# Method for Quantification of Fatty Acids in Ice Cores and Sea-Ice Cores Using Liquid Chromatography High-Resolution Mass Spectrometry

## TL;DR

This paper introduces a new method to measure fatty acids in ice cores and sea ice, which can help reconstruct past sea-ice conditions.

## Contribution

The study presents an improved HPLC-HRMS method with preconcentration and reduced contamination for fatty acid analysis in ice.

## Key findings

- The method can detect and quantify 10 fatty acids with recoveries above 70% and low detection limits.
- A range of fatty acids was detected in sub-Antarctic ice cores, with varying concentrations between samples.
- The first results of fatty acid concentrations in Antarctic pancake sea ice are reported.

## Abstract

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