Development and first application of the edge plane pyrolytic graphite electrode modified with graphene nanoplatelets for highly sensitive voltammetric determination of oxolinic acid

In this paper, a graphene nanoplatelets (GNPs) were used as a modifier of an edge plane pyrolytic graphite electrode (EPPGE) surface, and the graphene nanoplatelets modified edge plane pyrolytic graphite electrode (GNPs-EPPGE) was prepared by simple drop casting procedure. The as-prepared GNPs-EPPGE was characterized by a cyclic voltammetry (CV), a scanning electron microscopy (SEM), and an atomic force microscopy (AFM). The electrochemical behavior of OxA on the EPPGE and the GNPs-EPPGE was performed using the cyclic voltammetry and an electrochemical impedance spectroscopy (EIS). Further, a sensitive and selective square-wave voltammetric (SWV) procedure using the GNPs-EPPGE was developed for the determination of a quinolone antibiotic oxolinic acid (OxA). An oxidation peak of OxA was observed in Britton-Robinson buffer solution with the highest response at pH 5.0 at potential c.a. +1.4 V vs. Ag/AgCl reference electrode. Compared to the unmodified EPPGE, the EPPGE modified GNPs exhibited a marked enhancement in the current response of OxA. Calibration curve on the GNPs-EPPGE was constructed in the concentration range of 3.0 × 10−7-9.1 × 10−6 mol L−1 with a correlation coefficient of 0.9997, a sensitivity of 1.39 μA L μmol−1, a limit of detection (LOD) of 5.2 × 10−8 mol L−1, and a limit of quantification (LOQ) of 1.7 × 10−7 mol L−1. The determination of OxA in the spiked human urine samples was carried out using the GNPs-EPPGE with the satisfactory recovery of 99.6%. The selectivity of the developed method for the determination of OxA using the GNPs-EPPGE was tested.