| A simple, sensitive and reliable method was developed for simultaneous determination of residues of ten prohibited drugs including zeranols(ZALs), pentachlorophenol(PCP), sodium nitrophenolate(PNP), diethylstilbestrol(DES), chloramphenicol(CAP) in swine urine using high-performance liquid chromatography-tandem mass spectrometry(LC-MS/MS). Acetonitrile and 5 mmol/L ammonium acetate were chosen as mobile phases. Target compounds were separated well on Zorbax SB-C18(150 mm × 2.1 mm i.d., 3.5 ?m) by following the optimized gradient elution program and determined by liquid chromatography-tandem mass spectrometry in negative electrospray ionization mode.Swine urine samples were lyophilized to dryness in vacuum freeze-drying machine, and then the residues were dissolved with 50% acetonitrile in water for LC-MS/MS analysis. Analytes were quantified using the matrix-matched external calibration curves, which were made by diluting mixed stock solutions with blank swine urine extracts. The results indicated that the calibration curves of ten analytes were good linearity in their corresponding concentration ranges, with correlation coefficients(r2) more than 0.99. Blank swine urine samples spiked with ten drugs at 5, 10 and 20 mg/L, the average recoveries of target compounds were between 80.7% and 107.7%, with coefficient variances of 0.5% ~ 10.4%. The limits of detection(LODs) and limits of quantification(LOQs) were in range of 0.1 to 2.0 mg/L and 0.2 to 5.0 mg/L, respectively.The Qu ECh ERS sample preparation approach was applied in this study. Swine urine samples were extracted with acetonitrile, followed by liquid-liquid partition with the addition of anhydrous magnesium sulfate and sodium chloride. The upper organic layer(5 m L) was cleaned up by PSA. The supernatant was dried under a stream of nitrogen, and the residues were re-dissolved in 1 m L of 50% acetonitrile in water, and finally target analytes were analyzed by LC-MS/MS. Analytes were quantified using the matrix-matched external calibration curves. The results showed that the calibration curves of ten drugs were good linear with the correlation coefficients more than 0.99. The LODs and LOQs were in range of 0.1 to 1.0 mg/L and 0.2 to 2.0 mg/L, respectively. Average recoveries for all target compounds spiked at 5, 10 and 20 mg/L were in the range of 73.5% to 103.3% with the coefficient variances less than 15%.Lyophilization approach reduced the use of organic solvents and obtained better recoveries. Qu ECh ERS method utilized adsorption dispersant of PSA to purify the extracts, and reduce matrix effect during analysis. The two sample preparation approaches have the advantages of simple operation process and a small amount of analytes loss. The LC-MS/MS method based on the two procedures are satisfied for the demand of drugs residue analysis and can be applied to the residues analysis of ten prohibited drugs in swine urine. |
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