Analyzing organic vapors in exhaled breath using a surface acoustic wave sensor array with preconcentration: Selection and characterization of the preconcentrator adsorbent

William Arthur Groves, Edward T. Zellers, Gregory C. Frye

Research output: Contribution to journalArticle

119 Citations (Scopus)

Abstract

The analysis of organic vapors in exhaled breath can provide information about chemical exposures and health status. This article describes work aimed at developing a small prototype instrument that employs an array of four polymer-coated surface acoustic wave (SAW) sensors and a thermally desorbable adsorbent preconcentrator for rapid breath analysis. The adsorbent used in the preconcentrator is critical to achieving adequate sensitivity and compensating for the high background of water vapor. Eight granular adsorbents packed into narrow bore glass tubes wrapped with NiCr wire were evaluated individually and in selected dual-bed configurations with respect to the pressure drop of the packed bed, retention of water vapor, and adsorption/desorption efficiency of each of several organic solvent vapors. Although adsorbents of Tenax GR(®) and Carbotrap(®) performed well, a highly porous styrene-divinylbenzene resin demonstrated superior overall performance and was selected for further testing. Solvents ranging in vapor pressure from 8mm of Hg (m-xylene) to 420mm of Hg (dichloromethane) were efficiently trapped from 0.25-l spiked breath samples and efficiently desorbed at 170°C. Incorporating an intermediate dry-air purge step prior to thermal desorption of samples selectively removed co-adsorbed water and reduced the limits of detection (LOD) by an order of magnitude. Results of detailed breakthrough studies were considered in the context of the modified Wheeler and Langmuir adsorption models and used to determine the minimum quantity of adsorbent required to prevent saturation of the adsorbent bed for each test vapor. Measurement of vapors at concentrations ranging from sub-ppm to 200ppm was demonstrated. Copyright (C) 1998 Elsevier Science B.V.

Original languageEnglish (US)
Pages (from-to)131-143
Number of pages13
JournalAnalytica Chimica Acta
Volume371
Issue number2-3
DOIs
StatePublished - Oct 5 1998

Fingerprint

divinyl benzene
Steam
Sensor arrays
acoustic wave
Surface waves
Adsorbents
surface wave
Adsorption
desorption
water vapor
Vapors
Acoustic waves
sensor
adsorption
Vapor Pressure
Styrene
Methylene Chloride
health status
xylene
pressure drop

All Science Journal Classification (ASJC) codes

  • Analytical Chemistry
  • Environmental Chemistry
  • Biochemistry
  • Spectroscopy

Cite this

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abstract = "The analysis of organic vapors in exhaled breath can provide information about chemical exposures and health status. This article describes work aimed at developing a small prototype instrument that employs an array of four polymer-coated surface acoustic wave (SAW) sensors and a thermally desorbable adsorbent preconcentrator for rapid breath analysis. The adsorbent used in the preconcentrator is critical to achieving adequate sensitivity and compensating for the high background of water vapor. Eight granular adsorbents packed into narrow bore glass tubes wrapped with NiCr wire were evaluated individually and in selected dual-bed configurations with respect to the pressure drop of the packed bed, retention of water vapor, and adsorption/desorption efficiency of each of several organic solvent vapors. Although adsorbents of Tenax GR({\circledR}) and Carbotrap({\circledR}) performed well, a highly porous styrene-divinylbenzene resin demonstrated superior overall performance and was selected for further testing. Solvents ranging in vapor pressure from 8mm of Hg (m-xylene) to 420mm of Hg (dichloromethane) were efficiently trapped from 0.25-l spiked breath samples and efficiently desorbed at 170°C. Incorporating an intermediate dry-air purge step prior to thermal desorption of samples selectively removed co-adsorbed water and reduced the limits of detection (LOD) by an order of magnitude. Results of detailed breakthrough studies were considered in the context of the modified Wheeler and Langmuir adsorption models and used to determine the minimum quantity of adsorbent required to prevent saturation of the adsorbent bed for each test vapor. Measurement of vapors at concentrations ranging from sub-ppm to 200ppm was demonstrated. Copyright (C) 1998 Elsevier Science B.V.",
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