用于氨氮检测的无透气膜安培型氨气微传感器及系统

Membrane-Free Amperometric Ammonia Microsensor and System for Measurement of Ammonia Nitrogen

设计并制备了一种无透气膜的安培型氨气微传感器,并构建了氨氮检测系统,该系统实现了将溶液中的氨氮转化为氨气,并应用所设计的微传感器检测气态氨氮.采用MEMS工艺制备组成该微传感器的微电极芯片,氨敏感材料选用铂黑,通过电化学方法修饰于微电极表面.在微电极芯片的SU-8微池中滴入微量LiCl溶液,形成可使氨气迅速扩散到电极表面的薄层电解液.使用自行设计的氨氮检测系统对不同浓度氨氮样品进行检测,对微传感器的时间响应特性、线性度、灵敏度及重复性进行了测试和分析.微传感器的线性范围为0.2 mg/L～4 mg/L,线性相关系数为0.984 7,检测下限为0.2 mg/L,达到90%响应信号所需的时间在3 min以内.结果表明,使用安培型氨气微传感器检测氨氮的方法是可行的.

A membrane-free amperometric ammonia microsensor was designed and prepared in this pa- per. An ammonia nitrogen measurement system, in which ammonia nitrogen was converted to gaseous am- monia and determined by the designed microsensor, was constructed. The mierosensor was composed of a microelectrode chip which was fabricated by MEMS. Platinum black was chosen as the ammonia sensing material and electrodeposited on the bare microelectrodes of the microsensor by electrochemical methods. A tiny amount of LiCl solution was dripped into SU-8 micro-pool of the microelectrode chip to form the thin electrolyte layer which facilitated the diffuse of ammonia onto the microelectrode surface. Various concentrations of ammonia nitrogen were investigated, using the self-designed measurement system, to obtain the characteristics of the microsensor, including response time, linearity, sensitivity and reproducibility. A linear calibration curve between 0.2 mg/L--4 mg/L is obtained with the correlation coefficient of 0. 984 7. The limit of detection is 0.2 mg/L. 90% of response is obtained within 3 min. The results prove the feasibility of ammonia nitrogen measurement using an amperometric ammonia microsensor.