Particle size reduction methods

IAEA/AL/095 1996). Both methods were suitable, but needed to be repeated several times to produce the small particle size that was required. The particle size reduction, e.g. of IAEA-395 from a median size of 30 pm to 3.5 pm, improved the homogeneity of elements. Sampling constants (the minimum mass that can be used to achieve a random error of i % at the 65 % confidence level) improved from a factor of 1.2 for Sc, up to a factor of 800 for Au. The average improvement was about a factor of 2-10. (Ni Bangfa et al. 1996). From these initial experiences, it is dear that preparation of reference materials is critical with respect to the final particle size distribution, which should exhibit a low maximum (<50 pm) and a narrow range in particle sizes. Milling techniques to meet such criteria are available today, and materials that show intrinsic uniformity are particularly suitable to achieve the desired properties. 

Obviously, the technology exists for obtaining analytical results without special preparation and analysis in a laboratory. However, at the present time there is no acceptable substitute for direct laboratory examination of samples if we want the kind of accuracy and confidence we have come to expect. All conventional methods for analysis of solid materials require one or more of the following preparation activities before an analytical method can be properly executed 1) particle size reduction, 2) homogenization and division, 3) partial dissolution, and 4) total dissolution. Let us briefly discuss each of these individually. 

Some of the current methods of increasing dissolution rates of drugs are particle size reduction, salt formation, and development of the optimized delivery systems, such as solid dispersion, soft gelatin encapsulation, etc. 

Mechanical methods of powder production, also known as mechanical attrition, typically require a brittle material, or at least one that becomes brittle during processing. There are various types of equipment that perform particle size reduction. 

The only significant production process today is by carbonation of lime slurry, itself obtained by calcination and hydration of a calcium carbonate mineral. The process is set out below and it can be seen that this is another example of using a chemical method to achieve a particle size reduction ... 

The advantages of the PGSS process over conventional methods of particle-size reduction are numerous. 

Ascorbate reduction This method (7) entails the fairly rapid addition of sodium ascorbate to chloroauric acid while stirring. If the reaction is carried out on ice, the gold particle size range is between 6 and 8 nm. Higher temperatures tend to increase the particle size The method is also really of academic interest nowadays, since it is not easy to control the final sphere diameter. 

Vat Dye Pigments. Vat clyes have been used for a long time for coloring textile fibers. As pigment technology evolved, new methods of particle size reduction have been successfully applied to largely insoluble dyes. Only... 

Sonophotocatalysis is photocatalysis with ultrasonic irradiation or the simultaneous irradiation of ultrasound and light with photocatalyst. Tnis method includes irradiation with alternating ultrasound and light. Ultrasound effects on heterogeneous photocatalytic reaction systems have been demonstrated by Mason,1 Sawada et al.,2) Kado et al.,3) and Suzuki et al.4) In these papers, not only acceleration of photocatalytic reactions but increase in product selectivity by ultrasonic irradiation has also been reported. It was postulated that ultrasound effects, such as surface cleaning, particle size reduction and increased mass transfer, were the result of the mechanical effects of ultrasound.1,5) Lindley reviewed these and other effects.5)... 

The dependence of dissolution rate to speciLc surface area is the basis for pursuing particle size reduction as a method of increasing the bioavailability of poorly water-soluble drugs. 

To manufacture this explosive, take AN which has been previously powdered to a very fine consistancy (see Powdered AN-AL explosive for methods of particle size reduction). To this is added the fuel oil or diesel in the proper amount. This is thoroughly mixed. If desired, the small amount of "Tide" is added to this mixture after it has been reduced to the consistancy of flour. This addition is highly recommended due to the enhancement of the detonation and sensitivity characteristics of the explosive and decreasing somewhat the sensitivity when packed or "dead pressed" with the subsequent loss of sensitivity. Of course this mixture should be kept from all moisture and stored in a waterproof container until ready for use. The explosive consists of the following ... 

The importance of size reduction in relation to pharmaceutical active agents and excipients is well known, and the aim of this chapter is to identify methods for particle size reduction, discuss how particle size and shape are characterized, and... 

Particle size reduction may be achieved with different kinds of miUing equipment such as media miUs. Alternatively, flow impingement or ultrasound methods can be used for dispersion. Some of the pigments can also be dissolved in certain solvents and reprecipitated as extremely fine particles. AU of these processes generate a considerable amount of fresh surface. If unstabilized, these surfaces collapse back together and particle size reduction... 

MOTIVATIONS AND METHODS FOR PARTICLE SIZE REDUCTION AND CONTROL... 

Suzuki E, Shirotani KI, Tsuda Y, Sekiguchi K. Studies on methods of particle size reduction of medicinal compounds VIII size reduction by freeze-drying and the influence of pharmaceutical adjuvants on the micromeritic properties of freeze-dried powders. Chem Pharm Bull 1979 27 1214-1222. 

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