. This direct mechanism is of relevance for colloid production during the weathering of freshly crushed rock in the unsaturated zone as for instance crushed rock in mine waste rock piles. Colloids produced by this mechanism, too, can influence the transport of contaminants such as actinides because these colloids have a large specific surface area and a high sorption affinity.
|Rheological and Light Scattering Properties of Flaxseed Polysaccharide Aqueous Solutions |
K.K.T. Goh, D.N. Pinder, C.E. Hall, Y. Hemar
Biomacromolecules 7 3098-3103 2006
Polysaccharides isolated from flaxseed meals using ethanol consisted of a soluble (7.5% w/w) and an insoluble fraction (2% w/w). The soluble fraction was dialyzed in various salt concentrations and characterized using viscometry and light scattering techniques. Observations using a size-exclusion column coupled to a multiangle laser light scattering (SEC-MALLS) revealed three molecular weight fractions consisting of a small amount (17%) of large molecular weight species (1.0 × 106) and a large amount (69%) of small molecular weight species (3.1 × 105 Da). Dynamic light scattering measurements indicated the presence of very small molecules (hydrodynamic radius ˜ 10 nm) and a very large molecular species (hydrodynamic radius in excess of 100 nm); the latter were probably aggregates. The intrinsic viscosity, [?], of the polysaccharide in Milli-Q water was 1030 ± 20 mL/g. The viscosity was due largely to the large molecular weight species since viscosity is influenced by the hydrodynamic volume of molecules in solution. The Smidsrod parameter B obtained was 0.018, indicating that the molecules adopted a semi-flexible conformation. This was also indicated by the slope (0.56) from the plot of root-mean-square (RMS) radius versus molar mass (Mw).
|Purification of an Elastin-Like Fusion Protein by Microfiltration |
X. Ge, K. Trabbic-Carlson, A. Chilkoti, C.D.M. Filipe
Biotechnology and Bioengineering Vol. 95, 3 424-432 2006
This article describes a simple and potentially scalable microfiltration method for purification of recombinant proteins. This method is based on the fact that when an elastin-like polypeptide (ELP) is fused to a target protein, the inverse phase transition behavior of the ELP tag is imparted to the fusion protein. Triggering the phase transition of a solution of the ELP fusion protein by an increase in temperature, or isothermally by an increase in salt concentration, results in the formation of micron-sized aggregates of the ELP fusion protein. In this article, it is shown that these aggregates are efficiently retained by a microfiltration membrane, while contaminating E. coli proteins passed through the membrane upon washing. Upon reversing the phase transition by flow of Milli-Q water, soluble, pure, and functionally active protein is eluted from the membrane. Proof-of principle of this approach was demonstrated by purifying a fusion of thioredoxin with ELP (Trx-ELP) with greater than 95% recovery of protein and with greater than 95% purity (as estimated from SDS–PAGE gels). The simplicity of this method is demonstrated for laboratory scale purification by purifying Trx-ELP from cell lysate using a syringe and a disposable microfiltration cartridge. The potential scalability of this purification as an automated, continuous industrial-scale process is also demonstrated using a continuous stirred cell equipped with a microfiltration membrane.
|Determination of antidepressants in surface and waste water samples by capillary electrophoresis with electrospray ionization mass spectrometric detection after preconcentration using off-line solid-phase extraction |
M. Himmelsbach, W. Buchberger, C. W. Klampfl
Electrophoresis 27 220–1226 2006
A method for the quantitative determination of seven major antidepressants in surface waters and sewage treatment plant effluents by CE using ESI-MS is presented. Calibration curves for the selected analytes were prepared in Milli-Q purified water and Danube river water extract covering a concentration range of at least one order of magnitude. LODs achieved were between 6 and 13 mg/L for Trazodone and 39 and 53 mg/L for Sertraline in the Milli-Q purified water and Danube river water matrix, respectively. For sample preparation eight different SPE materials were investigated. Best results were obtained for a resin based on hydrophilic divinylbenzene (recoveries from Milli-Q purified water 93–96%; from Danube river water 85–99%). Finally, a series of eight sewage treatment plant effluents were investigated with respect to their content in the selected antidepressants. Six of these samples were tested positive for antidepressants, in particular Venlafaxine, Citalopram and Trazodone in concentrations between 36 and 322 ng/L.
|Nanostructured polymer matrix for oligonucleotide separation |
J Zhang, C Burger, B Chu
Electrophoresis 27 3391–3398 2006
A nanostructured copolymer matrix has successfully separated oligonucleotides with high resolution by CE using a very short separation channel which simulates the real microchip condition for the first time. The triblock copolymer, E45B14E45 (B20-5000) with E, B, and subscript denoting oxyethylene, oxybutylene, and segment length, respectively, has a unique temperature-dependent viscosity-adjustable property and a dynamic coating ability in 16TBE buffer (89 mM Tris, 89 mM boric acid, 2 mM EDTA in Milli-Q water). The B-block is hydrophilic at low temperatures, e.g., 47C, and the polymer solution has a very low viscosity of about 100 cP in a 32.5% w/v solution. At room temperatures, the B-block becomes hydrophobic due to a breakdown of hydrogen bonds between B-blocks and water, and the polymer matrix forms a body-centered cubic structure at high concentrations. Oligonucleotide sizing markers ranging from 8 to 32 base could be successfully separated with one-base resolution in a 1.5 cm long separation channel by E45B14E45 in its gel-like state.
|Rapid detection of the addition of soybean proteins to cheese and other dairy products by reversed-phase perfusion chromatography |
M. C. García ; M. L. Marina
Food Additives & Contaminants: Part A 23:4 339-347 2006
The undeclared addition of soybean proteins to milk products is forbidden and a method is needed for food control and enforcement. This paper reports the development of a chromatographic method for routine analysis enabling the detection of the addition of soybean proteins to dairy products. A perfusion chromatography column and a linear binary gradient of acetonitrile-water-0.1% (v/v) trifluoroacetic acid at a temperature of 60 C were used. A very simple sample treatment consisting of mixing the sample with a suitable solvent (Milli-Q water or bicarbonate buffer (pH¼11)) and centrifuging was used. The method enabled the separation of soybean proteins from milk proteins in less than 4 min (at a flow-rate of 3 ml/min). The method has been successfully applied to the detection of soybean proteins in milk, cheese, yogurt, and enteral formula. The correct quantitation of these vegetable proteins has also been possible in milk adulterated at origin with known sources of soybean proteins. The application of the method to samples adulterated at origin also leads to interesting conclusions as to the effect of the processing conditions used for the preparation of each dairy product on the determination of soybean proteins.
|Humic-like substances extracted from composts can promote the photodegradation of Irgarol 1051 in solar light |
A. Amine-Khodja, O. Trubetskaya, O. Trubetskoj, L. Cavani, C. Ciavatta, G. Guyot, C. Richard
Chemosphere 62 2006
Humic-like substances (HLS) were extracted from a mixture of sewage sludges and trimmings (70–30%, w/w) after different times of composting (0, 70 days and 130 days). HLS were analyzed by elemental analysis, UV–visible and fluorescence spectroscopy and also tested for their ability to photosensitize the degradation of Irgarol. The rate of Irgarol photodegradation in artificial solar light was found to be 2.5- to 4.3-fold higher in the presence of HLS than in buffered Milli-Q water. These results were confirmed by experiments in solar light that evidenced the photodegrading properties of HLS in a more striking way. Using 2-propanol as hydroxyl radical scavenger, we could show that hydroxyl radicals contributed to the photosensitized Irgarol degradation for about 25%. The photodegrading activity of HLS, their absorbance and their emissive properties were all found to increase between 0 and 70 days of composting and to remain quite constant between 70 and 130 days. The degree of humification varied in the same way, linking all these properties to the humification process.
|In vitro fertilization of in vitro matured canine oocytes using frozen–thawed dog semen |
M. De los Reyes, R. Carrion C. Barros
Theriogenology 66 1682–1684 2006
Experiments were conducted to evaluate in vitro fertilization (IVF) of in vitro matured (IVM) bitch oocytes using dog spermatozoa frozen in three different extenders. Sperm-rich fraction from eight ejaculates of five dogs was frozen in each one of three egg yolk Tris extenders with additional: (A) 1.4g citric acid and 0.8g glucose; (B) 0.7g citric acid and 3.5g glucose; or (C) 1.4g citric acid and 0.8g fructose (all with 5% glycerol in 100mL milliQ water). Thawed sperm were co-incubated with IVM bitch oocytes for 6h. Oocytes were fixed and evaluated under an epifluorescence microscope; penetrated oocytes were defined as those having sperm heads in the perivitelline space or in the oocyte cytoplasm. Higher penetration rates (P<0.05) were obtained in oocytes cultured with spermatozoa frozen in extenders B and C than those frozen in extender A (33.1, 34.2 and 26.4%, respectively).
