Separation and Determination of Arsenic (V) and Arsenic (III) in Sea Water by Solvent Extraction and Atomic Absorbtion Spectrophotography Via the Hydride Generation Technique

Abstract

Arsenic(III) and arsenic(V) species exist in sea water at concentration levels of less than 0.2 ng/ml to greater than 50 ng/ml. The concentration levels of these species in sea water are currently questionable due mostly to possible interferences. A reliable analytical method has been developed to separate and determine these species in sea water. The method involves the extraction of APDC-As(III) complex into a chloroform layer at a pH range of 4.0- 4.5. Wet ashing of the chloroform layer followed by reduction of arsenic(V) to arsenic(III) by potassium iodide makes it possible to determine arsenic by the atomic absorption spectrometry-hydride generation technique. The various parameters such as pH, percent APDC, interferences, efficient reducing agents and wet ashing methods have been investigated in this study. A detection limit of 0.031 ppb and a sensitivity of 0.140 ng/ml have been achieved. Precision as judged by % RSD (0.6-5.4) indicates good reproducibility of the results when synthetic sea water samples spiked with arsenic(III) and natural sea water samples are analyzed.