Group-type fractionation of environmental PAC metabolites

Frequently, newspapers report about forest fires, incomplete biomass burns or hazardous anthropogenic emissions by engine exhaust or incinerator in households and the accompanied emergence of fine dust and smog. Polycyclic aromatic compounds (PACs) are formed by mentioned incidents but are also found in fossil fuel or tar deposits after leaking of fuel storage tanks, oil spills etc. Consequently, PACs are ubiquitous in the soil environment and are accumulated in higher concentrations in the topsoil of industrials and urban areas. Since their high toxicity, standards and regulations for exposure have been established by governmental bodies 16 PAHs have to be monitored as representatives for the carcinogenic and mutagenic compounds. It has recently been recognized that significant amounts of other more polar PACs exist in our environment. Bacterial or fungal degradation of PACs result into hundreds of PAC metabolites which are toxic and highly leachable into water but they are seldom included in risk-assessment programs due to lack of knowledge and regulations. Thus, there is a high demand of detailed analysis of these newly discovered, NSO-PACs but the high sample complexity and low analyte concentrations is a challenge for standard analytical platforms. In collaboration with Prof. Christensen, an analytical scientist at the University of Copenhagen, this project investigates new analytical approaches which combine modern chemical fingerprint analysis with a prior group-type fractionation and thus a reduction of sample complexity. By intelligent development of so-called solid phase extraction (SPE) procedures we are able to selectively bind and release polar, acidic and water-soluble compounds which leads to separated and enriched fractions. The fractions of reduced complexity are then separated into individual components by state-of-the- art chromatographic instrumentation and analyzed by mass spectrometry resulting into detailed knowledge of structure, and mass size. Among others, self-made materials are applied for SPE optimization which already demonstrated potential efficiency for the selective isolation of acidic water-soluble compounds such as health-promoting phenolic acids in complex plant extracts or analgesics in biological and environmental samples. Additionally, a new material for the fractionation of oxygen- and nitrogen containing PACs will be synthesized and performed in a separation column which can directly be connected to the chromatography-mass spectrometry instrumentation. This material includes immobilized rare earth metal showing high interaction with oxygen- and nitrogen rich components. Their binding and releasing mechanism has already been theoretically and experimentally proven previously.

Environmental pollution caused by industrial activity is of worldwide concern. For instance, polycyclic aromatic compounds (PACs), formed during gasification or by incomplete combustion of organic matter (pyrogenic sources), are accumulated in the topsoil at industrial and urban sites. With respect to environmental pollution, transformation of petrogenic compounds including PACs plays a key role, but little attention has been given to emerging potentially toxic transformation products. Current analytical methods are still challenged by the low concentration levels of transformed compounds and very high sample complexity. Therefore, sample preparation is required to extract, pre-concentrate and fractionate chemical subgroups to increase the selectivity and the detection limits for compound identification and quantitative analysis. In this project, we focused on isolation and fractionation strategies by solid phase extraction (SPE) for a broad range of environmentally related organic acids which are primary degradation products. Three SPE materials possessing various characteristics were compared with respect to the extraction and fractionation efficiency. Quantitative analysis was obtained using an optimized and validated liquid-chromatography mass spectrometry method (LC-MS). Furthermore, fractionation of carboxylic acids into aliphatic and aromatic acids by an intelligent SPE was achieved. With that knowledge we have then implemented an analytical platform to identify and quantify known environmental acids but were also able to tentatively characterize unknown, emerging polar degradation products deriving from polluted sites. Apart from liquid chromatography, gas chromatography (GC) was applied to additionally identify polar non-acidic compounds. We applied this newly developed setup for three cases to verify the method but also to investigate upcoming environmentally related concerns. Case I comprised the investigation of degradation products from a mixture of PACs under simulated sunlight which normally occur in every oil-spill scenario. In case study II the SPE recovery of acids spiked into diesel- spilled harbor water was determined to prove the method applicability for a highly complex sample. Finally, case III investigated two samples from a soil remediation project in Greenland in which drained water from a PAC-polluted site is collected in two basins. This project has originally been financed by the Danish Ministry of Defense and was established in 2011. The main goal was to screen for potential acidic PAC transformation products in the basins using a so-called non-targeted approach.