Mid-Infrared Quantum Cascade Laser Sensor System with Molecularly Imprinted Polymer Solid Phase Enrichment for Diclofenac Monitoring

Real-time monitoring of pharmaceutical micropollutants in wastewater remains challenging due to complex matrices and low target concentrations, limiting timely detection of emerging contaminants. We report a field-deployable wastewater spectroscopic analyzer (WSA) that combines mid-infrared quantum cascade laser spectroscopy (QCL) absorption spectroscopy with selective sample preconcentration to quantitatively identify diclofenac (DCF), a widely used anti-inflammatory drug and recognized EU priority pollutant, in wastewater. Raw samples are first filtered to remove particulates, then selectively concentrated using a diclofenac-molecularly imprinted polymer-based solid phase extraction (MIP-SPE), and finally eluted as a methanol solution into a mid-infrared flow cell for spectral quantification. This integrated workflow enables autonomous operation with minimal manual intervention, addressing a key limitation of conventional laboratory-based analysis. The technique was validated against reference chromatography/mass spectrometry methods during filed deployment at a hospital and a municipal wastewater treatment plant, showing strong agreement (91-92%) and confirming its potential as a practical tool for autonomous, real-time pharmaceutical surveillance and early-warning monitoring in wastewater.