Portable Device for Ammonia Detection in Liquids and Biological Fluids

Researchers at the University of Milan have developed a compact, portable device capable of detecting gaseous ammonia released from liquid samples, which is essential for monitoring environmental contamination and industrial processes, ensuring food safety, and diagnosing health conditions. The device uses a polyaniline-based chemoresistive sensor and interdigitated electrodes, enclosed in a gas-permeable hydrophobic membrane, which permits ammonia in the vapor phase to reach the sensing layer while protecting from liquid interference. The device has demonstrated reliable performance across a concentration range of 1.7 to 170 ppm with strong logarithmic correlation.

Key Takeaways:

• The portable device detects gaseous ammonia released from liquid samples, which is essential for environmental monitoring, industrial processes, food safety, and health diagnosis.
• The device uses a polyaniline-based chemoresistive sensor and interdigitated electrodes, enclosed in a gas-permeable hydrophobic membrane.
• The device has demonstrated reliable performance across a concentration range of 1.7 to 170 ppm with strong logarithmic correlation.
• The sensor design limits the impact of water vapor, a known source of interference in polyaniline-based sensors.
• A tailored signal processing strategy extracts the slope of resistance variation over time as a robust metric for ammonia quantification.
• The device is suitable for point-of-care (POC) use due to its compactness, portability, and simple design.
• The research was supported by Fondazione UNIMI and University of Milan.

Statistics:

• Concentration range detected by the device: 1.7 to 170 ppm.
• Logarithmic correlation coefficient (R) of the device's performance: 0.99.
• Linear correlation coefficients (R) in low and high subranges: 0.96 and 0.97, respectively.
• Average nanoparticle size of PANI: 120 nm.

Sources:

• Gaseous Ammonia Sensing from Liquids via a Portable Chemosensor with Signal Correction for Humidity. Biosensors, 2025;15(7):407.
• Elsevier (www.elsevier.com)
• Mdpi (www.mdpi.com)
• Polytechnic University Milan (via Ilaria Porello, Dept. of Chemistry, Materials and Chemical Engineering G. Natta)