The Department of Forest Zoology and Forest Conservation uses up-to-date methods of instrumental chemical analysis for the characterisation of odour mixtures. The most important method is gas chromatography that allows to separate volatile compounds according to their boiling point. The detection of the compounds after separation can be done with a universal detector like a flame ionisation detector (FID). The use of a mass spectrometer as a detector is more beneficial since it allows an identification of the detected compounds.
In the mass spectrometer the molecules are ionised and fragmented by bombardment with electrons. The resulting pattern of fragments (the so-called mass spectrum) is recorded by counting all fragments in a specific mass range (e.g. 20 - 300 "atomic mass units"). The mass spectrum is characteristic for the fragmented molecule and can be used for its identification by comparison with a computer based mass spectral library.
Most beneficial are hyphenated techniques that combine the advantages of several methods, e.g. the use of insect antenna as electroantennographic detector (EAD) parallel to a FID or - for the first time applied in the Department of Forest Zoology and Forest Conservation - parallel to a mass spectrometer.
Techniques applied in the Department of Forest Zoology and Forest Conservation:
Field sampling techniques
- Active sampling with miniaturised pumps and adsorbent traps
- Passive sampling with SPME (solid-phase-micro-extraction)
- Headspace (direct analysis of air)
Sampling and injection techniques
- Liquid injection of odour extracts
- SPME (solid-phase-micro-extraction)
- Thermodesorption of adsorbent traps
Gas chromatography and hyphenated techniques