Routine analytical method for monitoring the main metabolites for a recurrent group of parabens and pharmaceuticals in wastewater and tap water.

The presence of parabens and pharmaceuticals on the aquatic environment has been widely evaluated in the last years. Nevertheless, there is scarce information about the occurrence of their metabolites and/or degradation products in spite of the fact that they can be more toxic or more concentrated than their parent compounds. One of the main drawbacks for their monitoring is the lack of simple and reliable analytical methods for their routine determination. In this work, an analytical method has been developed and validated for the simultaneous extraction and determination of the main metabolites of the pharmaceuticals diclofenac, ibuprofen, sulfamethoxazole, carbamazepine and caffeine and of the parabens methylparaben and propylparaben and their parent compounds in wastewater and tap water samples. Sample extraction was carried out by conventional solid-phase extraction with OASIS HLB cartridges. Analytical determination was carried out by liquid chromatography-tandem mass spectrometry with electrospray ionization. Average accuracy was in the range from 66 to 120% in wastewater and from 86 to 120% in tap water. Precision, expressed as relative standard deviation, was lower than 17% for all the compounds. Method quantification limits were in the range from 1.0 to 33 ng L-1 in wastewater and from 0.5 to 28 ng L-1 in tap water. The method was applied to wastewater and tap water samples. None of the target compounds was detected in tap water whereas all of them were detected in wastewater. Concentrations of the metabolites were similar or higher than those of the parent compounds. Graphical abstract.