Abstract
The ammonia purge-and-trap (P&T) preconcentrator system is a device to separate ammonia from complicated matrices, which combining the concept of purge-and-trap and ammonia stripping. After the P&T pretreatment, the collected sample from trap vessel would be analyzed by ortho- Phthaldialdehyde (OPA) fluoresce derivatization or ion chromatography. The main research purpose of this thesis is to widen the P&T preconcentrator’s linear range under the same efficiency to previous work. And to measure ammonia’s Henry’s law constant under different temperature and different sodium hydroxide concentration. To extend the linear range under the same efficiency, the following parameters should take into account：affect of ultrasound, purging time, volume of trap solution, the composition of trap solution and its concentration. The advanced system broaden its linear range about 3 order to 20 ppb~100 ppm, make it possible to deal with wide ammonia concentration samples. Furthermore, directly ammonia measurement in the purge vessel can verify this system is keep mass balance. Both measurements of ammonia’s KH from purge vessel and trap vessel are very close to the theoretical value and the reference ones. Therefore, this system can not only apply to the pretreatment of wide ammonia concentration samples but also measure ammonia’s KH precisely.