An Innovative Simple Electrochemical Levofloxacin Sensor Assembled from Carbon Paste Enhanced with Nano-Sized Fumed Silica

A new electrochemical sensor for the detection of levofloxacin (LV) was efficiently realized. The aim was to develop a new, cheap, and simple sensor for the detection of LV, which is used in various infections due to its pharmacological importance. It consists of carbon paste (CP) enhanced with nano-sized fumed silica (NFS). NFS has a very low bulk density and a large surface area. The carbon paste-enhanced NFS electrode (NFS/CPE) showed great electrocatalytic activity in the oxidation of 1.0 mM LV in Britton–Robinson buffer (BR) at pH values ranging from 3.0 to 8.0. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used; the peak current value (Ip) of the NFS/CPE sensor was 2.7 times that of the bare electrode, ensuring its high electrocatalytic activity. Electrochemical impedance spectroscopy (EIS) was performed at a peak potential (Ep) of +1066 mV, yielding a resistance of 10 kΩ for the designed NFS/CPE sensor compared to 2461 kΩ for the bare electrode, indicating the high conductivity of the modified sensor and verifying the data observed using the CV technique. Surface descriptions were determined by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The variation in the concentration of LV (2.0 to 1000 µM) was considered in BR buffer (pH = 5.0) at a scan rate (SR) of 10 mV/s by the NFS/CPE. The detection and quantification limits were 0.09 µM and 0.30 µM, respectively. To evaluate the application of LV in real samples, this procedure was established on Quinostarmax 500 mg tablets and human plasma samples. Reasonable results were obtained for the detection of LV