Online air monitoring for trace levels of H2S, mercaptans (thiols) and other reduced sulphur compounds

Technical Note (TDTS) # 32

Markes has re-issued technical note 32 (downloadable from this website as a PDF file).
UNITY-Air Server configured with GC-PFPD, or equivalent sulphur detector, has now been shown to allow H2S, mercaptans and other reduced sulphur compounds to be monitored in air at sub-ppb and low-ppb levels. Extensive supporting data are available from both the method development process and from subsequent field operation at multiple sites. The first half of the application note gives the method details.

The analysis is carried out on whole air samples (no sorbent tubes) i.e. canisters, bags or online air streams. Field monitoring is typically carried out unattended and online on a continuous basis. A controlled flow of air is drawn from the sample manifold directly into the electrically-cooled focusing trap of UNITY, before trap desorption injects the retained analytes into the GC analytical system and triggers the start of the run. Collection of the next air sample can begin as soon as the focusing trap has re-equilibrated at the trapping temperature.

Key applications include:

• Landfill odour
• Odours in urban air
• Fenceline monitoring of petrochemical plant and other industrial installations
• Odour from sewage treatment works