Levoglucosan, which is emitted from the combustion of cellulose and hemicelluloses, can be transported over a long range of time to ice caps, where it may indicate fire activity both regionally and globally.
Researchers at the CNR-Institute of Polar Sciences in Italy, the University of Venice, and Utrecht University in The Netherlands have collaborated on a new study targeting detection of levoglucosan in ice cores from Switzerland, using continuous flow analysis coupled with fast liquid chromatography and tandem mass spectrometry (CFA–FLC–MS/MS) to find evidence of past fire events (1).
Published in the journal Talanta, the 13-author study specifically upgraded the CFA–FLC–MS/MS technique to quantify levoglucosan, which is one of a few key tracers of biomass burning also including vanillic and syringic acids. Levoglucosan is produced by the combustion of cellulose and hemicelluloses, and once emitted in the atmosphere, can undergo long-range transport to eventual preservation in snow and ice (1). Although levoglucosan is chemically reactive, it cannot distinguish what type of vegetation has been burnt, as some of the other tracers can. But over time, the researchers said, it can be a marker of fire activity anywhere from a regional to a global scale, providing a much-desired boost to a field of study in which data is lacking.
The samples from Switzerland were chosen as high-altitude alpine glaciers can preserve higher concentrations of levoglucosan than ice from polar areas, the logic behind this being the alpine ice’s relative proximity to urban areas (1). Although fast ion chromatography (FIC) has also been used with a CFA system in the past, the CFA–FLC–MS/MS approach, in use for more than 20 years, was preferred here for its semi-continuous detection, used in this application for the first time, along with more traditional advantages such as high sensitivity and accuracy and low detection limits. Semi-continuous detection, the researchers said, minimizes both sample preparation and contamination (1).
Previously, levoglucosan in melted ice samples had been detected below a limit of 30 μg/L, prompting prior researchers to preconcentrate their samples through evaporation by a factor of 50 – ultimately allowing for a 0.6 μg/L detection limit per 100 mL of sample (1). The upgraded CFA–FLC–MS/MS method used here showed high sensitivity, with a detection limit of 66 ng/L. Relative standard deviations for nine concentration values obtained results lower than 10% except at the 0.1 μg/L level, where the RSD was just slightly higher, at 14%.
This research team also tested their proposed method for repeatability by using pairs of parallel ice sticks, theorizing that concentrations should be similar in each. Such tweaks to approaches that have been in use for decades provided sufficient evidence for this study to conclude that with specific attention paid to levoglucosan determination, CFA–FLC–MS/MS is viable in providing clues to fire activity and its effects over time (1).
(1) Spagnesi, A.; Barbaro, E.; Feltracco, M.; et al. An upgraded CFA–FLC–MS/MS system for the semi-continuous detection of levoglucosan in ice cores. Talanta 2023, 265, 124799. DOI: 10.1016/j.talanta.2023.124799