Determination of Cyanide in Blood by High Performance Liquid Chromatography with Fluorescence Detection

Simultaneous determination of inorganic ions including cyanide by photometric ion chromatography was useful for a cyanide analysis in drinks, but not applicable to that in blood, because of its poor resolution for cyanide and chloride. In this report, to determine cyanide in blood, we adopted a selective and sensitive method for cyanide based on a fluorometric reaction with 2,3-naphthalenedialdehyde (NDA) and taurine to afford 1-cyanobenz[f]isoindole derivative. Cyanide was extracted from blood by adding water and methanol to whole blood, and then derivatized with NDA and taurine. The cyanide derivative was analyzed on a reversed-phase high performance liquid chromatograph system with fluorescence detector.   In the analysis of standard solutions, the reagent blank showed a minor peak of cyanide corresponding to ca. 0.04 ng/ml. Thus the lower detection limit for cyanide standard solution was 0.1 ng/ml as 2.5-fold concentration of the reagent blank peak. The peak seemed to be due to trace cyanide in reagents, however, it was so minor peak that it didn't interfere with cyanide determination in blood. The calibration curve for cyanide standard solution was linear in the range 0.1-200 ng/ml. In the blood analysis, the method enabled us to determine cyanide from healthy persons level (ca. 10 ng/ml) to fatal level (ca. 3000 ng/ml) employing the same treatment.