Automated solid phase extraction of environmental lipid biomarkers

Lipids produced by different organisms are preserved as fossils in sediments and soils. These so-called lipid biomarkers and related organic proxies represent valuable tools to reconstruct past changes in ecosystems. For example, C₃₇ alkenones produced by microalgae (Isochrysidales) represent biomarkers specific for these organisms. Furthermore, an index based on C₃₇ alkenones can be used as proxy to estimate past changes in surface water temperature. However, before analysis by gas or liquid chromatography and mass spectrometry, biomarkers extracted from the sediment are treated by solid phase extraction (SPE), a process which is time-consuming and requires the use of organic solvents which can be harmful to health and environment. Here, we compared a routinely applied manual SPE (mSPE) analytical method with an automated SPE (aSPE) method using a PrepLinc platform automated sample preparation system (J2 Scientific). The analysis of marine sediments from the North Sea and the Southeast Pacific conducted with both mSPE and aSPE resulted in mainly statistically similar results, although care has to be taken when compound co-elution occurs. aSPE resulted in a higher recovery rate, but consumed more solvents, mainly for rinsing. The use of the PrepLinc platform for automated SPE, which can process up to 27 samples in a single run, allows saving not only time, but also fume hood space as the PrepLinc platform has a completely closed circuit. The PrepLinc platform represents, thus, a valuable instrument to perform automated SPE for the analysis of environmental lipid biomarkers with a high repeatability.