Determination of Hydrazoic Acid and Sodium Azide in Workplace Air by Ion Chromatography with Suppressed Conductivity Detection
A method for the determination of hydrazoic acid and sodium azide in workplace air was established using ion chromatography with suppressed conductivity detection. Vapor and mist states of hydrazoic acid were collected in 40 mg·L−1 KOH absorption solution, while sol states of hydrazoic acid or sodium azide were collected on microporous membranes and eluted with 40 mg·L−1 KOH. Separation was performed on a Dionex IonPac™ AS11-HC (250 mm × 4.0 mm) anion analytical column with KOH gradient elution, followed by suppressed conductivity detection. The azide ion (N3−) exhibited good linearity in the range of 0.005–0.5 mg·L−1, with a correlation coefficient (r) of 0.9997. The limit of detection (S/N=3) was 0.002 mg·L−1, and the limit of quantification (S/N=10) was 0.005 mg·L−1. The minimum quantifiable concentrations in air were 0.00256 mg·m−3 for hydrazoic acid and 0.00387 mg·m−3 for sodium azide, based on a 10.0 mL sample solution and a 20 L air sample. Spiked recoveries ranged from 92.0% to 100.4%, with relative standard deviations (RSD, n=6) between 0.76% and 2.51%. The method is efficient, accurate, and sensitive, suitable for monitoring and safety assessment of hydrazoic acid and sodium azide in workplace air.