Measurements of Glyphosate at Nanomolar Level via POF-Based Unconventional Sensors

Glyphosate (GLY) contamination is a current problem that requires increasingly high-performance devices capable of detecting ultra-low concentrations of this difficult-to-monitor herbicide. For this reason, this study proposes an optical sensor based on unconventional surface plasmon resonance (SPR) phenomena, capable of detecting GLY concentrations at the nM level, exploiting the binding between the specific sites of a selective molecularly imprinted polymer (MIP) and GLY that occurs into the core of a modified plastic optical fiber (POF). Specifically, the MIP is located in a POF's micro-hole drilled upstream of the SPR region. Therefore, the samples are dropped into the MIP-filled micro-hole, while water is fixed on the SPR surface to excite the plasmonic phenomena. In this way, the interaction between the GLY and the MIP changes the refractive index in the POF core, and so do the SPR conditions downstream. The proposed configuration is based on a simple POF chip connected to a white light source and a spectrometer, obtaining an innovative platform with performances similar to those already present in the literature in terms of detection range, affinity constant (Kaff), and limit of detection (LOD).