Article

The use of multi-channel silicone rubber traps as denuders for polycyclic aromatic hydrocarbons.

Department of Chemistry, Faculty of Natural and Agricultural Sciences, University of Pretoria, South Africa.
Analytica chimica acta (Impact Factor: 4.31). 06/2012; 730:71-9. DOI: 10.1016/j.aca.2011.11.013
Source: PubMed

ABSTRACT Atmospheric polycyclic aromatic hydrocarbons are ubiquitous environmental pollutants, which may be present both in the gaseous phase and adsorbed onto the surface of particles. Denuders are sampling devices which have been effectively employed in such partitioning applications. Here we describe and characterise a novel miniature denuder consisting of two multi-channel silicone rubber traps (each 178 mm long, 6 mm o.d. containing 22 silicone tubes), separated by a quartz fibre filter for particle phase collection. The denuder only requires a small portable personal sampling pump to provide sampling flow rates of ∼0.5 L min(-1). Theoretical considerations indicated that the air flow through the denuder was expected to be laminar, and the linear velocity arising from longitudinal diffusion was found to be negligible. The calculated particle transmission efficiency through the denuder was found to be essentially 100% for particles>50 nm, whilst the experimental overall efficiency, as determined by CPC and SMPS measurements, was 92 ± 4%. The size resolved transmission efficiency was <60% for particles below 20 nm and 100% for particles larger than 200 nm. Losses could have been due to diffusion and electrostatic effects. Semi-volatile gaseous analytes are pre-concentrated in the silicone of the trap and may be thermally desorbed using a commercially available desorber, allowing for total transfer and detection of the collected analytes by GC-MS. This enhances detection limits and allows for lower sampling flow rates and shorter sampling times, which are advantageous for studies requiring high temporal resolution.

0 Bookmarks
 · 
89 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this article the role of vapor-particle partitioning in the atmospheric removal of semivolatile organic compounds (SOC) such as pesticides, PCBs, and PAHs is explored. Prediction of atmospheric fluxes of SOCs is limited by the uncertainties inherent in wet and dry deposition of particles, plus uncertainties in air-to-water vapor exchange and vapor-particle partitioning. Despite artifact problems in hi-vol sampling, it is encouraging that the filter-retained fraction agrees within about a factor of 3 with {phi} calculated from Junge's model, and that apparent aerosol-bound percentages correlate with depositional properties. Additional study is needed on methods to distinguish gaseous and particulate SOCs in the atmosphere, on details of the interactions between SOC vapors and atmospheric particulate matter, and on the physical properties of SOCs.
    Environmental Science and Technology 03/1988; 22:5. · 5.48 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The overall efficiency of silicone-grease-coated denuders was determined for the collection of selected 3- and 4-ring polynuclear aromatic hydrocarbons (PAH). PAH studied were fluorene, phenanthrene, anthracene, acenaphthene and pyrene. Fluorene was subsequently eliminated from consideration because of analytical problems caused by the reactivity of this compound. Results are interpreted in terms of the collisional reaction efficiencies (γ) for these compounds. An analysis of the effects of uncertainties in diffusion coefficients and γ values for these compounds on overall phase distributions derived from experimental data suggests that the consequences of these uncertainties are less significant than normal variations due to sampling and analysis effects.
    Atmospheric Environment Part A General Topics 10/1992; 26(15):2831-2834.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Measurement of the loss of semi-volatile organic compounds from particles collected with a filter is carried out by comparing the amounts collected by comparable filter pack and diffusion denuder samplers. The sorbents used to collect organic compounds in the denuder and sorbent filters must have the same efficiency for collection of all gas-phase organic compounds present. Interpretation of the data requires that the efficiency of collection of gas-phase compounds by the denuder be known. In theory this can be accomplished by determination of the deposition pattern of all organic compounds collected in the denuder, but in practice this is very difficult if the organic material consists of a wide variety of compounds. An alternative approach is to determine the breakthrough of organic compounds in a sampler with a particle-collection filter preceding the denuder and sorbent filter. In such a sampler only gas-phase organic material enters the denuder. We have developed both a multi-channel parallel plate diffusion denuder sampler and a comparable sampler in which the denuder is preceded by a filter. Samples can be collected with the multisystem sampler at a flow rate of 35 sLpm. The denuder surfaces and the sorbent filters are made from sheets of an activated charcoal-impregnated filter paper. Collection of semi-volatile compounds by the samplers has been characterized and the systems have been field tested. The samplers are now being used for the routine collection and determination of semi-volatile organic compounds in particles at Canyonlands National Park in southeastern Utah. Available data from this field program show significant losses of particulate organic compounds on a quartz filter due to volatilization during sampling.
    Atmospheric Environment Part A General Topics 06/1993;

Full-text (2 Sources)

Download
10 Downloads
Available from
Jul 21, 2014