We employed an Agilent 1200 series high-performance liquid chromatography- 6460A triple quadrupole-mass spectrometer (HPLC-QQQ-MS) equiped with an autosampler and a masshunter quanlitative workstation. The advantage of this LC-MS is its high sensitivity and a wide linear dynamic range for the quantification of organic compounds. The target molecules of this instrument include glycerol dialkyl glycerol tetraethers (GDGTs), bacteriopolyhopanols (BHPs), ladderane fatty acids, intact polar lipids (IPL) and heterocyst glycolipids, which are membrane lipids that are increasingly important and useful in paleoenvironment reconstruction and biogeochemistry study. We now focus on GDGTs and developed a variety of methods to analyze them. Due to a high sensitivity and a low detection limit (~10pg) for the GDGT analysis, this instrument can be used to quantify GDGTs in stalagmites as well as sediments dated back as early as Permian, where only trace amounts of GDGTs were present. This allows to develop and use GDGT proxies in very ancient sedimentary achives to reconstruct temperature and hydroclimate. With the ONCE project, we will investigate the environmental controls on GDGTs in a wide range of sedimentary achives, including mineral soils, peats, stalagmites, lake sediments, and marine sediments across China and developed new temperature and hydroclimate proxies based on GDGTs, i.e. SSM and Ri/b, with applications in loess-paleosols over the last 350 ka.
