Particle analyzers

Phase Doppler particle analyzers are essentially single-particle counters because they measure one particle at a time within a small sampling volume. This volume must be kept small to minimize the probabiUty of having more than one droplet in the volume at any given instant. This probabiUty increases as the concentration of droplets becomes greater, and there is more risk of measurement errors. 

FIG. 20-6 Diagram of the Leeds and Northnip Ultrafine Particle Analyzer (UPA). 

Fraunhofer rules do not include the influence of refraction, reflection, polarization and other optical effects. Early Iziser particle analyzers used Fraunhofer approximations because the computers of that time could not handle the storage cuid memory requirements of the Mie method. For example, it has been found that the Fraunhofer-based instrumentation cannot be used to measure the particle size of a suspension of lactose (R.I. = 1.533) in iso-octane (R.I. = 1.391) because the relative refractive index is 1.10, i.e.- 1.533/1.391. This is due to the fact that diffraction of light passing through the particles is nearly the same as that passing around the particles, creating a combined interference pattern which is not indicative of the true... 

The major disadvantages in application of the AEM method relative to AAS is the time required for specimen preparation and analysis. Care must be taken that the particles analyzed are characteristic of the bulk material, that they are thin enough to meet the "thin-film criteria" of Equations (2) and (3), and that enough particles are analyzed to reduce the random error to acceptable levels. The AEM analyses shown in Figure 6 took several days to collect and involved considerble operator attention. 

Many laser-based droplet diagnostic techniques have evolved from the fields such as spray combustion and spray drying. Phase-Doppler particle analyzer is now recognized as the most successful and advanced diagnostic instrument for spray characterization. Other proven diagnostic techniques include laser velocimetry and... 

The phase-Doppler method is capable of accurately measuring particle size distribution and velocity J655] The most recent models ofphase-Doppler particle analyzer (PDPA) can generate data of droplet size and velocity simultaneously as a function of time, from that droplet drag can be calculated and clustering phenomenon can... 

Inorganic analysis was conducted in conjunction with the mineral analysis. Particles analyzed previously for mineral content were analyzed for their inorganic content, and an overall analysis conducted. The resultant EDS spectra output was fed into a spreadsheet software package which was adapted by the authors to allow the calculation of a quantitative elemental analysis. 

Using the particle analyzer, count particles greater than or equal to 0.5 pm in diameter at heights of 40 in. in the center of each grid. 

Frequently, a major limitation of DS-based collection systems is that they operate at substantially subquantitative collection efficiencies at the typical sampling rates used. This situation increases the probability of error because of large thermal variations that affect diffusive transport. For these reasons, should wet denuders (vide infra) prove to be viable continuous collection devices, they may well replace DS-based systems. Their ability to more quantitatively remove gases may also spur the development of combined gas-particle analyzer systems in which, for example, the acid gases are removed by the denuder and analyzed the particles are then collected by the impactor equivalent of a wet denuder, and the acidity associated with... 

Spray Dynamic Structure. Detailed measurements of spray dynamic parameters are necessary to understand the process of droplet dispersion. Improvements in phase Doppler particle analyzers (PDPA) permit in situ measurements of droplet size, velocity, number density, and liquid flux, as well as detailed turbulence characteristics for very small regions within the spray. 

This section contains a general description of the principles by which the Coulter Model N4 Sub-Micron Particle Analyzer, used in this study to characterize artificial gas-in-water emulsions (see Section 10.4), determines sample particle size. The measuring principles are based on the theory of Brownian motion and photon correlation spectroscopy (ref. 464,465 see also Sections 10.2 and 10.4). 

The Coulter Model N4 Sub-Micron Particle Analyzer, used to obtain the measurements in this section on artificial gas-in-water... 

Example 1.1 One of the applications of using Stokes s law to determine the particle size is the Sedigraph particle analyzer. Table El.l shows the relationship between the cumulative weight percentage of particles and the corresponding particle terminal velocities for a powder sample. The densities of the particle and the dispersing liquid are 2,200 and 745 kg/m3, respectively. The liquid viscosity is 1.156 x 10-3 kg/m s. Find out the relationship of the mass fraction distribution to the equivalent dynamic diameter. 

Typically, the phase Doppler method is good for the measurement of particle sizes ranging from 1 /u.m to 10 mm with a variation by a factor of 40 at one instrument setting. As a rule of thumb, the maximum measurable concentration is 1,000 particles per cubic millimeter (mm3). Commercial instruments using this technique are available, e.g., the phase Doppler particle analyzer (PDPA) (Aerometrics) and the Dantec particle dynamics analyzer (DPDA) (Dantec Electronics). 

An important advance in continuous analyzers uses both particle size data and single-particle chemical composition. These instruments employ a method of rapid depressurization of the aerosol that produces a particle beam and irradiation of particles to generate ions that are analyzed by mass spectroscopy. The single particle analyzers have been employed in atmospheric research recently but have not reached the stage where they are used routinely in air monitoring. 

Results from AFM studies are supported by light-scattering data. The particle size distribution in the MDMO-PPV solutions can be analyzed by means of light-scattering measurements using a Microtrac Ultrafine Particle Analyzer. This technique allows us to determine the particle size (PS) in solutions. It can be expressed as a number distribution or a volume distribution. The results for MDMO-PPV dissolved in toluene and chlorobenzene with different concentrations (0.0625%, 0.125% and 0.25%) are given in Table 5.1. 

To monitor nanoparticle swelling in salt environment, we employed laser diffraction Mastersizer Micro Particle Analyzer MAF5000 (Malvern) with a dynamic range of 0.3 to 300 pm. This instrument utilizes Mie scattering algorithm with the Fraunhofer approximation. 

Fig. 12. Mass spectra of Rice Yellow Mottle Virus (RYMV) and Tobacco Mosaic Virus (TMV) particles analyzed with an electrospray ionization charge detection time-of-flight mass spectrometer. Inset, electron micrographs of the icosahedral RYMV (diameter 28.8 nm) and the cylindrical TMV (-300 nm long and 17 nm in diameter). The known molecular weight of RYMV and TMV are 6.5X106 and 40.5X106 Daltons,respectively...

Mullard Film Scanning Particle Analyzer, Mullard Tech. Leaflet., 167... 

Allen, T. (1992), Centrifugal particle analyzer. US Patent 5,095,451,407 Allen. T. (1992), Proc Conf Particle Size Analysis, PSA 91 Loughborough University, Anal. Div. Chem Soc, publ. Heyden,407 Allen. T. (1991), Proc. Int. Symp. Particle Size Analysis, publ. Royal Soc. Chem., ed. Stanley-Wood, N.G. and Lines, R., pp 498-5l3,40[Pg.444]

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