Detection of known and unknown naturally produced organohalogen Compounds in Marine ENvironmental Samples
Natalie Rosenfelder, Joseph R. Pawlik and John Kucklick
Anthropogenic organohalogen compounds (OHCs), such as polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs), are well known as serious environmental contaminants and their thorough determination is an important task in environmental sciences. Beside the better-known anthropogenic OHCs, over 4,500 halogenated natural products (HNPs) have been identified, with new compounds continuously being discovered especially in marine environmental and food samples. The detection of these HNPs at high concentrations (high μg/kg or even mg/kg range) in top predators of marine food webs indicate that HNPs have the ability to bioaccumulate similarly to anthropogenic OHCs. For this reason, HNPs are more and more recognized as environmental contaminants. The predominant sources of halogenated secondary metabolites are sponges, algae and cyanobacteria. In many cases, the biological source of a particular HNP is unknown. However, to understand the real impact of OHCs to the environment, all OHCs present should be known and investigated. The characterization of HNPs in environmental samples is hampered by the large diversity of compounds and the lack of authentic standards and control materials for this group of compounds. In addition, most analytical methods used during environmental monitoring have been optimized for specific target compounds thereby overlooking HNPs. Many biological samples that are potential producers of HNPs have been investigated by liquid chromatography (LC), but gas chromatography (GC) coupled to mass spectrometry (MS) using non-targeted approaches has been less frequently used. GC/MS-based techniques can be used to detect HNPs that are likely missed by LC-based determination.
For this reason, different GC/MS based non-targeted approaches for a sensitive detection of seldom analyzed HNPs are applied to different environmental samples. This not only includes the detection of HNPs in marine mammal tissue but also the analysis of sponges that are a possible source of HNPs. This comprehensive GC/MS analysis of over ten different sponge species from Florida and the Bahamas allowed for the detection of numerous OHCs. The patterns of OHCs as well as their concentrations in the sponge tissue varied among the species. Compounds that have been previously detected in marine mammal samples could be detected in the sponge tissue. A recently developed GC/electron ionization MS non-targeted screening using the selected ion monitoring (SIM) mode was and will be further used to identify several new compounds and assign structures. Future work on this project will also include the search for HNPs, detected in the different sponges, in marine mammal tissue as well as quantitative analyses of detected HNPs using different GC/MS methods.