Separation and preconcentration of ultratrace levels of cadmium(II) in a sequential injection (SI) system with a PTFE packed column as a mimic sequential injection lab-on-valve (SI-LOV) system with renewable column employing detection by electrothermal atomic absorption spectrometry (ETAAS)

A sequential injection (SI) on-line separation and preconcentration system furnished with an external column packed with PTFE beads, serving as a mimic renewable microcolumn used in a sequential injection lab-on-valve (SI-LOV) system, was investigated for the determination of ultratrace levels of cadmium(II) by detection with electrothermal atomic absorption spectrometry (ETAAS). The non-charged complex formed between the analyste and the chelating reagent diethyldithiophosphate (DDPA) was selectively adsorbed on the surface of the PTFE beads and eluted by ethanol before being directed to the ETAAS. Two kinds of sorbents were investigated, that is, granular Algoflon® PTFE and Aldrich PTFE. A mimic external packed column was employed since difficulties of aspirating and discarding beads plus a high background signal were encountered in the renewable microcolumn SI-LOV system. As compared with the Aldrich PTFE material, the Algoflon® beads exhibited much higher sensitivity (1.6107 versus 0.2956 μg l-1 per integrated absorbance (s)), and better retention efficiency (82% versus 74%) and enrichment factor (20.8 versus 17.2), although a slightly smaller linear dynamic range (0.05-0.25 μg l-1 versus 0.05-1.00 μg l-1). Moreover, no flow resistance was encountered under the experimental conditions used. The results obtained on three standard reference materials were in good agreement with the certified values.