Electropolymerization of thionine as a stable film along with carbon nanotube for sensitive detection of tetracycline antibiotic drug

Herein, a simple, rapid, cost-effective and sensitive poly(thionine)-based electrochemical sensor is described to determine trace amounts of tetracycline. In the present work, electropolymerization of thionine was performed to create a stable film on the surface of carbon nanotube paste electrode. The modified electrode surface was investigated by scanning electron microscopy (SEM) and its complete formation was confirmed. Moreover, the unmodified and modified electrodes were then studied by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) technique. The linear sweep voltammetry (LSV) technique was used for the quantification of tetracycline 0.1 M phosphate buffer solution (PBS) at pH 6.0 by the modified electrode as a poly(thionine)/carbon nanotube/carbon paste electrode (PTH/CNT/CPE). Also, the effects of different experimental parameters including type of the supporting electrolyte, pH value, and scan rate were evaluated. The proposed sensor indicated a linear range of 0.50–20.0 µM, a limit of quantification and detection of 0.05 µM and 0.13 µM, respectively, under the optimized conditions. Low relative standard deviation values confirmed that the repeatability and reproducibility of the modified electrodes are acceptable in preparation and determination fully procedures. Finally, the proposed method was successfully applied for tetracycline determination in urine and 250 mg TC tablet with satisfactory results.