New analytical method for the determination of levoglucosan, polyhydroxy compounds, and 2-methylerythritol and its application to smoke and rainwater samples.

Biomass burning is an important source of smoke aerosol particles, which contain water-soluble inorganic and organic species, and thus have a great potential of affecting cloud formation, precipitation, and climate on global and regional scales. In this study, we have developed a new chromatographic method for the determination of levoglucosan (a specific tracer for biomass burning particles), related polyhydroxy compounds, and 2-methylerythritol (recently identified as isoprene oxidation product in fine aerosols in the Amazon) in smoke and in rainwater samples. The new method is based on water extraction and utilizes ion-exclusion high-performance liquid chromatography (IEC-HPLC) separation and spectroscopic detection at 194 nm. The new method allows the analysis of wet samples, such as rainwater samples. In addition, aliquots of the same extracts can be used for further analyses, such as ion chromatography. The overall method uncertainty for sample analysis is 15%. The method was applied to the analysis of high-volume and size-segregated smoke samples and to rainwater samples, all collected during and following the deforestation fires season in Rondonia, Brazil. From the analysis of size-segregated samples, it is evident that levoglucosan is a primary vegetation combustion product, emitted mostly in the 0.175-1 microm size bins. Levoglucosan concentrations decrease below the detection limit atthe end of the deforestation fires period, implying that it is not present in significant amounts in background Amazon forest aerosols. The ratio of daytime levoglucosan concentration to particulate matter (PM) concentration was about half the nighttime ratio. This observation is rationalized by the prevalence of flaming combustion during day as opposed to smoldering combustion during night. This work broadens the speciation possibilities

Analysis of semivolatile organic compounds in atmospheric aerosols by direct sample introduction thermal desorption GC/MS.

A technique for identifying trace amounts of semivolatile organic compounds in atmospheric aerosols and in the NIST Urban Dust standard (SRM1649a) is presented. The technique is based on direct sample introduction (DSI) of small samples followed by thermal desorption in a conventional GC injector. The method enables injection of both solid and liquid samples. Validation of the method, including quantitative determination of EPA-targeted polycyclic aromatic hydrocarbons (PAHs), as well as the reproducibility and recovery efficiency tests are presented. The advantages of using aluminum foil as sampling filter are also discussed. Determination of different classes of compounds such as quinolines, methylquinoline isomers, PAHs, and n-monocarboxylic acids in the ambient size-segregated aerosol sample is also performed. The method was directly applied to the determination of C6-C16 n-monocarboxylic acids, eliminating the need for a complex sample preparation procedure. The small quantities needed for the analysis as well as the lack of complicated sample preparation steps enable fast characterization of semivolatile organic species present in time-resolved or size-segregated aerosol samples. Thus, this method can potentially be employed for air quality monitoring and field measurements as well as for fast screening of the organic content of ambient particles.