Add to cart Buy now. Sign in to add to Wish List. Details Author: Capes, C. Handbook of Powder Technology, Volume 1: Particle Size Enlargement is the first of a series which will together form a Handbook of Powder Technology, primarily intended for engineers and scientists working in industry. The scope of the Handbook can be defined as being concerned with that part of chemical engineering which deals with processes involving the handling and treatment of material in solid particulate form. This book deals with methods used to create larger entities from fine particles so that the bulk properties of particulates can be improved.
These so-called ""size enlargement"" methods evidently concern a broad spectrum of technical disciplines and industries ranging from the relatively small scale requirements of pharmaceutical manufacturers through the tonnage requirements of the fertilizer and minerals processing industries. A primary objective in preparing this book was to present a generalized account of the many size enlargement techniques scattered throughout these diverse industries, with emphasis on similarities and unifying characteristics whenever possible.
The book devotes one chapter to each of the principal methods used to bring particles together into agglomerates: agitation methods— tumbling agglomeration, agitation methods—mixer agglomeration, pressure methods, thermal methods, spray and dispersion methods, and agglomeration from liquids. Kortext is an ebook and etextbook provider for universities, university students and for anyone who loves to read. In addition, particle shape information may be required if particle shapes have significant influence on mixing and flow properties of final powder blends.
The particle shape effects on mixing and tabletting processes have been reported in the literature . In addition to direct compression, tablets can be manufactured by either wet or dry granulation processes. Granulation is essentially one of the size enlargement processes, which can improve both flow and compression characteristics . In a dry granulation process, the powder particles of API and diluents are aggregated under high pressure either by slugging to form a slug or by roller compaction to form a ribbon and then broken down to granules by milling and sieving before compression.
In a wet granulation process, a liquid is added to the powder particles of API and diluents to produce agglomerates and then broken down to granules by drying, milling, and sieving before compression. In either case, since the properties of the individual API and diluent particles are masked at least to a certain extent by granulation, the quality of tablets is directly influenced by granules mixtures of API and diluents instead of the individual API and diluent particles.
Therefore, controls of the size distribution and the flow property of granules are potentially critical for final blending and compression processes. This is particularly important for the comparison of the biobatch with production batches and also, when processes are modified or changed. The particle size profile will provide useful information for demonstrating comparability.
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The size and even the type of granule can affect the pore size in a tablet and have an effect on dissolution. For example, a dissolution failure for a coated tablet was attributed to a change in the milling screen size, yielding a granulation with larger granules and resulting in slower dissolution .
Hence, the particle size specification for the granules is recommended for a granulation process. Since there is a pre-mixing process during the wet or dry granulation, control of PSDs of API and key excipients will be required if particle size effects of these components are significant on homogeneity of powder blend as well as the final tablets.
Figure 1 - Variations of pellet size distributions during multi-layer coating processes. Many extended-release ER drug products are comprised of capsules filled with small, coated sugar pellets. Manufacture of these pellets involves drug layer coating and ER layer coating processes, which are essentially size enlargement processes.
An example of growth of pellet sizes during multi-layer coating processes is shown as Figure 1. Monitoring and control of variations of pellet sizes at different coating stages may provide an effective way for control of the drug product quality. Heinicke et. In addition to imaging analysis, even a simple sieving analysis can be used to assess the variations of pellet sizes at different stages quantitatively.
Table 1 presents an example to demonstrate how the pellet size distribution is changed at different manufacturing stages. These pellet size profiles measured at different stages provide useful information for comparison of batch to batch consistency. Furthermore, since a broad pellet size distribution may result in pellet segregation and affect content uniformity, control of pellet size distribution is critical not only for coating but also for blending processes.
Particle forming / size enlargement equipment innovations for dry material handling operations
It is recommended to establish a particle size specification with appropriate acceptance criteria for initial sugar pellets, drug layered pellets, ER coated pellets, and final blended pellets for the multi-layer coating process. With regard to the drug substance, a particle size specification is not generally required if the drug substance is totally dissolved in the coating solution.
However, if the drug substance is suspended in the coating solution, a particle size specification should be established as well. In addition to control of pellet size distributions, coating uniformity for both the drug layer and the ER layer is critical for the drug product quality. Due to the small size of pellets, measurement of weight gain is not meaningful for control of coating uniformity. Instead, for each coating stage, coating uniformity should be assessed by assay and content uniformity of API for the unit-dose samples collected by an appropriate sampling plan at multiple locations.
When the mean assay value of API is significantly different from the expected quantity, or there are large between-location variances of assay values, the coating process is probably not under control.
Similarly, the in-process dissolution testing of samples collected by an appropriate sampling plan at multiple locations within the final blender or container before encapsulation is a useful tool for assessment of coating uniformity of the ER layer. Once it is determined that a particle size specification of pharmaceutical powder is needed, the next question is how to establish an appropriate particle size specification.
Therefore, it is important to understand what information should be included in the particle size specification to meet the regulatory requirement. Per ICH guideline Q6A, a specification is defined as a list of tests, references to analytical procedures, and appropriate acceptance criteria, which are numerical limits, ranges, or other criteria for the tests described .
In the following, the establishment of an appropriate particle size specification, including analytical procedures, method validation, and acceptance criteria, will be discussed. Since sieving and laser diffraction are the most common methods used in drug applications for solid oral dosage forms, the discussion will mainly focus on these two particle sizing methods. However, the USP requirements are not fully addressed or followed in many submissions. In general, particle size analysis by the sieving or laser diffraction method includes the following steps: 1 sampling of bulk powders, 2 sub-sampling of bulk samples for specimen, 3 specimen preparation or dispersion, 4 instrument set-up and verification, 5 size measurements, 6 data analysis and interpretation, and 7 report of size results .
Therefore, a complete analytical procedure should include all these information. During these stages, how to get a small amount of specimen with a representative PSD from the bulk powders is critical. Allen has demonstrated that selecting an appropriate sampling device will greatly improve reproducibility of the particle size measurements .
In addition, how to select an appropriate sample dispersion method is critical for sizing of small or cohesive particles which have a tendency to form agglomerates.
The goal of sample dispersion is to eliminate as much particle agglomeration as possible from the sample analyzed and at the same time to avoid particle attrition or milling due to use of excessive dispersion forces . In general, most errors in size measurements arise through poor sampling or poor sample dispersion but not through instrument inadequacies. Therefore, for a particle size specification, it is recommended to describe in detail the steps of sampling and sample dispersion strategies in the analytical procedure section. For the laser diffraction method, data analysis and interpretation is also important as inappropriate choice of the optical model i.
Particle Size Enlargement
Therefore, it is essential that the optical model and the refractive index values used are reported in order to obtain reproducible results. Since several significant differences exist, both in hardware and software, not only among instruments from different vendors but also among different types from one vendor, it is recommended to provide adequate information with regard to the laser diffraction instrument as well as software used into the analytical procedure section.
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