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Workplace Air Sampling of Gases and Vapors on Solids Sorbents.

Wright, Michael D. (1990) Workplace Air Sampling of Gases and Vapors on Solids Sorbents. Doctoral thesis, University of Surrey (United Kingdom)..

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Abstract

The rationale of air sampling in testing for compliance with occupational hygiene standards, and the complementary relationship between air sampling and biological monitoring has been reviewed briefly. The criteria for selection of solid sorbents has been discussed and thermal desorption compared with solvent desorption, with respect to sample recovery and other factors. The synthesis of a novel polyimide sorbent prepared from the condensation product of bis(4-amino)sulphone and pyromellitic dianhydride has been described, together with an evaluation of the thermal properties of some polyimides. The chromatographic theory of asymmetric elution profiles from short sampling cartridges has been discussed, with reference to the definitions of mean residence time, peak median and centroid. Enthalpies of adsorption and retention volumes of organic solvents on Tenax, Chromosorb 106, Spherocarb, activated charcoal and some polyimides have been determined by extrapolation of chromatographic retention volumes at different temperatures. It has been found that the breakthrough volumes of some solutes on Tenax were smaller than would be expected from their mean residence time and it has been proposed that some steric factor is responsible for increasing the mass transfer resistance between gaseous and sorbed phase. The advantages of diffusive sampling for organic vapours in the workplace have been presented. The theory of diffusive sampling has been reviewed extensively, with discussions of the application of Fick's first law to the 'ideal' sampler, the effects of air velocity, the sampling of 'transients', and the effects of sorbent saturation in thin-bed and thick-bed samplers. It has been shown how the gas chromatographic retention volume parameter can be related to a simple model of uptake as a function of time. The operation of a dual-capillary thermal desorption analytical system has been described. Retention index data showing the effects of ageing on cross-linked silicone phases has been presented. The change over 3 years was about 1-2 index units. Recovery data has been given for 42 common organic solvents stored on Tenax thermal desortion tubes for up to one year, and the effectiveness of long-term methods of sealing the tubes has been assessed. The recovery after one year was >95% for most solvents.

Item Type: Thesis (Doctoral)
Divisions : Theses
Authors : Wright, Michael D.
Date : 1990
Additional Information : Thesis (M.Phil.)--University of Surrey (United Kingdom), 1990.
Depositing User : EPrints Services
Date Deposited : 30 Apr 2019 08:07
Last Modified : 20 Aug 2019 15:32
URI: http://epubs.surrey.ac.uk/id/eprint/851176

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