# THE FT-MICROWAVE SPECTROMETER: A NEW TOOL FOR ANALYTICAL CHEMISTS

Please use this identifier to cite or link to this item: http://hdl.handle.net/1811/29679

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 Title: THE FT-MICROWAVE SPECTROMETER: A NEW TOOL FOR ANALYTICAL CHEMISTS Creators: Suenram, R. D.; Lovas, F. J.; Grabow, Jens-Uwe; Hight Walker, A. R.; Fraser, G. T. Issue Date: 1995 Publisher: Ohio State University Abstract: Over the years a number of improvements in Fourier Transform Microwave (FTMW) Spectroscopy have lowered the detection limits for gas phase species down to the 1 - 100 ppb range. This high sensitivity coupled with 100% species selectivity, millisecond response times and complete automation of the instrument provides analytical chemists with a new technique for the determination of trace gas species that are present in industrial chemical processes. The technique can be used either in-lieu-of or as a complementary detection technique to gas chromatography mass spectrometric techniques (GCMS) for the detection of gas phase species. We have carried out sensitivity tests using NIST's FTMW spectrometer using 800 ppm samples of a wide range of species containing different chemical functional groups. Using these samples and the known isotopic abundances of $^{13}C = 1.1%, ^{18}O = 0.2%$, and $^{2}H = 0.015%$, detection limits in the range of 1 - 100 ppb were attained for most species when neon is used as a carrier gas. Air can also be used as a carrier gas with some loss in sensitivity (typically a factor of 10-50). We are currently in the process constructing a mobile instrument which can be transported to an industrial environment for use in process control and monitoring situations. Advantages of FTMW in monitoring trace gas constituents include the 100% certainty of the identity of the species being monitored. Using a pulsed molecular beam nozzle in conjunction with a specially designed flow nozzle which operates at cycle speeds of several Hertz, allows rapid response to changes in industrial process flow streams. The cooling provided by the pulsed molecular beam permits larger molecular species to be monitored with the same ease as smaller species since only the lowest rotational energy levels will of any species will be populated at the low temperature of the molecular beam. Description: Author Institution: National Institute of Standards and Technology, Gaithersburg, MD 20899 URI: http://hdl.handle.net/1811/29679 Other Identifiers: 1995-RI-09