Abstract: In order to determine the ammonia delivery in mainstream cigarette smoke accurately, an ion chromatography method was developed by using a Dionex IonPac CS19 column to separate ammonium from other analytes, instead of Dionex IonPac CS12A or CS16. The new method achieved a better resolution of ammonium from sodium ions, methylamine ions and ethylamine ions presented in mainstream cigarette smoke. When CS16 column was used to separate ammonium from other cationic species, some smoke constituents (e.g., nicotine) were strongly adsorbed to ion chromatographic column, which affected the separation and contamination of the analytical column. These problems were well solved by the new method. The spiked recoveries of the new method ranged from 92.3% to 109.0% with linear correlative coefficients better than 0.999. The relative standard deviation (RSD) and detection limit were 5.2% (n=5) and 0.05 μg/cig, respectively. The results showed that the new method could determine the ammonia delivery in mainstream cigarette smoke accurately.