Scientists tested a new analytical method for a fast and comprehensive characterization of organic compounds in marine sediments. The Rapid Analyte Detection and Reconnaissance (RADAR) method couples atmospheric pressure photoionization in positive ion mode (APPI-P) with Fourier transform ion cyclotron mass spectrometry (FTICR-MS). Twelve minutes of analysis provided a simultaneous detection and identification of thousands of compounds not typically monitored by traditional methods, including the discovery of potential novel molecular species. Knowledge of the natural background biogenic species composition in sediments is necessary to establish pre-Deepwater Horizon benchmarks and to better understand the effects of the marine oil snow sedimentation event. The researchers published their work in Rapid Communications in Mass Spectrometry: A rapid method to assess a broad inventory of organic species in marine sediments using ultra-high resolution mass spectrometry.
Scientists can reconstruct past environments, processes, and communities using organic biomarkers found in marine sediments to better understand how complex variables, such as carbon cycling, climate change, and pollution, affect marine ecosystems. Traditional methods analyze sedimentary biomarkers using gas or liquid chromatography coupled to mass spectrometry. However, these methods typically include time-intensive sample preparation and target only a small amount of sedimentary species. This study presents a faster and more comprehensive analytical strategy that targets a broad range of known and potential biomarkers.
FTICR-MS ionizes samples with a negative or positive charge (in the case of this study) and introduces them into a strong magnetic field, where they are accelerated to a circular trajectory. Each molecule’s movement gives off a distinct frequency based on its mass-to-charge ratio (i.e., lighter molecule ions spin faster than heavier molecule ions with the same charge). Scientists can use this frequency to identify a plethora of compounds up to a mass difference of only one electron in milligram-sized samples.
The researchers tested the RADAR method using a sediment core collected at 1100 m water depth, identifying 3,000 – 5,000 compounds per sample with 90% showing an absolute error lower than 200 ppb. The detected species belonged to the NO1–7, N4O2–8, O1–9, HC, N, and OS compound classes and included known biomarker species and potential biomarkers with currently unknown molecular structures.
Study author Jagos Radovic explained that FTICR-MS is the only technique that can perform this rapid and detailed characterization and classification of heavy petroleum fractions and oxidized weathering products . “These oil constituents have the potential to be very recalcitrant and can persist in marine environments as deep water sediments or dissolved organic matter,” he said. “Furthermore, the bioavailability and toxicity of such compounds are still poorly understood, mainly due to the limitations of conventional analytical strategies. FTICR-MS and RADAR can overcome these limitations.”
Data are publicly available through the Gulf of Mexico Research Initiative Information & Data Cooperative (GRIIDC) at doi:10.7266/N71R6NGQ.
This research was made possible in part by a grant from the Gulf of Mexico Research Initiative (GoMRI) to the Center for the Integrated Modeling and Analysis of Gulf Ecosystems II (C-IMAGE II). Other funding sources included the Canada Foundation for Innovation (CFI), the Natural Sciences and Engineering Research Council of Canada (NSERC) and Canada Research Chairs (CRC), PRG, and the University of Calgary.
The Gulf of Mexico Research Initiative (GoMRI) is a 10-year independent research program established to study the effect, and the potential associated impact, of hydrocarbon releases on the environment and public health, as well as to develop improved spill mitigation, oil detection, characterization and remediation technologies. An independent and academic 20-member Research Board makes the funding and research direction decisions to ensure the intellectual quality, effectiveness and academic independence of the GoMRI research. All research data, findings and publications will be made publicly available. The program was established through a $500 million financial commitment from BP. For more information, visit http://gulfresearchinitiative.org/.
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