Determination of azide in blood and urine by gas chromatography-mass spectrometry

A sensitive and simple method for determining azide in blood and urine using an extractive alkylation technique was devised. This inorganic anion was alkylated with pentafluorobenzyl bromide using tetradecyldimethylbenzylammonium chloride as the phase-transfer catalyst. 1,3,5-Tribromobenzene was used as an internal standard. The obtained derivative was analyzed by gas chromatography-mass spectrometry using the negative ion chemical ionization mode with isobutane as the reagent gas. The calibration curves for azide were linear over the concentration range from 1 to 200 nmol/mL in blood and urine, and the lower limit of detection was 0.5 nmol/mL for blood and urine. The accuracy and precision of the method were evaluated, and the coefficients of variation were found to be lower than 10%.