Levoglucosan concentrations in ice-core samples from the Tibetan Plateau determined by reverse-phase high-performance liquid chromatographyÂŒmass spectrometry

Levoglucosan is a unique marker for biomass burning that can be transported in the atmosphere and preserved in archives such as ice cores. A new method to determine the concentrations of levoglucosan in Tibetan ice-core samples using high-performance liquid chromatography with electrospray ionization mass spectrometry (HPLC-ESI/MS) was developed. Levoglucosan was separated from coeluting water-soluble organic compounds using a C18 column with a gradient program from 50% to 90% methanol in ultrapure water. An external standard calibration curve (R = 0.9958) was established by plotting the ion m/z 163 [M+H] peak area versus the amount of analyte. The repeatability ranges between 11% and 2% at a concentration around 10 and 150ngmL. The limit of detection was 10 ngmL and the limit of quantification was 40 ngmL. Levoglucosan concentrations ranged from 10 to 718ngmL in the Muztagh Ata ice core and from 10 to 93 ngmL in the Tanggula ice core. These concentrations, up to 1000 times higher than those measured in samples from Antarctic and Greenland, showed the higher vulnerability of the Tibetan Plateau glaciers to biomass burning events.