High resolution continuum source atomic absorption spectrometry and solid phase extraction for the simultaneous separation/preconcentration and sequential monitoring of Sb, Bi, Sn and Hg in low concentrations

Abstract

A rapid method was developed for separation, pre-concentration and sequential determination of antimony, bismuth, tin and mercury by flow injection solid phase extraction coupled with on-line chemical vapor generation electrothermal atomic absorption spectrometry. The system is based on chelating/cationic retention of the analytes onto a mini-column filled with a mesoporous silica functionalized with 1,5 bis(di-2-pyridyl)methylene thiocarbohydrazide. Several variables (sample flow rate, eluent flow rate, eluent concentration and reductant concentration) were considered as factors in the optimization process. Interactions between analytical factors and their optimal levels were investigated using three central composite designs. The optimized operating conditions were: sample pH = 2.2, sample flow rate 3 mL min⁻¹, eluent flow rate 2.5 mL min⁻¹, eluent 3.1% HCl for Sb, Bi and Sn, and 4.6% thiourea for Hg, and 0.6% NaBH₄ reductant. The optimum conditions established were applied to the determination of Sb, Bi, Sn and Hg in sea water and river water by flow injection solid phase extraction coupled with on-line chemical vapor generation high resolution continuum source electrothermal atomic absorption spectrometry (FI-SPE-CVG-CS ETAAS). For the quality control of the analytical performance and the validation of the newly developed method, the analysis of two certified samples, TM 24.3 and TMDA 54.4, Fortified Lake Waters was addressed. The results showed good agreement with the certified values.