Diffusive sampling

A. Berlin, R. H. Brown, and K. J. Saunders, eds.. Diffusive Sampling An Alternative Approach to Workplace Air Monitoring Royal Society of Chemistry, London, 1987. 

This assumes that the gas-solid exchange kinetics at the interface is rapid. When this process affects the exchange kinetics significantly dieii analysis of concentrations layer by layer in die diffused sample is necessaty. This can be done by the use of SIMS (secondary ion mass spectrometry) and the equation used by Kihier, Steele and co-workers for this diffusion study employs a surface exchange component. 

BS ISO 16000 Indoor formaldehyde and other carbonyl compounds Active and diffusive sampling... 

Hafkenscheid TL, Mowrer J (1996) Intercomparison of tube-type diffusive sampling for the determination of volatile hydrocarbons in ambient air. Analyst 121 1249-1252. 

Copper and nickel are also common contaminants in Si and can often be introduced during annealing treatments. Both of these impurities are extremely rapid diffusers and cannot be retained in electrically active form even by rapid quenching of diffused samples (Weber, 1983). Quite often, complexes involving Cu or Fe impurities are observed by DLTS in heat-treated Si. All of these centers are hole traps, with Cu giving rise to levels at Ev + 0.20 eV, Ev + 0.35 eV and Ev + 0.53 eV, whereas Ni is related to levels at Ev + 0.18 eV, Ev + 0.21 eV and Ev + 0.33 eV. All of these levels are passivated by reaction with atomic hydrogen (Pearton and Tavendale, 1983), and are restored by annealing at 400°C. 

The line at 2287.7 cm"1 in InP visible in Fig. 18 is clearly the same as the one observed in plasma diffused sample by Pajot et al. (1989) and which is the spectroscopic evidence of the zinc acceptor neutralized by hydrogen. The line at 2272 cm"1 observed only in InP doped with manganese is very... 

Because of the lattice damage, the absorptions due to the local modes of vibration are usually broader in implanted materials than, for instance, in plasma diffused samples. For proton energies around 1 MeV, the line-widths are in the range 5-100 cm-1 (as compared with 0.1-5 cm-1 for plasma hydrogenation). 

A comparison of active (using pumps) and passive (relying on diffusion) sampling techniques for the determination of nitrobenzene, benzene and aniline in air was mentioned in Section IV.A77. Several LLE methods for nitroaromatic compounds dissolved in water were evaluated. High recoveries were achieved with discontinuous or continuous extraction with dichloromethane, adsorption on a 1 1 1 mixture of Amberlite XAD-2, -4 and -8 resins and elution with dichloromethane445. 

The evaluation of diffusion samplers reported in this paper was initiated as an internal project at Arthur D. Little, Inc., to develop for ourselves a base of data which would help us to judge the utility of diffusion samplers in our work. Diffusion samplers were purchased from the two firms active in the marketplace when the field study began (early 1979), Abcor and 3M. A program was devised wherein, during each of approximately 50 surveys being undertaken in plastic fabrication plants, four to six diffusion samplers would be exposed, each adjacent to a charcoal tube personal sample. At the conclusion of the field sampling, a data base of over 100 pairs of samples (each pair including a diffusion sample and a charcoal tube sample) had been compiled for each of the two diffusion samplers. 

For fine particles, despite the fact that the major rationale behind diffusive sampling of a gas is to achieve discrimination from the concurrently present atmospheric aerosol, relatively little attention has been paid to actually characterizing the particle transmission through these systems. A summary of existing data has been presented (40). The only thorough charac-... 

Martin, N.A., Marlow, D.J., Henderson, M.H., Goody, B.A. and Quincey, P.G. (2003) Studies using the sorbent Carbopack X for measuring environmental benzene with Perkin-Elmer-type pumped and diffusive samples. Atmospheric Environment, 37, 871-9. 

This chapter discusses the principles governing diffusive sampling and the factors that can influence sampler performance, and reviews some of the studies that have applied the technique for the measurement of VOCs in indoor air. 

This consideration of the principles of diffusive sampling identifies a range of factors which may influence the performance of a diffusive sampler for monitoring VOC concentrations in indoor air. These factors will potentially be a source of error in such measurements and add to the overall uncertainty of the result given by the measurement procedure. In addition the amount of uncertainty will be influenced by other factors including amount and consistency of background contamination of sorbents, repeatability of analytical determination, formation of artifacts, stability of analyte on the sorbent, recovery of analyte during analyses and presence of interferents. 

Brown, V., Crump, D. and Yu, C. (1993) Long term diffusive sampling of volatile organic compounds in indoor air. Environmental Technology, 14, 771-7. 

EN (2005a) 14662-5. Ambient Air Quality-Standard Method for Measurement of Benzene Concentrations Diffusive Sampling Followed by Solvent Desorption and Gas Chromatography, The British Standards Institution, London, UK. 

Hafkenscheid, T., Langelaan, F., Baldan, A. and Wilkinson, G. (2001) Determination of uptake rates for 4-week diffusive sampling of chlorinated butadienes in indoor air. Proceedings of International Conference on Measuring Air Pollutants by Diffusive Sampling, Montpellier, France, 26-29 September 2001, pp. 229-34. 

ISO (2004c) 16000-4. Indoor Air-Determination of Formaldehyde-Diffusive Sampling Method, International Organization for Standardization, Geneva, Switzerland. 

Figure 5.14 shows the toluene distribution of the solvent-diffused sample (5 min cured). The image contrast is based on the difference in swelling capability throughout the sample. More toluene is imbibed into the PBD-rich matrix and less solvent is imbibed into the ZDA-rich domains. Therefore, the ZDA-rich domain is shown as low intensity (blue) and PBD-rich region is shown as high intensity (red, yellow or green). The difference in toluene distribution results from the differences in solubility and crosslink density. 

Figure 5.14 Toluene distribution of the solvent-diffused sample (5 min cured). Reproduced from figure 2 of Ref. 28, with permission.

Hermeken, H., Lindahl, R., Ostin, A., Vogel, M., Levin, J-0., Karst, U. (2003). Diffusive sampling of methyl isocyanate using 4-nitro-7-piperazinobenzo-2-oxa-1,3-diazole (NBDPZ) as derivatizing agent. J. Environ. Monit. 5 100-5. 

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