Results of a European inter-laboratory comparison study for the quantification of biomass burning molecular tracers (levoglucosan, galactosan, mannosan) in atmospheric particulate samples

Abstract : Levoglucosan, mannosan and galactosan (anhydrous sugars) are molecular tracers of biomass burning widely used in aerosol source apportionment studies. A European inter-laboratory comparison (ILC) for their analysis in ambient air particulate matter was organized within the European ACTRIS project. The ILC was led by INERIS with the help of LGGE for quality control analyses. Four test materials were sent to the participants including two ambient air filter samples (corresponding to high winter range concentrations), one laboratory blank filter and one standard reference material (NIST SRM). The main purpose of the ILC was to evaluate the analytical repeatability and reproducibility standard deviations obtained by the participants using their own analytical methods and to highlight any bias or influencing factor on the measurement quality of the biomass burning molecular tracers. Thirteen participants submitted their results and most of them obtained satisfactory Z-scores (Figure 1). Only two laboratories showed outliers for levoglucosan, and only one more also showed unsatisfactory results for mannosan and/or galactosan. One laboratory showed a very high blank value for levoglucosan. Only 3 laboratories showed standard deviations of repeatability larger than 10 %. Standard deviations of reproducibility were about 20-25 % for levoglucosan and mannosan, while values in the range 30-60 % were obtained for galactosan. All the results obtained showed that the analytical procedure had no influence on the quantification of levoglucosan and its isomers. Expanded uncertainties obtained were satisfactory (e.g. < 52 % for levoglucosan) and, for example, consistent with the one required for the measurement of benzo[a]pyrene in ambient air PM10 (European Directive 2004/107/CE). Finally, results of this ILC could be used as reference for the certification of the NIST SRM 1649b (urban dust).