δ Deuterium leaf wax isotopes from sediment core of Lake Alchichica in Mexico

The isotope analyses were performed on subsamples from a 57-cm-long sediment core retrieved from Lake Alchichica (19° 24' 38 N, 97° 24' 14 W, 2322 masl) at a water depth of ~ 60 m using a Uwitec® coring device equipped with a 9-cm coring tube. n-alkanes were extracted from 20 dried samples (1.3–2.8 g) using DCM:MeOH (9:1) in a DIONEX ASE-200 at 100°C and 1000 psi for 5 minutes, repeated thrice, with squalane as an internal standard. Lipid extracts were concentrated under N₂, treated with activated copper to remove sulfur, and saponified with 6% KOH in MeOH at 80°C for 2 hours. Hydrocarbons, ketones, and alcohols were extracted with hexane, and non-polar hydrocarbons were isolated using silica gel and silver nitrate-silica columns. Saturated fractions were analyzed by GC/FID at MARUM, University of Bremen, with retention time comparison for compound identification and