Rapid and simple identification of trace amounts of sodium azide in beverages and bodily fluids followed by derivatization and liquid chromatography–electrospray ionization tandem mass spectrometry

Abstract

RationaleSodium azide (NaN3) is a toxic chemical agent to humans by ingestion and inhalation with a growing number of intentional exposures and accidental cases over the last few decades. Due to its low molecular weight and lack of any chromophore, its retention and detection by reverse‐phase liquid chromatography–ultraviolet–mass spectrometry methods are a challenging task.MethodsTo be able to confirm azide exposure, we have developed a method to identify azide in both beverages and bodily fluids. The identification of azide (N3−) is based on derivatization with N‐(2‐(bromomethyl)benzyl)‐N,N‐diethylethanaminium bromide (CAX‐B) at 25°C for 15 min followed by LC/ESI‐MS/MS analysis, with no other sample preparation.ResultsThe azide after derivatization (CAX‐N3) was stable, retainable by LC and sensitively detected by selected reaction monitoring. The ESI‐MS/MS fragmentation of the M+ precursor ion produced characteristic product ions at m/z 118, 100, 91 and 86. The calibration curves for CAX‐N3 showed linearity over two orders of magnitude with R2 value of 0.99. Low limits of identification of 0.1–0.5 ng/mL were obtained in all investigated matrices (drinking water, tea, orange juice, plasma and urine).ConclusionsCompared with previously reported chromatography‐based methods, this method that was based on derivatization and LC/ESI‐MS/MS analysis was substantially more sensitive, simpler and faster. The method can be used for forensic investigation to confirm azide exposure from fatal use to much smaller intoxication dose.