Monitoring Sulfadiazine and Sulfamethazine Residues in Eggs Using Polymer Monolith Microextraction Coupled with High Performance Liquid Chromatography

The method for the quantitative monitoring of sulfadiazine and sulfamethazine residues in eggs was established by coupling polymer monolith microextraction (PMME) with high performance liquid chromatography and ultra-violet detection (HPLC/UV). The PMME is an effective sample preparation technique, which has been developed on the basis of in-tube solid-phase microextraction. A poly (methacrylic acid-ethylene glycol dimethacrylate) monolithic capillary column was selected as an extraction device. To obtain the optimum extraction efficiency, several parameters related to PMME, including extraction flow-rate, extraction volume, and pH value of the sample matrix, were investigated. The sample solution can be directly injected into the device for extraction after simple extraction with ethanol, dilution with phosphate buffer solution, and centrifugation. Because of the high extraction capacity of the monolith column, low detection limits (S/N=3) (8.8 ng/g for sulfamethazine and 11.2 ng/g for sulfadiazine) and quantification limits (S/N=10) (29.3 ng/g for sulfamethazine and 37.5 ng/g for sulfadiazine) were obtained. The method showed good linearity ranging from 50 to 5000 ng/g. Excellent reproducibility of the method was found by intraday and interday precisions, yielding the relative standard deviations of ≤7.6% and ≤8.2%, respectively. Recoveries for them were higher than 65%. Compared with the standard methods used in China, improved results were obtained using this method. The proposed method was proved to be simple, rapid, sensitive, and competent in monitoring sulfadiazine and sulfamethazine residues in eggs.