Particle size, measurement resolutions

In the present paper we report on an experimental investigation of SEC. Main emphasis is placed on particle size measurement using analytical methods of correcting for imperfect resolution. 

Finally, proper alignment to ensure correct positioning of the laser beam, sample, and photodetector are critical for accurate particle size measurements 185 ]. This is especially important for multiangle measurements because misalignment will produce large systematic errors that are difficult to detect and do not average out. In his review, Stepanek [49] discusses the additional experimental complications of wide correlation functions, square root bias, other sources of systematic error, and resolution of <5 function or sharp peaked PSDs. 

Particle size measurements were made using an UV-laser, shadow photographic technique. The particle sizing system displayed real-time droplet images onto a television monitor. The images (shadows) were obtained when a pulsed (30 times per second) UV-laser beam was directed through a spray scene onto a synchronized UV-sensitive vidicon camera/recorder. The narrow depth of field used by this system can record shadows from 300 in-focus droplets per second with a resolution down to approximately 0.3 /un in diameter. 

A computer controlled particle size measurement device with veiy high resolution was presented by Foerdeneuther [18] based on the Brookliaven optical and x-ray disc centrifuges. 

PCS is a rapid, absolute, nondestructive and rapid method for particle size measurements, but it does have some limitations. The main disadvantage is the poor resolution of particle size distribution, and it also suffers from the limited size range (absence of any sedimentation) that can be accurately measured. Several instruments are commercially available, for example by Malvern, Brookhaven, and Coulter. The most recently developed instrument that is convenient to use is HPPS, supplied by Malvern (UK). This allows the particle size distribution to be measured without the need for too much dilution (which may cause some particle dissolution). 

Field-flow fractionation (FFF) is a relatively new analytical technique applicable to the separation of fine particles, polymers and macromolecules in solutions. Recent efforts concerned with Sedimentation field-flow fractionation (SdFFF) is to separate a wide variety of particulate species and to apply it to the particle size measurement. That is because SdFFF has advantages that it employs the fractional collection sorted by the particle mass, and has a high resolution over a wide range of particle size compared to other methods of sub-micrometer particle size determination. 

The electrical aerosol analyzer and the optical counter are used to measure particle size distributions. Describe the size range and resolution characteristics of each of these instruments. 

The efficiency of a column can be assessed in a similar manner to that described for HPLC and values for the resolution index of two solutes, the number of theoretical plates and the height equivalent to a theoretical plate may also be calculated. Although it is easier to measure gas pressure, it is the actual gas flow, which is affected by the particle size and compression of the packing, that should be used in column assessment investigations. 

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