|Inactivation Kinetics of the Cyanobacterial Toxin Microcystin-LR by Free Chlorine |
I. Xagoraraki, G.W. Harrington, K. Zulliger, B. Zeier, W. Krick, D.A. Karner, J.H. Standridge, J. Westrick
Journal of Environmental Engineering July 818-823 2006
Worldwide, the increasing occurrence of toxins produced by cyanobacteria in water bodies used as source waters for drinking water has become an important public health issue. Microcystin-LR is one of the most commonly found cyanotoxins. A detailed evaluation of the free chlorine induced inactivation kinetics of extracellular microcystin-LR is presented in this study. Rate constants needed for chlorine inactivation of the toxin were derived from the data. The effects of varied pH, chlorine dose, toxin concentration, and temperature on the rate of inactivation were evaluated. Batch chlorination experiments were run using carbonate-buffered Milli-Q water at three different initial toxin concentrations (1, 2, and 8 µg/L), three different chlorine doses (1, 3, and 9 mg/L), and three different pH values (6.0, 7.5, and 9.0) at 11, 20 and 29°C. The study showed that extracellular microcystin-LR was inactivated by free chlorine and the inactivation rate was affected by pH. The highest inactivation rates were observed at pH 6.0 and the lowest at pH 9.0.Artículo Texto completo
|Inactivation of Escherichia coli by ozone under bench-scale plug ﬂow and full-scale hydraulic conditions |
P.W.M.H. Smeets, A.W.C. van der Helm, Y.J. Dullemont, L.C. Rietveld, J.C. van Dijk, G.J. Medema
Water Research 40 3239-3248 2006
To determine the disinfection efficacy of ozonation, water companies can apply several disinfection calculation methods. The goal of this study was to evaluate the use of the T10 and continuous stirred tank reactor (CSTR) method to extrapolate inactivation rates of ozone sensitive microorganisms observed in laboratory tests to full-scale ozonation in drinking water treatment. The inactivation efficacy of the ozonation at the Amsterdam water treatment works was assessed by determining Escherichia coli concentrations in large volume samples before and after ozonation over a period of 1 year. The inactivation of dosed E. coli WR1 was tested in a bench-scale dissolved ozone plug flow reactor (DOPFR) on the same feed water as the full-scale ozonation in which a concentrated ozone solution in Milli-Q® water was dosed. Applying the T10 method on the inactivation rates observed in the DOPFR strongly overestimated the inactivation capacity of the full-scale ozonation. The expected inactivation based on the CSTR method (LT2ESWTR) approached the observed inactivation at full-scale. Therefore, the CSTR method should be preferred to calculate inactivation of ozone sensitive organisms such as E. coli, viruses, Giardia and Campylobacter by full-scale ozonation.
|Sensitive, real-time PCR detects low-levels of contamination by Legionella pneumophila in commercial reagents |
H. Shen, S. Rogelj, T.L. Kieft
Molecular and Cellular Probes 20 147–153 2006
In a real-time PCR assay of Legionella pneumophila (targeting the L. pneumophila-speciﬁc mip gene and using SYBR Green dye for DNA detection in conjunction with the iCycler system) we detected as few as 1.3 copies of a mip gene in a 50-ml reaction from serially diluted L. pneumophila genomic DNA. However, cycle threshold (CT) were yielded and DNA product detected in our no-template negative controls and the phenomenon persisted when two separate batches of PCR reagents and water from two different biochemical companies were tested. Since L. pneumophila can be widespread in municipal water supplies, the commercial reagents, especially the reagent water (80% of the reaction volume), could be the source of contamination. To test this hypothesis, we treated Millipore Milli-Q water by ﬁltering through a 0.2 mm-pore-size polycarbonate ﬁlter to remove bacteria prior to autoclaving. Real-time PCR using this water had no contamination. Our ﬁnding is indirect evidence that commercially available puriﬁed water can harbor low level contamination by L. pneumophila DNA that has escaped puriﬁcation processes. This presents a challenge when developing a sensitive DNA-based bacterial detection method if the target organism or its DNA is a common contaminant of necessary reagents.
|Assays on the simultaneous determination and elimination of chloroanisoles and chlorophenols from contaminated cork samples |
S. Insa, V. Salvadó, E. Anticó
Journal of Chromatography A 1122 215–221 2006
A method for the simultaneous determination of the chloroanisoles and chlorophenols in cork samples with gas chromatography has been evaluated in view to its application. All the stages of the suggested procedure have been submitted to an in-depth examination using spiked ground corks. The recoveries of the method, which involves a simultaneous extraction with n-pentane followed by a second extraction using an aqueous basic solution where the phenolic derivates are transferred and, subsequently, derivatised, have been satisfactory for the all analytes at the studied spiking concentration levels. Good precision data and limits of detection between 1 ng/g and 2 ng/g were obtained for almost all compounds. As real samples, naturally contaminated cork slabs taken from different sources have been analysed, showing the presence of 2,4,6-trichloroanisole (TCA) and, in lesser extent, its direct precursor, 2,4,6-trichlorophenol (TCP). Removal studies have been performed by washing these tainted cork slabs with different solutions: Milli-Q water, sodium hydroxide and commercial products. Sodium hydroxide solutions have led to better analyte elimination, and the complete removal of TCP from the cork has been accomplished together with 72% of TCA reduction has been achieved.
|Determination of sixteen polycyclic aromatic hydrocarbons in aqueous and solid samples from an Italian wastewater treatment plant |
F. Busetti, A. Heitz, M. Cuomob, S. Badoer, P. Traverso
Journal of Chromatography A 1102 104–115 2006
A robust procedure for the determination of 16 US EPA PAHs in both aqueous (e.g. wastewaters, industrial discharges, treated effluents) and solid samples (e.g. suspended solids and sludge) from a wastewater treatment plant (WWTP) is presented. Recovery experiments using different percentages of organic modifier, sorbents and eluting solvent mixtures were carried out in Milli-Q water (1000 mL) spiked with a mixture of the PAH analytes (100 ng/L of each analyte). The solid phase extraction (SPE) procedures applied to spiked waste water samples (1000 mL; 100 ng/L spiking level) permitted simultaneous recovery of all the 16 PAHs with yields >70% (6–13% RSD). SPE clean up procedures applied to sewage and stabilized sludge extracts, showed percent recoveries in the range 73–92% (7–13% RSD) and 71–89% (7–12% RSD), respectively. The methods were used for the determination of PAHs in aqueous and solid samples from the WWTP of Fusina (Venice, Italy). Mean concentrations, as the sum of the 16 PAHs in aqueous and suspended solid samples, were found to be approx. in the 1.12–4.62 μg/L range. Sewage and stabilized sludge samples contained mean PAH concentrations, as sum of 16 compounds, in the concentration range of 1.44–1.26 mg/kg, respectively. Extraction and clean up procedures for sludge samples were validated using EPA certified reference material IRM-104 (CRM No. 912). Instrumental analyses were performed by coupling HPLC with UV-diode array detection (UV-DAD) and fluorescence detection (FLD).
|Evaluation of mixed mode solid phase extraction cartridges for the preconcentration of beta-lactam antibiotics in wastewater using liquid chromatography with UV-DAD detection |
E. Benito-Peña, A.I. Partal-Rodera, M.E. Leόn-González, M.C. Moreno-Bondi
Analytica Chimica Acta 556 415–422 2006
Novel and simple method has been developed for the simultaneous determination of beta-lactam antibiotics (BLAs) (penicillin G, amoxicillin, ampicillin, penicillin V, oxacillin, cloxacillin, dicloxacillin and nafcillin) in wastewater. The method is based on solid-phase extraction (SPE) and high performance liquid chromatography with UV-diode array detection (UV-DAD). Two SPE cartridges have been compared for sample clean up and preconcentration: a reversed-phase silica-based cartridge (Bond Elut C18, Varian Inc.) and a strong polymeric mixed mode anion exchanger (Oasis MAX, Waters). The penicillins have been separated using a LUNA™ C18 (2) (150 mm × 4.6 mm, 5 μm) HPLC column and gradient elution with mobile phases consisting of aqueous trifluoroacetic acid and acetonitrile. The analytical wavelength was set at 220 nm. Under optimised conditions it was possible to preconcentrate up to 1000 mL of Milli-Q water in the Oasis MAX cartridges with recoveries in the range 82–97% (R.S.D. 2–9%) for all the antibiotic tested, except amoxicillin (52%, R.S.D. 8%), and limits of detection in the range of 8–24 ng L−1. The matrix components in industrial and urban wastewater samples reduce the preconcentration efficiency in both sorbents, especially for the Bond Elut C18. The use of the Oasis MAX allowed detection limits between 2.9–25.6, 2.5–12.4 and 2.2–12.7 μg L−1, when processing 250 mL of industrial, influent and effluent sewage treatment plant (STP) samples. Recoveries ranged between 46–91, 28–91 and 39–114% (industrial, influent and effluent STP, respectively) for samples spiked with all the antibiotics at 25 and 75 μg L−1 (n = 3 for each level).
