A Printed and Microfabricated Sensor Device for the Sensitive Low Volume Measurement of Aqueous Ammonia

• Published in: Electroanalysis (New York, N.Y.) N.Y.), 2017-01, Vol.29 (1), p.162-171
• Main Authors: Brannelly, N. T., Killard, A. J.
• Format: Article
• Language: English
• Subjects: Air flow; Ammonia; Buffers; Devices; Electrodes; impedance; membrane; Membranes; microfabrication; Nanostructure; polyaniline; sensor; Sensors
• ISSN: 1040-0397; 1521-4109
• DOI: 10.1002/elan.201600556

The measurement of low concentrations of ammonia in small sample volumes is required in biological, biomedical and environmental measurement applications. However, achieving this without instrumentation remains challenging. Here, sensor devices for the measurement of ammonia in a liquid were developed. These were based on the fabrication of polyaniline nanoparticle films onto screen printed interdigitated electrodes using inkjet printing and their integration into a polymer microfabricated device with polytetrafluroethylene membrane and air flow path between the membrane and the sensor. Samples of ammonia in phosphate buffered saline of 52 μL were measured using electrochemical impedance. While water vapour and ions from the buffer did result in a decrease in sensor impedance, this was eradicated by displacement of the headspace above the sensor with air. This, in combination with the adjustment of the sample to pH to 11 allowed the quantification of ammonia from 0 to 200 μM with a limit of detection of 25 μM. The device has the potential to be used for sensitive, low volume measurement applications of ammonia at point‐of‐test and point‐of‐care.