Reverse micelle coacervate-based extraction combined with electrothermal atomic absorption spectrometry for the determination of arsenic in water and oyster tissue samples

A novel method was developed for preconcentration of arsenic prior to its determination by electrothermal atomic absorption spectrometry. The method is based on the extraction of As(III) as o,o-diethyldithiophosphate (DDTP) complex with coacervates made up of decanoic acid reverse micelles in water/tetrahydrofuran (THF) mixture. The determination of total arsenic and hence indirectly As(V) involves the pre-reduction of As(V) to As(III) by a mixture of potassium iodide and ascorbic acid. Several important factors affecting extraction efficiency such as concentrations of decanoic acid, THF and DDTP, stirring rate and extraction time were investigated and optimized. Under optimum conditions, the calibration graph was linear in the range 0.1-5 mu g L(-1) with a correlation coefficient 0.999. The limit of detection and enhancement factor were found to be 0.04 mu g L(-1) and 64, respectively. The method was validated by the analysis of standard reference materials and applied to the determination of As(III) and As(V) in environmental samples.