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

• Published in: Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment Chemistry, analysis, control, exposure & risk assessment, 2003, Vol.20 (6), p.528-534
• Main Authors: Ghidini, S, Zanardi, E, Varisco, G, Chizzolini, R
• Format: Article
• Language: English
• Subjects: acetic acid; amoxicillin; cattle; centrifugation; cephalexin; cephapirin; detection limit; dicloxacillin; filtration; food additives; ionization; milk; monitoring; raw milk; reversed-phase liquid chromatography; screening; spectrometers; tandem mass spectrometry
• ISSN: 1944-0049; 1944-0057

A procedure for the simultaneous determination of the residues of seven β-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 β-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 μg l−1. Amoxicillin was found in three samples at concentrations ranging from 8.5 ± 0.1 to 53.7 ± 2.3 μg l−1. Cephapirin was found in two samples at 5.7 ± 0.1 and 6.4 ± 0.3 μg l−1.