Das Projekt "SAMPLER: Probenahmegeraet fuer die Messung von Proxy-Radikalen in atmosphaerischen Systemen in Labor- und Feldversuchen" wird vom Umweltbundesamt gefördert und von Ecole Polytechnique Federale de Lausanne, Institut de Genie de l'Environnement durchgeführt. The general objective of the proposed work is the development of an instrument which allows the quantitative in-situ measurement of peroxy radicals in an outdoor smog chamber. A matrix-isolation cryosampler for the collection of air samples in outdoor chamber experiments will be constructed for the determination of the time-dependent peroxy radical concentration under tropospheric conditions. Analysis of the samples will be carried out in the laboratory by using electron spin resonance spectroscopy. Since the samples have to be transported over a long distance from the place of sampling to the analytic arrangement, and the loss of radicals in the matrix should be negligible, the proposed work includes also the development of a novel storage and transport device. The oxidation of selected hydrocarbons under tropospheric conditions in an outdoor simulation chamber will serve as a first test of the improved instrumentation, which is necessary for the validation of the measured peroxy radical concentrations. For these experiments, ethene or propene will be chosen, since they represent controllable, well known reaction systems. The final goal is the application of the new sampling facility in the investigation of the smog chamber oxidation of complex VOC mixtures which lead to photooxidant formation. This work - supported by chemical modelling - will provide important data which will enable the better organisation of future field measurements towards specific atmospheric problems.