Colorimetric sensing of calcium carbide over banana peels using 5,5′-dithiobis-(2-nitrobenzoic acid) (DTNB) as a rapid chemoreceptor: a point of care tool for food fraud analysis

Point-of-care sensing systems have led to the rapid development of smart and portable devices in the field of analyte detection technology. The high flow of artificially ripened fruits (ARFs) in the market results in severe health risks, and simultaneously, the unavailability of consumer-level 1st screening tool flares up its exigency. Calcium carbide (CaC 2 ) is a hazardous artificial fruit ripening agent. In this study, a portable one-step colorimetric sensor was developed for the detection of CaC 2 on the surface of ARFs. The presence of CaC 2 was detected using 5,5′-dithiobis-(2-nitrobenzoic acid). The colorimetric reaction of DTNB detected CaC 2 by the free sulfhydryl group detection method which produced a yellow color; the free sulfhydryl group is present as an impurity in CaC 2 . The proposed assay displayed an LOD of 50 ppm with a detection time of a few seconds to 1 minute. It exhibited a rapid, highly sensitive and highly selective response, with a linear dynamic range of 0-4000 ppm and R 2 values of 0.993 and 0.994 for 323 and 412 nm peaks, respectively. The development of this inexpensive, naked eye, portable, and easily accessible CaC 2 sensor reinforces the suggestion that it could bridge the gap between conventional detection techniques and consumer-level detection methods. Our sensor could be useful as a 1st screening tool in various fields, including agriculture, food, and cosmetics industries. A point of care tool for colorimetric detection of calcium carbide over banana peels.