An online SPE LC-MS/MS method for the analysis of antibiotics in environmental water

A fast and simple method for the analysis of 17 commonly used antibiotics in Finland in water samples was developed. The method combines online solid phase extraction using a reusable online trapping column combined with analytical separation on a C-18 analytical column and detection by a triple quadrupole mass spectrometer. The method was fully validated for detection and quantification limits as well as linearity, repeatability, and matrix effects. The method gave an excellent linear response (r (2) > 0.99) and detection limits for all compounds (1-10 ng(-1)), except for tetracycline (20 ng l(-1)) and roxithromycin (50 ng l(-1)). The repeatability was evaluated at two concentrations, and the values at 5 ng l(-1) ranged from 5 to 39% and at 100 ng l(-1) ranged from 3 to 19%. To test the method on real samples at low environmental concentrations, water samples collected from a river receiving discharges from two wastewater treatment plants were analyzed as well as samples from a pristine river. Seven antibiotics as well as carbamazepine were detected in the samples. The concentration of the compounds ranged from 5 to 81 ng l(-1).