Light scattering techniques, aerosol

Other light scattering techniques, e.g., using several different scattering wavelengths, have also been used to probe PSCs and aerosols (e.g., Larsen et al., 1995 ... 

Dusts, Mists, Aerosols and Fumes. The P-5 Digital Dust Indicator is another sensor currently available for use as a component of the Chronotox System. Suitable for the measurement of silica, lead fumes, pharmaceutical powders as well as many other types of particulates found in manufacturing or laboratory situations, the battery-operated P-5 uses the light scattering technique to measure dusts over a range of either 0.01-100 mg/m or 0.001-10 mg/m (Figure 6). 

Optical measurements of airborne combustion aerosols have been carried out for a number of years, usually with light scattering techniques. However, due to the particle size dependence of light scattering and the variable particle size distributions of smokes, it is extremely difficult to relate light scattering properties to particulate mass concentrations. The measurement of light absorption by particles can be directly related to particle mass if two conditions are met ... 

Light-scattering techniques (Figure 39) are primarily used to investigate aerosols and air pollutants. They analyze the light scattered by particles if they... 

The time-avemged scattered intensity / is the basis of conventional light-scattering techniques used for aerosol measurements. 

Gas-phase measurement techniques can be divided into two categories—in situ and extractive. Light-scattering techniques fall into the former category while traditional aerosol measurement instruments fall into the latter. Extractive techniques require that a sample of the aerosol-laden gas be removed from its environment and transferred to the location where the measurement is made. The transfer must be made without biasing the sample, which is often difficult to accomplish. In situ techniques can often overcome these limitations. 

It is known that health hazards are caused by inhalation of sub-micron aerosol particles. Drinker and Hatch (1936) stated that vast numbers of particles below 0.25-pm radius are generated by industrial processes and they considered this sub-micron aerosol to be quite dangerous. Particles below 0.1-pm radius are too small for direct microscopic observation. Likewise, the standard light scattering techniques cannot be used. Consequently, the methods in use depend on observation of the particles with the ultramlcroscope or electron microscope. 

Merkus HG, Marijnissen JCM, Jansma HL, Scarlett B (1994) Droplet size distribution measurements for medical nebulizers by the forward light scattering technique ( laser diffraction ). J Aerosol Sci 25(Suppl 1) 319... 

One of the newest particle sizing techniques is light scattering. This technique is used to measure particle size distribution, colloid behavior, particle size growth, aerosol research, clean room monitoring, and pollution monitoring. 

Methods for analysis of the particle size distribution in the aerosol cloud include techniques such as time of flight measurement (TOE), inertial impaction and laser diffraction. Dynamic light scattering (photon correlation spectroscopy) is confined to particles (in suspension) in the submicron range. In addition to the size distribution, the particle velocity distribution can be measured with the Phase Doppler technique. 

To test the applicability of statistical techniques for determination of the species contributions to the scattering coefficient, a one-year study was conducted in 1979 at China Lake, California. Filter samples of aerosol particles smaller than 2 ym aerodynamic diameter were analyzed for total fine mass, major chemical species, and the time average particle absorption coefficient, bg. At the same time and location, bgp was measured with a sensitive nephelometer. A total of 61 samples were analyzed. Multiple regression analysis was applied to the average particle scattering coefficient and mass concentrations for each filter sample to estimate aj and each species contribution to light scattering, bgn-j. Supplementary measurements of the chemical-size distribution were used for theoretical estimates of each b pj as a test of the effectiveness of the statistical approach. 

The major limitation of LA-ICP-MS is the need for standards that closely match the properties of the samples. In some cases it is possible to use NIST glass standard reference materials for calibration in the analysis of geological materials [67,68], Internal standardization employing MS signals from elements at known concentrations has been used to improve precision and accuracy. Other techniques, such as acoustic [69] and light scattering [70] measurements, have been used in an attempt to monitor the relative amount of material ablated. These approaches seem to work well for variations in the amount of material sampled for similar sample matrices but not for very different types of solids. Dual-sample introduction systems with either wet [71] or dry [72] aerosol introduction in addition to laser ablation have also been reported. 

Although DLS is most often used to size solid colloidal particles, the technique has also been applied to characterize aerosols [78,86,87], emulsion droplets [88,89], amphiphilic systems [90-92], and macromolecular solutions [12,16,93]. Another common application is the study of the fractal structure and kinetics of colloidal aggregation [94-102], More information about dynamic light scattering and its applications can be found in Refs. 23. 103 (104), and 105, in reviews, Refs. 11, 13, 36, 37, 49, 50, and 106, and in collections of papers Refs. 12. 14. 16. 93 (107), 105, and 108-114. 

Additional detection techniques that can be employed to help solve mass balance issues with RP-HPLC are MS [30], chemiluminescent nitrogen-specihc detector [31], evaporative light-scattering detector, ELSD [32], and corona charged aerosol detection [CAD] [33],... 

Laser diffraction technique is able to generate the envelope diameter distribution of the aggregates in the aerosol cloud, as well as the surface and mass fractal dimensions as explained in Light Scattering under both Boundary and Surface Fractal Dimensions and Mass Fractal Dimension. However, validation of Eq. (25) by comparison studies between the impaction and laser diffraction techniques is required. 

Kaye, B.H. Characterization of Powders and Aerosols Wiley-VCH Weinheim, 1999. The Use of Fourier Techniques to Characterize the Shape of Profiles in Ch. 2, Direct Measurement of Larger Fineparticles and the Use of Image Analysis Systems to Characterize Fineparticles, 21-58, and Ch. 7, Light Scattering Methods for Characterizing Fineparticles, 205-232. 

In a series of papers (24-29) Eicke and co-workers reported results of thorough studies performed on inverse micellar systems involving hydrocarbons such as benzene or isooctane and surfactants such as AY or AOT aerosols. Dielectric, conductance, ultracentrifugation, NMR, light scattering, fluorescence depolarization and photon correlation spectroscopy techniques were used. The main conclusions arrived at are the following ones, as expressed in C29). For water-to-AOT molar ratios smaller than 10, water-in-isooctane systems consist of dispersions of hydrated soap aggre-... 

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