MICROEXTRACTION SEPARATION AND DETERMINATION OF INORGANIC ARSENIC FORMS BY INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY IN NATURAL WATERS

The results of microextraction separation and ICP-MS determination of inorganic arsenic forms in natural waters are presented. The necessity of separate determination of analytes is substantiated, since arsenites are tens of times more toxic than arsenates. Separation was carried out by the method of selective liquid-liquid microextraction of As(III) complex compounds with sodium diethyldithiocarbamate into the organic phase. Conditions of extraction of As(III) compounds with the highest degree of recovery of ~95% were established. Complex compounds of As(III) with sodium diethyldithiocarbamate were extracted into the organic phase with carbon tetrachlormethane and methanol as an extractant and dispersant, respectively. The matrix effect of elements on the extraction of analytes from water was eliminated by double microextraction of analytes. The content of total inorganic arsenic and As(V) compounds was established based on the results of ICP-MS analysis of the samples of the original water and the aqueous extract after separation of the material forms of inorganic arsenic. The concentration of As(III) in water was calculated by the difference between the total arsenic content and the content of As(V) compounds. The limits of determination of As(III) and As(V) in waters were the same and amounted to 0.010 μg/L in the linearity range of 0.05–100 μg/L, R2 = 0.9998. The added-found method established the correctness of the determination of inorganic arsenic forms in water. The analysis procedure was tested on model waters and real samples of drinking and natural waters.