Two novel enzyme-free colorimetric sensors for the detection of glyphosate in real samples

The intensive use and accumulation of glyphosate cause many environmental and ecological problems. There is an urgent need for an effective detection method for glyphosate. Many studies in the literature determine glyphosate by an enzyme-based method, requiring appropriate temperature, pH, substrate and ionic strength. In this study, we presented a simple enzyme-free reaction system. Two new simple Schiff base derivatives, 4-(((3-chloropyridin-4-yl)imino)methyl)-N,N-dimethylaniline (BNP-Cl) and 4-((3-((3-chloropyridin-4-yl)imino)propenyl)-N,N-dimethylaniline (CNP-Cl), were prepared by combining a pyridine moiety with a cinnamaldehyde or a benzaldehyde moiety. The pyridine moiety contains a chlorine atom, and this chlorine atom is replaced by the nitrogen or oxygen of glyphosate (Glyp) in ACN/Tris buffer (pH=8.14, 10 mM, v/v 2:1). This binding caused color changes ranging from colorless to yellow for BNP-Cl and yellow to orange for CNP-Cl. The sensors BNP-Cl and CNP-Cl have a rapid and excellent selectivity for glyphosate with low detection limits (1.78 µM for BNP-Cl and 1.60 µM for CNP-Cl). The sensors were also successfully applied to detect Glyp in real samples such as soil, tap water, and potatoes.