|Benefits of the pretreatment step in purifying water for LC-MS analyses |
C. Regnault, S. Mabic
LC-GC The Column Vol 1 issue 9 12-15 2005
Solvent and reagent quality has long been a topic of interest to analytical chemists using liquid chromatography. While several articles describe chromatography methods, few references address the purity of solvents used to prepare mobile phases. Some data to support the water quality suitable for HPLC and LC-MS analysis have been presented previously, but little has been published on the means required to achieve such water quality. Starting from a customer case study, data reported here show the benefits of optimizing each step of the water purification process. Indeed, water purification can be divided into two major basic steps, the pre-treatment step and the polishing step. Since water delivered at the final purification stage is used to prepare the mobile phase,it seems to be an obvious target for optimization., However, the initial pretreatment step is equally critical. Several pretreatment technologies are discussed for their ability and suitability to be utilized in complete water purification processes dedicated to produce water for HPLC and LC-MS work.
|Benefits of the pretreatment step in purifying water for LC-MS analyses|
|New approach to calibrating conductivity meters in the low conductivity range |
P. Spitzer, B. Rossi, Y. Gaignet, S. Mabic, U. Sudmeier
Accred. Qual. Assur. 10 78-81 2005
There is currently a major issue with the calibration of conductivity meters used for high purity water: the lack of availability of a reference material or reference methods for low conductivity ranges (conductivity below 1 mS cm 1 at 25.0 C, resistivity >1 MW cm at 25.0 C). This paper describes the current status of conductivity measurements in high purity water. A new and improved approach, currently being investigated, should allow us to make the calibration of conductivity meters used for low conductivity ranges traceable to the SI.
|New approach to calibrating conductivity meters in the low conductivity range|
|A challenging organic contaminant in high purity water: the endocrine disrupters |
S. Mabic, I Naoe, I. Kano
Ultrapure Water 27-31 2005
Endocrine disrupters are substances or mixtures that alter functions of the endocrine system and consequently cause adverse health effects in an intact organism or its progeny. They have structures that resemble the natural hormone, and interfere with natural hormones by binding to the hormonal receptor. For example, bisphenol A, nonylphenoll and stylbazol all have a common sub-structure close to oestradiol, and they all interact with the estrogen receptor.Developing analytical methods sensitive enough to identify and quantify the presence of endocrine disrupters at low levels in drinking water and environmental monitoring requires high purity water free of endocrine disrupters. The combination of technologies normally embedded in water purification systems bring concentrations of endocrine disrupters to a low level, and in cases where Endocrine Disrupter-free water is required, traces can be removed with a specific polisher at the point of use of the purification system.
|One-Dimensional Plasmon Coupling by Facile Self-Assembly of Gold Nanoparticles into Branched Chain Networks |
S. Lin, M. Li, E. Dujardin, C. Girard, S. Mann
Adv. Mater 17 2553–2559 2005
Short chains and complex networks of interconnected Au nanoparticle chains (see Figure) are produced by a simple template-free approach. Optical spectroscopy and computer simulations show that surface plasmons from individual non-contacting nanoparticles are strongly coupled in the resulting 1D superstructures. These chains may provide a unique way to fabricate complex subwavelength optical waveguides.
|Optimization of extraction and estimation of viruses in silty freshwater sediments |
U. R. Fischer, A. K. T. Kirschner, B. Velimirov
Aquatic Microbial Ecology 40 (3) 207-216 2005
he present study focused on the optimization of procedures for the extraction of viruses from silty freshwater sediments for subsequent enumeration. Viral abundance in 2 different shallow backwater systems of the River Danube (Austria) ranged from 1.45 × 109 to 9.58 × 109 particles ml–1 wet sediment. The highest virus yields from the bulk of the sediments were obtained by 1 min sonication (3 × 20 s intervals, with 10 s interruptions). An increase in sonication time of up to 5 min decreased viral counts by an average of 15%. Since dissolved DNA within sediment samples could bind to the nucleic acid stain and thereby inflate viral estimates, sediment samples are often treated with DNase before the staining procedure. Moreover, they are usually centrifuged and diluted to a high extent in order to avoid interference of particulate material with virus counting. Centrifugation led to a reduction of viral numbers by 2 to 36% compared to untreated samples and did not reduce the background fluorescence; thus counting of viruses was not facilitated. Diluting 2000× with Milli- Q water always provided an average of 19% lower viral numbers than diluting 4000×. Treatment with DNase had no significant effect on virus counting, with viral numbers in untreated samples being on average 96% of those in DNase-containing samples. Additionally, 2 different nucleic acid stains were compared—viruses stained with SYBR Gold fluoresced brighter than those stained with SYBR Green I and fluorescence lasted longer, while background fluorescence was reduced sufficiently, thus facilitating virus counting. Viral numbers using SYBR Gold were on average twice of those obtained with SYBR Green I. The mean efficiency of virus extraction was 88.8% using the protocol outlined in this paper, and was thus slightly higher than that obtained in previous sediment investigations.Artículo Texto completo
|IPNs based on chitosan with NVP and NVP/HEMA synthesised through photoinitiator-free photopolymerisation technique for biomedical applications |
L. Ng, S. Swami
Carbohydrate Polymers 60 523–528 2005
|A sensitive and selective LC–MS–MS method for simultaneous determination of picroside-I and kutkoside (active principles of herbal preparation picroliv) using solid phase extraction in rabbit plasma: Application to pharmacokinetic study |
K. Vipul, M. Nitin, R.C. Gupta
Journal of Chromatography B 820 221–227 2005
A rapid, sensitive and selective LC–MS–MS method for the simultaneous quantitation of picroside-I and kutkoside (active constituents of herbal hepatoprotectant picroliv) was developed and validated in rabbit plasma. The analytes and internal standard (Amarogentin) were extracted using Oasis® HLB solid phase extraction cartridges. Analysis was performed on Spheri RP-18 column (10 µm, 100 mm × 4.6 mm i.d.) coupled with guard column using acetonitrile:MilliQ water (50:50, %v/v) as mobile phase at a ﬂow rate of 1 ml/min with a retention time of 1.39, 1.33 and 1.42 min for picroside-I, kutkoside and amarogentin, respectively. The quantitation was carried out using an API-4000 LC–MS–MS with negative electro spray ionization in multiple reaction monitoring (MRM) mode. The precursor to product ion transitions for picroside-I, kutkoside and amarogentin were m/z 491 > 147, 199; 511 > 167, 235; 585 > 227, respectively. The method was validated in terms of establishing linearity, speciﬁcity, sensitivity, recovery, accuracy and precision (within-and between-assay variation), freeze–thaw (f–t), auto injector and dry residue stability. Linearity in plasma was observed over a concentration range of 1.56–400 ng/ml with a limit of detection (LOD) of 0.5 ng/ml for both analytes. The recoveries from spiked control samples were >60 and >70% for picroside-I and kutkoside, respectively. Accuracy and precision of the validated method were within the acceptable limits of <20% at low and <15% at other concentrations. The analytes were stable after three freeze–thaw cycles and their dry residues were stable at −60 oC for 15 days. The method was successfully applied to determine concentrations of picroside-I and kutkoside post i.v. bolus administration of picroliv in rabbit.
|AFM study of cationically charged polymer brushes: switching between soft and hard matter |
T. Farhan, O. Azzaroni, W.T. S. Huck
Soft Matter 1 66–68 2005
AFM studies on cationic polymer brushes in water (a good solvent) show that brushes in an extended conformation can be easily deformed or indented by an AFM tip. Experiments on polymer brushes in a more collapsed conformation, using methanol–water as a ‘poor solvent’ environment, show similar properties. Conversely, this ‘soft’ behaviour is dramatically different in the presence of electrolytes containing anions that are strongly coordinated to cationic groups of the polymer brush. Our initial studies in electrolyte solutions at different concentrations show that these brushes become so rigid that they cannot be indented or deformed by the AFM tip, even at high loads.
