Study of stereoselective degradation of pharmaceuticals and illicit drugs in wastewater and receiving water bodies

Pharmaceuticals and illicit drugs have been detected within wastewater and environmental matrices for several years now. However, to date, little emphasis has been placed upon the enantiomeric profile of those drugs. This may however lead to erroneous estimations of toxicity as the enantiomeric profile of chiral drugs plays an important role in both their pharmacodynamic and pharmacokinetic properties. Chiral analysis and enantioselective toxicology is well established within drug design, however ecotoxicology and analysis of chiral drugs in the environment is still usually assessed using whole parent drugs.
This talk will comprise two related topics, firstly the development of a novel method to analyse chiral drugs from both liquid and solid complex matrices and secondly the study of the mechanisms involved in the transformation of chiral drugs within the environment.
Enantiomeric profiling of chiral drugs within liquid environmental matrices has been demonstrated previously. However we have now also developed and validated a novel method which allows for the enantiomeric profiling of 25 chiral pharmaceuticals and illicit drugs from solid matrices (including illicit amphetamine-like drugs, beta blockers, anti-depressants, an anti-arrhythmic, an analgesic and a bronchodilator). This will allow for a more accurate measurement of environmental concentrations of drugs using chiral methodologies, particularly those which preferentially adsorb to solid material, as well as the study of enantiomeric profiles from solid matrices. Using this novel methodology in combination with established methods for liquid matrices we can present concentrations and enantiomeric fractions from a much wider variety of matrices than has been previously presented giving a more detailed picture of where and how chiral drugs transform within the environment. Results from wastewater and receiving waters will be presented. In brief, the methodology includes freeze drying, microwave assisted extraction followed by Solid Phase Extraction (SPE) and finally chiral Liquid Chromatography-Tandem Mass Spectrometry (chiral LC-MS/MS).
In order to study the mechanisms involved in the transformation and degradation of pharmaceuticals and illicit chiral drugs within receiving waters, microcosms (90% river water, 10% wastewater effluent) were set up to study biological (anoxic and aerobic, in the presence and absence of light) and abiotic factors (oxygenated, anoxic, light and dark processes). These were spiked with a mixture of 25 chiral drugs and samples taken every day for 2 weeks. The samples were then analysed in order to compare the rate of degradation as well as any change in the enantiomeric profile of the parent drug as a result of degradation under differing conditions.