Rapid and sensitive multi-residue method for the determination of 235 organic microcontaminants in environmental water samples using direct injection coupled to ultra-high performance liquid chromatography-tandem mass spectrometry.

A rapid and sensitive direct injection (DI) method is proposed for the monitoring of 235 organic microcontaminants (OMCs), including those listed in the recently adopted Directive (EU) 2024/3019 and the 5th Watch List, in treated wastewater (WW) and drinking water (DW), using ultra-high performance liquid chromatography coupled to mass spectrometry (UHPLC-MS/MS). No pre-concentration stages were applied thanks to the advantages of a state-of-the-art triple quadrupole (QqQ) instrument, minimizing sample handling up to a filtration step. The polarity switching mode was used for the analysis of the selected OMCs from different classes (pharmaceuticals, antibiotics, pesticides, artificial sweeteners, metabolites and transformation products) in a single injection. LC-MS/MS parameters, including injection volume, capillary voltage, source temperature and mobile phase composition, were optimized. The proposed method was successfully validated in urban WW effluents and DW at 10, 100 and 1000 ng/L. Trueness (average expressed as relative recovery) was in the range of 72-127% and inter and intra-day precision (expressed as relative standard deviation, RSD) was always ≤21%. Limits of quantification (LOQs) were in the range of 0.5-500 ng/L for WW and 0.1-100 ng/L for DW. The suitability of the method was demonstrated by analysing 28 WW samples from 2 wastewater treatment plants (WWTPs) and 10 DW samples from different locations. 150 OMCs with sum of concentrations ranging from 17.7 to 239.9 μg/L were detected in WW samples and 0.1 to 1.0 μg/L in DW samples, respectively. All of 12 compounds included in EU Directive 2024/3019 were detected in WW samples with individual concentrations ranging from 46 (metoprolol) to 6667 ng/L (hydrochlorothiazide).