Determination of known and unknown compounds in complex environmental matrices by high resolution mass spectrometry

Part 1. Identification of omeprazole, 5-hydroxyomeprazole and their degradation products in waste water influent and effluent Omeprazole is widely prescribed and one of the most commonly consumed drugs in the western world. It is used to treat gastric disorders and, although it forms several metabolites, is mainly excreted unchanged and as 5-hydroxyomeprazole. After excretion the waste containing the pharmaceutical and metabolites enter the waste water treatment plant and if not effectively broken down can be discharged into rivers and have a detrimental impact on the environment.

In this study the degradation products of omeprazole and 5-hydroxyomeprazole were characterised by high resolution mass spectrometry (HRMS) and subsequently semi-quantified in influent and effluent samples. The artificially generated degradation products produced singly and doubly charged dimers and rearranged monomers which provided interesting data interpretation from a mass spectrometry perspective. The method used direct injection with filtration and 100 µL injection volume. The data for omeprazole and its degradation product was inconclusive. 5-hydroxyomeprazole and its main degradant were determined in the influent but were not detected in the effluent and were well removed.

Part 2. Determination of perfluorinated alkyl substances in fertilisers by liquid chromatography - high resolution mass spectrometry Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are manmade fluorinated organic compounds with different functional groups and alkyl chain lengths. They are ubiquitous in the environment and have been added to the list of persistent organic pollutants (POPS). Unlike some of the other POPS, such as polychlorinated biphenyls, less is known about the bioavailability of these chemicals and how they travel through the environment.

There are thousands of PFASs but, perfluoroalkyl carboxylic acids (PFCA) and perfluoroalkyl sulphonic acids (PFSA) are currently of most concern. These acids vary in alkyl chain length, the most common being C4 – C14. It is the C8 homologues - perfluorooctanoic acid (PFOA) and perfluorooctane sulphonic acid (PFOS) and their derivatives which are regarded as “substances of very high concern” and are also indicative of the presence of other perfluorinated substances.

The presence of these materials in sewage and sludge can have implications for resource recovery in the circular economy, for example the recovery of phosphorus. Phosphate rock is currently mined and is one of the main components in fertiliser, it is a finite resource and was added to the EU critical raw material list in 2014. It is estimated 45% of the phosphorus required could be provided by recovery of phosphorus from municipal sewage water.
Sewage water and sludge are a rich source of many essential elements but can also contain harmful contaminants. Therefore, it is important to ensure the recovered product does not contain harmful chemicals such as PFAS.

Five commercially available fertilisers recovered by different methods were tested for perfluoroalkyl carboxylic acids and perfluoroalkyl sulphonic acids. PFAS were determined in two of the samples derived from biosolids. Both samples contained perfluorooctanoic acid and one contained perfluorooctane sulphonic acid. There are no limits for these pollutants in fertiliser however, both were below the current limit for drinking water. Although the concentrations detected were low, this work demonstrates the need to monitor recovered material for harmful contaminants to ensure a toxic free environment.