Preparation of TEMPO-Modified Electrodes by Electrochemical Polymerization in Aqueous Solution for Use in Electrochemical Analysis of Pharmaceuticals

In this study, we evaluated the preparation conditions, stability, and durability of 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO)-modified glassy carbon (GC) electrodes prepared using electrolytic polymerization in an aqueous solvent, and examined the applicability of the electrodes as electrochemical sensors for pharmaceutical analysis. First, we synthesized a TEMPO-substituted phenol (2-PH-TEMPO) and examined the conditions for its efficient immobilization on an electrode using the electrolytic polymerization method in an aqueous solvent. The TEMPO-modified GC electrode showed high stability and durability in a low-concentration substrate environment and effectively functioned as an electrolytic oxidation catalyst for ethanol, a compound with a hydroxyl group. In an analysis of pharmaceuticals, a high oxidative response was obtained for lidocaine, clarithromycin, and azithromycin, which have tertiary amines or multiple oxidizable hydroxyl groups, suggesting that the electrode can function as a highly sensitive electrochemical sensor. The use of this modified electrode enables quantification in the clinical concentration range of vancomycin, and it is expected to be applied to rapid and accurate pharmaceutical concentration measurements in therapeutic drug monitoring. These results suggest that TEMPO-modified GC electrodes are useful as stable and sensitive electrochemical sensors in the fields of pharmaceutical analysis and biosensors, and are expected to contribute to the development of quantitative electrochemical methods.