Electroanalytical application of thiol-grafted laponite to the sensitive quantification of ciprofloxacin antibiotic

Abstract

In this study, a sensitive and selective voltammetric sensor was proposed for the detection of ciprofloxacin (CFX) fluoroquinolone-based antibiotic, using a glassy carbon electrode (GCE) modified by a thin film of thiol functionalized laponite (LaSH). The employed organolaponite was prepared by surface grafting of 3-mercaptopropyltrimethoxysilane (MPTMS), then characterized by XRD, FTIR spectroscopy, thermal analysis and CHS elemental analysis. The electrochemical behavior of CFX was investigated on the thin film GCE/LaSH by cyclic voltammetry, which showed a single irreversible oxidation peak at 1.3 V (vs. Ag/AgCl) in a Britton-Robinson buffer solution at pH 2. The CFX current response on the organoclay modified electrode was significantly improved, due to favorable interactions between thiol functional groups and CFX. Differential pulse stripping voltammetry was then applied for quantitative determinations, and key parameters such as pH of detection medium, accumulation time, agitation and CFX concentration were optimized. In optimum experimental conditions, a linear relationship between the peak current density and CFX concentration was observed in the range 10.0–110.0 µM, with a detection limit of 2.69 × 10–7 M (S/N = 3). Kinetic and chronocoulometric studies were also performed to characterize the diffusion of CFX at the modified organoclay electrode. The effect of some important potential interfering compounds on the stripping signal of CFX was also examined, followed by the application of the developed sensor in the determination of CFX in a pharmaceutical formulation using the standard addition method. Laponite clay mineral functionalised with thiol groups from MPTMS, exhibited more affinity towards Ciprofloxacin antibiotic, allowing its voltammetric detection in a commercial pharmaceutical sample