| Arsenic speciation analysis in drinking water is of considerable importance due to the toxic effects associated even with low levels inorganic arsenic compounds. Methods were developed here for the simultaneous speciation analysis of the inorganic forms of arsenic, antimony and selenium, and selected organic forms of arsenic.;The precision and accuracy of the methods developed were evaluated analyzing two certified reference materials, namely EP-L-1 and EP-H-1, at low and high levels of elements in water samples of natural origin. Values obtained in this work agreed very well with the certified ones. This method was applied to the analysis of water reference materials with detection limits of 5.1,2.9,1.6,3.8, 25, 9.4, 4.0, 13.8, 6.0, 14, 74 ng mL-1 for As(III), As(V), MMA, DMA, total arsenic, Se(IV), Se(VI), total selenium, Sb(III), Sb(V) and total antimony, respectively.;A combination of solid phase extraction, coprecipitation, and neutron activation analysis was used to develop a method for eight important species, namely As(III), As(V), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), Sb(III), Sb(V), Se(IV), and Se(VI). The As(V), MMA, Se(IV) and Se(VI) species were separated and concentrated using a strong anion exchange column which was connected in series to a strong cation exchange column for the separation of Sb(III) and DMA. Arsenic(III) and Sb(V) remained in the effluent and were preconcentrated by bismuth sulphide coprecipitation. Solutions of 0.1 M acetic acid buffer at pH 3.4, a citrate buffer pH 2.1, and 1 M nitric acid were used to selectively elute MMA, Se(IV) and Se(VI), respectively, and As(V) using the last two solutions. The cation exchange column was also eluted with 1 M nitric acid for Sb(III) and DMA. This method was used to study the stability and interconversion of the inorganic species in synthetic water samples at ppb levels. No interconversion was observed for As(III) and Sb(V) when present alone but As(III) reduced Se(VI) to Se(IV). Selenium(IV) oxidized to Se(VI) when both species were present together. Arsenic(V) and Sb(III) experienced spontaneous interconversion to As(III) and Sb(V), respectively, and also in presence of other species. |
