Method for\nQuantification of Fatty Acids in Ice Cores\nand Sea-Ice Cores Using Liquid Chromatography High-Resolution Mass\nSpectrometry

Marine-sourced fatty acids provide a promising new suite\nof proxies\nfor past sea-ice reconstructions, validated using ice cores from Bouvet\nIsland, Greenland, and Alaska. Despite showing great potential as\na sea-ice proxy, the transport, deposition, and preservation of these\nfatty acids within the ice sheet are poorly understood. Additionally,\ncomplementary data of the same suite of fatty acids in the source,\nthe surrounding sea ice, is lacking in number, spatial distribution,\nand seasonal variety, especially in the Antarctic. This study presents\nan improved method using high-performance liquid chromatography high-resolution\nmass spectrometry (HPLC-HRMS) for the determination of marine-sourced\nfatty acids in ice cores and sea ice. The method presents a new preconcentration\nstep using stir bar sorptive extraction (SBSE) as well as reduced\nbackground contamination using a trapping column tandem analytical\nsystem in HPLC. The method is suitable to detect and quantify a suite\nof 10 fatty acids with recoveries above 70% and with limits of detection\nin the low ppb and subppb levels. A range of fatty acids were detected\nand quantified in samples from two sub-Antarctic ice cores, taken\nfrom Peter first Island and Young Island. The results from these cores\ndisplayed a variety of fatty acids present in both ice cores (lauric\nacid, myristic acid, oleic acid, linoleic acid, palmitoleic acid,\nheptadecanoic acid, pentadecanoic acid, docosahexaenoic acid, eicosapentaenoic\nacid, and arachidonic acid) as well as a large difference in concentrations\nbetween different fatty acids and between the two ice cores. Additionally,\nthis study presents the first results of fatty acid concentrations\nin the pancake sea ice collected from the Antarctic Marginal Ice Zone.