Fast determination of pesticides and other contaminants of emerging concern in treated wastewater using direct injection coupled to highly sensitive ultra-high performance liquid chromatography-tandem mass spectrometry

- A simple and rapid analytical method using direct sample injection has been validated for the determination of pesticides and contaminants of emerging concern in wastewater samples.
- High sensitive LC-QqLIT-MS/MS analysis has been successfully applied.
- By direct injection it was possible to detect ng L−1 levels in real water samples, up to 67 compounds could be accurately identified and quantified.
- The method can be easily implemented in wastewater studies.

It is well known that wastewater treatment plant (WWTP) effluents usually contain micropollutants such as pharmaceuticals (or their transformation products, TPs) or pesticides, which is a major issue when evaluating their possible reuse (e.g. for irrigation in agriculture). In search for an improved accuracy and simplicity, methods based on the direct injection of the sample (DI) represent a recent trend taking advantage of the increasing sensitivity of new mass spectrometry (MS) instruments. Thus, the present study shows the development and validation of a DI-based method by ultra-high-performance liquid chromatography quadrupole-linear ion trap analyser (UHPLC-QqLIT-MS/MS). The proposed method was applied to the monitoring of 115 organic microcontaminants (including pharmaceuticals, TPs and pesticides) at the ng L−1/μg L−1 level in wastewater effluents from urban WWTPs. Sample pre-treatment was reduced to acetonitrile addition and filtration of the mixture previous to LC-MS analysis. Total analysis time was <15 min. A subsequent validation protocol was carried out in treated WW (TWW), following indications of SANTE and Eurachem Guidelines. Linearity and matrix effect were evaluated in the range of 10-1000 ng L−1. 70% of the analytes showed a moderate matrix effect (≤25%). Trueness (expressed as recovery) and precision (calculated as relative standard deviation, RSD) were evaluated at four concentration levels (20, 50, 500 and 1000 ng L−1) in TWW samples. The LODs ranged from 1 to 357 ng L−1 and the LOQs from 10 to 500 ng L−1. 92% of the compounds showed limits of quantification ≤100 ng L−1. In most cases, mean recoveries were in the range 70-120%, and RSD values were ≤20%. The validated method was successfully applied to the analysis of 10 TWW samples, demonstrating the occurrence of 67 target compounds at concentration levels from 26705 ng L−1 (4-aminoantipyrine) to 10 ng L−1 (tebuconazole and bezafibrate).