Simultaneous determination of polyether ionophores, macrolides and lincosamides in hen eggs by liquid chromatography-electrospray ionization tandem mass spectrometry using a simple solvent extraction.

A liquid chromatography-electrospray ionization tandem mass spectrometric (LC-ESI-MS/MS) method was developed and validated for the determination of residues of 6 polyether ionophores (lasalocid, maduramicin, monensin, narasin, salinomycin, semduramicin), 3 macrolides (erythromycin, tylosin, clarithromycin) and 1 lincosamide (lincomycin) in eggs. Nigericin was used as qualitative internal standard. Samples were deproteinizated/extracted with acetonitrile without pH adjustments. Aliquots of the extracts were evaporated and reconstituted for injection in the instrument operated in positive multiple reaction monitoring (MRM) mode. The stability of the antibiotics and the intensity of the formed ions were considered in order to select a suitable solvent for the reconstitution of the obtained dry extracts. No clean-up steps were required and matrix effects were controlled by sample dilution, selection of appropriate chromatographic conditions and reduced injection volume. Good within-laboratory reproducibility was obtained, with relative standard deviations (RSD(R)) from 4.0 (semduramicin at 5 µgkg(-1)) to 18.6 (erythromycin at 25 µgkg(-1)) for the ionophores and macrolides. Lincomycin showed the least precise results, with a maximum RSD(R) of 20.2% at 75 µgkg(-1)). Satisfactory decision limits (CCα) and detection capabilities (CCß) were also attained. Method limits of detection (LODs) from 0.04 (salinomycin) to 1.6 µgkg(-1) (lincomycin) were achieved. Method limits of quantification (LOQs) were from 0.14 to 5.3 µgkg(-1) for the same drugs, respectively. All the LOQs, except that obtained for maduramicin were remarkably below the lowest validation level. The proposed method is suitable for routine application in commercial egg samples.

Pilot survey of hen eggs consumed in the metropolitan area of Rio de Janeiro, Brazil, for polyether ionophores, macrolides and lincosamides residues.

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method, which has recently been developed and validated, was used for the identification and quantification of polyether ionophore, macrolide and lincosamide residues in commercial eggs sold in the metropolitan area of Rio de Janeiro, Brazil. The method was applied to 100 samples and the results showed a high incidence of polyether ionophore residues (25%). Salinomycin was detected in 21% of samples, but only two non-compliant results (5.3 and 53 µg kg(-1)) were found if maximum limits (tolerances) established by European Union were adopted in Brazil and if a method decision limit (CCα) of 3.4 µg kg(-1) was considered. In 8% of analyzed samples, more than one studied coccidiostat was found. The lincosamide, lincomycin, and the macrolide, tylosin, were detected at trace levels in 4 and 1% of the samples, respectively. Lasalocid, clarithromycin and erythromycin were not found.

Pilot survey of commercial pasteurized milk consumed in the metropolitan area of Rio de Janeiro, Brazil, for tetracyclines residues, including the 4-epimers of oxytetracycline, tetracycline and chlortetracycline.

This pilot survey aimed to assess the occurrence of tetracyclines and the 4-epimers of oxytetracycline, tetracycline and chlortetracycline in commercial pasteurized milks sold in the metropolitan area of Rio de Janeiro, Brazil, between October 2009 and March 2010. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method, developed and validated in our laboratory, was used. All 100 analyzed samples were compliant, but 14 contained oxytetracycline in concentrations ranging from the method limit of detection (3.7 µg l(-1)) to the method limit of quantification (12.2 µg l(-1)). One sample contained oxytetracycline and tetracycline simultaneously (at a concentration slightly higher than method limit of quantification, 7.0 µg l(-1)). The presence of 4-epioxytetracycline and 4-epitetracycline in contaminated samples with the parent drugs could not be confirmed as traces were detected only in the quantification MRM transition. No other tetracyclines were detected.