DEVELOPMENT AND CHARACTERIZATION OF A METHOD FOR THE DETERMINATION OF TOTAL As IN WATER BY HYDRIDE GENERATION AND OPTICAL EMISSION DETECTION IN ARGON CAPACITIVELY COUPLED PLASMA MICROTORCH

Abstract

Arsenate was firstly prereduced to arsenite in 0.01 mol L^-1 HCl (pH 2.00 ± 0.01) and 0.3% L-cysteine, than arsine was generated with 0.5% NaBH₄ solution stabilized in 0.5% NaOH and introduced into a capacitively coupled plasma microtorch (10 W, 150 ml min^-1 Ar) for measurement of As 228.812 nm emission with the Ocean Optics QE65 Pro spectrometer of low resolution. The optimization steps for arsine generation and plasma operation are presented. Under optimal operating conditions, linearity of calibration curve covers the range 0 – 100 µg L^-1, while detection and quantification limits are 0.2 and 0.6 µg L^-1 respectively. Thus, the proposed method is able for As quantification in drinking and groundwater at levels below maximum admitted concentration (10 µg L^-1). The method was validated by analyzing certified reference water samples containing 10 – 60 µg L^-1 As with recovery of 99 ± 6%^. (95% confidence level, n = 5 measurements). The analytical capability of the method was demonstrated in the analysis of test samples (drinking-, ground- and waste water) with As concentration in the range 0.6 – 80 µg L^-1 As with a precision of 1.2 – 10.8%. The completely miniaturized instrument including the capacitively coupled plasma microtorch has analytical potential to be used for monitoring the quality of water sources.