Green stopped-flow microfluidic electrochemical sensor based on magnetic molecularly imprinted polymers for selective tramadol determination.

Inspired by green chemistry principles, recent progress in fabricating electrochemical sensors and microfluidic devices has paved the way for cutting-edge integrated systems. This study introduces an eco-friendly microfluidic electrochemical sensor for the selective detection of tramadol (TRA), employing magnetic molecularly imprinted polymer nanoparticles (MMIPNPs) for extraction, followed by voltammetric analysis at the microchannel outlet using a magneto-multiwalled carbon nanotube/carbon paste electrode (MMWCNTs/CPE). The MMIPNPs were synthesized with TRA as the template molecule, involving the coating of Fe3O4@SiO2 nanoparticles with a polyaminoimide homopolymer. Comprehensive characterization of the magnetic adsorbent via TEM, FTIR, XRD, and magnetometry revealed excellent dispersion and rapid magnetic separation from the microchannel post-adsorbate loading. Optimization studies on key parameters influencing MMIPNPs extraction efficiency underscored their superior selectivity and sensitivity toward TRA. The MMWCNTs/CPE was evaluated through electrochemical impedance spectroscopy, cyclic voltammetry, and differential pulse voltammetry (DPV). DPV-based analysis of TRA oxidation enabled selective quantification across a linear range of 0.01-15.0 μmol L-1, with a detection limit of 0.004 μmol L-1 under optimized conditions. The device exhibited excellent selectivity (relative error ≤ ±5% against interferents), repeatability (RSD 1.7-4.8%), and recovery rates (96.9-105%) in human serum and urine samples.