Multi-commuted flow system for cadmium determination in natural water by cold vapour atomic absorption spectrometry

Abstract

The present paper proposes the use of a multi-syringe flow injection analysis (MSFIA) system for the determination of Cd in natural water by cold vapour atomic absorption spectrometry (CV-AAS). The chemical and physical conditions for vapour generation were investigated and optimized using multivariate optimization methodology. Some complexing reagents were tested as additives to increase the analytical signal. Thiourea showed a positive effect, whereas L-cysteine reduced the signal of Cd. The method allows the direct determination of Cd, i.e. without sample pre-concentration, with limits of detection and quantification of 5.8 and 19.3 ng L⁻¹, respectively, and employing external calibration technique. The precision expressed as a relative standard deviation varied between 1.4% and 2.9% for two levels of cadmium (0.25 and 2.5 μg L⁻¹). Using 2 mL of sample volume, an injection throughput of 87 h⁻¹ was achieved. The accuracy was confirmed by the analysis of a certified reference sample of seawater (CASS-4) furnished by National Research Council of Canada and addition/recovery tests, obtaining recoveries between 94% and 101%. The method was satisfactorily applied for the determination of Cd in seawater and ground water samples from Mallorca, Spain.