Glyphosate is an organophosphorus herbicide that is applied to the leaves of plants and crops to kill broadleaf plants and grasses. In this paper, for the first time, a field deployable, user-friendly, portable and rapid electrochemical pesticide sensing system is presented that can screen for glyphosate in produce run-off/extract. ElectrochemSENSE comprises the following parts: A polymer based disposable substrate with metallized electrodes that are surface treated with polyclonal antibodies of glyphosate and a custom electronic reader capable of reporting pesticide contamination. Utilizing the principles of capacitive current changes due to selective binding of glyphosate to its capture probe, reporting was achieved rapidly (in under 5 min). ElectrochemSENSE was tested to screen for glyphosate concentrations on produce samples above or below the globally accepted metric criterion, otherwise known as the Maximum Residue Level (MRL). Experiments were conducted on 4 produce types-apples (MRL: 0.2 ppm), strawberries (MRL: 0.2 ppm), bell peppers (MRL: 0.1 ppm) and carrots (MRL: 5 ppm). To further add functionality and increase prediction accuracy- a machine learning binary classifier was integrated with the device as a proof-of-concept so that sensor's response can be trained and characterized to perform with high accuracy, thereby serving as an analytics medium which minimizes error rate. Utilizing this system-the sensor's limit of detection has been determined to be 0.01 ppm (10 ng/mL) considering the permissible Field Operating Range (FOR) for glyphosate residue in various tested produce.
Keywords: Glyphosate on-produce detection; Label-free detection; Organophosphate pesticide; Run-off water.
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