Portable and low-cost colorimetric sensor for detection of urea in milk samples

• Published in: IEEE sensors journal Vol. 23; no. 14; p. 1
• Main Authors: Nandeshwar, Ruchira, Mandal, Poulami, Tallur, Siddharth
• Format: Journal Article
• Language: English
• Published: New York IEEE 15.07.2023; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Color; colorimetric sensor; Dairy products; Data acquisition; Low cost; milk adulteration; Optical amplifiers; Optical buffering; Optical device fabrication; Optical filters; Optical variables measurement; p-dimethylaminobenzaldehyde (p-DMAB); Phase sensitive detection; Preprocessing; Sensors; urea; Ureas
• ISSN: 1530-437X; 1558-1748
• DOI: 10.1109/JSEN.2023.3282810

Presence of excess urea in milk above the maximum permissible limit can result in serious health issues, including kidney failure. While several tests exist for measuring urea concentration in milk, such tests typically require significant preprocessing of samples in a laboratory setting and result in long turnaround time and increased cost of testing due to use of expensive equipment operated by trained analysts. In this work, we present a point-of-use sensor for quantification of urea concentration in milk samples, with minimal sample preprocessing and seamless readout. The assay involves addition of p-dimethylaminobenzaldehyde (p-DMAB) to supernatant obtained after precipitation of milk solids, to form a yellow-green color chromogen. The intensity of the color is proportional to the amount of chromogen produced, and is probed using a low-cost optical phase sensitive detection (PSD) system assembled using high performance albeit inexpensive consumer grade components. The data acquired by the sensor is streamed wirelessly to a smartphone for further analysis. We present preliminary results obtained using milk samples spiked with urea, with concentration ranging from 0.1mg/mL (safe level) to 0.7mg/mL (maximum permissible limit), with limit of detection (LOD) of 0.19mg/mL.