GENERATION OF VOLATILE CADMIUM SPECIES WITH SODIUM TETRAHYDROBORATE FROM ORGANIZED MEDIA - APPLICATION TO CADMIUM DETERMINATION BY INDUCTIVELY-COUPLED PLASMA-ATOMIC EMISSION-SPECTROMETRY

Continuous flow generation of volatile cadmium species (assumed to be the hydride) as a means of gaseous sample introduction into an inducti vely coupled plasma atomic emission spectrometer has been investigated in detail. Different 'organized molecular assemblies' (micelles and v esicles) have been tried in order to improve the generation of such ca dmium species using NaBH4 as the reducing agent. Didodecyldimethylammo nium bromide (DDAB) vesicles were found to be the most appropriate for the purpose. The advantages of this 'assumed' cadmium hydride generat ion from vesicular media are discussed and critically compared in term s of sensitivity, selectivity and accuracy, with the determination of low levels of cadmium by inductively coupled plasma atomic emission sp ectrometry (ICP-AES). The proposed method for the determination of cad mium by ICP-AES using DDAB and NaBH4 provided 5-fold lower detection l imits (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 an d selectivity studies were carried out. The proposed method was applie d to the determination of low levels of cadmium in tea infusion. Valid ation of the method was performed by analysis of the same samples by e lectrothermal atomic absorption spectrometry with satisfactory results .