Determination of cyanide and thiocyanate in biological fluids by gas chromatography-mass spectrometry.

A sensitive, specific and accurate method is described for the determination of cyanide and thiocyanate in biological fluids. Potassium cyanide containing 95% 15N is added to the sample as internal standard and both endogenous cyanide and standard are separated by gas-phase diffusion into sodium hydroxide solution. Cyanogen chloride is prepared by reaction with sodium p-toluenesulphonchloramide and extracted into n-heptane. Quantitative analysis is carried out by gas chromatography-mass spectrometry (GC-MS) with selective ion monitoring of the molecular ions at m/e 61and m/e 62. Thiocyanate levels are determined by a similar procedure in which 15N-labelled sodium thiocyanate is used as internal standard. The method is applicable to a wide range of biological samples and is free from interference by other sample components.