Rapid determination of 88 veterinary drug residues in milk using automated TurborFlow online clean-up mode coupled to liquid chromatography-tandem mass spectrometry.

A novel method based on TurborFlow online solid phase extraction (SPE) combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been established for simultaneous screening and confirmation of 88 wide-range veterinary drugs belonging to eight families (20 sulfonamides, 7 macrolides, 15 quinolones, 8 penicillins, 13 benzimidazoles, 4 tetracyclines, 2 sedatives, and 19 hormones) in milk. The preparation method consists of sample dilution and ultrasonic extraction, followed by an automated turbulent flow cyclone chromatography sample clean-up system. The detection was achieved in selected reaction monitoring mode (SRM). The total run time was within 39 min, including automated extraction, analytical chromatography and re-equilibration of the turboflow system. The optimization of different experimental parameters including extraction, purification, separation, and detection were evaluated separately in this study. The developed method was validated and good performing characteristics were obtained. The linear regression coefficients (R(2)) of matrix-match calibration standard curves established for quantification were higher than 0.9930. The limits of detection (LOD) were in the range of 0.2-2.0 µg/kg given by signal-noise ratio ≥3 (S/N) and the limits of quantification (LOQ, S/N≥10) ranged between 0.5 µg/kg and 10 µg/kg. Average recoveries of spiked target compounds with different levels were between 63.1% and 117.4%, with percentage relative standard deviations (RSD) in the range of 3.3-17.6%. The results indicated that the developed method has great potential for the routine laboratory analysis of large numbers of samples on measuring different classes of compounds. In comparison to traditional procedures, the automated sample clean-up ensures rapid, effective, sensitive analyses of veterinary drugs in milk.

Simultaneous determination of 13 aminoglycoside residues in foods of animal origin by liquid chromatography-electrospray ionization tandem mass spectrometry with two consecutive solid-phase extraction steps.

A confirmatory and quantitative method based on liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) has been developed for simultaneous determination of 13 aminoglycoside antibiotics in various samples. The aminoglycoside analytes were released and extracted from different matrices with 5% trichloroacetic acid. The influence of pH values on the solid-phase exaction (SPE) procedure has been studied. Due to different pK(a) values of the compounds, seven aminoglycosides (AGs) were quantitatively retained on Oasis HLB cartridges at pH<1 and then six aminoglycosides were retained at pH 8.5. Thus, the combination of two HLB SPE cartridges with different pH values was involved to simultaneously purify 13 aminoglycosides. The proposed two SPE steps produced high recovery yields for every aminoglycoside in five different matrices. The LC-MS/MS method was validated according to the European Union Commission directive 2002/657/EC. Good performance characteristics were obtained for recovery, precision, calibration curve, stability, specificity, decision limits (CCalpha) and detection capabilities (CCbeta) in different matrices. The optimized procedure has been successfully applied to real samples in our laboratories (n> or =200) for 1 year. It demonstrated that the new method was robust and useful for identification and quantification of 13 aminoglycosides residues in foods of animal origin.