ACA-25-200 Rev Clean version Automatised online SPE-LC-MS/MS method for the enantioselective determination of chiral β-blockers and antidepressants in wastewater

Background

Pharmacologically active compounds are emerging pollutants of greatest concern because of their continuous release to the aquatic media and potential effects on non-target organisms. Nevertheless, in spite that many pharmaceuticals are chiral compounds which enantiomers may have different environmental behaviour and effects, their enantiomeric determination has been scarcely evaluated. This fact can be explained by the great challenge to overcome when developing an analytical method for the individual determination of compounds with the same physical-chemical properties, as it is the case of enantiomers.

Results

In this work, an automatised method based on online solid phase extraction (SPE) coupled to liquid chromatography-tandem mass spectrometry (LC-MS/MS) was optimised and validated for the enantiomeric determination of highly prescribed (β-blockers (atenolol, metoprolol and propranolol), antidepressants (citalopram, fluoxetine, sertraline, duloxetine and venlafaxine) and two of their metabolites in influent and effluent wastewater. Three of them (metoprolol, citalopram and venlafaxine) have been recently included in the European Union Directive 2024/3019 as substances that should be measured in wastewater. Method quantification limits in the range from 0.1 to 50 ng L^-1 for most compounds. Accuracy ranged from 60.8 to 114 % and precision, expressed as relative standard deviation, was lower than 12.5 % for all the compounds. Method application to wastewater samples revealed the presence of the target compounds at concentrations between 1.06 and 1213 ng L^-1 and a preferential degradation of some enantiomers: S-(-)-atenolol, metoprolol-E1, venlafaxine-E1 and O-desmethylvenlafaxine-E1.

Significance and novelty

This method is the first one for online SPE-chiral-LC-MS/MS determination of two therapeutic groups of chiral pharmaceuticals in wastewater. The method allows their automatised enantiomeric determination, including sample treatment, SPE column wash and conditioning, and LC-MS/MS determination, in 40 min with enantioresolution from 0.51 to 1.24. The online SPE method developed provides a fast way to obtain information about chiral compounds in wastewater reducing labour intensity, exposure to organic solvents, analyte loss and plastic waste