Dual descriptor analysis of cetylpyridinium modified carbon paste electrodes for ascorbic acid sensing applications

Abstract

Cationic surfactants, increases the number of surface active electron transfer (ET) sites on the carbon paste electrode (CPE) surface. In general, a combination of frontier molecular orbitals and Fukui function employed to locate the redox-active sites on bare and different surfactants modified electrodes. However, these methods quite tedious, confusing, and require plotting oxidation and reduction sites separately. Therefore, we are proposing dual descriptor to locate redox-active sites on cetylpyridinium, cetyltrimethylammonium, and benzethonium ions in a single plot. For the above mentioned surfactants oxidation sites located on the head and reduction sites located on the tail. Our results also reveal that the phenyl group of cetylpyridinium ions acts as an additional ET site at the electrode interface and its the main reason for sensing improvement. Cyclic voltammetry used to validate theoretical observation and results clearly indicates that there is an increase in active ET sites on the electrode surface after modifications from cationic surfactants. The cetylpyridinium increases maximum number of ET sites on CPE surface when compared to cetyltrimethylammonium and benzethonium ions. As a part of the work cetylpyridinium modified electrode was used to sense ascorbic acid concentration in urine with a satisfactory recovery of up to 106%.