Analysis, storage stability and reference values for urinary chromium and nickel

Simple direct dilution methods are described for the analysis of urinary chromium and nickel with electrothermal atomic absorption spectrometry. The day-to-day variation of the methods is in the order of 5%, and the detection limits 20 and 0.1 nmol/l (1.2 and 0.0052 micrograms/l) for urinary nickel and chromium, respectively. At levels corresponding to occupational exposures, both metals are stable (within 20%) in urine specimens in the refrigerator for the least ten months. The stability does not require acidification. Geometric mean values for urinary nickel and chromium in the non exposed population in Finland (n = 299 and 155) are 70 and 1.5 nmol/l (4.8 and 0.078 micrograms/l), and the upper 95% confidence limits from a log-normal distribution, are 170 and 11 nmol/l (10 and 0.57 micrograms/l), respectively.