Over 200 organic compounds have been detected in human breath samples by gas chromatography. These compounds include hydrocarbons, ketones, alcohols, aldehydes and sulfur-containing compounds. The organic components in breath samples are representative of blood-bourn concentrations because of rapid exchange in the lungs. Thus, breath analysis by GC provides a simple and non-invasive means for assessing recent exposure to a drug or an environmental pollutant. In addition, breath analysis should be capable of detecting certain disease states of an individual. The principle limitation to the use of breath analysis for exposure monitoring and as a medical diagnostic tool is the lack of suitable, low-cost portable instruments. Concentrations of organic compounds in human breath samples range from ppm to ppt levels, and pre-concentration is need prior to analysis. An in-line, multi-bed sorption trap has been developed for breath analysis at low and sub ppb levels. The beds consist of various grades of graphitized carbon and carbon molecular sieves. The beds are arranged so that the weakest sorbent is upstream during sample collection. For desorption and injection to the GC column, the flow direction in the device is reversed so that the weakest bed is downstream, and the trap is heated to thermally desorb the sample. Injection plug widths are 0.7-1.5 s, and no cryo-focusing is required. Desorption is quantitative, and no memory effect occurs. Some thermal degradation of sensitive compounds including some aldehydes and terpenes is observed. The effects of desorption temperature and carrier gas flow on thermal degradation and injection-plug width will be described. Characterization of breath samples and decomposition products with time-of-flight MS will be discussed. Breath sample chromatograms using both conventional and micro-fabricated GC columns will be presented.
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