Graphene Oxide-Reinforced Hollow Fiber Solid-Phase Microextraction Coupled with High-Performance Liquid Chromatography for the Determination of Cephalosporins in Milk Samples

An effective and sensitive method to determine six cephalosporins (cefadroxil, cephapirin sodium, cefixime, cefuroxime sodium, cefoxitin sodium, and ceftiofur hydrochloride) in milk samples was developed using graphene oxide-reinforced hollow fiber solid-phase microextraction (GO-HF-SPME). After extraction, analytes were desorbed and analyzed using high-performance liquid chromatography-photodiode array detection (HPLC-PDA). The graphene oxide (GO) was dispersed in N,N-dimethyl formamide by ultrasonication and then immobilized into the pores of a hollow fiber (HF). Several factors of GO-HF-SPME experiment, such as the pH of the sample solution, type of organic desorption solvent, pH of the desorption solvent, extraction time, and desorption time, were optimized to achieve the highest extraction efficiency. Under the optimized extraction conditions, the method showed good linear ranges (0.05-10 mu g/mL) with correlation coefficients higher than 0.9950, low limits of determination (LODs, 0.01-0.02 mu g/mL), and good recoveries (71-108 %) at three different spiked levels. The results demonstrated that GO-HF-SPME would be a promising method for the enrichment of cephalosporins in dairy products.