Speciation Analysis of Arsenic in Soil Samples by Liquid-Liquid Extraction and Electrochemical Detection with Gold micro-wire electrode

Soil collected from random areas of non-ferrous mines and smelters was studied in order to develop a low-cost but effective method for quantifying arsenic (III), arsenic (V), and total arsenic in contaminated soil. Hydrochloric acid microwave extractions have been used as a method to digest arsenic from soil in a form of solution suitable for speciation. Arsenic (III) is selectively extracted into benzene as arsenic trichloride from a highly concentrated hydrochloric acid solution. This was followed by the arsenic being extracted back into water. The total inorganic content of arsenic (V) can be directly determined by anodic oxidation of a gold screen-printed electrode using electrochemical detection. The amount of available Arsenic (III) in the sample is determined by pre-oxidation with KMnO4 directly added to the electrochemical cell or by directly increasing the pH of the medium. ICP-MS was used to confirm all analyses for the various arsenic species as well as the discovery of total arsenic in the soil. It was discovered that the electrochemical method used allows for the cheap, quick, and selective determination of micro amounts of arsenic forms in contaminated soils.