An optimised method for the extraction and analysis of lipid biomarkers from stalagmites

Lipid compositions preserved in stalagmites have significant potential for use in reconstruction of global climate change and regional vegetation cover, but the low organic content of stalagmites poses a problem both for clean extraction and for obtaining a high temporal resolution in palaeoenvironmental records. Here, we present an acid digestion method optimised for cleanliness and maximum lipid recovery. The use of acid digestion and hydrolysis improves lipid yields not only by releasing organic matter trapped within individual calcite crystals, but also by allowing access to the chemically-bound pool of lipids, particularly acidic compounds such as alkanoic acids, hydroxy acids, and alkanedioic acids. The technique also considerably reduces contamination problems in comparison to conventional soxhlet extraction.