Kinetics of As reduction for analysis using hydride-generation

The kinetics of As reduction for analysis using hydride-generation are presented. As III, As V and Organic arsenic species are all hydride forming depending on conditions used. For total As analysis all As species are reduced to +III oxidation state using KI and then reacted with NaBH4 to produce a hydride. Difference methods are employed by labs for calculation of As species. Acetic acid and citric acid buffers have been reportedly used for the selective reduction of As III by NaBH4 (assuming that only fully protonated species form hydrides), however As V can still be reduced to As III by NaBH4.Selectivity using acetic acid was investigated at pH ~6. HG-ICP-OES is a good method for total As. As V reduction by KI is highly dependant on acidity. As hydride formation is dependant on acidity and is not selective for As III, therefore calculating As V by difference is not an option. HG-OES gives a DL for total As comparable with that of MS, ~ 0.5ug/L, with good reproducibility at concentrations close to the detection limit. Speciation could be done using IC-HG-OES if time-resolved integration was possible in the Winlab software