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.

RATIONALE

Sodium azide (NaN ) 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.

METHODS

To be able to confirm azide exposure, we have developed a method to identify azide in both beverages and bodily fluids. The identification of azide (N ) 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.

RESULTS

The azide after derivatization (CAX-N ) 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-N showed linearity over two orders of magnitude with R 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).

CONCLUSIONS

Compared 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.