A sensor probe for the continuous in situ monitoring of ammonia leakage in secondary refrigerant systems

Ammonia is becoming more widely used in refrigeration systems due to the phasing out of CFCs and HCFCs. However, ammonia is a toxic gas and its leakage from refrigeration systems can lead to human exposure and contamination of refrigerated food stuffs. There is a lack of devices capable of the direct and continuous monitoring of leakage of ammonia into secondary refrigerant systems. Here we demonstrate an ammonia measurement probe for continuous contact monitoring of secondary refrigerants. The probe was based on an ammonia-sensitive film of inkjet printed polyaniline nanoparticles deposited onto an interdigitated electrode array and enclosed behind a polytetrafluoroethylene membrane. When operated impedimetrically, the probe was capable of the detection of ammonia across the industrially relevant range of 0 to 100 ppm from +4 to -15°C in water and brine. Operation of the probe as a simple threshold alarm without the requirement for temperature monitoring or calibration is illustrated. © 2013 The Royal Society of Chemistry