Residues of β-lactam antibiotics in bovine milk: confirmatory analysis by liquid chromatography tandem mass spectrometry after microbial assay screening

Abstract

A procedure for the simultaneous determination of the residues of seven beta-lactam antibiotics (penicillin G, ampicillin, oxacillin, amoxicillin, dicloxacillin, cephalexin, cephapirin) in bovine raw milk using tandem liquid chromatography mass spectrometry (LC-MS/MS) is described. The antibiotics were extracted by an acetic acid solution after centrifugation and filtration. The beta-lactams were separated using reversed-phase liquid chromatography. A triple quadrupole mass spectrometer was used in positive-ion mode as a detector via a Turbo Ionspray interface for electrospray ionization (ESI). The limits of detection and quantitation of the method were below the legal tolerances, except for ampicillin. The method was used to confirm 53 samples found positive by a microbial method (Delvotest SP) at the Istituto Zooprofilattico Sperimentale per la Lombardia e l'Emilia Romagna of Brescia during 2001. Penicillin G was found in 26 samples at concentrations ranging from less than 4 to 6240+/-550 microg x l(-1). Amoxicillin was found in three samples at concentrations ranging from 8.5+/-0.1 to 53.7+/-2.3 microg x l(-1). Cephapirin was found in two samples at 5.7+/-0.1 and 6.4+/-0.3 microg x l(-1).

LC/MS/MS measurement of penicillin G in bovine plasma, urine, and biopsy samples taken from kidneys of standing animals

“…A simple extraction method was reported for seven betalactams in milk, including penicillin G [8]. The extraction consisted only of acidification and centrifugation followed by detection in positive ion mode and calibration by external standard.…”

Comparative study of the LC–MS/MS and UPLC–MS/MS for the multi-residue analysis of quinolones, penicillins and cephalosporins in cow milk, and validation according to the regulation 2002/657/EC

“…Although it is also possible to find multi-class published methods [8,[16][17][18][19][20][21][22][23][24], some are not quantitative or do not determine the quality parameters necessary for validating the method according to European legislation [25]. Quinolones and penicillins regulated except AMOX and PENG, have been previously analysed in milk by ultra-high-performance liquid chromatography-time of flight-mass spectrometry (UPLC-TOF-MS) [19], while other authors [8] simultaneously measured the complete series of quinolones, penicillins and cephalosporins regulated by the EU in raw milk samples using UPLC with TOF to screen 150 veterinary drugs.…”

“…Liquid chromatography (LC) coupled to several detectors have been used to analyse samples, although mass spectrometry (MS) detection has recently gained popularity since its selectivity and sensitivity enables the determination of drug residues in complex matrices [16,17,21,22,23]. An optimal method for routine analysis should allow rapid detection of a large number of compounds.…”

Termoestabilidad de sustancias antimicrobianas en la leche.

“…Sin embargo estas técnicas tienen algunas limitaciones como la baja sensibilidad y selectividad que pueden presentar en ocasiones, además de requerir de una costosa fase previa de purificación de la muestra para eliminar las interferencias de la matriz (Sorensen et al, 1997;Taguchi et al, 1999;Ghidini et al, 2003).…”

“…Los porcentajes de recuperación también son adecuados con valores dentro del intervalo (70-110%) recomendado por la Decisión 2002/657/CEE, excepto en dos de los estudios (Daeseleire et al, 2000;Ghidini et al, 2003), que presentan recuperaciones más bajas entre el 57-88% y 28-82% respectivamente.…”