VESICLE-ASSISTED DETERMINATION OF ULTRATRACE AMOUNTS OF CADMIUM IN URINE BY ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY AND INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY

Two methods for the determination of ultratrace amounts of Cd, based o n vesicular hydride generation, including in situ trapping electrother mal atomic absorption spectrometry (ETAAS) and inductively coupled pla sma mass spectrometry (ICP-MS), are described and compared for Cd dete rmination in urine. The human urine samples are diluted 1+1 with ultra pure water and no other sample pre-treatment is necessary. Thus, the r isk of contamination at basal or 'normal' metal levels in urine is min imized. Using how injection hydride generation ICP-RIS (FI-PIG-ICP-MS) , the detection limits observed for Cd in water and urine (50 mu l sam ple volume) were 3.5 and 7 pg, respectively, and the observed relative standard deviation for ten replicate analyses of 50 pi of a 5 mu g l( -1) aqueous CD solution was +/- 3.2%, In situ trapping allows preconce ntration in the graphite tube; by preconcentrating 1.4 ml of urine the detection limit achieved by ETAAS was 10 ng l(-1) (14 pg, absolute). The use of silicone as an antifoam agent for vesicular cadmium hydride generation allowed a throughput of about 20 samples h(-1) by FI-HG-IC P-MS detection. The concentration of Cd in human urine was evaluated d irectly by aqueous standard calibration as no matrix interferences wer e observed for both methods under study. NIST SRM 2670 Toxic Metals in Freeze-Dried Urine was analysed by the two methods with excellent res ults. The accuracy of the results was demonstrated in two ways because the reported values for the SRM agreed well with the results obtained using either of the two methods under investigation.