Determination of azithromycin residue in pork using a molecularly imprinted monolithic microcolumn coupled to liquid chromatography with tandem mass spectrometry.

Using spiramycin as a dummy template, a molecularly imprinted polymer monolithic micro-column with high selection to azithromycin was prepared in a micropipette tip. The imprinting factor of the monolithic micro-column prepared was approximately 2.67 and the morphological structure of the polymers was characterized by scanning electron microscopy. A simple, sensitive, and reproducible method based on the imprinted monolithic micro-column coupled to liquid chromatography with tandem mass spectrometry was developed for determining the residues of azithromycin in pork. Pork samples were extracted with acetonitrile, cleaned up under the optimal monolithic micro-column conditions, and analyzed using liquid chromatography with tandem mass spectrometry in the multiple reaction monitoring mode. The assay exhibited a linear dynamic range of 0.50-50 µg/L with the correlation coefficient (r(2) ) above 0.99. In the three spiking levels of 0.50, 1.0, and 10 µg/kg, the average recoveries of azithromycin from pork samples were between 85.8 and 96.5% with a relative standard deviation below 10%. The limit of detection and limit of quantitation were 0.03 and 0.1 µg/kg, respectively.

Determination of 26 veterinary antibiotics residues in water matrices by lyophilization in combination with LC-MS/MS.

A sensitive, simple and reliable multi-residue method was developed for the determination of 26 widely used veterinary antibiotics including 6 macrolides, 2 pleuromutilins, 4 tetracyclines, 2 lincosamides, 6 fluoroquinolones and 6 sulfonamides in different water matrices using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Water samples were lyophilized to dryness. Target compounds were separated on Zorbax SB-Aq column (150mm×2.1mm i.d., 3.5µm) and determined by LC-MS/MS operating in positive electrospray ionization mode. Spiked at concentration levels of 0.02, 0.4 and 4µgL(-1), recoveries of all target compounds were over 70% except sulfaquinoxaline (59.0% at 0.02µgL(-1)) with relative standard deviations below 20%. Limits of detection (LOD) and limits of quantification (LOQ) of 26 drugs ranged from 0.1 to 6.5ngL(-1) and from 0.3 to 19ngL(-1), respectively. The developed method was successfully applied to the analysis of 26 antibiotics residues in fish pond water, groundwater, biogas digester water, and lagoon wastewater samples collected from local pig farms.

Simultaneous determination of major type-B trichothecenes and the de-epoxy metabolite of deoxynivalenol in chicken tissues by HPLC-MS/MS.

In this study, a specific and sensitive LC-MS/MS method for the simultaneous analysis of type-B trichothecenes (deoxynivalenol, 3-acetyldeoxynivalenol, and 15-acetyldeoxynivalenol) and the de-epoxy metabolite of deoxynivalenol (de-epoxy-deoxynivalenol) in chicken muscle, liver, kidney, and fat tissues was developed and validated. The method involved an extraction step using ethyl acetate, followed by the evaporation of the supernatant, which was further purified by an Oasis HLB SPE cartridge (Waters, Milford, MA, USA). Chromatographic separation was performed on a C18 column by detection with MS in multiple-reaction monitoring mode and using a gradient elution program with 0.1% formic acid in water and methanol. The correlation coefficients (r) for each calibration curve were >0.99 within the experimental concentration range. The extraction recoveries ranged from 73.7 to 106.4%, with intraday and interday RSD < 11.6% at three levels of concentrations of 2, 10, and 100 µg/kg. The decision limits and the detection capabilities of the analytes in the chicken tissues ranged from 0.16 to 0.92 and 0.68 to 2.07 µg/kg, respectively. The results demonstrated the applicability of this sensitive procedure to the determination of trichothecenes in chicken tissue samples.