Analysis of macrolide antibiotics in river water by solid-phase extraction and liquid chromatography–mass spectrometry

A liquid chromatography–mass spectrometry (LC–MS) method was developed for the determination of five macrolides in natural water samples, using kitasamycin as surrogate. The macrolides were extracted from water samples using Oasis HLB cartridges. Pre-concentration factors up to 250 were obtained. Separation was carried out in an end-capped silica-based C18 column and mobile phases consisting of water/acetonitrile mixtures containing ammonium acetate. Detection was performed by mass spectrometry with a single quadrupole and a triple quadrupole using an electrospray interface. The quality parameters obtained with these two approaches were compared. The detection limits of the whole process were about 1 ng l−1. The recoveries from 250 ml of water samples spiked at 25–125 ng l−1 level were in the range 85–115%, except for azithromycin levels, which were around 70%. Erythromycin-H2O, clarithromycin and azithromyzin were found, at the sub ng l−1 level, in the studied rivers.