Direct measurement of ammonia in simulated human breath using an inkjet-printed polyaniline nanoparticle sensor

A sensor fabricated from the inkjet-printed deposition of polyaniline nanoparticles onto a screen-printed silver interdigitated electrode was developed for the detection of ammonia in simulated human breath samples. Impedance analysis showed that exposure to ammonia gas could be measured at 962 Hz at which changes in resistance dominate due to the deprotonation of the polymer film. Sensors required minimal calibration and demonstrated excellent intra-electrode baseline drift (≤1.67%). Gases typically present in breath did not interfere with the sensor. Temperature and humidity were shown to have characteristic impedimetric and temporal effects on the sensor that could be distinguished from the response to ammonia. While impedance responses to ammonia could be detected from a single simulated breath, quantification was improved after the cumulative measurement of multiple breaths. The measurement of ammonia after 16 simulated breaths was linear in the range of 40–2175 ppbv (27–1514 μg m⁻³) (r² = 0.9963) with a theoretical limit of detection of 6.2 ppbv (4.1 μg m⁻³) (SN⁻¹ = 3).