Chromolith® RP-18e Standard HPLC Columns

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Chromolith® RP-18 endcapped HPLC columns are the ideal choice for fast and robust separation of hydrophobic to medium polar compounds, for example carbidopa or steroids, at low column back pressure.

In contrast to conventional particle-packed columns, our Chromolith® RP-18 columns consist of monolithic high-purity silica with a bimodal structure of macropores and mesopores. The large macropores reduce column back pressure and thus allow significantly faster flow rates. The fine mesopore structure of the material, on the other hand, creates a very large active surface area for high-efficiency separations. Thanks to the low back pressure, several columns can be coupled to achieve even higher resolution.

Moreover, column lifetime is substantially enhanced thanks to the rigid monolithic material, and their high-purity silica base minimizes the adverse effects of trace metals. Chromolith® RP-18e HPLC columns are chemically modified with n-alkyl chains with high ligand density and then fully endcapped in order to reduce the effects of unmodified silanol groups.

Easy Method Transfer

The chemical basis of Chromolith® RP-18 endcapped columns is identical to that of high-end particulate silica columns (e.g. Purospher®). They are manufactured from thesame metal-free silanes and undergo the same surface modification procedures. As a result, their selectivity is comparable to high-quality C18 endcapped reversed-phase particle-packed columns. Thus, chromatographers can easily use standard methods when developing new protocols, and method transfer from particulate columns to monolithic Chromolith® RP-18 columns is simple and seamless.

Chromolith® RP-18e columns are included in the US Pharmacopoeia in category L1.

Features and Benefits

  • High throughput at high flow rates with the best overall column quality
  • Possibility of flow gradients
  • Added column performance by column coupling
  • Rigid monolithic structure for longer column lifetime
  • Lower matrix sensitivity
  • Simple method transfer from particulate columns

Different Lengths to Suit Your Applications

Column length is directly proportional to efficiency, back pressure, and retention times. Moreover, increasing column length increases resolution due to the higher number of theoretical plates per column. Chromolith® RP-18e standard columns are available with various lengths and internal diameters (i.d.) in order to perfectly match your application’s requirements. Moreover, two or even more Chromolith® HighResolution columns can be easily coupled thanks to the low back pressure.

Internal Diameter
Ordering Number
Chromolith® Flash RP-18e, (L) 25 mm – For ultra-fast separation of simple mixtures
Chromolith® Flash RP-18 endcapped (available with 2, 3 and 4.6 mm i.d.) is the fastest HPLC column on the market. Due to the very short length of the column, its number of theoretical plates is sufficient for easy separations.
2 mm
3 mm
4,6 mm
Chromolith® SpeedROD and FastGradient RP-18e, (L) 50 mm – For fast separation of simple mixtures
These short, fast columns – available with 2 or 3 mm i.d. (FastGradient) and 4.6 mm (SpeedRod) – are perfect for rapid screening of samples during in-process controls as well as for laboratories specialized in research or organic synthesis (e.g. combinatorial chemistry).

2 mm
3 mm
4,6 mm

Chromolith® Performance RP-18e, (L) 100 mm – For rapid separation of more complex mixtures
Our 100 mm Chromolith® RP-18e column is ideally suited for use as a routine analytical tool in quality control laboratories or research laboratories where more complex mixtures are analyzed.
2 mm
3 mm
4,6 mm
Validation kits – For accurate method validation
Validation kits are available for Chromolith® Performance (4.6 or 3 mm i.d.) & Chromolith® FastGradient (2 mm i.d.) RP-18e columns. They each contain three columns from three different production batches. This allows you to easily compare batch-to-batch reproducibility and quality, making the validation kit an ideal tool for quality control and validation laboratories.
2 mm
3 mm
4,6 mm

Application Examples

Chromolith® Performance RP-18e

Column Chromolith® Performance, 100-4.6 mm
Mobile phase A: Acetonitrile
B: 20 mM Phosphate
buffer pH 4.5  
Gradient Time/min %A %B
0.0 20 80
3.0 60 40
Flow rate 4 mL/min
Detection 230 nm
Temperature 22° C
Injection volume 10 μl

1. Ascorbic acid
2. 4-Hydroxybenzoic acid
3. Benzoic acid
4. Sorbic acid
5. Methyl 4-hydroxybenzoate
6. Ethyl 4-hydroxybenzoate
7. Propyl 4-hydroxybenzoate

100 μg/mL
100 μg/mL
100 μg/mL
50 μg/mL
100 μg/mL
150 μg/mL
100 μg/mL

Merck:/Freestyle/LE-Lab-Essentials/Chromatography/Diagrams/LE-Chromolith Performance RP-18e-250x274-11102014.jpg

Chromolith® SpeedROD RP-18e

Column Chromolith® SpeedROD RP-18 endcapped, 50-4.6 mm
Mobile phase A: Acetonitrile
B: 0.01M Phosphate
buffer pH 5.0
Gradient Time/min %A %B
0.0 3 97
2.5 3 97
2.6 8 92
5.0 8 92
Flow rate 4 mL/min
Detection 227 nm
Temperature Ambient
Injection volume 10 μl

1. Acesulfame-K
2. Saccharin
3. Benzoic acid
4. Sorbic acid
5. Caffeine
6. Aspartame

23 μg/mL
29 μg/mL
13 μg/mL
14 μg/mL
47 μg/mL
100 μg/mL

  Merck:/Freestyle/LE-Lab-Essentials/Chromatography/Diagrams/LE-Chromolith SpeedROD RP-18e-300x312-11102014.jpg
Separation of carbidopa

Column Chromolith® Performance RP-18 endcapped, 100-4.6 mm
Mobile phase A: Methanol
B: 0.1% TFA in water
Gradient Time/min %B
0.0 100
1.0 100
10 80
Flow rate 2 mL/min
Detection UV 282 nm
Temperature Ambient
Injection volume 5 μl

1. 2,4,5 Trihydroxyphenalalanine
2. Levodopa
3. Methyldopa
4. Dopamine
5. Carbidopa
6. 3,4-Dihydroxyphenylacetic acid
7. 3-o-Methylcarbidopa

125 μg/mL
235 μg/mL
160 μg/mL
190 μg/mL
175 μg/mL
185 μg/mL
105 μg/m

  Merck:/Freestyle/LE-Lab-Essentials/Chromatography/Diagrams/LE-Separation of carbidopa-300x270-11102014.jpg
Separation of steroids

Column 2 columns of Chromolith® Performance RP-18 endcapped
Mobile phase A: Acetonitrile
B: Water  
Gradient Time/min %B
0.0 80
7.0 10
Flow rate 3.0 mL/min
Detection 220 nm
Temperature Ambient
Injection volume 10 μl

1. Prednisolone
2. Cortisone
3. Nortestosterone
4. Estradiol
5. Testosterone
6. Corticosterone
7. Estrone
8. Progesterone

  Merck:/Freestyle/LE-Lab-Essentials/Chromatography/Diagrams/LE-Separation of steroids-300x304-11102014.jpg


Silica type High-purity
Particle size Monolithic
Macropore size 1.5 µm (2 mm i.d. columns);
2 µm (25, 10, 4.6 and 3 mm i.d. columns)
Mesopore size 13 nm (130 Å)
Pore volume 1.0 mL/g
Total porosity >80 %
Surface area 300 m2/g
Surface modification RP-18 endcapped
Carbon content 18 %
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