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A dual-adsorbent preconcentrator for a portable indoor-VOC microsensor system.

Authors
Lu-C-J; Zellers-ET
Source
Anal Chem 2001 Jul; 73(14):3449-3457
NIOSHTIC No.
20042732
Abstract
The development and testing of a miniature dual-adsorbent preconcentrator for a microsensor-based analytical system designed to determine complex volatile organic chemical (VOC) mixtures encountered in indoor working environments at low part-per-billion levels is described. Candidate adsorbents were screened for thermal-desorption bandwidth and breakthrough volume against 20 volatile organic vapors and subsets thereof as a function of several relevant variables. A glass capillary (1.1 mm i.d.) packed with 3.4 mg of Carbopack X and 1.2 mg of Carboxen 1000 provides sufficient capacity for a 1-L dryair sample containing all 20 vapors at concentrations of 100 ppb as well as providing a composite half-height peak width of <3 s at a desorption temperature of 300 C and a flow rate of 4 mL/min. Required adsorbent masses increase to 7.0 and 1.5 mg, respectively, for the same mixture at component concentrations of 1 ppm. Vapor breakthrough volumes for the Carbopack X are unaffected by humidity from 0 to 100%RH, but those for the Carboxen 1000 are significantly reduced, requiring an additional 0.9 mg of the latter to avoid premature breakthrough at the 100 ppb level. Good peak shapes, efficient chromatographic separation of preconcentrated sample mixture components, and detection limits in the low-partsper- billion range using an integrated surface-acousticwave (SAW) sensor are achieved. Preconcentrator design and operating parameters are considered in terms of the vapor bed-residence times and breakthrough volumes in the context of the modified Wheeler equation.
Keywords
Analytical-processes; Volatiles; Organic-chemicals; Work-environment; Vapors; Organic-compounds; Temperature-effects; Chromatographic-analysis; Air-quality
CODEN
ANCHAM
Publication Date
20010701
Document Type
Journal Article
Funding Type
Grant
Fiscal Year
2001
NTIS Accession No.
NTIS Price
Identifying No.
Grant-Number-R01-OH-003692
Issue of Publication
14
ISSN
0003-2700
Source Name
Analytical Chemistry
State
MI
Performing Organization
University of Michigan, Ann Arbor
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