Reliable determination of cyanide, thiocyanate and azide in human whole blood by GC–MS, and its application in NAGINATA–GC–MS screening

Purpose: Cyanide, its metabolite thiocyanate and azide in human biological fluids are commonly analyzed by gas chromatography–mass spectrometry (GC–MS) after derivatization with pentafluorobenzyl bromide using extractive alkylation. However, the reported methods have some drawbacks. We examined each step of these reported methods and attempted to establish a more reliable method to determine the levels of the above compounds in human whole blood. We also examined the applicability of the established method to NAGINATA–GC–MS screening. Methods: The deproteinization method, internal standard (IS), the cause of column damage, and the effect of the addition of ascorbic acid were examined, and the best procedure was selected. The obtained data, including mass specta, retention times and calibration curves were registered to the database of NAGINATA software. Results: The analysis of cyanide in whole blood was possible only when the blood was deproteinized with trichloroacetic acid. A high recovery of thiocyanate and azide was obtained without the deproteinization step. K¹³C¹⁵N (for cyanide) and tribromobenzene (for thiocyanate and azide) were selected as ISs. The column damage caused by the phase transfer catalyst was successfully eliminated by passing the catalyst containing solution through an ethyl benzoic sulfonic silica gel column. By these improvements, a more reliable determination method was established. All anions were rapidly identified using NAGINATA software, and the approximate concentration of each compound in whole blood was obtained at the same time. Conclusions: Because NAGINATA–GC–MS screening can rapidly identify these poisons without using toxic compounds as reference standards, it should be useful in forensic and emergency medicine laboratories.