Abstract
Purge and trap system is often widely applied to the pretreatment of the sample in complicated matrix. With purge and trap system, the ion, NH4+(aq), separated from the concentrated salt solution would be injected to the ion chromatography for analysis. In this study, we improved the efficiency of the purge and trap system and stability. In addition, we developed the theoretical model of the purge and trap system based on the two-film theory. What is more, we utilized this model to obtain the relation between the Henry’s law constant of NH3 and temperature. The parameters which affect the efficiency of the purge and trap system include the concentration of NaOH, the height of liquid of purge vessel, type of gas, flow rate, purge time and the temperature of the system. With the improved pretreatment system, the efficiency could be raised from 65 % to 90 %, and the signal of the blank decreased to lower than 20 ppb which is one-third of the original system. It was convinced of the measurement in low concentration.