| abstract |
Method and apparatus to detect chemical compounds in the gaseous phase. Specific, stabile enzymes are prepared in conjunction with a color indicator responsive to pH, oxidation or to other chemical input of the compound to be detected in the gas phase. In the preferred embodiment, the enzymes are immobilized on selected organic or inorganic solid supports and dehydrated under controlled conditions. As selected and prepared, the enzymes are capable of rapid catalysis of reactions of the chemical compounds present in the gas phase even in low concentration. A sharp, well-defined color change occurs as a result of these reactions when the enzyme is exposed to a gas containing the substance of interest. In one form of the invention, the quantity of the indicator is adjusted according to a calibration curve for use as a qualitative detector of a minimum level of a chemical compound. In another form, calibration curves are utilized for the quantitative detection of chemical compounds wherein the color is measured by spectrophotometric means or by comparison with color standards. The method and apparatus are useful for, but not limited to, detection of ethyl alcohol in the breath and of formaldehyde and other toxic compounds in gas streams. |