An intercomparison study of analytical methods used for quantification of levoglucosan in ambient aerosol filter samples

Abstract

Abstract. The monosaccharide anhydrides (MAs) levoglucosan, galactosan and mannosan are products of incomplete combustion and pyrolysis of cellulose and hemicelluloses, and are found to be major constituents of biomass burning aerosol particles. Hence, ambient aerosol particle concentrations of levoglucosan are commonly used to study the influence of residential wood burning, agricultural waste burning and wild fire emissions on ambient air quality. A European-wide intercomparison on the analysis of the three monosaccharide anhydrides was conducted based on ambient aerosol quartz fiber filter samples collected at a Norwegian urban background site during winter. Thus, the samples' content of MAs is representative for biomass burning particles originating from residential wood burning. The purpose of the intercomparison was to examine the comparability of the great diversity of analytical methods used for analysis of levoglucosan, mannosan and galactosan in ambient aerosol filter samples. Thirteen laboratories participated, of which three applied High-Performance Anion-Exchange Chromatography (HPAEC), four used High-Performance Liquid Chromatography (HPLC) or Ultra-Performance Liquid Chromatography (UPLC), and six resorted to Gas Chromatography (GC). The analytical methods used were of such diversity that they should be considered as thirteen different analytical methods. All of the thirteen laboratories reported levels of levoglucosan, whereas nine reported data for mannosan and/or galactosan. Eight of the thirteen laboratories reported levels for all three isomers. The accuracy for levoglucosan, presented as the mean percentage error (PE) for each participating laboratory, varied from −63 to 23%; however, for 62% of the laboratories the mean PE was within ±10%, and for 85% the mean PE was within ±20%. For mannosan, the corresponding range was −60 to 69%, but as for levoglucosan, the range was substantially smaller for a subselection of the laboratories; i.e., for 33% of the laboratories the mean PE was within ±10%. For galactosan, the mean PE for the participating laboratories ranged from −84 to 593%, and as for mannosan 33% of the laboratories reported a mean PE within ±10%. The variability of the various analytical methods, as defined by their minimum and maximum PE value, was typically better for levoglucosan than for mannosan and galactosan, ranging from 3.2 to 41% for levoglucosan, from 10 to 67% for mannosan, and from 6 to 364% for galactosan. For the levoglucosan to mannosan ratio, which may be used to assess the relative importance of softwood vs. hardwood burning, the variability only ranged from 3.5 to 24%. To our knowledge, this is the first major intercomparison on analytical methods used to quantify monosaccharide anhydrides in ambient aerosol filter samples conducted and reported in the scientific literature. The results show that for levoglucosan the accuracy is only slightly lower than that reported for analysis of SO42− on filter samples, a constituent that has been analyzed by numerous laboratories for several decades, typically by ion chromatography, and which is considered a fairly easy constituent to measure. Hence, the results obtained for levoglucosan with respect to accuracy are encouraging and suggest that levels of levoglucosan, and to a lesser extent mannosan and galactosan, obtained by most of the analytical methods currently used to quantify monosaccharide anhydrides in ambient aerosol filter samples, are comparable. Finally, the various analytical methods used in the current study should be tested for other aerosol matrices and concentrations as well, the most obvious being summertime aerosol samples affected by wild fires and/or agricultural fires.

Methods for the determination of levoglucosan and other sugar anhydrides as biomass burning tracers in environmental samples – A review

“…Samples of aerosols are collected on filters, e.g. microporous poly(tetrafluoroethylene) filter membrane (PTFE) [1,2,4,31], quartz fiber filter [3,5,[7][8][9]16,20,23,24,30,34,35], or glass fiber filter [10,29].…”

“…It is assumed that LG is stable in environment, it shows resistance to photochemical oxidation and acid catalyzed hydrolysis . However, the Hennigan et al.…”

“…The exact composition can differ depending on environmental aspects, types of biomass (softwood, hardwood, grass), and its genus. Upon burning, each individual plant emits a "chemical fingerprint" of organic constituents with unique and specific composition [3][4][5]9,11,13,[15][16][17][18][19][20][21][22][23][24][25]. At temperature below 300 • C cellulose depolymerize, water is eliminated, fragmentation and oxidation lead to formation of char.…”

“…At temperature below 300 • C cellulose depolymerize, water is eliminated, fragmentation and oxidation lead to formation of char. At the temperature above 300 • C, cellulose undergoes pyrolysis involving bond cleavage, fission, and disproportionation leading mainly to 1,6-anhydride of glucose, polar dehydrated glucose with a ketal functional group-levoglucosan, (LG; 1,6-anhydro-β-D-glucopyranose) [3][4][5]9,11,[17][18][19][20][21][22][23][24][25][26][27][28].…”

“…It is assumed that LG is stable in environment, it shows resistance to photochemical oxidation and acid catalyzed hydrolysis [2,3,[6][7][8][9][10][11]23]. However, the Hennigan et al [32] shows in his work that LG is not inert, it reacts with hydroxyl radical and LG lifetime depends upon OH concentration.…”