Determination of Tetracycline Using a Graphite-Polyurethane Composite Electrode Modified with a Molecularly Imprinted Polymer

A graphite-polyurethane composite electrode (GPUE) was modified with methacrylate molecularly imprinted with tetracycline (TC) as the template molecule for the first time. The work aimed to contribute to improve the selectivity in the presence of other tetracyclines. Density functional theory was also used to evaluate the binding affinity selectivity of the template structure examining the main intermolecular interactions with the monomers. Differential pulse anodic stripping voltammetry was used to compare the performance of the unmodified and modified GPUE with the molecularly imprinted polymer containing tetracycline (GPUE-MIP-TC) and nonimprinted polymer (GPUE-NIP). The resulting limits of detection were 2.70 µmol L−1, 0.555 µmol L−1, and 4.71 µmol L−1, respectively, without the requirement of surface renovation between the measurements. Linear responses were observed from 8.0 to 60.0 µmol L−1, 4.0 to 60.0 µmol L−1, and 20.0 to 100.0 µmol L−1, respectively, for the GPUE, GPUE-MIP-TC, and GPUE-NIP. The GPUE-MIP-TC was also evaluated regarding the selectivity to chlortetracycline (CTC) and oxytetracycline (OTC). In all cases, the interferences of GPUE-MIP-TC was lower than those observed with GPUE-NIP, confirming that the GPUE-MIP-TC was more selective at recognizing the analyte in presence of these similar molecules. The GPUE-MIP-TC electrode was also used for determination of the tetracycline in commercial formulations and in a synthetic urine sample. The results were compared to a standard high performance liquid chromatography protocol with agreement at the 95% confidence level according to the Student's t-test.