In the proposed research the optoacoustic effect will be investigated for analytical trace detection of environmental carcinogens. Although the proposed methods should have wide application, detection of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD or """"""""dioxin"""""""") will be the primary objective. This work will focus on adoption of the demonstrated high sensitivity of laser-optoacoustic detection for use in conjunction with gas chromatography. Development of a highly sensitive instrument will be the primary focus of this research. Several designs for a low volume, high temperature acoustic detection cell will be evaluated for maximizing sensitivity. An acoustic transducer using a helium-neon laser beam deflected from a flexible diaphragm will be tested. A Helmholtz resonator used in conjunction with a conventional electret microphone maintained at room temperature will also be evaluated. To improve sensitivity, methods for reducing the signal from the cell windows will be investigated. In addition to designing the acoustic cell for elimination of this problem, frequency modulation of the carbon monoxide laser as an alternate solution will be studied. Following selection of the most appropriate detection configuration the relative advantages and disadvantages of this instrumentation for trace analysis will be ascertained. That is, the response of the instrument to various interfering compounds in the sample extract will be studied to determine the selectivity of this detection method as well as its sensitivity. A second approach based on """"""""chemical amplification"""""""" of the optoacoustic signal will be investigated. Here, the species of interest is photodissociated, and the concentration of radicals, and hence, the evolution of heat in the cell is increased through chemical reactions. Amplifications as great as 10 to the ninth power are predicted by theory. Successful completion of the proposed research will have a significant impact in the field of detection of environmental pollutants and our ability to realisticably determine the consequences of such contamination for public health.
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