Influence of the time of acidification after sample collection on the preservation of drinking water for lead determination.

Abstract

It has been suggested that to obtain accurate data for trace metal analysis of drinking water, immediate acidification at the time of collection is necessary. However, because of problems encountered by EPA in field operations and epidemiology studies, further injection into this requirement was pursued. Drinking water samples containing known concentrations of lead were acidified at different time intervals after collection. The water samples were then stored at room temperature for varying time intervals before being analyzed for lead. For each time period there were seven samples with three aliquots from each taken for analysis in duplicate by flameless atomic absorption spectrophotometry (AAS). All acidified samples that were spiked with lead gave a higher lead value than the unacidified samples having comparable lead concentrations. Lead recovery varied among the time periods studied; however, the results indicated that acidification of water samples after collection could be delayed up to 14 days without any adverse effect on lead concentration data. This would allow acidification after samples are received in the laboratory and thus facilitate field studies. 10 references, 5 figures, 2 tables.