The importance of measuring siloxanes has increased with the recent growth of the landfill-gas-to-energy (LFGTE) market. Siloxanes and other biogas impurities can form a residue upon combustion in engines that may increase maintenance and reduce engine lifetime. A siloxanes analysis can assist with either determining if a bioaas purification system is needed, or if a system is already in place, determining if it is operating properly. To date, various methods have emerged to measure siloxanes involving different sampling techniques and detectors. This paper summarizes the available methods for the determination of siloxanes in air to enable members of the LFTGE industry to select the most appropriate method for then* application.
This paper presents information not only from method development by Air Toxics Ltd.. but also from available technical literature by analytical laboratories. environmental consulting firms, and trade conferences. The specific sample collection techniques to be compared are:
- Collecting a whole air sample in a Summa™ canister; and
- Drawing sample air through methanol-filled impingers;
- Drawing sample air through a charcoal sorbent tube.
The specific analytical detectors to be compared are gas chromatography (GC) coupled with a:
- Flame ionization detector (FID):
- Atonic emission detector (AED): and
- Mass spectrometer (MS).
This paper specifically compares the performance of collection and analytical methods in terms of:
- Ease of sampling:
- Collection of a representative sample:
- Siloxane recovery;
- Detector selectivity and availability:
- Reporting limit: and
- Calibration techniques.