Comparing extraction methods for analyzing n-alkyl lipids in shelf sediments from the China Sea

Abstract

n-Alkyl lipids including n-alkanes, n-alkanols, and n-alkanoic acids, are essential biomarkers in oceanic sediments and have been widely employed in both modern- and paleo-ecological and environmental studies. The selection of appropriate extraction methods for different research purposes, particularly for compounds with different polarities, remains a challenge. In this study, we compared the efficacy of Bligh-Dyer extraction (BDE), ultrasound-assisted extraction (UAE), accelerated solvent extraction (ASE), as well as a combination of Bligh-Dyer extraction and ultrasound-assisted extraction (BD + UAE) to extract n-alkanes, free n-alkanols, and free n-alkanoic acids from ocean sediments. Our findings indicate that BD + UAE is a suitable method for extracting n-alkanes, ASE is an optimal for extracting free n-alkanols, and BDE provides a suitable method for simultaneous extraction of free n-alkanoic acids with intact polar lipids (IPLs). Additionally, BDE exhibited a preference for compounds with an odd carbon number and short chains, whereas the UAE favored compounds with an even carbon number and long chains, particularly for n-alkanes. These results offer novel insights into the investigation of past paleoclimate and sediment chemistry and serve as a basis for future research on organic matter extraction from ocean sediments.