|The combined SPE:ToxY-PAM phytotoxicity assay; application and appraisal of a novel biomonitoring tool for the aquatic environment |
S.M. Bengtson Nasha, U. Schreiber, P.J. Ralph, J.F. Müller
Biosensors and Bioelectronics 20 1443–1451 2005
Mounting concerns regarding the environmental impact of herbicides has meant a growing requirement for accurate, timely information regarding herbicide residue contamination of, in particular, aquatic systems. Conventional methods of detection remain limited in terms of practicality due to high costs of operation and the specialised information that analysis provides. A new phytotoxicity bioassay was trialled for the detection of herbicide residues in filter-purified (Milli-Q) as well as natural waters. The performance of the system, which combines solid-phase extraction (SPE) with the ToxY-PAM dual-channel yield analyser (Heinz Walz GmbH), was tested alongside the traditional method of liquid chromatography–mass spectrometry (LC–MS). The assay methodology was found to be highly sensitive (LOD 0.1 ng L−1 diuron) with good reproducibility. The study showed that the assay protocol is time effective and can be employed for the aquatic screening of herbicide residues in purified as well as natural waters.
|Dependence of copolymer composition, swelling history, and drug concentration on the loading of diltiazem hydrochloride (DIL.HCl) into poly[(N-isopropylacrylamide)-co-(methacrylic acid)] hydrogels and its release behaviour from hydrogel slabs |
R. G. Sousaa, A. Prior-Cabanillasa, I. Quijada-Garridoa, J.M. Barrales-Rienda
Journal of Controlled Release 102 595–606 2005
The loading of an antihypertensive cationic drug, diltiazem hydrochloride (DIL.HCl), into poly(N-isopropylacrylamide) [P(N-iPAAm)], poly(methacrylic acid) [P(MAA)], and their poly[(N-isopropylacrylamide)-co-(methacrylic acid)] P[(N-iPAAm)-co-(MAA)] hydrogels as well as their release behaviour have been investigated. For this purpose, two series of hydrogels have been tested, one previously soaked under acidic pH (treated hydrogels) and the other from the synthesis and washed in deionized water (untreated hydrogels). For the drug loading, these two series of hydrogels have been soaked in drug solutions with different concentrations. DIL.HCl amounts loaded by the gels as well as swelling degrees as a function of both hydrogel composition and DL.HCl concentration in the loading solution have been analyzed. Due to the interactions among DIL.HCl and the MAA group, “untreated” enriched MAA copolymer hydrogels present the highest drug load and loading efficiency. A DIL.HCl concentration of 320 μm/mL has been employed to load copolymers for release experiments, because for this concentration, hydrogels reach relative high drug load with a still high efficiency of loading. Release has been tested in three media, namely, fresh water (Milli-Q grade, pH 7.0), 0.1 N hydrogen chloride (pH 1.2), and a phosphate buffer (pH 7.0). In general, release is lower in fresh water and acidic media than in phosphate buffer. To explain these results, the effect of temperature, medium, and composition on the pH and thermo sensitivity of the hydrogels as well as the diltiazem–polymer interactions have been taken into account.
|Effect of sodium dodecylbenzene sulfonate on the motion of three-phase contact lines on the Wilhelmy plate surface |
S. I. Karakashev, C.M. Phan, A.V. Nguyen
Journal of Colloid and Interface Science 291 489–496 2005
The combined approach of the molecular-kinetic and hydrodynamic theories for description of the motion of three-phase gas–liquid–solid contact lines has been examined using the Wilhelmy plate method. The whole dynamic meniscus has been divided into molecular, hydrodynamic, and static-like regions. The Young–Laplace equation and the molecular-kinetic and hydrodynamic dewetting theories have been applied to describe the meniscus profiles and contact angle. The dissipative forces accompanying the dynamic dewetting have also been investigated. The experiments with a Wilhelmy plate made from an acrylic polymer sheet were carried out using a computerized apparatus for contact angle analysis (OCA 20, DataPhysics, Germany). The extrapolated dynamic contact angle versus velocity of the three-phase contact line for Milli-Q water and 5×10−4 M SDBS solution was experimentally obtained and compared with the combined MHD models with low and moderate Reynolds numbers. The models predict similar results for the extrapolated contact angle. SDBS decreases the equilibrium contact angle and increases the molecular jumping length but does not affect the molecular frequency significantly. The hydrodynamic deformation of the meniscus, viscous dissipation, and friction were also influenced by the SDBS surfactant.
|Determination of pesticide residues in olives and olive oil by matrix solid-phase dispersion followed by gas chromatography/mass spectrometry and liquid chromatography/tandem mass spectrometry |
Carmen Ferrer, M. Jose Gomez, Juan F. Garcia-Reyes, Imma Ferrer, E. Michael Thurman, Amadeo R. Fernandez-Alba; Journal of Chromatography A, 1069 (2005) 183–194
Journal of Chromatography A, 1069 (2005) 183–194 2005
|Environmental Analysis, High Performance Liquid Chromatography (HPLC)|
|A validated HPLC method for determining residues of a dual active ingredient anti-malarial drug on manufacturing equipment surfaces |
Madalina Brindusa Boca, Zeno Apostolides, Etheresia Pretorius; Journal of Pharmaceutical and Biomedical Analysis, 37 (2005) 461–468
Journal of Pharmaceutical and Biomedical Analysis, 37 (2005) 461–468 2005
|High Performance Liquid Chromatography (HPLC), Sample Prep|
|Using ultrapure water in ion chromatography to run analyses at the ng/L level |
I. Kano, E. Castillo, D. Darbouret and S. Mabic
Journal of Chromatography A (2004) 1039, 27-31 2004
Thanks to enhanced capabilities, ion chromatography (IC) occupies an increasing position in many types of applications. Achieving ideal performances for an extended life-time can only be reached, however, if the IC system is operated in optimum experimental conditions. Among the various parameters that need to be controlled, water is particularly important, because it is used throughout the analysis, from sample preparation to column rinsing, elution, and mobile phase preparation. More and more, devices are included in IC systems to generate the eluent in situ, and ultrapure water becomes the major reagent. Data of pre-concentration of high purity water show that detection limits at the ng/L level can be expected with water purified using the right combination of technologies.
|Qualification of an electro-deionization module via experimental design and ion chromatographic studies |
E. Castillo, D. E. Coleman, D. Darbouret, T. Dimitrakopoulos, E. Feuillas, L. E. Vanatta
Journal of Chromatography A 1039 63-70 2004
To meet the needs of the laboratory-water market, a modified electro-deionization (EDI) module has been developed to produce Type 2 purified water. An EDI module consists of desalting and concentrating fluidic compartments that are both filled with anion and cation ion-exchange resins; an anode and a cathode electrode are at opposite ends. In the design in this research, the anode electrode is segmented into three parts and individual dc amperages are applied to each segment; the cathode electrode is a single common electrode. Critical to the performance and longevity of this type of EDI module are: (1) the optimization of the applied dc amperages and (2) the ionic mass balance (i.e., the concentrations of specific and total ions of the RO feedwater to the module compared to the concentrations in the water exiting the module via the desalting and concentrating compartments). To determine a suitable current for each electrode pair, a full-factorial experimental design was developed and employed. For the application of this combination of amperages, the critical parameter of specific-ion mass balance was determined using ion-chromatographic measurements.
|Ultrapure water for liquid chromatography-mass spectrometry studies |
C. Regnault, I. Kano, D. Darbouret and S. Mabic
Journal of Chromatography A 1030 289-295 2004
Improvements in trace enrichment techniques combined with the sensitivity of mass spectrometry offer enhanced opportunities to analyze ever lower concentrations of drugs, metabolites, pesticides or environmental pollutants. To perform HPLC and liquid chromatography–mass spectrometry (LC–MS) analyses under optimum conditions, the water used for mobile phase preparation needs to be highly purified and delivered on demand. Indeed, both UV photodiode array detection and MS detection methods are sensitive to organic contaminants (total organic carbon, TOC), and the water quality has a direct impact on the achievable detection limits. The benefits of UV photooxidation on TOC reduction for LC–MS studies were highlighted using electrospray ionization MS detection by comparing HPLC-grade bottled water, freshly produced UV185/254-treated water, and freshly produced non-UV-treated water.
