Rapid and sensitive analytical method for the determination of amoxicillin and related compounds in water meeting the requirements of the European union watch list.

The presence of antibiotics in the aquatic environment is becoming one of the main research focus of sci-entists and policy makers. Proof of that is the inclusion of four antibiotics, amongst which is amoxicillin, in the EU Watch List (WL) (Decision 2020/1161/EU)) of substances for water monitoring. The accurate quantification of amoxicillin in water at the sub-ppb levels required by the WL is troublesome due to its physicochemical properties. In this work, the analytical challenges related to the determination of amoxicillin, and six related penicillins (ampicillin, cloxacillin, dicloxacillin, penicillin G, penicillin V and oxacillin), have been carefully addressed, including sample treatment, sample stability, chromatographic analysis and mass spectrometric detection by triple quadrupole. Given the low recoveries obtained us -ing different solid-phase extraction cartridges, we applied the direct injection of water samples using a reversed-phase chromatographic column that allowed working with 100% aqueous mobile phase. Matrix effects were evaluated and corrected using the isotopically labelled internal standard or correction factors based on signal suppression observed in the analysis of spiked samples. The methodology developed was satisfactorily validated at 50 and 500 ng L - 1 for the seven peni-cillins studied, and it was applied to different types of water matrices, revealing the presence of ampi-cillin in one surface water sample and cloxacillin in three effluent wastewater samples. (c) 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ )

Automated summary

The accurate quantification of amoxicillin and related penicillins in water was addressed in this study using direct injection of samples and mass spectrometric detection. The methodology was validated and applied to different water matrices, detecting the presence of ampicillin and cloxacillin in specific water samples.