A Novel Molecular Imprinted Dual-Polymer Infused Capacitive Sensor for Quercetin Detection in Agro Products

A novel, cost-effective capacitive sensor using molecularly imprinted dual polymer (MIP) was developed for precise quercetin (QT) detection in agro-products. A unique composite sensing material, molecularly imprinted polydopamine-polyethylene glycol (M2P-QT@C), deposited onto a copper (Cu) plate, forms the sensing heart of the sensor. The sensing material's characteristics were investigated employing a trio of techniques: i) scanning electron microscopy (SEM) for high-magnification structural visualization, ii)X-ray diffraction (XRD) for atomic arrangement analysis, and iii)UV-Vis spectroscopy to confirm template molecule removal and assess potential structural changes. Frequency variation of three electrical parameters: parallel capacitance (C<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pqt</sub>), impedance (Z<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">qt</sub>), and phase angle (θ<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pq</sub>t) have been investigated. The sensor responded linearly to QT concentrations from 10 to 50 ppm, with exceptional sensitivity (LOD: 0.035 μg/kg, LOQ: 0.116 μg/kg). To predict the amount of QT in real samples, two statistical methods: i) principal component regression (PCR), and ii) partial least squares regression (PLSR) have been applied, which exhibit high accuracy and recovery, exceeding 90% with minimal error (RMSEC: 0.0015). Additionally, the sensor demonstrated excellent selectivity with remarkable stability for QT recognition in real samples. Even after three months of use, the maximum parallel capacitance (C<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pqtm</sub>) increased by only 0.4 %, highlighting minimal performance degradation over time.