On-line preconcentration and speciation of arsenic by flow injection hydride generation atomic absorption spectrophotometry.

Abstract A flow injection-column preconcentration-hydride generation atomic absorption spectrophotometric (FI-column-HGAAS) method was developed for determining μg/l levels of As(III) and As(V) in water samples, with simultaneous preconcentration and speciation. The speciation scheme involved determining As(V) at neutral pH and As(III + V) at pH 12, with As(III) obtained by difference. The enrichment factor (EF) increased with increase in sample loading volume from 2.5 to 10 ml, and for preconcentration using the chloride-form anion exchange column, EFs ranged from 5 to 48 for As(V) and 4 to 24 for As(III + V), with corresponding detection limits of 0.03–0.3 and 0.07–0.3 μg/l. Linear concentration range (LCR) also varied with sample loading volume, and for a 5-ml sample was 0.3–5 and 0.2–8 μg/l for As(V) and As(III + V), respectively. Sample throughput, which decreased with increase in sample volume, was 8–17 samples/h. For the hydroxide-form column, the EFS for 2.5–10 ml samples were 3–23 for As(V) and 2–15 for As(III + V), with corresponding detection limits of 0.07–0.4 and 0.1–0.5 μg/l. The LCR for a 5-ml sample was 0.3–10 μg/l for As(V) and 0.2–20 μg/l for As(III + V). Sample throughput was 10–20 samples/h. The developed method has been effectively applied to tap water and mineral water samples, with recoveries ranging from 90 to 102% for 5-ml samples passed through the two columns.