Particle size determination optical microscopy

Seven surfactants were selected with differing HLB (Hydrophile Lipophile Balance) numbers and used at concentrations of 0.5 - 2.5% w/v in aqueous solution. An intermediate concentrate was prepared by high shear mixing and subsequently diluted with 1% methylcellulose solution to give a final drug concentration of 10% w/v. Methods of analysis included laser diffraction particle size determination, optical microscopy and dissolution into an aqueous medium. The suspensions were analysed immediately after preparation and after 4 and 96 hours. 

For particle size characterization, optical microscopy and SEM are commonly employed. Recently, a three-wavelength extinction technique has been used to determine the median diameter of RESS particles on-line (20). Other characterization techniques, such as differential scanning colorimetry (DSC) and x-ray diffraction (XRD), are used to determine crystallinity. 

Microspheres intended for nasal administration need to be well characterized in terms of particle size distribution, since intranasal deposition of powder delivery systems is mostly determined by their aerodynamic properties and particle sizes. Commonly used methods for particle size determinations described in the literature are sieving methods [108], light microscopy [58], photon correlation spectroscopy [66], and laser diffractometry [25,41,53,93], The morphology of the microparticles (shape and surface) has been evaluated by optical, scanning, and transmission electron microscopy [66, 95],... 

The specific surface area of a solid is one of the first things that must be determined if any detailed physical chemical interpretation of its behavior as an adsorbent is to be possible. Such a determination can be made through adsorption studies themselves, and this aspect is taken up in the next chapter there are a number of other methods, however, that are summarized in the following material. Space does not permit a full discussion, and, in particular, the methods that really amount to a particle or pore size determination, such as optical and electron microscopy, x-ray or neutron diffraction, and permeability studies are largely omitted. 

In order to define the extent of emissions from automotive brakes and clutches, a study was carried out in which specially designed wear debris collectors were built for the dmm brake, the disk brake, and the clutch of a popular U.S. vehicle (1). The vehicle was driven through various test cycles to determine the extent and type of brake emissions generated under all driving conditions. Typical original equipment and aftermarket friction materials were evaluated. Brake relines were made to simulate consumer practices. The wear debris was analyzed by a combination of optical and electron microscopy to ascertain the asbestos content and its particle size distribution. It was found that more than 99.7% of the asbestos was converted to a nonfibrous form and... 

Particle Size Measurement. The best way to evaluate an emulsion s stability is probably to measure its particle size distribution. A number of methods are available for droplet size determination (see Sec. VIII.A). Optical microscopy, although a time-consuming technique, is a direct way of measuring droplets larger than 1 pm. Nowadays, laser lightscattering, diffraction, and transmission methods are becoming popular for routine determination of particle size [151, 152],... 

R Evans. Determination of drug particle size and morphology using optical microscopy. Pharm Technol... 

Different methods are available for the determination of the particle-size distribution of powdered solids [30]. These are optical microscopy (usually combined with image analysis), sieve analysis, laser light scattering of suspended particles, and electrical zone sensing. 

FIGURE 6.10 Experimentally measured diameter of submicron fused silica particles as a function of particles diameter determined from scanning electron microscopy measurements. Dashed line corresponds to 1 1 size relationship. (From Shcheslavskiy, V., Petrov, G. I., Faustov, A., Yakovlev, V. V., and Saltiel, 5. Optics Lett., 31(10) 1486-1488, 2006. Used with permission.)... 

Optical microscopy and scanning electron microscopy (SEM) were used to evaluate the drug incorporation and surface shape of the microspheres prepared under the various conditions. Particle size was determined using a Tiyoda microscope. Samples of microspheres (180-200) were dispersed on a slide and their diameter was then sized using suitable objectives. 

The size distributions of the particles in cloud samples from three coral surface bursts and one silicate surface burst were determined by optical and electron microscopy. These distributions were approximately lognormal below about 3/x, but followed an inverse power law between 3 and ca. 60 or 70p. The exponent was not determined unequivocally, but it has a value between 3 and 4.5. Above 70fi the size frequency curve drops off rather sharply as a result of particles having been lost from the cloud by sedimentation. The effect of sedimentation was investigated theoretically. Correction factors to the size distribution were calculated as a function of particle size, and theoretical cutoff sizes were determined. The correction to the size frequency curve is less than 5% below about 70but it rises rather rapidly above this size. The corrections allow the correlation of the experimentally determined size distributions of the samples with those of the clouds, assuming cloud homogeneity. 

Laser diffraction is the most commonly used instrumental method for determining the droplet size distribution of emulsions. The possibility of using laser diffraction for this purpose was realized many years ago (van der Hulst, 1957 Kerker, 1969 Bohren and Huffman, 1983). Nevertheless, it is only the rapid advances in electronic components and computers that have occurred during the past decade or so that has led to the development of commercial analytical instruments that are specifically designed for particle size characterization. These instruments are simple to use, generate precise data, and rapidly provide full particle size distributions. It is for this reason that they have largely replaced the more time-consuming and laborious optical and electron microscopy techniques. 

Microscopy is often referred to as an absolute method for the determination of size and size distribution of small particles because it allows direct visualization and measurements of individual particles. Three commonly used types are optical microscopy, transmission electron microscopy (TEM), and scanning electron microscopy (SEM). 

If the sizes of particles, droplets, bubbles, or their aggregates in a dispersion are large enough, then optical microscopy can be used to determine the shape, size, and size distribution, but if they are smaller than about 0.5 pm they will not be resolved... 

The mass versus particle size distribution of several polymer latices with diameters in the range of 30 nm to 1500 nm was determined in less than 20 minutes using an integrated hydrodynamic chromatograph. Distributions obtained were compared with those found by other particle sizing techniques such as electron microscopy to verify validity of the technique. The instrument employed was able to analyze latices re-producibly with different optical properties, even though some of the injected particles may have been trapped within the column. Latex properties were correlated with particle size distribution data to illustrate the benefit of this particle sizing technique. 

The suspension produced had a wide range of particle sizes (as identified by optical microscopy) with an average size of 1 um, determined using a Coulter Counter (Model TAII). 100 g leg ... 

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