Determination of inorganic arsenic(III) in ground water using hydride generation coupled to ICP-AES (HG-ICP-AES) under variable sodium boron hydride (NaBH4) concentrations

The determination of inorganic arsenic species in ground water matrices using hydride generation coupled online to ICP-AES (HG-ICP-AES) is suggested on the fact that the As(III)-species shows significantly higher signal intensities at low sodium boron hydride (NaBH4) concentrations than the As(V)-species. The sodium boron hydride concentration used for the determination of As(III) without any considerable interferences of As(V) was at 13.3 mmol/L NaBH4 (0.05 wt/v%), whereas the concentration for the total As. determination was at 158.4 mmol/L NaBH4 (0.6 wt/v%). The interferences of As(V) during the As(III) measurements were very small: at concentrations below 100 mu g/L of total arsenic, the interferences of As(V) were smaller than 2%. An amount of As(III) higher than 10% of the total As amount could be determined exactly and reliably. The total amount of arsenic is measured after reducing the sample with 20 mmol/L L-cysteine (C3H7NO2S). Finally, the amount of the As(V)-species is calculated by the difference between the As(III)-species and the total arsenic. Therefore, this analytical method requires the absence of organic arsenic species, but if they still appear, they could be frozen out with liquid nitrogen after the hydride generation system. The linearity of calibration reaches from 2 mu g/L up to 1000 mu g/L with a detection limit routinely of about 1 mu g/L for each species. The advantages of this method in com parison to AAS measurements are the higher extent of the linear calibration range (3 orders of magnitude) and a higher sensitivity. Additional merits of the method developed are easy handling and high sampling rates.