Application of magnetic chitosan gel combined with magnetic solid phase extraction based on deep eutectic solvent for the residue analysis of ofloxacin and enrofloxacin in milk

Abstract

A sensitive, efficient and accurate extraction method using deep eutectic solvent (DES) combined with Fe₃O₄@Chitosan gel (Fe₃O₄@CS gel), magnetic solid phase extraction (MSPE) and high performance liquid chromatography with diode array detector (HPLC-DAD) was developed for the determination of ofloxacin and enrofloxacin in milk samples. Several parameters influencing the extraction efficiency, including DES volume, extraction method, vortex time, desorption solvent type, pH, and salt concentration, were investigated. Under the optimum conditions, good linearity was obtained for fluoroquinolones in the range of 0.50-15 μg mL^-1, the LOD and LOQ values of ofloxacin were 0.0059 and 0.0198 μg mL^-1, and the LOD and LOQ values of enrofloxacin were 0.0067 and 0.0225 μg mL^-1, the extraction recoveries were in the range of 91.2-102.1 %. Intra-day and inter-day precision were below 7.8 % and 5.4 % (n = 3). The method was successfully applied to determine the ofloxacin and enrofloxacin residues in milk samples.

Keywords: Deep eutectic solvent; Fluoroquinolone antibiotics; Food substrate; Magnetic chitosan; Magnetic solid phase extraction.