Simultaneous determination of trace lead, tin and cadmium in biological samples by a chemical vapor generation-four-channel atomic fluorescence spectrometry dual gas–liquid separator system

Abstract

A novel, accurate, and precise method is described for simultaneous determination of trace lead (Pb), tin (Sn) and cadmium (Cd) in biological samples by chemical vapor generation (CVG) coupled with non-dispersive atomic fluorescence spectrometry. A chemical vapor generation dual gas–liquid separator system for Pb, Sn and Cd determination assembled with atomic fluorescence spectrometry was proposed. The system consists of two peristaltic pumps as the liquid driver, two gas–liquid separators and an atomic fluorescence detector. In the first gas–liquid separator system, the main Cd vapor and some SnH₄ were carried out with reductant solution I, and in the second gas–liquid separator system, the main PbH₄ and some SnH₄ were carried out with reductant solution II. Cadmium vapor generation was based on hydrochloric acid, cobalt chloride, thiourea and KBH₄ concentrations of the first system, SnH₄ generation was based on hydrochloric acid and KBH₄ concentrations, and PbH₄ was based on hydrochloric acid, potassium ferricyanide and KBH₄ concentrations of the second system. The operating conditions of the instrumentation were optimized, including the flow rates of carrier and shield gas. The conditions of chemical vapor generation for Pb, Sn and Cd were studied in detail. Under optimized experimental conditions, the blank signal was satisfactorily minimized, giving limits of detection of 0.071, 0.058 and 0.002 ng ml⁻¹ for Pb, Sn and Cd respectively. The relative standard deviation (R.S.D.) was respectively 1.3%, 3.4% and 2.9% for 10 ng ml⁻¹ of Pb, Sn and 2 ng ml⁻¹ of Cd (n = 7). Finally, the proposed method was successfully applied to the simultaneous determination of Pb, Sn and Cd in a series of Chinese certified biological reference materials using simple aqueous standard calibration techniques, with analytical results in good agreement with the certified values.