Thin Layer Ammonia Microsensor Chip and System for Measurement of Ammonia Nitrogen

Abstract

An ammonia microsensor chip based on a thin liquid layer in micro-pool has been designed and prepared.An ammonia nitrogen measurement system utilizing such a miniaturized sensor chip has been constructed.The method of ammonia nitrogen measurement using an amperometric ammonia microsensor was investigated.The sensor chip was fabricated by microelectromechanical system(MEMS).Platinum nanoparticles,possessing excellent electrochemical catalysis to ammonia,were modified on the bare microelectrodes of the sensor by electrochemical methods to enhance the sensitivity.A tiny amount of propylene carbonate(PC) was dripped into SU-8 micro-pool to form the thin layer electrolyte which facilitated ammonia to diffuse to the microelectrode surface,thus achieving a fast response time.Measurement of ammonia nitrogen using the self-designed measurement system was presented.The characterizations of the sensor,including relationship between response and sample concentration,response times,reproducibility and selectivity were demonstrated.A linear calibration curve between 0.1-5 mg/L was obtained.Meanwhile a limit of detection,0.1 mg/L,was achieved.The response time was less than 1 minute.The relative standard deviation(RSD) was 4.0%.