Online Measurement of Trace Compounds in Air

Air analysis includes the real-time measurement of gas and aerosol components in the atmosphere, in indoor work or living environments, and in closed manufacturing spaces. Such measurements may be related to climate change research, air quality, quality control, or process monitoring. At trace concentration levels, the chemical composition of air is complex and compounds of interest may be undergoing rapid changes in concentration related to, for instance, dynamic changes in their source. Because they are capable of resolving and simultaneously monitoring large numbers of compounds at sub ppb levels with extremely high time resolution, our TOFs are frequently used for online air measurements.

Volatile Organic Compounds (VOCs) are critically important constituents of air in all of the forementioned environments. The Vocus PTR-TOF is the most sensitive available mass spectrometer for online VOC analysis – able to detect sub-ppt components in seconds – and its high resolving power enables identification of individual compounds within complex mixtures, often replacing the need for GC before mass spectrometry.

The API-TOF is widely used with other chemical ionization schemes that are selective for organic compounds of varied volatitility. The EESI ionization source extends this sensitive, molecular analysis capability to the aerosol phase. Our atmospheric science customers have run the API-TOF on all 7 continents – making measurements at remote field sites and aboard mobile research platforms.

Adding an IMS dimension to MS analyses – with the IMS-TOF – can be of major benefit for online air analysis. For instance, atmospheric researchers are often faced with the problem that many molecules from organic aerosols cannot be sufficiently well identified based on MS alone. Yet, these identifications, especially for isomeric molecules, are crucial for establishing chemical mechanisms that inform climate models.