Exploiting the intrinsic electro-activity of β-Lactams antibiotics: an electrochemical strategy for Cefquinome detection in raw milk samples.

Abstract

The detection of beta-lactams antibiotic residues in milk is a fundamental issue for diary companies, consumers and authorities. On-site and rapid analytical tools as sensors are required to assure milk safety and quality. The electroactive behavior of certain antibiotic can be exploited for their detection, as for cefquinome (CFQ) or nafcillin (NAF). In this project, molecularly imprinted polymers (MIPs) electropolymerized on MCWNT modified screen-printed graphite electrodes (MWCNTs-G-SPEs) is proposed for the electrochemical detection of CFQ in raw milk. The electropolymerization was performed directly on the MWCNTs-GSPEs in sulfuric acid solution by cyclic voltammetry (CV), using para-amino benzoic acid (4-ABA) as monomer and CFQ as template. All the steps have been carefully optimized: the best electrode modification , the electropolymerization and MIP analytical protocol. To evaluate the electrochemical behavior of the final modification, the polymeric films were characterized in the presence of a redox probe by CV and electrochemical impedance spectroscopy, as well as by Raman spectroscopy and scanning electron microscopy. Under the up to now selected conditions, it was not possible to reach the maximum residue limit (MRL) and further optimization of the proposed protocol is required. Nevertheless, a selectivity test respect to interfering compounds confirmed the high selectivity of the electrochemical detection strategy proposed. To minimize milk matrix effects a simple pre-treatment step was designed allowing the final semi-quantitative determination of CFQ in real milk samples. The present work is considered as a starting point for the development of an on-site multi-target analytical tool.