Abstract:

Quantifying PAHs in seafood by developing an imaging approach with matrix-assisted laser desorption ionization (MALDI) mass spectrometry. Approximately one-third of oil from oil spills such as the Deepwater Horizon spill consists of polycyclic aromatic hydrocarbons (PAHs), which are soluble in water, toxic, and can be absorbed by seafood. Not only is the product potentially tainted by the resulting smell, it can be hazardous to consume. Standard methods for quantification of PAHs in seafood inv olve gas chromatography and mass spectrometry. This approach is sensitive, but requires time-consuming extractions and separation steps that can take many hours to complete. The goal of this project is to adapt the much faster method of matrix-assisted laser desorption ionization (MALDI) mass spectrometry to the analysis. MALDI MS is rapid and can provide results in a few minutes. MALDI can also be used to obtain the spatial profile of chemical compounds in tissue (MALDI imaging). In the proposed research, seafood samples (shrimp and oysters) obtained from the LSU Agricultural Center will be frozen, sectioned, and analyzed with MALDI imaging. This is a novel application of MS imaging and will involve the development of new matrix materials and sample preparation methods that can be used widely throughout the research community. Samples will be run in parallel by GC/MS for comparison and quantification. Our objective was to develop a MALDI imaging approach to seafood analysis. The challenges are in sample preparation and the addition of matrix to the tissue or tissue sections. The removal of salt from the samples was a greater challenge than was initially anticipated and required a special desalting approach. However, the development of approaches to identify biomarkers of shrimp species was developed into a general protocol for the identification of shrimp species. In the MALDI imaging component of the project, the challenge is the addition of matrix that will enable detection of the hydrophobic PAH components of the tissue. This protocol has been developed and is currently being applied to shrimp samples, focusing on the occurrence of PAHs in shrimp tissue. The appearance of eyeless and deformed shrimp the Gulf of Mexico gives us the additional opportunity to correlate physical deformities of the shrimp.