Glyphosate Detection Through Piezoelectric and Fiber Optic Sensors Based on Molecular Imprinted Polymers

Glyphosate (N-(phosphonomethyl)glycine) is a popular broad-spectrum systemic herbicide commonly used to kill weeds and grasses that compete with crops. It is one of the most used herbicides worldwide that has been already detected in soils and groundwater. Its toxicity and persistence to humans and environment have been pointed out in literature. The detection and quantification of glyphosate or its degradation product (aminomethyl)phosphonic acid (AMPA) are thus an urgent need. In this article, we use molecularly imprinted polymers (MIPs) integrated with different sensing platforms for glyphosate detection. The platforms are based on a piezoelectric quartz crystal and on fiber optics. The assembled piezoelectric quartz crystal system allowed to rapidly characterize MIP binding to glyphosate, with sensitivity of 0.769 and 0.496 Hz/(mg/L) and good selectivity to several tested interferents (selectivity coefficients lower than 0.04 for AMPA and inorganic salts). Optical fiber systems, namely an optical fiber tip and a dip probe fiber bundle, were further developed and combined with a fluorescent MIP selective layer, allowing a proof of concept toward an in situ operational system for glyphosate detection. Fiber tip sensor displayed higher sensitivity to glyphosate compared to dip probe, 0.19 and 0.048 (mg/L)
$^{-{1}}$
, respectively, but with linear behavior in different concentration ranges, up to 1 mg/L and between 2 and 7 mg/L, respectively. The developed sensing platforms allowed fast measurements directly in the solution, making them promising probes for practical deployment for environmental monitoring.