|Simultaneous determination of selected endocrine disrupters (pesticides, phenols and phthalates) in water by in-field solid-phase extraction (SPE) using the prototype PROFEXS followed by on-line SPE (PROSPEKT) and analysis by liquid chromatography-atmospheric pressure chemical ionisation-mass spectrometry |
P. López-Roldán, M. J. López de Alda, D. Barceló
Anal Bioanal Chem 378 599–609 2004
In this study, a new procedure, based on on-line solid-phase extraction (SPE) and analysis by liquid-chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS), has been developed for the simultaneous, multianalyte determination of 21 selected pesticides, phenols and phthalates in water. SPE was carried out on polymeric PLRP-s cartridges by percolating 20 mL-samples. For sample preconcentration, the performance of a prototype programmable field extraction system (PROFEXS) was evaluated against the commercial laboratory bench Prospekt system used for method development. The Profexs is designed for the automated on-site sampling, SPE preconcentration, and storage of up to 16 samples in SPE cartridges. These cartridges are further eluted and on-line analyzed with the Prospekt coupled to the chromatographic system. In the optimized method, where completely on-line SPE-LC-MS analysis of the samples is carried out with the Prospekt in the laboratory, detection limits lower than 100 ng/L, and satisfactory precision (relative standard deviations <25%) and accuracies (recovery percentages >75%) were obtained for most investigated compounds from the analysis of spiked Milli-Q water. The extraction efficiency achieved with the Profexs was comparable to that of the Prospekt for most compounds and somewhat lower for the most apolar analytes, probably due to adsorption on the pump filters. The completely on-line optimized method was applied to the analysis of surface water, ground water and drinking water from a waterworks in Barcelona. Some pesticides and phenols were found in both surface water and groundwater at ng/L or µg/L levels, but not in the final drinking water. Di(2-ethylhexyl)phthalate (DEHP) was present in all samples investigated, including blanks. To the author's knowledge, this is the first work describing the application of a fully automated on-line SPE-LC-MS method for the simultaneous analysis of pesticides, phenols, and phthalates in water, and the second one that examines the possibilities of the prototype Profexs for automated on-site SPE preconcentration of organic pollutants from water samples.
|Biosensor for seven sulphonamides in drinking, ground and surface water with difficult matrices |
J. Tschmelak; M. Kumpf; G. Proll; G. Gauglitz
Analytical Letters 37(8) 1701-1718 2004
Environmental monitoring of antibiotics and other pharmaceuticals in real water samples with difficult matrices places high demands on chemical analysis. Biosensors have suitable characteristics like their efficiency in a fast, sensitive, and cost-effective detection of pollutants. In this article, we present a recently developed immunoassay for seven sulphonamides (sulphadiazine, sulphamethoxazole, sulphadimidine, sulphamethizole, sulphadimethoxine, sulphathiazole, and sulphamethoxypyridazine) which can only be detected separately. For the simultaneous determination of multiple sulphonamides in the future we performed measurements with different combinations of binary mixtures. The results of the immunosensor were compared to a mathematical model which was developed in our group. Using an automated biosensor system it was possible for the first time to achieve limits of detection (LOD) below 10 ng L-1 and limits of quantification (LOQ) below 100 ng L-1 without sample pre-concentration for these sulphonamides. Sulphonamide calibrations with different immobilised analyte derivatives were made in Milli-Q water. Unstrained spiked and un-spiked real water samples with complex matrices (drinking, ground, and surface water) were measured. In compliance with the Association of Analytical Communities (AOAC) International most recovery rates obtained were between 70% and 120%. The reproducibility was checked by measuring replica of each sample within independent repetitions. Robustness could be demonstrated by long-term stability tests of the biosensor surface. These studies show that the biosensor used offers the necessary reproducibility, precision, and robustness required for an analytical method. The measuring data of the binary mixtures show a systematic error compared to the mathematical model at high concentrations of both sulphonamides, because the approximation uses only the standard calibration curves (data of the logistic fit function) as input data. It is also hard to adequately describe the cross-reactivity and the behaviour of a mixture of polyclonal antibodies.
|Determination of Phytate in Urine by High-Performance Liquid Chromatography–Mass Spectrometry |
J. Perello, B. Isern, J.A. Munoz, M. Valiente, F. Grases
Chromatographia 60(5/6) 265-268 2004
An indirect method is described for determination of phytate in human urine. The method is based on hydrolysis of the phytate and determination of myo-inositol, one of the hydrolysis products. Chromatographic separations were performed on an Aminex HPX-87C column with Milli-Q water as mobile phase; 5 mM ammonium acetate was added post-column. The detector counted positive ions by monitoring m/z=198, which corresponds to the adduct of myo-inositol with the ammonium cation. The relative standard deviations obtained for standards containing 0.5, 1, and 1.5 mg L–1 phytate were 4.1, 3.0, and 2.7% respectively (n=5). The limit of detection was 60 g L–1. Different urine samples were analyzed both by this method and by an alternative analytical method based on GC–MS. The results from both methods were comparable.
|High-performance liquid chromatography–ultrasonic nebulizer high-power nitrogen microwave-induced plasma mass spectrometry, real-time on-line coupling for selenium speciation analysis |
A. Chatterjee, Y. Shibata, H. Tao, A. Tanaka, M. Morita
Journal of Chromatography A 1042 99–106 2004
The coupling of a high-power nitrogen (N2) microwave-induced plasma (MIP) mass spectrometry – (MS) (1.3 kW) with high-performance liquid chromatography, connected with concentric nebulizer (CN), ultrasonic nebulizer (USN) and a hydride generation (HG) systems, for the optimization and determination of selenium compounds, has been carried out. The MIP-MS system fulfils the ideal requirement being an on-line real-time chromatographic detector for Se speciation analysis. Interchanging of MIP-MS system fabricated nebulizer (concentric) with an ultrasonic nebulizer increases about 3.4–12 (peak height) and 6.5–10 (peak area) times ion signals for the selenium compounds. The detection limits for selenate, selenite, trimethylselenonium ion (TmSe), selenomethionine (Semet) and selenoethionine (Seet) (in Milli-Q-water) obtained with the optimized HPLC–USN-N2MIP-MS system are 0.11, 0.14, 0.09, 0.14 and 0.10 µg L-1, respectively, about 12–48 times lower than the HPLC–CN-MIP-MS and 1.5–4.4 (peak height) times lower compared to the HPLC–CN-inductively coupled plasma (ICP)–MS coupling. Considering peak area, the repeatability (R.S.D. for three successive analyses) and intermediate precision (R.S.D. for three successive analyses performed on three different days), achieved for five Se compounds are 0.8–5.6, and 1.1–5.9%, comparable with the HPLC–CN-ICP-MS, HPLC–HG-MIP-MS and HPLC–CN-MIP-MS systems. The combined HPLC–USN-N2MIP-MS has been adequately applied for the determination of Se compounds in certified National Institute for Environmental studies human urine CRM No. 18. The results reasonably agree with the HPLC–CN-ICP-MS values. This encouraging combination may be an alternative ion source of mass spectrometry for coming generation in regard to the selenium speciation analysis.
|Influence of dewetting kinetics on bubble-particle interaction |
A. V. Nguyen, H. Stechemesser
Phys. Chem. Chem. Phys. 6 429-433 2004
Bubble–particle dewetting kinetics relevant to froth flotation was experimentally studied on a modelled system using a CCD high-speed video microscopy. The experimental system included a gas–liquid interface formed at the bottom of a glass capillary filled with either deionized Milli-Q water or a solution of dodecylamine chloride (DAC) and hydrophobic glass beads dropping onto the interface in the solution inside the capillary under gravity. The dewetting process was observed underside the gas–liquid interface with a metallographic inverted microscope and a CCD high-speed video system operating at about 1000 frames s 1 for imaging the dewetting process. The velocities of the dewetting process showed a maximum in the pH-domain where the flotation recovery also showed a maximum. This good correlation between the dewetting kinetics and flotation recovery indicates that the dewetting kinetics is equally necessary as the thinning and rupture of the intervening liquid film between bubbles and particles for success of the flotation process. The discussion highlighted the need of developing a better understanding of the particle–bubble contact interaction, in particular, the difference in contact angles on micron-sized particles and flat surfaces.Artículo Texto completo
|Pattern proﬁling of the herbal preparation picroliv using liquid chromatography–tandem mass spectrometry |
V. Kumar, N. Mehrotra, J. Lal, R.C. Gupta
Journal of Chromatography A 1045 145–152 2004
At present, the construction of chromatographic ﬁngerprints of complex herbal preparations in combination with mass spectrometry plays an important role in their development and standardization as potential therapeutic agents. Picroliv, an extract from roots and rhizomes of Picrorhiza kurroa, is a herbal hepatoprotective developed by CDRI. We report for the ﬁrst time pattern proﬁling of various constituents of picroliv along with a precise and accurate method to estimate relative concentration of major components in the preparation by liquid chromatography–tandem mass spectrometry. In total, 27 components could be detected in multiple reaction monitoring (MRM) mode out of which fourteen could be quantiﬁed in terms of their relative concentration. Seven components were structurally correlated and conﬁrmed based on the fragmentation pattern and information available in literature. The detection was carried out using MRM in negative ionization mode with analytes quantiﬁed from the summed total ion value of their most intense molecular ion transitions. The separation of various components was achieved using a gradient elution on RP-18 column with acetonitrile and Milli-Q water as mobile phase at a ﬂow rate of 1.0 ml/min. The method was validated in terms of linearity, accuracy and precision (within-and between-assay variation) for 5 days. Linearity range was different for various components depending upon their sensitivity and abundance in the herbal preparation. Within-and between-assay accuracy (%bias) and precision (%R.S.D.) were within acceptable limits. The method was successfully applied to detect and determine relative concentrations of various components in two different batches of picroliv.
