Water for GFAA

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.

Ions/Metals
The water used as diluent for samples and standards, for 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.

Bacteria
Water that is contaminated by bacteria could contain degradation by-products such as ions which could interfere with the analysis (see “Ions/Metals” above).

Table 1 shows the calculated concentrations of As, Cd, Cr, Pb, and Se in ultrapure water (from a Direct-Q 3 UV system), as well as the detection limit for the GFAA method. Under these detection limits, none of these elements were detected in ultrapure water. This suggests that it is an excellent choice for use in GFAA analyses, since there would be no concern over inaccuracy or lack of precision that may come from the presence of trace elements in the water.

Element	Detection limit (ppb)	Concentration in ultrapure water (ppb)
As	0.10	Not detected
Cd	0.010	Not detected
Cr	0.10	Not detected
Pb	0.10	Not detected
Se	0.015	Not detected

Table 1. Concentration of As, Cd, Cr, Pb, and Se in ultrapure water from a Direct-Q 3 UV system as measured by GFAA.

Other sources of contaminants

Acids and modifiers - Use only the highest quality reagents
Laboratory atmosphere - Laboratory atmosphere may cause contamination at any stage in the GFAA experiment, even when the sample is already in the atomization cell.
Washing procedure - Na, Mg, and Zn are frequently found after laboratory washing procedures.