Search for Conjugated Drug Metabolites in Surface Water and During Drinking Water Treatment
Pharmaceuticals for human or veterinary use are found, by various means, in aquatic environments and particularly in drinking water treatment plants. Pharmaceuticals are partially metabolized after ingestion (the percentage depends on the parent drug and falls between 1 and 99%), and consequently pharmaceuticals can be found in drinking water at concentrations ranging from the ng∙L‐1 to hundreds of ng∙L‐1. Different types of metabolites exist, among them conjugates that can represent up to 90% of the released metabolites of a pharmaceutical. The present work describes the development of an analytical method using "on-line Solid Phase Extraction" (SPE) - high performance liquid chromatography - tandem mass spectrometry (LC-MS/MS) for the determination and quantification of the active substances and their conjugates in surface waters and during drinking water treatment. These conjugates may be subjected to a deconjugation during treatment, resulting in the release of the parent pharmaceutical. Hence, it is necessary to focus on these molecules and in particular on the glucuronide conjugates. As all standards are not commercially available, a new synthetic route in an aqueous medium has been explored. Analyses are performed on the input and output of drinking water treatment plants to determine the concentrations of parent drugs and their conjugates. The obtained limits of detection and quantification are in the order of 1 to 10 ng∙L‐1.