Dispersive Micro-Solid Phase Extraction Combined with High-Performance Liquid Chromatography for the Determination of Three Penicillins in Milk Samples

A simple, rapid, and environmentally friendly microextraction termed COU-2-D-μ-SPE has been developed for the analysis of three penicillins (i.e., oxacillin, cloxacillin, and dicloxacillin) in milk samples. An ordered mesoporous carbon, COU-2, was synthesized and used as the sorbent in dispersive micro-solid phase for the extraction of selected penicillins prior to high-performance liquid chromatographyultraviolet detection (HPLC-UV). Several important parameters, namely, pH value, salt addition, desorption solvent, extraction time, desorption time, and amount of COU-2, were investigated and optimized. Under the optimum extraction conditions, the method showed good linearity in the range of 10–5,000 μg L (r≥0.9994), low limits of detection (2.0– 3.3 μg L), acceptable reproducibility (relative standard deviation (RSD) 6.2–8.8 %, n=9), and satisfactory relative recoveries (80.3–99.5 %) for studied penicillins in milk. The proposed COU-2-D-μ-SPE method has been successfully applied to six commercial milk samples, and the extraction of blank samples indicated that all samples were free from selected penicillin contamination.