A new analytical method to determine trace level concentrations of pharmaceuticals in influent wastewater: A tool to monitor human use patterns

The occurrence of pharmaceuticals in influent wastewater samples (IWW) is a recurrent issue. The monitoring of their presence is not only valuable from an environmental point of view, but also as a tool to analyze patterns of human use by the so-called wastewater-based epidemiology. The development of an analytical method based on solid-phase extraction followed by liquid chromatography coupled to tandem mass spectrometry to monitor the occurrence of a group of seventeen pharmaceuticals including the most representative for various therapeutic families in IWW samples is described in this work. The samples were collected during a monitoring week in six wastewater treatment plants located in different cities and towns across Spain. The developed method provides acceptable figures of merit with apparent recoveries in IWW ranging from 42% to 139%, and low matrix effect (in general lower than +/- 30%), and method quantification limits (MQL) between 1 ng/L and 24 ng/L for all compounds, except atenolol (58 ng/L). All the studied pharmaceuticals were found in all samples with concentrations ranging from < MQL to 10,393 ng/L, being the highest concentrations for tramadol. The population normalized daily loads revealed that the use of pharmaceuticals follows, in general, a similar pattern in all cities monitored.