Simultaneous determination of ß-lactams antibiotics in wastewater samples by solid phase extraction followed by high-performance liquid chromatography and tandem mass spectrometry

In the present work, an analytical method for the simultaneous determination of six β-lactam antibiotics (ampicillin, amoxicillin, penicillin V, penicillin G, oxacillin and cephalexin) is proposed for the determination of these compounds in wastewater treatment plants (WWPTs) influents and effluents. The β-lactams were extracted from water samples using Oasis HLB cartridges with preconcentration factors up to 250. The compounds have been separated using a Zorbax SB-C18 (50 mm x 2.1 mm, 1.8 µm) HPLC column and gradient elution with mobile phase consisting of aqueous formic acid and acetonitrile. Detection was performed by mass spectrometry with a triple quadrupole using an electrospray interface. The linear range of the standard curve was from 1.0 to 600 ngmL-1 (R2 >0.99). Average recoveries of β-lactams in fortified samples were generally above 74% with relative standard deviations (RSDs) lower than 11 %. Limits of detection were in the range 20-150 ngL-1 and 8-60 ngL-1 for influent and effluent wastewater samples, respectively. The described method was applied to the determination of the β-lactams in wastewater samples from a municipal WWTP.