Studies on the reaction between cadmium and potassium tetrahydroborate in aqueous solution and its application in atomic fluorescence spectrometry

The conditions for the vapour generation of cadmium by the reaction with potassium tetrahydroborate in aqueous solution were investigated using a programmable intermittent flow reactor. It was found that thiourea together with cobalt ion greatly enhanced the generation efficiency of the volatile species. Based upon the results of the investigation, the vapour generation system was used for the determination of ultra-trace amounts of cadmium by atomic fluorescence spectrometry. A detection limit of 8 pg ml−1 was obtained under optimized conditions and the precision of the measurements for 5 ng ml−1 of Cd was 1.2% R.S.D. The effects of 28 diverse ions on the generation of the cadmium volatile species were investigated. Serious signal depressions were observed from copper and lead but these were decreased by using potassium cyanide as masking agent for copper and by coprecipitation with barium sulphate for lead. The method was successfully applied to the determination of cadmium in NBS standard reference material (SRM) 1577a bovine liver, NBS SRM 1645 river sediment and other Chinese origin SRMs. The method was also applied to tap water analysis with full recovery of spiked samples.