OPTOACOUSTIC DETECTION OF ETHYLENE IN THE PRESENCE OF INTERFERING GASES

A study of the limitations of optoacoustic detection of ethylene in gas mixtures using a 12C16O2 laser is presented. Particular emphasis is given to the detection of ethylene in urban areas and in fruit storage chambers. Calculations indicate that in most cases of interest the practical minimum detectable and identifiable concentration of ethylene is about 5 ppb. A concentration of 1% of CO2 may increase this limit to 50 ppb. These limits are primarily due to inaccuracy in a priori knowledge of ir spectral signatures of interfering gases. As a practical example of the monitoring of ethylene in a realistic environment, a meausrement with a sensitive resonant optoacoustic cell in an urban area is reported. The same cell is also used to demonstrate the effectiveness of NaOH scrubbers for the elimination of interfering CO2. Measurements of absorption coefficients of ethylene for several 12C16O2 laser transitions are reported and compared with those given in the literature. Data are also given for the isotopic 13C16O2 laser transitions which may be useful in overcoming CO2 interference. © 1979 Optical Society of America.