Automated Gas Chromatographic Method for Neutral Lipid Carbon Number Profiles in Marine Samples

Abstract

A gas chromatographic (GC) lipid-profiling method is optimized for analysis of neutral lipids in highly unsaturated marine samples. Chemometrics are employed to optimize autoinjection procedures and column temperature programs. The use of large solvent plug sizes, fast injection rates, hydrogen carrier gas with high flow rates, and short capillary columns enhanced recoveries of high molecular weight neutral lipids. A hydrogenation step was required to avoid discrimination of the flame ionization detector (FID) responses in highly unsaturated lipids. Analyses of fatty acids, which are moieties of the neutral lipids, support the neutral lipid profile data. The identification of major sterols is confirmed by gas chromatography with mass spectrometry (GC-MS). The values of summed molecular species from each neutral lipid class determined by GC are linearly correlated with neutral lipid subclasses determined by Chromarod thin-layer chromatography with flame ionization detection (TLC-FID). Automated high temperature GC on hydrogenated samples is found to offer a precise tool for the measurement of highly unsaturated neutral lipid compounds, which are critical in understanding physiological characteristics of cold water species. The method is applied to a range of marine samples including algae, bivalves, polychaetes, fish eggs, and fish larvae and reveals, for the first time, neutral lipid carbon number distributions in marine species from cold oceans.