Low-molecular-weight (LMW) organic acids are key compounds in organic matter degradation and production in marine environments; however, few studies have been carried out on the cycling of these compounds in seawater mostly because the needed methodology with sufficiently low detection limits is not available. Also, existing techniques require extensive sample handling and manipulation, and have high blanks, resulting in high detection limits. Researchers from the University of Connecticut plan to develop a new method for determining LMW organic acid concentrations in seawater and sediment pore water by tagging highly fluorescent coumarin derivatives via an amide bond. They will test multiple methods for conjugating the coumarin to the acid in aqueous neutral or mildly acidic solutions to identify one with the highest efficiency combined with the lowest chemical blank. Great care will be taken in the selection and preparation of solvents and reagents to minimize contamination with formate or acetate. The scientists will also develop and validate HPLC protocols to separate and quantify a large range of LMW organic acid coumarin amides using fluorescence detection and implement the derivatization as a semi-automated on-line method, thereby significantly shortening the work-up time per sample and further decreasing contamination problems.
This research would provide the science community with a new analytical method to further our knowledge of the cycling of LMW organic acids in seawater. The co-PI (Christian Brueckner) would continue to participate in the annual Junior Science and Humanities Symposium held at the University of Connecticut Department of Chemistry, an event that provides high school students and teachers with an opportunity to carry out hands-on science experiments. Two graduate and two undergraduate students would be supported and trained as part of this project.
Understanding global cycling of organic carbon-containing compounds among land, air, and ocean reservoirs is important for understanding cycling of carbon dioxide, and therefore for reliable climate predictions. However, many carbon-containing compounds in the ocean are understudied due to lack of reliable methodology. Low-molecular-weight (LMW) organic acids are examples of an understudied compound group. LMW acids are key compounds in organic matter degradation and production in marine environments. The main problems with existing techniques for determination of LMW acid concentrations are that they require extensive sample handling and manipulation, and they are riddled with high blanks, which result in high detection limits. The high blanks stem primarily from the chemicals used for the organic acid derivatization and concentration. Thus, the specific objectives of the proposed research were: Development of a new method for determination of LMW organic acid concentrations in seawater and sediment pore water by tagging them with highly fluorescent coumarin derivatives via an amide bond. We tested multiple methods for binding the coumarin to the acid in aqueous neutral or mildly acidic solutions, to find the method with the highest efficiency combined with lowest chemical blank. Development and validation of HPLC protocols for separation and quantification of a range of LMW organic acid coumarin amides using fluorescence detection. The work was a collaboration between a marine organic geochemist (Skoog) in a Marine Science Department and a synthetic organic chemist (Brueckner) in a Chemistry Department. Skoog will provide the marine context, the HPLC expertise, and marine samples, while Brueckner will develop the synthetic methodology to derivatize LMW organic acids with coumarins under the boundary conditions that define this project. Intellectual Merit The work will advance the development of new substrate class-selective detection methodologies in aqueous solutions in general and, if successful, might have considerable impact on the ability to understand the global carbon cycle. Broader Impacts Practical, highly selective and sensitive, semi-automated LMW acid determinations are also desirable in the fields of food or environmental chemistry. Also, this work fosters collaborations across multiple disciplines and Departments, offering a multidisciplinary training ground for the PIs and students involved, spanning synthetic and analytical chemistry, and chemical oceanography. Synergistic effects with existing grants to the co-PIs (CB: sensor development, REU program; AS: sediment pore water research) are expected. The multidisciplinary nature of the research activity lends itself to dissemination in non-technical journals and as a subject of outreach activities. The proposal includes year-round undergraduate research projects and will become part of the undergraduate research programs, in the Departments of Chemistry and Marine Sciences, including our NSF-funded REU in Chemistry program.
