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Natural and synthetic dyes are added to different food commodities to enhance their appearance and acceptance by consumers. Acute and chronic exposure owing to the consumption of non-permitted dyes may lead to health concerns such as allergic reactions, eczema, and asthma. 4-(Dimethylamino)azobenzene (4-DMAAB) is a non-permitted dye that has been reported in adulterated mustard oil. Consumption of 4-DMAAB poses severe risks due to its mutagenic and carcinogenic properties. Several sensitive methods such as FT-NIR, FT-MIR and SERS are available for the detection of 4-DMAAB. Here, a spectrophotometric method was developed for the detection of 4-DMAAB. The developed method was translated to a point-of-test paper-based, chromogenic strip which showed a detection limit of 0.025 mM for 4-DMAAB. Also, an electrochemical sensor was developed by electro-depositing the test solution on a screen-printed electrode. The electrochemical sensor showed an LOD of 0.027 ± 0.008 mM with recovery in the range of 91–107% of 4-DMAAB. Oil samples collected from the market were processed by liquid–liquid extraction and the content of 4-DMAAB was assessed. The developed point-of-use sensors for the detection of 4-DMAAB have potential for use by the consumers, food industry and regulatory agencies for on-site analysis and assuring the quality of edible oils.

Plastics are ubiquitous in today's lifestyle, and their indiscriminate use has led to the accumulation of plastic waste in landfills and oceans. The waste accumulates and breaks into micro-particles that enter the food chain, causing severe threats to human health, wildlife, and the ecosystem. Environment-friendly and bio-based degradable materials offer a sustainable alternative to the vastly used synthetic materials. Here, a polylactic acid and carbon nanofiber-based membrane and a paper-based colorimetric sensor have been developed. The membrane had a surface area of 3.02 m2g−1and a pore size of 18.77 nm. The pores were evenly distributed with a pore volume of 0.0137 cm3g−1. The membrane was evaluated in accordance with OECD guidelines and was found to be safe for tested aquatic and terrestrial models. The activated PLA–CNF membrane was further used as a bio-based electrode for the electrochemical detection of nitrates (NO3−) in water samples with a detection limit of 0.046 ppm and sensitivity of 1.69 × 10−4A ppm−1mm−2, whereas the developed paper-based colorimetric sensor had a detection limit of 156 ppm for NO3−. This study presents an environment-friendly, low-carbon footprint disposable material for sensing applications as a sustainable alternative to plastics.

Hydrogen peroxide (H2O2) is commonly used as a preservative, disinfectant, bleach, and oxidizing agent. The prolonged consumption of H2O2adulterated milk is harmful to human health when consumed in the diet. Exposure to H2O2can lead to oxidative stress, cell damage and tissue injury. Due to the potential adverse effects, the use of hydrogen peroxide is regulated in certain applications, such as in food, water treatment plants and medical products. Several methods are available for the detection of H2O2in various matrices. Here, a method and QR code-integrated chromogenic paper strip for the detection of H2O2in aqueous samples has been developed. The spectrophotometric method showed an LOD and LOQ of 0.00087 ± 8.70 ×10−5% (v/v) and 0.0037 ± 0.0003% (v/v), respectively. The paper-based chromogenic strip prepared by immobilizing recognition solution onto a QR code was able to detect 0.0005% v/v of H2O2in aqueous samples. The QR integrated chromogenic paper strip sensors can serve as a useful tool for consumers, regulatory agencies, and the food industry to assess food quality and authenticity.