Speciation of arsenic in ground water samples by ion exchange chromatography with improved sample preparation technique

Abstract

Arsenic exists in the form of various chemical species differing in their physicochemical behavior, toxicity, bioavailability and biotransformation. The determination of arsenic species is an important issue for environmental, clinical and food chemistry. However, differentiation of these species is a quite complex analytical task. Numerous speciation procedures have been studied that include electrochemical, chromatographic, spectrometric and hyphenated techniques. Ion exchange chromatography is one of the techniques used to speciate inorganic arsenic i.e., arsenic (III) and arsenic (V). Both of these arsenic species are stable and exist as anions, arsenic (III) as arsenite (AsO33−) and arsenic (V) as arsenate (AsO43−). The proposed method can be used to perform the speciation of arsenic (III) and arsenic (V). It is a two-step process, first arsenic (V) is determined, followed by total arsenic determination by treating the sample with potassium permanganate solution to oxidize the arsenic (III) present in the sample to arsenic (V) and determining it as arsenic (V). Addition of potassium permanganate solution to the ground water samples for oxidizing the arsenic (III) to arsenic (V) is the newly adopted sample preparation technique and further determining it by ion exchange chromatography with conductivity detection. This method can be used for arsenic speciation in water samples from rivers and under the ground. Analytical validation and performance of the method is also discussed.