Interaction of the Polymeric Layer Derived from 3-(4-Trifluoromethyl)-phenyl)-thiophene with Synthetic Stimulants on the Phase Boundary

Abstract

Modification of an electrode surface with a selective layer leads to amplification of the electrochemical signal. A film derived from electrochemically oxidized 3-(4-trifluoromethyl)-phenyl)-thiophene deposited on a graphite electrode (ThPhCF3/G) was used to estimate the affinity for synthetic stimulants (2-aminoindane, buphedrone, naphyrone) using a combination of square wave voltammetry and electrochemical impedance spectroscopy. The modified surface was characterized using Raman spectroscopy, which confirmed that the presence of the –PhCF3 group is important for the recognition of synthetic stimulants. The determined values of the adsorption constants (Kads) showed the significance of charge–transfer and/or hydrogen bond interactions between—PhCF3 groups in the polymeric film and the analyte of interest: buphedrone (9.79 × 105) < naphyrone (1.57 × 106) < 2-AI (1.87 × 106). Compared to electrodes modified with nanomaterial, PThPhCF3/G-electrodes showed the highest sensitivity in concentration range of 1–11 μmol L−1 at neutral pH and a possibility of detection of 0.43–0.56 μg mL−1 (sr = 0.05–0.12). The analytical performance of ThPhCF3/G promises good perspectives for the detection of synthetic stimulants in forensic samples without prior pretreatment.