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

Abstract

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 μg) 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 μg/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.