A new specific method to detect cyanide in body fluids, especially whole blood, by fluorimetry

This study shows a simple, rapid, and specific method for the quantitative determination of cyanide ion in body fluids, especially blood, by fluorimetry. It is based upon the transformation of cyanide ion into hydrocyanic acid, which then reacts with 2,3-naphthalenedialdehyde and taurine in a self-contained system. The 1-cyano-2-benzoisoindole derivate thus formed is suitable for fluorimetric measurement (λ(EX) = 418 nm; λ(EM) = 460 nm). The fluorescence intensity can be determined by spectrophotometry or by high-performance liquid chromatography (HPLC) with fluorescence detection. The detection limit is 0.002 μg/mL. Linearity was excellent from 0.002 to 1 μg/mL for spectrophotometry and from 0.002 to 5 μg/mL for HPLC with fluorescence detection. The coefficient of variation for repeatability was 8% or less. Thiocyanate and sulfide did not interfere, even at high concentrations (200 μg/mL). The method was applicable to whole blood, so it should be suitable for both clinical and forensic purposes.