Solid-phase microextraction for the analysis of human breath

Solid-phase microextraction (SPME) has been applied to the quantitative determination of ethanol, acetone, and isoprene in human breath. The method involves extraction and preconcentration with a fused silica fiber coated with a polymeric stationary phase, desorption at 200 degrees C, and assay by gas chromatography/mass spectrometry. Three different fiber coatings have been evaluated with regard to sensitivity, linear range, precision, and detection limits. Typical RSD values in the range 2%-6% could be obtained, depending on the fiber coating and the compound investigated. The calibration curves for the compounds are reproducible and linear over the concentration ranges found in human breath samples. The method is capable of detecting concentrations of acetone and isoprene reported for healthy subjects. The influence of temperature and humidity on the extraction process has been studied in detail. A linear relationship between log K versus 1/T allows the calibration of the method for any given temperature. The device is portable, economical, and easy to use in patient sampling.