Automated detection and reporting of Volatile Organic Compounds (VOCs) in complex environments

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Description

This paper describes results from efforts to develop VOC sensing systems based on two complementary techniques. The first technique used a gated channeltron detector for resonant laser-induced multiphoton photoionization detection of trace organic vapors in a supersonic molecular beam. The channeltron was gated using a relatively simple circuit to generate a negative gate pulse with a width of 400 ns (FWHM), a 50 ns turn-on (rise) time, a 1.5 {mu}s turn-off (decay) time, a pulse amplitude of {minus}1000 Volts, and a DC offset adjustable from zero to {minus}1500 Volts. The gated channeltron allows rejection of spurious responses to UV laser ... continued below

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26 p.

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Hargis, P.J. Jr.; Preppernau, B.L. & Osbourn, G.C. March 1, 1997.

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  • Sandia National Laboratories
    Publisher Info: Sandia National Labs., Albuquerque, NM (United States)
    Place of Publication: Albuquerque, New Mexico

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Description

This paper describes results from efforts to develop VOC sensing systems based on two complementary techniques. The first technique used a gated channeltron detector for resonant laser-induced multiphoton photoionization detection of trace organic vapors in a supersonic molecular beam. The channeltron was gated using a relatively simple circuit to generate a negative gate pulse with a width of 400 ns (FWHM), a 50 ns turn-on (rise) time, a 1.5 {mu}s turn-off (decay) time, a pulse amplitude of {minus}1000 Volts, and a DC offset adjustable from zero to {minus}1500 Volts. The gated channeltron allows rejection of spurious responses to UV laser light scattered directly into the channeltron and time-delayed ionization signals induced by photoionization of residual gas in the vacuum chamber. Detection limits in the part-per-trillion range have been demonstrated with the gated detector. The second technique used arrays of surface acoustic wave (SAW) devices coated with various chemically selective materials (e.g., polymers, self assembled monolayers) to provide unique response patterns to various chemical analytes. This work focused on polymers, formed by spin casting from solution or by plasma polymerization, as well as on self assembled monolayers. Response from coated SAWs to various concentrations of water, volatile organics, and organophosphonates (chemical warfare agent simulants) were used to provide calibration data. A novel visual empirical region of influence (VIERI) pattern recognition technique was used to evaluate the ability to use these response patterns to correctly identify chemical species. This investigation shows how the VERI technique can be used to determine the best set of coatings for an array, to predict the performance of the array even if sensor responses change due to aging of the coating materials, and to identify unknown analytes based on previous calibration data.

Physical Description

26 p.

Notes

OSTI as DE97005908

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  • Other Information: PBD: Mar 1997

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  • Other: DE97005908
  • Report No.: SAND--97-0509
  • Grant Number: AC04-94AL85000
  • DOI: 10.2172/469115 | External Link
  • Office of Scientific & Technical Information Report Number: 469115
  • Archival Resource Key: ark:/67531/metadc675442

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  • March 1, 1997

Added to The UNT Digital Library

  • July 25, 2015, 2:21 a.m.

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  • June 10, 2016, 9:53 p.m.

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Hargis, P.J. Jr.; Preppernau, B.L. & Osbourn, G.C. Automated detection and reporting of Volatile Organic Compounds (VOCs) in complex environments, report, March 1, 1997; Albuquerque, New Mexico. (digital.library.unt.edu/ark:/67531/metadc675442/: accessed November 24, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.