A novel fluorescent sensor based on an enzyme-free system for highly selective and sensitive detection of glyphosate and malathion in real samples

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Malathion (Mal) and glyphosate (Glyp) are widely used organophosphorus pesticides to prevent or control insects and weed in agriculture. Unfortunately, the extensive and frequent commercial use of these compounds on farmland has caused their presence as residues in crops and livestock. Therefore, the design of new sensors with enhanced analyte selectivity and sensitivity is critical in this field. Here, we developed an optical sensor for the detection of malathion and glyphosate. The sensor, N,N-dimethyl-4-(3-(pyrazin-2-ylimino)prop-1-en-1-yl)aniline (CNP), was synthesized in a one-step reaction by condensation of 4-(dimethylamino)cinnamaldehyde with 2-aminopyrazine. CNP gives a rapid color change, absorbance and fluorescence response to Glyp and Mal in the presence of the metal ions and pesticides tested in the working system. The binding stoichiometry between the sensor and the pesticides (Glyp and Mal) was investigated by some spectrophotometric methods and the sensing mechanisms were eludicated by NMR titration experiments, suggesting that CNP responds to Glyp via H-bonding and to Mal via the coordination. The sensor has a high selectivity and rapid response to the pesticides (Glyp and Mal) with low detection limits. The sensor was also successfully used to monitor the pesticides in real samples; Mal in apple and tap water samples, and Glyp in potato, tap water and soil samples.