Retrospective LC-QTOF-MS analysis searching for pharmaceutical metabolites in urban wastewater

The presence of pharmaceuticals in the environment is a matter of major concern because of their wide consumption and their potential negative effect on the water quality and living organisms. After human and/or veterinary consumption, pharmaceuticals can be excreted in unchanged form as the parent compound and/or as free or conjugated metabolites. These compounds seem not to be completely removed during wastewater treatments and might finally arrive to surface and ground waters. Consequently, both parent pharmaceuticals and metabolites are target analytes to be considered in analytical methodologies. The satisfactory sensitivity in full-acquisition mode, high-resolution, exact mass measurements and MS/MS capabilities of hybrid quadrupole time-of-flight (QTOF) mass spectrometry make of this technique a powerful analytical tool for the identification of organic contaminants. In this study, the use of QTOF-MS with the aid of specialised processing-data application managers has allowed the retrospective analysis of pharmaceuticals metabolites in urban wastewater without the need for additional injection of sample extracts. Around 160 metabolites have been investigated in wastewater samples previously analysed only for parent compounds using LC-QTOF under MS(E) mode (simultaneous recording of two acquisition functions, at low and high collision energy). The retrospective analysis was applied to search for pharmaceutical metabolites in parent-positive effluent wastewaters from the Spanish Mediterranean region. Five metabolites, such as clopidogrel carboxylic acid or N-desmethyl clarithromycin, were identified in the samples.