Determination of the Environmental Fate of Drug Substances and the Matrix Effects of Complex Samples in SFC/ESI-MS

Abstract: Awareness of the potential problems caused by drug compounds in the environment has increased over the last decade, both among researchers and with the public. This thesis describes the development of analytical methods and their application to wetlands constructed for purification of wastewater from e.g. drug compounds. Different wetlands were investigated using microcosm-models, to determine their biodegradation. An enantioselective and sensitive SFC/ESI-QqQ method was developed and validated for the enantiomeric separation of atenolol, metoprolol, propranolol and metoprolol acid. It was applied measuring the enantiomeric fraction of the compounds in three different microcosm-models. The same microcosms were also used to investigate the transformation products formed in these wetlands. In this work, LC/ESI-QToF was used to identify the transformation products using standard references, the original compounds or analogs, comparing their accurate mass and product ions. One not previously observed major transformation product identified from propranolol were 1-naphthol. Several minor transformation products were also identified, showing how diverse the formation might be in wetlands.A second part compares the matrix effect of ESI/MS using SFC and reversed phase LC, utilizing general screening methods for drug compounds in plasma, horse urine and influent/effluent wastewater. These matrices are known to suffer from matrix effects when using the ESI-source, and if SFC would suffer less than LC it could be a great benefit. The matrix profiles showed that this is likely not the case: although SFC was affected by different interferences then LC. One example is the formation of clusters causing major ion suppression. This unique SFC-phenomenon was investigated further, showing that metal ions were separated and eluted at different retention times, forming clusters in the ion source between metal ions and the organic modifier and/or make-up solvent.In conclusion, the first part of this thesis describes analytical methods for determination of drug compounds in the environment, using LC and SFC, connected to both high and low resolving MS. The second part focuses on fundamental analytical chemistry, comparing the matrix effects of SFC/ESI-MS with LC/ESI-MS, and investigates the cluster phenomena observed for samples containing alkali ions and an organic modifier in the mobile phase in SFC/ESI-MS.