1. Field of the Invention
This invention relates to systems for performing gas chromatography and mass spectrometry on environmental samples, and in particular, pertains to an apparatus and method for sample injection for analysis of air samples for volatile organic compounds.
2. Description of the Related Art
Many volatile organic compounds (VOCs) are considered to be pollutants and a danger to health even when they are at such low levels in an indoor or outdoor environment that they are only detectable by sophisticated gas chromatography (GC) and mass spectrometry (MS). The sources of undesirable VOCs include such diverse sources as microbial emissions from decay or other biological processes, chemical spills, chemical release from synthetic products, and airborne emissions from industrial processes. VOCs include a wide variety of chemical compounds such as sulfur-containing compounds, aldehydes, alcohols, ketones, chlorinated hydrocarbons, aromatic hydrocarbons, amines, and terpenes.
The very low levels at which many VOCs are toxic or otherwise harmful, in comparison with the higher levels of other compounds present in an average gas sample, means that gas analysis techniques must be very sensitive to the VOCs being analyzed in the presence of higher levels of these other compounds. Techniques such as differential temperature treatment, cryogenic trapping, and use of solid sorbents, or combinations thereof, have been developed in an attempt to remove compounds not being measured and selectively enrich for the VOCs being measured.
It is therefore an object of this invention to provide a method and apparatus which allows detection and measurement of very low levels of VOCs even in samples containing water vapor and/or other components at relatively high levels. The invention thus allows determination of VOCs which may be hazardous to health and the quality of life.
Other objects and advantages will be more fully apparent from the following disclosure and appended claims.