Retention of Azide Ion on Zodiac HST N Column

Sodium azide is a salt derived from weak hydrazoic acid, with a pKa of approximately 4.5–4.7. It is highly toxic and commonly used as a stabilizer in aqueous solutions to inhibit bacterial growth.

Chromatographic separation of sodium azide is achieved on the Zodiac HST N column through weak ionic interactions between the partially ionized hydrazoic acid and the positively charged stationary phase. In addition, strong polar interactions occur due to the high acetonitrile content in the mobile phase.