Direct Potentiometric Method for the Determination of Cyanide in Biological Materials

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Abstract
A modified analytical procedure for routine isolation of cyanide from biological materials that makes use of a cyanide electrode for direct potentiometric measurement of the liberated cyanide is described. In this procedure, the sulfide interference is eliminated with a 30 g/liter lead acetate solution, and complete analytical recovery of various amounts of cyanide added to whole blood is attained. The total time per analysis is 20 minutes. The within-day coefficient of variation in the 11.6 to 85.5 µmol/liter range is 4.8% or less. The method is particularly useful for routine diagnostic analysis of biological materials in cases of acute cyanide poisoning. The effects of temperature and time of storage on cyanide concentration in biological materials are also investigated. The results suggest that the least in vitro change in cyanide concentration during storage occurs at refrigeration temperature (+ 4°C).