Selective reduction of arsenic species by hydride generation - atomic absorption spectrometry. Part 2 - sample storage and arsenic determination in natural waters

Arsenio total, As(III), As(V) e acido dimetilarsinico (DMA) foram determinados seletivamente em aguas naturais pela tecnica da geracao de hidretos ‐ espectrometria de absorcao atomica, em diferentes meios de reducao. Para as amostras de agua de rio investigadas os resultados mostraram ser arsenato a forma arsenical predominante. Os limites de deteccao encontrados para As(III) (tampao citrato), As(III) + DMA (acido acetico ) e As(III) + As(V) (acido cloridrico) foram, respectivamente, 0.6, 1.1 e 0.5 mg As L -1 . O estudo da estabilidade das formas arsenicais em amostras de aguas naturais revelou serem os proprios meios reacionais convenientes para uma preservacao adequada das amostras. Total arsenic, arsenite, arsinate and dimethylarsinic acid (DMA) were selectively determined in natural waters by hydride generation ‐ atomic absorption spectrometry, using sodium tetrahydroborate(III) as reductant but in different reduction media. River water samples from the north region of Parana State, Brazil, were analysed and showed arsenate as the principal arsenical form. Detection limits found for As(III) (citrate buffer), As(III) + DMA (acetic acid) and As(III) + As(V) (hydrochloric acid) were 0.6, 1.1 and 0.5 mg As L -1 , respectively. Sample storage on the proper reaction media revealed to be a useful way to preserve the water sample.