Use of GC-QMS for stable isotope analysis of environmentally relevant main and trace gases in the air

Abstract

When tracing the fluxes of N compounds (especially N oxides) and carbon dioxide in the system soil-atmosphere and applying ¹⁵N and ¹³C, it is necessary to simultaneously determine both the concentration of the substances and their isotopic composition. GC separation (packed column) was coupled to a mass spectrometer by a special interface. Variable sample volumes can be delivered by changing the split by means of the interface in front of the MS. Thus, both the concentration of a gaseous compound and its ¹⁵N content can be measured. Supplying sample volumes in a range between 5 μl and 5 ml, it is possible to measure both components of high content (e.g., nitrogen) and at the lower ppm(v)-content (e.g., dinitrogen oxide) in the air. Measurements of N₂, N₂O, NO and CO₂ are demonstrated, too.