Determination of cadmium in blood, plasma, and urine by electrothermal atomic absorption spectrophotometry after isolation by anion-exchange chromatography

The determination of cadmium in whole blood, urine, or plasma by atomic absorption using electrothermal atomization is described. In preparation for atomic absorption analysis, cadmium was concentrated on an anion-exchange column, significantly lowering the limit of detection and allowing for the first time the accurate and precise determination of plasma cadmium concentrations in persons/animals with low-level cadmium exposures. Recovery of 109Cd from spiked whole blood, plasma, and urine into supernatants of nitric acid-deproteinated samples averaged 99, 100, and 95%, respectively. Anion-exchange isolation of the anionic chlorocadmium complex removed 99.8% of the major elements associated with a deproteinated whole blood sample. The recovery of 109Cd from the anion-exchange column was 92.2 +/- 0.9% (mean +/- SE, N = 35). The separation of cadmium from constituents in blood, urine, or plasma in this manner allowed comparison of unknown samples to aqueous standards with a defined acid matrix using commercially available acids. The mean intra-assay coefficient of variation (CV) was 12 +/- 3% (mean +/- SE, N = 6) for blood, plasma, and urine samples having cadmium concentrations of 0.1-0.8 microgram/liter. The interassay CV was 13% (N = 7) for a blood sample containing 0.6 microgram Cd/liter. The recovery of known amounts of cadmium added to blood, plasma, and urine in the range of 0.2 to 5.0 micrograms Cd/liter was 97 +/- 6% (mean +/- SE, N = 4).