液相微萃取/离子色谱测定牛奶中的氨

Determination of Ammonium Ion in Milk by Ion Chromatography with Headspace Single-drop Microextraction

以水为微滴萃取溶剂，采用顶空液相微萃取／离子色谱检测了牛奶中的氨。优化了顶空液相微萃取的实验条件：pH=12，萃取温度为35℃，萃取时间为15min，搅拌速率为800r／min，萃取溶剂体积为5止。测定氨的线性范围为10～300ug·L^-1（尺。=0．998），检出限达1．8ug·L^-1，回收率为92％～105％。

A novel method for the determination of ammonium ion was developed by headspace single-drop microextraction combination of ion chromatography （SDME/IC）. The influences of some SDME parameters, such as the sample stirring speed, pH of sample and acceptor phase, extraction time and temperature, on extraction efficiency were investigated. The results showed the optimal conditions were as follows： pH = 12, extraction time 15 min, extraction temperature 35℃, stirring speed 800 r/min, volume of extraction solvent 5 uL. Under the optimized conditions, the calibration curve showed a good linearity for the concentration of NH4 in the range of 10 -300 ug/L（R2 = 0. 998） with a detection limit （ S/N= 3 ） of 1.8 ug,/L. The method was successfully applied in the determination of ammonia in milk. The recoveries of ammonia from milk samples spiked at two concentrations levels of 50 and 100 mg/L ranged from 92% to 105% .