Recent advances in metal–displacement approach for glyphosate detection: sensing strategies in environmental and food safety monitoring

The extensive use of pesticides in modern agriculture has raised serious concerns about environmental contamination, food safety, and human health. This necessitating rapid, selective, and cost–effective detection of pesticides. Glyphosate, the active ingredient in glyphosate-based herbicides (GBHs), has drawn particular attention due to its extensive use, potential endocrine-disrupting effects, and remarkable persistence in environmental, and food products. Recently, coordination chemistry has emerged as a powerful strategy for developing simple and highly selective optical sensing platforms for glyphosate detection. Although reviews discussing based on chromatographic techniques, biosensors, and nanomaterials for glyphosate detection exist, this review specifically focuses on the Metal Displacement Approach (MDA) for glyphosate detection using small-molecule optical probes (SMOPs). This review summarizes recent advances in MDA-based sensors, where glyphosate competitively binds to a metal center, displacing a chromophoric or fluorophoric ligand to produce a measurable optical change. The reported sensing systems mainly based on metal–ligand assemblies of Cu(II), Zn(II), Fe(III), Pb(II), and Ga(III) metal integrated with ligands such as peptides, dipicolylamine (DPA), azomethines, β–diketones, catechols, aza–heterocyles, and salen. These sensor systems achieve detection limits in the nanomolar to micromolar range, with some systems reaching as low as 0.5 nM. Importantly, many probes have demonstrated practical applicability in real samples including water, soil, and food matrices with recoveries between 80% and 140%. Further, integration with smartphone-based systems enables developing portable, point-of-care testing (POCT) devices. Overall, this review provides a comprehensive summary on MDA-based probes and their potential for real-time environmental monitoring and agricultural safety.