Determination of As(III) in Nonacidified Groundwater Samples for Inorganic Speciation Analysis Using Flow Injection Hydride Generation Atomic Absorption Spectrometry

A flow injection system coupled to hydride generation atomic absorption spectrometry with heated quartz tube atomizer was employed for the selective determination of As(III) in real groundwater samples under nonacidic conditions. The use of low-acidity conditions was carefully evaluated in order to minimize the interconversion of redox arsenic species. The As(III) hydride was generated using 0.1molL-1 HCl as carrier solution and 0.2% (m/v) NaBH4 in 0.025% NaOH as the reductant. A coil reaction larger than the used one for higher acidity conditions (480mm instead of 115mm) was selected. The generated hydride was transported to the atomizer by a nitrogen flow of 75mlmin-1. The main parameters that influenced the signal intensity and shape were studied. Under the best found experimental conditions, a detection limit (3 sigma) of 1.0 mu gL-1 As(III) was obtained for a 500 mu l sample volume. The analytical recovery ranged between 90% and 98%. In addition, the total inorganic arsenic concentration in the samples was determined on sample aliquots acidified with concentrated HCl and prereduced with 5% (m/v) KI-5% (m/v) C6H8O6 solution. HCl 1.2molL-1 as carrier solution, NaBH4 0.2% (m/v) as reductant, and a nitrogen flow rate of 75mlmin-1 were used in this case. The concentration of As(V) was calculated by difference between the total inorganic arsenic and As(III) concentrations.