Generation of volatile cadmium species with sodium tetrahydroborate from organized media: application to cadmium determination by inductively coupled plasma atomic emission spectrometry

Abstract

Continuous flow generation of volatile cadmium species (assumed to be the hydride) as a means of gaseous sample introduction into an inductively coupled plasma atomic emission spectrometer has been investigated in detail. Different ‘organized molecular assemblies’(micelles and vesicles) have been tried in order to improve the generation of such cadmium species using NaBH₄ as the reducing agent. Didodecyldimethylammonium bromide (DDAB) vesicles were found to be the most appropriate for the purpose. The advantages of this ‘assumed’ cadmium hydride generation from vesicular media are discussed and critically compared in terms of sensitivity, selectivity and accuracy, with the determination of low levels of cadmium by inductively coupled plasma atomic emission spectrometry (ICP-AES). The proposed method for the determination of cadmium by ICP-AES using DDAB and NaBH₄ provided 5-fold lower detection limits (1 ng ml^–1) as compared with conventional nebulization ICP-AES. A precision of 2% at the 50 ng ml^–1 level of the metal was achieved and selectivity studies were carried out. The proposed method was applied to the determination of low levels of cadmium in tea infusion. Validation of the method was performed by analysis of the same samples by electrothermal atomic absorption spectrometry with satisfactory results.