Capacitive sensing of N-formylamphetamine based on immobilized molecular imprinted polymers

•A capacitive biosensor with a high sensitivity was developed to monitor trace amounts of the amphetamine precursor (N-FA).•The sensor consists of a gold electrode, which surface was modified by immobilization of molecular imprinted polymers (MIPs).•N-FA MIPs were synthesized using thermo- and UV-initiated polymerization and integrated with sensor device.•A proportional relation between analyte concentration and capacitance change was observed in concentrations between 10 and 250 μM.

A highly sensitive, capacitive biosensor was developed to monitor trace amounts of an amphetamine precursor in aqueous samples. The sensing element is a gold electrode with molecular imprinted polymers (MIPs) immobilized on its surface. A continuous-flow system with timed injections was used to simulate flowing waterways, such as sewers, springs, rivers, etc., ensuring wide applicability of the developed product. MIPs, implemented as a recognition element due to their stability under harsh environmental conditions, were synthesized using thermo- and UV-initiated polymerization techniques. The obtained particles were compared against commercially available MIPs according to specificity and selectivity metrics; commercial MIPs were characterized by quite broad cross-reactivity to other structurally related amphetamine-type stimulants. After the best batch of MIPs was chosen, different strategies for immobilizing them on the gold electrode's surface were evaluated, and their stability was also verified. The complete, developed system was validated through analysis of spiked samples. The limit of detection (LOD) for N-formyl amphetamine was determined to be 10 μM in this capacitive biosensor system. The obtained results indicate future possible applications of this MIPs-based capacitive biosensor for environmental and forensic analysis. To the best of our knowledge there are no existing MIPs-based sensors toward amphetamine-type stimulants (ATS).