Determination of aminoglycoside and macrolide antibiotics in meat by pressurized liquid extraction and LC-ESI-MS.

A simple method for the simultaneous determination of dihydrostreptomycin, spectinomycin, spiramycin, streptomycin, tilmicosin, and tylosin in meat has been developed using pressurized liquid extraction and LC-triple quadrupole MS (LC-ESI-MS/MS). The pressurized liquid extraction operational parameters were optimized and no protein precipitating and fat removing steps were required. A gradient HPLC separation was developed with ion-pair mobile phases consisting of aqueous 1 mM heptafluorobutyric acid water and methanol. Protonated molecules were used as precursor ions for CID. Data acquisition under MS/MS was achieved by applying multiple reaction monitoring of three fragment ion transitions to provide a high degree of sensitivity and specificity. Dirithromycin and sisomycin were selected as internal standards. A validation study was conducted for these antibiotics in poultry meat samples. All selected compounds could be detected (monitoring ions by multiple reaction monitoring) in meat samples at amounts below the regulatory level of concern. Using the internal standards, pressurized liquid extraction recovery rates were from 70 to 96% (RSD 12-25%). LC-ESI-MS/MS method detection limits of the selected antibiotics were 1-6 microg/kg. Good method reproducibility was found by intra- and inter-day precisions at maximum residue level, yielding the RSDs less than 15 and 16%, respectively.