Development and application of a comprehensive thermal desorption/photoionisation mass spectrometry instrument for the determination of the nature of the carbonaceous fraction and the oligomeric/polymeric content of ambient participate matter

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A better understanding of the chemical composition of carbonaceous material from tropospheric aerosol is very important with respect to climatic and health research. Recent investigations revealed that in addition to volatile and semivolatile organic species (OC) as well as so called elementary carbon fractions (EC) also polymeric (e.g. humic like substances) and highly polar, polyfunctional compounds (e.g. sugar derivatives) are present in urban aerosol. This is especially valid also for carbonaceous secondary aerosol particles (SOA). Low volatile organic constituents of aerosol are hardly accessible analytically up to now. Applying innovative thermal methods for determination of OC and EC fractions by releasing the carbonaceous portion of particulate matter (PM) sampled on filter with a succession of temperature steps from approx. 100 to 850 °C (by desorption, pyrolysis, and oxidation) enables detection of chemically different bonded carbon as non-specific sum parameters. In the proposed project a novel analytical technique will be developed, by which the thermal analytical method for releasing carbonaceous molecules or pyrolysis products is hyphenated with a new photo ionisation mass spectrometer (soft single and multi photon ionisation, SPI and REMPI). By doing so, a direct chemical analysis of the evolved products is possible. A successful preliminary feasibility study in the temperature range up to 340°C showed, that molecular components of PM, e.g. polycyclic aromatic hydrocarbons as well as pyrolysis products of polymeric aerosol constituents are detectable. After development and optimisation of the novel technique, in addition to an improved characterisation of oligomeric and polymeric fractions of carbonaceous PM distinction of anthropogenic and biogenic portions of SOA will be attempted.