Simultaneous determination of eight antibiotics from distinct classes in surface and wastewater samples by solid-phase extraction and high-performance liquid chromatography-electrospray ionisation mass spectrometry

A reliable multiclass method has been developed and validated for the determination of eight antibiotics from distinct classes (sulfonamides, macrolides, fluoroquinolones, tetracyclines, cephalosporins and dihydrofolate reductase inhibitors) in wastewater - influent and effluent and surface water from Porto Alegre, Brazil. The pre-concentration and clean-up was conducted with a simple and fast protocol using solid-phase extraction allowing a 100-fold concentration factor. The proposed method was validated by using spiked blank wastewater samples in terms of linearity, repeatability, reproducibility, recovery, matrix effects and limits of detection and quantification. Recovery was obtained in the range of 66-149%. Method limit of quantification ranged between 1.6 and 61.7 ng L-1. Samples (n = 16) were taken from January to August 2011 in one wastewater treatment plant, which uses conventional biological treatment. Sulfamethoxazole and trimethoprim show higher concentration, ranging from >10 to <6500 ng L-1, whereas erythromycin presented the lower amount. Differences between influent and effluent profiles were discussed. Surface water samples (n = 8) were collected in Arroio Diluvio, in four sampling points, in February 2012. From the eight antibiotics analysed, five were detected: sulfamethoxazole, trimethoprim, azythromicyn, ciprofloxacin and norfloxacin, in a concentration range of 376-572 ng L-1, 27-94 ng L-1, 24-40 ng L-1, 16-66ng L-1 and 30-54 ng L-1, respectively.