Spring 2018 – GoMRI Researcher Interview with Dr. Andres Campiglia
– JUNE 19, 2018
(From Spring 2018 Newsletter) Dr. Andres Campiglia from the University of Central Florida answered a few questions about his RFP-V project, A Combined Analytical and Synthetic Approach Based on Line Narrowing Spectroscopy for Specific Isomer Determination of Petroleum Oil Spills, and his work as a co-principal investigator on the RFP-VI project, Biodegradation of “Hidden” High Molecular Weight Polycyclic Aromatic Hydrocarbons: Closing Critical Research Gaps.
1. Thank you so much for talking with us! Tell us about your RFP-V research project, “A Combined Analytical and Synthetic Approach Based on Line Narrowing Spectroscopy for Specific Isomer Determination of Petroleum Oil Spills.” What are the goals of your project?
The main goal of this project is to develop methodology for the analysis of polycyclic aromatic hydrocarbons (PAHs) in the Gulf of Mexico. PAHs are one of the main chemical components of petroleum. After the Deepwater Horizon (DWH) event, risk assessment in the Gulf of Mexico paid attention to the 16 PAHs listed in the priority pollutants list from the Environmental Protection Agency (EPA). The molecular weights (MW) of EPA-PAHs range from approximately 128 to 278 g mol-1. Our project tackles a different aspect of PAHs analysis as it focuses on the detection and characterization of high molecular weight PAHs (HMW-PAHs), i.e., PAHs with MW equal or higher than 302 g mol-1. Of particular concern is dibenzo[a,l]pyrene (DB[a,l]P, MW ≈ 302 g mol-1), which is the most potent carcinogenic PAH yet reported. There are numerous possible HMW-PAH isomers of MW 302 g mol-1. Unfortunately, established methodology fails to identify or quantify individual isomers of MW 302 g mol-1. If the analytical characterization techniques cannot distinguish isomers, conclusions drawn from risk assessment studies could be seriously in error. Our purpose is to fill this gap.
2. You are also a co-principal investigator on the RFP-VI project, “Biodegradation of Hidden High Molecular Weight Polycyclic Aromatic Hydrocarbons: Closing Critical Research Gaps.” Could you tell us about your work on this project?
Dr. Melanie Beazley (Department of Chemistry, University of Central Florida) is the principal investigator of this project, whose central goal is to understand the biological degradation pathways of HMW-PAHs. Microorganisms are the primary drivers of petroleum degradation in the environment. Previous studies have identified several bacterial species capable of degrading low molecular weight PAHs. Microbial interactions with HMW-PAHs remain unknown. Our role is to develop methodology for the trace analysis of degradation products of HMW-PAHs.
3. What is your background, and how did you get involved with this kind of work?
I am a chemist. I obtained my B.S. and M.Sc. degrees at the University of Brasilia and my Ph.D. degree at the University of Florida. My area of expertise is analytical chemistry. My interest in photoluminescence spectroscopy dates back to my undergraduate studies at the University of Brasilia. The ability to measure photoluminescence phenomena in broad-ranging applications from human health to the environment and criminal justice still fascinates me.
4. Can you talk a bit more about why HMW-PAHs are so difficult to detect and what makes them toxic?
Established methodology is based on chromatographic techniques. PAHs are separated in a chromatographic column containing a stationary phase, eluted from the column with a liquid or a gas mobile phase, and detected at the exit of the column with the aid of a mass spectrometry detector. PAHs with high affinity for the stationary phase tend to remain longer in the chromatographic column than PAHs with low affinity for the stationary phase. The time a PAH spends in a chromatographic column is known as the retention time of the PAH. Complete separation in the chromatographic column requires finding a set of experimental conditions that provides a specific retention time for each PAH in the sample. Unfortunately, numerous cases exist where two or more isomers of MW 302 g mol-1 co- elute from the chromatographic column. In addition to the same retention times, many co-eluting isomers with the same molecular weight present almost identical mass fragmentation patterns that yield undistinguishable detector responses.
Not all the isomers with molecular weight 302 g mol-1 are equally toxic. Their level of toxicity depends on their molecular structures, which present variations in the relative positions of their aromatic rings. Parent PAHs are biologically inert molecules but can become carcinogenic upon metabolic activation. A rich heterogeneous mixture of products is created by metabolism, and some of these can covalently bind to DNA in a process believed to be the first critical step in tumor formation. For instance, the metabolic activation of DB[a,l]P produces diol epoxides with strong affinity for DNA. Since the carcinogenic properties of these PAHs differ significantly from isomer to isomer, it is of paramount importance to determine the most toxic isomers, even if they are present at much lower concentrations than their less toxic isomers.
5. What are some of the most significant or exciting findings so far in your GoMRI- funded research?
We have developed analytical approaches that provide the unambiguous determination of co-eluting isomers with the same molecular weight. We have made this possible with the combination of chromatographic and vibrational spectroscopic techniques. Photoluminescence vibrational spectra generated at liquid nitrogen (77K) and liquid helium (4.2K) temperatures provide fingerprint identification of PAH isomers with identical mass spectra. PAH identification is confirmed by monitoring the intensity of the photoluminescence signal as a function of time (photoluminescence lifetime). We have extended the developed methodology to the analyses of alkylated- PAHs and polycyclic aromatic sulfur heterocycles (PASHs). We are able to detect all these pollutants at the parts-per-trillion concentration levels (pictograms/ milliliter) in micro-litters of analytical sample.
6. What are alkylated-PAHs (APAHs) and polycyclic aromatic sulfur heterocycles (PASHs)? Are they similar or different than high molecular weight PAHs?
PAHs and APAHs are heterocyclic compounds with only carbon and hydrogen atoms in their molecular structures. APAHs are alkyl derivatives of parent PAHs. When compared to parent PAHs, APAHs comprise a relatively large fraction of the total number and mass of PAHs found in crude oil and crude-contaminated marine organisms. PASHs are heterocyclic compounds with carbon and hydrogen in which one or more carbon atoms are replaced by sulfur atoms. Sulfur is the principal heteroatom in coal, crude oil, tar, and their by- products. Some PASHs have shown similar mutagenic and carcinogenic potential to PAHs.
7. If funding were not an issue, what would you add to your GoMRI-funded projects?
Time. During the first two years of the project, we developed and validated the new methodology for HMW-PAHs, APAHs, and PASHs with the aid of standard reference materials from the National Institutes of Standards and Technology. We are now in a unique position to interact with other scientists involved in GoMRI. Our ability to track down specific isomers in complex environmental extracts could provide unique insights to understand the environmental impact of the DWH accident. Since not much is known on the long- term effects of these pollutants in the ecosystem, it is our hope to establish long-term interactions that go beyond the three-year duration of this project.
8. Can you describe your interactions with other GoMRI researchers?
The analysis of samples from the Gulf of Mexico through collaborations with scientists involved in GoMRI is an exciting component of our proposition. We have initiated a collaboration with Dr. Behzad Mortazavi and researchers from the Alabama Center for Ecological Resilience (ACER) consortium to analyze sediment cores collected at the Chandeleur Islands. We expect to do the same with water samples that will be collected this summer by Dr. Tracey Sutton and researchers from the Deep Pelagic Nekton Dynamics of the Gulf of Mexico (DEEPEND) consortium. We are seeking collaborations with researchers interested in the analysis of marine organisms as well.