|Mercury dynamics in a small Northern Minnesota lake: water to air exchange and photoreactions of mercury |
N.A. Hines, P.L. Brezonik
Marine Chemistry 90 137 –149 2004
Mercury speciation at a small seepage lake in Northern Minnesota was shown to be influenced by photoreduction and photooxidation. Fluxes of Hg0 from water to air were greatest in the warmer, sunnier months in 2001 to 2002; however, correlation with solar radiation was weak. The daytime evasional loss was generally from water to air and was estimated at 5.3 pmol m-2 h 1 for 2001 and 6.2 pmol m-2 h-1for 2002 using a two-layer gas transfer model. Losses of Hg0(aq) in the dark over 10 days were observed in lake water (0.02 h-1), Milli-Q water, and HPLC grade water (0.002 h -1) and agreed with reported pseudo-first-order loss rates in the dark in other freshwaters. Using a mercury arc lamp, the pseudo-first-order loss rate of Hg0 in water from Spring Lake was found to range from 0.39 to 0.76 h-1. Other sinks for Hg0 exist through reaction with ozone, hydroxyl radical, and possibly singlet oxygen. A second-order reaction rate constant for Hg0(aq) and •OH of 1.0 x 109 M-1 s-1 was estimated based on data from experiments and the literature. Although less reactive, there is a higher steady state concentration of ozone in lake water compared to hydroxyl radical. Consequently, loss of Hg0(aq) by ozone may predominate. Potential oxidation of Hg0(aq) by singlet oxygen using rose bengal as a sensitizer could not distinguish between oxidation by rose bengal and by singlet oxygen itself. Chloride enhanced the oxidation of Hg0(aq) and should be considered in the mercury cycle in the ocean.
|Chemical stability of chlortetracycline and chlortetracycline degradation products and epimers in soil interstitial water |
T. Søeborg, F. Ingerslev, B. Halling-Sørensen
Chemosphere 57 1515–1524 2004
Tetracyclines and tetracycline degradation products and epimers end up in the environment. In order to predict the persistence of the potential dominating species of the chlortetracyclines in the environment, the chemical stability of chlortetracycline (CTC) and four major CTC degradation products and epimers (iso-CTC, 4-epi-CTC, anhydro-CTC, and 4-epi-anhydro-CTC) was studied in milliQ water and soil interstitial water (SIW) under environmentally relevant conditions (oxygen, light, pH (3–9), and temperature (6 °C and 20 °C)). The chemical stability of the compounds was evaluated by following the decrease in amount of parent compound over time. In order to compare the results obtained under the varying conditions, apparent pseudo-first-order rate constants (kobs) for the disappearance of the parent compound and corresponding apparent half-lives were calculated. A statistical evaluation of the data showed that the chemical stability of the chlortetracyclines was generally dependent on photolysis, temperature, and matrix. The presence or absence of oxygen did not influence on the chemical stability. The presence of calcium and magnesium ions in SIW is believed to account for the significant differences in half-lives between milliQ water and SIW, although numerous of other factors are believed to influence as well. Generally, the five compounds were more persistent at pH 3–4 than at pH above 5.
|Detection of Noroviruses in Tap Water in Japan by Means of a New Method for Concentrating Enteric Viruses in Large Volumes of Freshwater |
E. Haramoto, H. Katayama, S. Ohgaki
Applied and Environmental Microbiology April 2154–2160 2004
A virus concentration method using a cation-coated filter was developed for large-volume freshwater applications. Poliovirus type 1 (LSc 2ab Sabin strain) inoculated into 40 ml of MilliQ (ultrapure) water was adsorbed effectively to a negatively charged filter (Millipore HA, 0.45-µm pore size) coated with aluminum ions, 99% (range, 81 to 114%) of which were recovered by elution with 1.0 mM NaOH (pH 10.8) following an acid rinse with 0.5 mM H2SO4 (pH 3.0). More than 80% poliovirus recovery yields were obtained from 500-ml, 1,000-ml, and 10-liter MilliQ water samples and from tap water samples. This method, followed by TaqMan PCR detection, was applied to determine the presence of noroviruses in tap water in Tokyo, Japan. In a 14-month survey, 4 (4.1%) and 7 (7.1%) of 98 tap water samples (100 to 532 liters) contained a detectable amount of noroviruses of genotype 1 and genotype 2, respectively. This method was proved to be useful for surveying the occurrence of enteric viruses, including noroviruses, in large volumes of freshwater.
|Determination and quantitation of sulfonylurea and urea herbicides in water samples using liquid chromatography with electrospray ionization mass spectrometric detection |
E. Ayano, H. Kanazawa, M. Andoa, T. Nishimura
Analytica Chimica Acta 507 211–218 2004
A multianalyte method has been developed for the confirmation and quantitation of five sulfonylureas, bensulfuron-methyl, imazosulfuron, pyrazosulfuron-ethyl, flazasulfuron and halosulfuron-methyl, and for three ureas, siduron, dymron (daimuron) and diuron (DCMU) in water. Samples were extracted from water by off-line solid-phase extraction (SPE) with a polystyrene polymer cartridge (PS2), an ODS C18-bonded silica cartridge (C18) and an N-vinylpyrrolidone polymer cartridge (Oasis). Analyte determination and quantitation were performed by liquid chromatography with mass spectrometry (LC–MS). Extraction efficiency experiments demonstrated the ability of this method to extract sulfonylureas and ureas from water samples. Confirmatory analysis was carried out by LC-electrospray mass spectrometry (LC–ESI–MS) instrumentation equipped with a single-quadrupole mass filter. MS data acquisition was performed by a single or two-ion selected ion monitoring (SIM) program. It is required for confirmation that LC–MS retention times of the analytes are within 1% of the retention times of the standards, and that the molecular ion or characteristic fragment ion is present for each analyte. Fragment ions from distinctive structures must be obtained to identify and characterize specific herbicide molecules. These were obtained by controlled decomposition of sulfonylurea and urea adduct ions after suitably adjusting the electrical field in the desolvation chamber. The eight herbicides were also measured in fortified pure water (water purified by a milli-Q system), tap water and river water. Average recoveries of the eight analytes from water samples were in the range of 70–120% with relative standard deviations (R.S.D.s) of <20%. The limit of quantitation (LOQ) for each of the eight herbicides was between 10 and 100 ng l−1.
|Determination of myo-inositol in biological samples by liquid chromatography–mass spectrometry |
J. Perelló, B. Isern, A. Costa-Bauzá, F. Grases
Journal of Chromatography B 802 367–370 2004
Due to the absence of HPLC methods to determine myo-inositol using mass detection and considering its sensitivity and selectivity, a high performance liquid chromatography-mass spectrometry method for the analysis of myo-inositol is described and applied to its direct determination in urine and saliva samples. Successful resolution of myo-inositol and its related substances was achieved with a stationary phase Aminex HPX-87C Column with milli-Q water as mobile phase and 5 mM ammonium acetate added post-column. The detector counted positive ions by monitoring m/z=198, which corresponds to the myo-inositol adduct with ammonium cation. Urine and saliva samples were previously purified by passing through an anion-exchange resin. Concentrations as low as 138 and 461 μg/l in saliva and urine could be respectively quantified. Intra-day R.S.D. ranged from 0.83 to 1.02%, whereas inter-day R.S.D. was between 1.54 and 3.58%.
|A dot–blot method for quantification of apurinic/apyrimidinic sites in DNA using an avidin plate and liposomes encapsulating a fluorescence dye |
H. Yanagisawaa, A. Hiranob, M. Sugawara
Analytical Biochemistry 332 358–367 2004
A dot–blot method for quantification of apurinic/apyrimidinic (AP) sites in genomic DNA (calf thymus DNA) is described using an avidin-modified glass slip and biotinylated liposomes containing sulforhodamine B as a fluorescence marker. Aldehyde reactive probe (ARP)-tagged DNA was found to be strongly adsorbed on an avidin slip, even if treated with ethanolamine and biotin, with an efficiency of 51% due to the positive surface charge of avidin, and unbound ARP was easily washed out of the surface with Milli-Q water. In the assay protocol, calf thymus DNA containing AP sites is reacted with ARP in solution and immobilized on an ethanolamine- and biotin-treated avidin slip (EAB–avidin slip), followed by incubation with streptavidin. The AP sites were finally quantified with biotinylated liposomes containing 1.5 mM sulforhodamine B as a fluorescence marker. The mean fluorescence intensity over the surface of the slip was an analytically relevant measure of the amount of AP sites in calf thymus DNA. By using the dot–blot assay, 1–5 AP sites per 104 nucleotides in 5 and 100 ng of DNA were quantified. The current dot–blot method has potential for quantification of AP sites in genomic DNA at a level of several nanograms.
