Determination of cobalt in urine by gas chromatography-mass spectrometry employing nickel as an internal standard.

A gas chromatographic-mass spectrometric method for the determination of cobalt in biological materials employing stable enriched 62Ni as an internal standard and using lithium bis(trifluoroethyl)dithiocarbamate as a chelating agent is described. The method involves the addition of a known amount (1 microgram) of 62Ni to the sample, the formation of the chelate and the determination by selected-ion monitoring of the m/z 571/574 ratio, which corresponds to 59Co/62Ni. No appreciable memory effect was observed, and an acceptable dynamic range of 100 was found. There was good agreement between the cobalt concentration values determined by gas chromatography-mass spectrometry and electrothermal atomic absorption spectrometry. The present method has high sensitivity and can be used for the quantitation of cobalt at concentrations as low as 1 microgram/l. The use of enriched 62Ni circumvents the problem caused by endogenous nickel and simultaneously provides data on the nickel concentration in the biological sample without any additional experimental effort.