Environmentally friendly analytical method to assess enantioselective behaviour of pharmaceuticals and pesticides in river waters

Abstract

Reported herein is the first enantioselective method for simultaneous separation of chiral pharmaceuticals and pesticides using ultra-high-performance liquid chromatography-tandem mass spectrometry. Separation was achieved using a ChiralPak IG-U® column (amylose tris(3-chloro-5-methylphenylcarbamate) stationary phase) and ethanol as a ‘green’ mobile phase organic modifier. Minimum enantiomer resolutions ranged from 0.5 to 6.9 for 28 pharmaceuticals, herbicides, fungicides and insecticides. The total run time was 26 min and is considerably shorter than other multi-residue enantioselective methods for similar numbers of pesticides, and is the first to facilitate simultaneous pharmaceutical separation. Direct injection of river water samples enabled omission of acetonitrile and methanol from the sample treatment step (and the whole methodology). This approach was considerably faster than enantioselective methodologies that rely on solid phase extraction and avoids the need for large sample volumes for analysis. The suitability of this approach was demonstrated by the method's sensitivity with enantiomer method quantitation limits in the range 0.005–0.6 μg L-1. The new method was applied to river water microcosms to investigate enantiospecific transformation of racemic pharmaceuticals and pesticides. The pharmaceutical omeprazole, fungicide prothioconazole and insecticide profenofos were all subject to enantioselective transformation under biotic conditions, represented by a change in enantiomeric fraction of ≥0.1 units. Individual enantiomer microcosms revealed chiral inversion of R-omeprazole to S-omeprazole in the environment for the first time. In conclusion, this method offers comparatively fast enantioselective analysis for a high number of pharmaceuticals and pesticides in river water, and is achieved in an environmentally friendlier way than previously reported liquid chromatography methods.