|A total water purification system |
BioPharm International, August 2004: 22-24 2004
Many of the analytical and molecular biology applications that require the use of water include high-performance liquid chromatography (HPLC), total organic carbon (TOC) analysis, sample and media preparation, rinse steps in assays, and gel electrophoresis. Different types of laboratories run experiments that require varying levels of water purity. What is needed in one lab might not be needed in another. Therefore, professional organizations have established water quality standards or guidelines to facilitate laboratory water purification within various industry sectors
|A total water purification system|
|Impact of purified water quality on molecular biology experiments. |
S. Mabic and I. Kano
Clin. Chem. Lab. Med., 41: 486-91 (2003) 2003
Purified water is a reagent used in a variety of molecular biology experiments, for sample and media preparation, in mobile phases of liquid chromatography techniques, and in rinsing steps. The combination of several technologies in water purification systems allows delivering high-purity water adapted to each application and technique. Through a series of examples, the importance of water quality on biotechnology experiments, such as single nucleotide polymorphism (SNP) analysis by denaturating HPLC, RNA preparation and PCR, is presented. Results obtained on DNA mutation and single nucleotide polymorphism analysis using the denaturating HPLC (DHPLC) technique highlight the benefits of organic removal by UV photooxidation process. Comparative gel electrophoresis data show that ultrafiltration is as efficient as diethylpyrocarbonate (DEPC) treatment for suppressing RNase activity in water. Gel electrophoresis and densitometry measurement also point out the benefits of ultrafiltration to carry out reverse transcriptase-polymerase chain reaction quantitatively.
|TOC in ultrapure water : importance of pretreatment technologies |
D. Darbouret, N. Ishii, M. Kanasawa, I. Kano and S. Mabic
International Labmate 28 11-12 2003
Organics present in high purity water can interfere in many ways with applications and laboratory instruments. In Liquid Chromatography, organics induce coating of chromatography media in the column, generating high back pressure and reducing column lifetime, impairing separation by modifying elution of the analytes, decreasing the signal: noise ratio and increasing the background levels. Similarly, organics interfere with detection devices, whether it is UV photodiode arrays, Light Scattering, Mass Spectrometry or Fluorescence Detection. In addition, many biological experiments are sensitive to organics present in water used to prepare buffers and media: cell culture, gene expression, and bio-reactions using enzymes, such as the Polymerase Chain Reactions (PCR). Organics are also a source of nutrients for bacteria that can grow to form biofilms. Finally, organics can foul the water purification media itself, and decrease its capacity. This paper focuses on the importance of the initial step in laboratory water purification systems devoted to the production of high purity water.
|Matching purified water quality with experimental detection limits |
S. Mabic, I. Kano and D. Darbouret
LabPlus International April/May 16-18 2003
The reliability of chemical analyses can be directly influenced by the quality of the water used in the analytical process. Depending on the sensitivity required, different analyses need water of different purity. This article reviews the various methods of producing pure water. For water used for ultra sensitive analyses, it should be noted that apparent contamination can come from the lab environment and not from the water system itself. In such cases, water purification systems able to deliver water under clean room conditions should be used.
|Matching purified water quality with experimental detection limits|
|Improved method for measurement of human plasma xanthine oxidoreductase activity |
X. Liu, W.M. Lin, X.H. Yan, X.H. Chen, J.R. Hoidal, P. Xu
Journal of Chromatography B 785 101–114 2003
The XOR activity in human plasma was measured by quantifying the XOR-derived uric acid (UA) in plasma using the high-performance liquid chromatography (HPLC) equipped with a UV detector. Chromatographic separation consisted of the mobile phase (a mixture of 0.1% trifluoroacetic acid in Milli-Q water and 0.085% trifluoroacetic acid in acetonitrile in a mix ratio of 99:1) running through a Zorbax StableBond SB-C18 column at a flow-rate of 1 ml/min. Deproteinization with heat-treatment of plasma samples after the reaction was used in the assay to avoid splitting of the UA and xanthine peaks caused by acid deproteinization that could interfere the accurate determination of human plasma XOR activity in our case. Based on the examination of the dependence of XOR activity on added amounts of xanthine and reaction times, the amount of xanthine and reaction time for XOR activity assay were determined to prevent the errors caused by the limiting effect of substrates and plateau phase of the reaction. Using this method, human plasma XOR activities of 25 healthy people were measured. The average human plasma XOR activity was 2.1±0.8 (×10-3 U/ml).
|Macromolecular source as dependent on osmotic pressure and water source: effects on bovine in vitro embryo development and quality |
P. Duque, C. O.Hidalgo, E. Gómez, B. Pintado, N. Facal, C. Díez
Reprod. Nutr. Dev. 43 487–496 2003
This study evaluated the protective effect of protein, as dependent on osmolarity, and the quality of water sources used to prepare embryo culture media. In Experiment 1, two concentrations of NaCl were used to obtain culture media with normal (280 mOSM) and low (245 mOSM) osmolarity, each supplemented with either bovine serum albumin (BSA) or polyvinyl alcohol (PVA). Low osmolarity improved blastocyst rates in the presence of BSA (P < 0.01) and tended to do it in medium containing PVA (P < 0.07). Furthermore, low osmolarity allowed PVA to increase inner cell mass (ICM) numbers and ICM/total cell rate (P < 0.05), while trophectoderm (TE) and total cell counts tended to decrease (P < 0.08). In Experiment 2, culture media were prepared with two water sources (Milli-Q and Sigma-W3500-) in combination with BSA or PVA. Both water sources yielded similar embryo development rates, but in the presence of BSA, Milli-Q water produced embryos with increased ICM/total cells rates (P < 0.05). On the contrary, Sigma water tended to increase trophectoderm cell counts (P < 0.08). In conclusion, the present study showed that low osmolarity is beneficial to embryo development and combinations of macromolecule and osmolarity influence trophectoderm differentiation. Both Milli-Q and Sigma supported embryo development at comparable rates, although in the presence of BSA, blastocysts obtained in the medium prepared with Milli-Q water had superior quality in terms of ICM/total cells rates.
|Photochemical fate of pharmaceuticals in the environment: Naproxen, diclofenac, clofibric acid, and ibuprofen |
J.L.Packer, J.J.Werner, D.E.Latch, K. McNeill, W.A. Arnold
Aquat. Sci 65 342–351 2003
The aqueous photochemistry of four pharma-ceutical compounds detected in surface waters (naproxen, diclofenac, ibuprofen, and clofibric acid) was in-vestigating in purified (Milli-Q) water and in Mississippi River water (MRW). Both direct photolysis and hydroxyl radical-mediated indirect photolysis (using a combination of probe and quencher experiments) were studied. Singlet oxygenation was also investigated for naproxen. Second-order rate constants for reaction with hydroxyl radical were determined using Fenton’s reagent. Naproxen was rapidly transformed via direct photolysis in sunlight in both Milli-Q and MRW. The radical quencher isopropyl alcohol (IPA), had a similar effect in both systems, and this effect was interpreted as a reaction of a carboxyl radical intermediate of naproxen. Diclofenac was found to undergo rapid direct photolysis under sunlight, confirming the results of prior studies. Addition of IPA led to more rapid transformation, possibly due to formation of other radical species or photoreduction with IPA serving as the H-source. When irradiated under natural sunlight, slow direct photolysis of clofibric acid is observed in Milli-Q water, and a combination of direct photolysis and radical mediated indirect processes appear responsible for clofibric acid photolysis in MRW. The dominant photochemical loss process for ibuprofen irradiated with a medium pressure Hg-vapor lamp was identified as reaction with photo-generated radicals. These results suggest that photolytic processes are important removal mechanisms for pharmaceutical compounds discharged into sunlit surface waters.
|Comparison of standard capillary and chip separations of sodium dodecylsulfate–protein complexes |
Z. Deyl , I. Miksık, A. Eckhardt
Journal of Chromatography A 990 153–158 2003
Conditions for converting a set of five standard proteins to electrochemically active sodium dodecylsulfate (SDS) complexes were worked out with the aim of using such complexes for conductivity detection with a a chip electrophoresis system. The results obtained were compared with standard capillary electrophoresis (37 cm (effective length 30 cm)×75 μm I.D. capillary, 10 kV, negative polarity at the inlet). The chip separations were run at 500 V per chip (100 V/cm) as compared to the standard capillary arrangement, which was run at 266.6 V/cm. For the capillary set-up the protein complexes were prepared in aqueous solution (Milli-Q water) made 10 mM with respect to SDS. If the SDS concentration was increased to 50 mM, the separation in the capillary was incomplete. On the other hand with the chip system both approaches yielded acceptable results. The chip separations were slightly (but not distinctly) shorter and offered better separations than the standard set-up. The concentration of the surfactant used for the preparation the complexes results in alternations of the elution sequence, which is preserved if the chip separation is used instead of the capillary set-up. Apparently the full capacity of protein–SDS binding is not exploited for the preparation of the adducts.
