Automatic on-line column preconcentration system for determination of cadmium by electrothermal atomic absorption spectrometry

Abstract

An automatic separation–preconcentration system coupled to an electrothermal atomic absorption spectrometer is described. The preconcentration step is performed on a chelating resin microcolumn [silica gel functionalized with 1,5-bis(di-2-pyridyl)methylene thiocarbonohydrazide] placed in the autosampler arm. The combination of a peristaltic pump for sample loading and the atomic absorption spectrometer pumps for elution through a selection valve simplifies the hardware. The peristaltic pump and the selection valve are easily controlled electronically with two switches placed in the autosampler, which are activated when the autosampler arm is down. Thus, the process is fully automated without any modification of the software of the atomic absorption spectrometer. The system is applied to the determination of cadmium in sea-water. Validation is carried out against the certified reference materials BCR CRM 403 Sea-Water and BCR CRM 505 Estuarine Water, and by determining the analyte content in sea-water and synthetic sea-water. The results showed good agreement with the certified values and the recoveries of Cd added to water samples were 94–104%.