Chemical vapor generation of Cd and on-line preconcentration on a resistively heated W-coil prior to determination by atomic absorption spectrometry using an unheated quartz absorption cell

Abstract

A resistively heated W-coil was used as an on-line trap for preconcentration and reatomization of Cd, using chemical reduction by NaBH₄. The collected analyte species were reatomized rapidly and sent to an unheated quartz T-tube absorption cell for AAS measurement. Cadmium is revolatilized from the trap surface as atoms. The experimental parameters were optimized for the highest vapor generation, trapping and reatomization efficiencies. The concentration limit of detection calculated by the 3s of blank solution was found to be 4.0 ng l⁻¹ for Cd using a sample volume of 4.2 ml; the enhancement factor in the sensitivity was 31 when compared to conventional HGAAS. These values are comparable with those obtained by in situ trapping in graphite furnaces or even ICP MS found in the literature. Sensitivity can be improved further using larger sample volumes since there are no apparent blank contamination problems. Three different standard reference materials, NIST SRM 1566b Oyster Tissue, NIST SRM 1573a Tomato Leaves and CRM 403 Trace Elements in Sea Water, were analyzed for the assessment of accuracy of developed method for Cd and the results were found to be in agreement with the certified values.