|Determination of oxytetracycline and its degradation products by high-performance liquid chromatography–tandem mass spectrometry in manure-containing anaerobic test systems |
P. Duque, C. O.Hidalgo, E. Gómez, B. Pintado, N. Facal, C. Díez
Journal of Chromatography B 783 2003
Little is known about the occurrence and the fate of veterinary drugs in the environment. Therefore, a liquid chromatography/tandem mass spectrometry method was developed and employed to investigate in detail the distribution and persistence of the frequently used tetracyclines and tylosin in a field fertilized with liquid manure on April 2000 and April 2001; soil sampling was performed in May 2000, November 2000, and May 2001. We detected 4.0 mg/kg tetracycline and 0.1 mg/kg chlortetracycline in the liquid manure of April 2000, as well as comparable amounts in the liquid manure of April 2001. In the soil samples of May 2001, the highest average concentrations of 86.2 (0−10 cm), 198.7 (10−20 cm), and 171.7 μg/kg (20−30 cm) tetracycline and 4.6−7.3 μg/kg chlortetracycline (all three sublayers) were found. At soil depths between 30 and 90 cm, as well as in soil or groundwater, tetracyclines could not be detected. In addition, oxytetracycline and tylosin could not be detected in any sample investigated. We conclude that tetracyclines enter the environment in significant concentrations via repeated fertilizations with liquid manure, build up persistent residues, and accumulate in soil. Therefore, tetracyclines may have a potential risk and investigations on the environmental effects of these antibiotics are necessary.
|Dissolution of calcium-deficient hydroxyapatite synthesized at different conditions |
E. Mavropoulosa, A.M. Rossia, N.C.C. da Rochab, G.A. Soaresc, J.C. Moreirad, G.T. Moure
Materials Characterization 50 203– 207 2003
The dissolution characteristics of several calcium-deficient hydroxyapatites (HA) have been investigated. Eleven samples were produced by varying synthesis parameters like temperature, pH, digestion time, reagent concentration and velocity of addition. Powder characterization was conducted using X-ray diffraction. Sample crystallinity was variable and samples examined by transmission electron microscopy showed acicular or plate-like morphology. After sample dissolution in Milli-Q water for 168 h, the calcium and phosphate contents in solution were measured by induced coupled plasma optical emission spectrometry (OES). The dissolution behavior of calcium-deficient HA was highly dependent on the sample calcium/phosphorus (Ca/P) molar ratio of the original HA. Dissolution in water was enhanced with decreasing HA sample molar ratio. However, the dissolution process equilibrium was not achieved at the end of 168 h (7 days).
|Optimized POU device for the removal of RNases and endotoxins in high purity water |
Mabic, Stephane, Daniel Darbouret, and Ichiro Kano
Ultrapure Water, March 2003: 53-59 2003
Performances of a disposable point-of-use (POU) UF device are described here, in terms of endotoxin and RNase removal. Following a brief description of technical features and data on extractables, the efficiency of the UF on endotoxin and RNase removal is illustrated with a number of typical experiments.
|Pretreatment Techniques Improve Final Water Quality |
Darbouret, Daniel, Naoe Ishii, Masanori Kanazawa, Ichiro Kano and Stephane Mabic
R&D Magazine May 50 2003
Research involving laboratory work requires the use of high purity reagents, such as ultrapure water. There are three main steps in the water purification chain: an initial pretreatment system, pretreated water storage, and a final ultrapure polishing system. The initial pretreatment step produces purified water from a well or potable tap water and can consist of deionization (DI) cartridges, distillation, reverse osmosis (RO) or a combination of reverse osmosis and electrodeionization (EDI). The pretreatment method is crucial because it affects the quality and the efficiency of the final polishing system, as well as the degree of organic and ionic contamination.
|Pretreatment Techniques Improve Final Water Quality|
|Determination of chloramphenicol residues in shrimps by liquid chromatography-mass spectrometry |
M. Ramos, P. Munoz, A. Aranda, I. Rodriguez, R. Diaz, J. Blanca; Journal of Chromatography B, 791 (2003) 31–38
Journal of Chromatography B, 791 (2003) 31–38 2003
|Environmental Analysis, High Performance Liquid Chromatography (HPLC)|
|A theoretical approach to measuring pH and conductivity in high-purity water |
C. Nora, S. Mabic and D. Darbouret
Ultrapure Water October 56-61 2002
The theoretical pH and conductivity for high purity water were calculated. Calculations show that a resistivity of 18.2 Mega-Ohms cm can only be reached when the pH is very close to 7.0
|Evaluation of HPLC reagent water purity via LC-MS and total organic carbon analysis |
B. Stewart and B. L. Williamson
American Biotechnology Laboratory, 0749-3223 2001, Vol. 19, No. 13, pp. 16-18 [2 page(s) (article)] (7 ref.) 19 16-18 2001
An important factor in optimizing LC-MS analysis is the use of solvents and chemical reagents of high purity. When converting from HPLC with UV detection to LCMS, the purity of water used for the mobile phase becomes critical. In addition to column blinding, ghost peaks, and other problems caused by excess organics in HPLC, organic contamination creates high background and causes a loss of sensitivity in LC-MS. Although confirmation via MS-MS, for example, would be required for precise identification of species detected in the water,2 the presence and magnitude of the selected spectra reasonably indicate the relative purity of these waters. This was particularly visible when using bottled HPLC-reagent waters. Analysis of HPLC-grade water using UV detection at 214 and 254 nm is not a suitable quality control for LC-MS applications. On-line measurement of organics as TOC appears to provide a rapid and timely indication of the organic purity of water suitable to successfully perform LC-MS. Additionally, ion exchange combined with UV photooxidation offers a benefit to LC-MS users over conventional water systems that use ion-exchange media alone. The observations and methods used may provide a screening method to monitor the quality of reagent waters used in HPLC and LC-MS in order to obtain optimal results.Artículo Texto completo
|Evaluation of HPLC reagent water purity via LC-MS and total organic carbon analysis|
|Chemiluminescent Immunoblot Detection w Enhanced Luminol HRP Substrates |
McCauley TJ, Feather-Henigan K, Hines K, Kelley D; American Biotechnology Laboratory 2001;19(10):80-81
American Biotechnology Laboratory 2001;19(10):80-81 2001
|Hydrophilic Interaction Capillary Electrochromatography for the Separation of Polar Compounds |
Ye M, Zou H, Kong L, Lei Z, Wu R, Ni J; LCGC. 2001;19(10):1076-1086
LCGC. 2001;19(10):1076-1086 2001
|Hybridization of High-Density Filter Arrays of a Brugia malayi BAC Library with Biotinylated Oligonucleotides and PCR Products |
Foster JM, Kamal IH, Daub J, et.al.; Biotechniques 2001;30(6):1216-1224
Biotechniques 2001;30(6):1216-1224 2001
|Surface-MALDI Investigation of Protein Adsorption on Contact Lens Surfaces |
Kratos Analytical; Kratos Analytical-http://www.kratos.com/Mapps/NewApps/Apps23.html
Kratos Analytical-http://www.kratos.com/Mapps/NewApps/Apps23.html 2001
|Ultrapure Water Blank for Boron Trace Analysis |
J. Anal. At. Spectrom.
J. Anal. At. Spectrom. 15 1395-1399 2000
Weakly charged elements, or elements that are not well dissociated in water, are not removed efficiently by conventional water-purfication technologies. In the production of high-purity water, silica and boron are generally the first ions to breakthrough into purfied water when the ion-exchange resin approaches depletion. In this study, the behavior of these two elements was studied through various steps in a water-purification chain. An optimized system configuration is proposed that combines reverse osmosis and electrodeionization technologies in the pre-treatment phase, and results in the efficient removal of boron. These initial purification steps produce high-resistivity water, presenting a low ionic challenge to ultrapure polishing resins. In addition, a specific chelating adsorbent enhances the retention capacity of boron. Typical values achieved for the most important parameters assessed while producing ultrapure water are described.
|Total Polychlorinated Biphenyl Quantification by Rapid Dechlorination Under Mild Conditions |
Engelmann M, Cheng IF; LCGC 2000
LCGC 2000 2000
|Homogeneously Aligned Liquid Crystal Polymer Brushes |
Peng B, Ruhe J, Johannsmann D*; Advanced Materials 2000;12:821
Advanced Materials 2000;12:821 2000
|A Protocol for High-Throughput Drug Mixture Quantitation: Fast LC–MS or Flow Injection Analysis |
Yu K, Balogh M; LCGC 2000;19(1): 60-72
LCGC 2000;19(1): 60-72 2000