Impact of Water
Analysis by AA requires the use of high purity reagents and solvents to ensure the accuracy and precision of measurements. In particular, graphite furnace AA (GFAA) is a sensitive method suitable for the routine measurement of trace elements. Since the detection limits for most elements are well below ppb levels, it is important that reagents and solvents are free of the element under investigation because this would lead to inaccurate results. Water is used to prepare blanks, standards, and in the sample preparation procedure, hence it should be free of the elements under investigation, as well as any elements and compounds whose presence could interfere with the analysis.
The water used as diluent for samples and standards, for method blank, and wash solution should have extremely low ionic content. Contamination by metallic ions under investigation would lead to inaccurate result (i.e., higher concentration than the actual concentration in sample) and an increase in blank signal
In Flame AA, particles could block the nebulizer and prevent efficient spraying of the sample solution into the flame.
Water that is contaminated by bacteria could contain degradation by-products such as ions which could interfere with the analysis (see “Ions/Metals” above).
Other sources of contaminants
- Acids and modifiers - Use only the highest quality reagents
- Laboratory environment - Laboratory atmosphere may cause contamination at any stage in the AA experiment, even when the sample is already in the atomization cell.
- Washing procedure - Na, Mg, and Zn are frequently found after laboratory washing procedures.
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