brGDGTs-based temperatures during the last deglaciation in Jierguoshan Tianchi (Moon Lake)
This dataset includes a time series of reconstructed summer temperature during the last deglaciation from the crater lake Jierguoshan Tianchi (Moon Lake) , Northeast China.
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GDGTs were extracted from 0.5-1 g of freeze-dried sediment samples using an organic solvent composed of a dichloromethane: methanol (9:1, v/v) mixture which was ultrasonicated 5-7 times until the solvent was colorless. After evaporating the solvent, the dry samples were successively treated with n-hexane and methanol via silica-gel chromatography to purify and separate the material into polar and non-polar fractions. The polar fractions were dissolved in DCM and passed through a 0.45 μm PTFE filter to purify the GDGTs. GDGTs analyses were performed using HPLC-APCI-MS (Agilent 1260 HPLC system with 6100 MS) with auto-injection. Samples were brought up in 300 μL n-hexane: ethyl acetate (EtOA) (84:16, v/v), and the injection volume was 10 μL. The 5- and 6-methyl brGDGTs isomers were separated by three Hypersil Gold Silica LC columns in sequence (each 100 mm × 2.1 mm, 1.9 μm, Thermo Fisher Scientific; USA), maintained at 40°C. Detection was achieved by positive ion APCI of the eluent. Selected ion monitoring (SIM) was used to target specific [M+H]+ at m/z 744 for the C46 standard and 1050, 1048, 1046, 1036, 1034, 1032, 1022, 1020, 1018 for the brGDGTs. The 5- and 6-methyl brGDGTs were assigned as described by (De Jonge et al., 2014).