Laser diffraction particle analyzer

The geometric size distribution of lyophilized powders was measured with a Sympatec Helos LF laser diffraction particle analyzer using a Sympatec Rodos SR dispersing module (Sympatec GmbH, Clausthal-Zellerfeld, Germany) with 0.5-1.0 bar dispersion pressure and evaluated with the Fraunhofer option of the Windox 3.4 software [15]. 

A laser diffraction particle analyzer can measure, in principle, the size distribution of particles suspended in a gas. However, if one attempts to determine the size distribution of agglomerates, laser diffraction may not give a very accurate result due to the nonsphericity of agglomerates. See also the discussion of this method below. Laser diffraction does not give a dynamically equivalent particle size. 

The particle size distribution of each powder was determined using a Sympatec Helos/ Rodos laser diffraction particle size analyzer (Sympatec Inc., Princeton, New Jersey, U.S.A.) with dry powder dispersion capability. The powder dispersion pressure was varied between 0.5 and 2.0 bar (depending on the tendency for agglomeration) with direct feed into the dispersion funnel. The optical concentration was maintained in the range of 5% to 20%. The mean value of duplicate determinations is reported. 

The model solutions discussed above were compared with experimental data collected using a laser diffraction particle size analyzer. Hematite was dispersed in solutions at various pH values and moderate ionic strength (0.02 M) such that aggregation rates varied from slow to fast, and aggregation was allowed to occur in quiescent solution. The aggregating dispersion was sampled over time, and data was represented in three dimensions as the change in particle size distributions over time. Figure 10a shows hematite... 

Particle agglomerate sizes can be determined using a laser diffraction particle size analyzer, such as a Brinkmann PSA-2010. With this instrument, the principle of particle size measurement is based on various light scattering angles generated by paiTicles of... 

The nanocomposites of PDLL//3-TCP are very promising and desirable biomaterials applied in tissue engineering [171], and have been used clinically in various forms [172-174]. These nanocomposites with different /3-TCP are prepared in the same way as that of PDLL/HA nanocomposites described in the previous section. The average particle size of J3-TCP used in this work was approximately 720nm with particle distribution of 200-1,500 nm as determined by laser diffraction particle size analyzer. The effect of in vitfo degradation on the shape-memory capability... 

Figure 7.7. Optical arrangement of a typical laser diffraction particle size analyzer.

The particle size distributions were determined by means of laser diffraction (Particle Size Analyzer, Sympatek, model Helos KA). The filler suspensions were prepared under the same conditions as the corresponding flotation tests (pH, water hardness, collector concentrations, stirring conditions). The solid material concentration was between 40 and 100 mg/1. 

Inaba, K., Matsumoto, K., the Measurement of Particle Concentration using a Laser Diffraction Particle Size Analyzer,- . Soc. Powder Technol. Japan, 1997, 34,490-498. 

A laser diffraction spectrometer can measure particles as small as 0.2 pm and up to about 1000 pm. Some instruments allow the operation of the analyzer for... 

Optical examination of etched polished surfaces or small particles can often identify compounds or different minerals hy shape, color, optical properties, and the response to various etching attempts. A semi-quantitative elemental analysis can he used for elements with atomic number greater than four by SEM equipped with X-ray fluorescence and various electron detectors. The electron probe microanalyzer and Auer microprobe also provide elemental analysis of small areas. The secondary ion mass spectroscope, laser microprobe mass analyzer, and Raman microprobe analyzer can identify elements, compounds, and molecules. Electron diffraction patterns can be obtained with the TEM to determine which crystalline compounds are present. Ferrography is used for the identification of wear particles in lubricating oils. 

Laser diffraction is most suitable for analyzing dilute emulsions that are fluid, and therefore competes directly with electrical pulse counting methods, which are applicable to similar systems (see Alternate Protocol). Most laser diffraction instruments can cover a wider range of particle sizes (i.e., 0.01 to 1000 pm) than electrical pulse counting instruments (i.e., 0.4 to 1000 pm using a number of different aperture sizes), and do not require the presence of electrolyte in the aqueous phase, which could destabilize some electrostatically stabilized emulsions. Nevertheless, electrical pulse counting techniques are considered to have greater resolution. 

These practical issues of particle shape and dispersion are not intended to cast aspersions on the laser diffraction technique rather, these factors have been discussed to bring awareness around the analytical results that are obtained when these factors are present. Laser diffraction has proven itself to be a reliable, robust technique for particle size analysis. When the assumption of nonaggregated spherical particles is violated, there are clear manifestations in the calculated particle size distribution. When analyzing drug substances that are used in low-dose solid oral formulations, the impact of these manifestations can be particularly impactful as there is often a limited number of API lots to be used for method development. Therefore, the analyst must be aware of these issues prior to the commencement of method development to avoid these pitfalls. In addition to the information contained in ISO 13320, Snorek et al. have written a summary around the general practices of laser diffraction measurements in the pharmaceutical industry.19... 

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. 

Figure 7 (a) Inhalation measurement cell with Malvern Spraytec laser diffraction analyzer, combined with Andersen cascade impactor (76). (b) Time-history showing the mean particle size measured during the actuation of the Clickhaler containing the micronized (M-SX) and supercritically produced (S-SX) salme-terol powders in formulation with lactose and at the airflow rate 49 L/min. 

A typical laser diffraction apparatus is shown in I ig-ure 34-1. The beam from a continuous-wave (CW) laser, usually a Hc-Nc laser, is collimated and passed through the sample, where scattering from particles occurs, The beam is then focused on a detector array where llic scattering pattern, shown in Figure 34-1 as a diffraction pattern, is measured, The scattering pattern is then analyzed according to theoretical models to give the particle size distribution,... 

The particle size distribution and mean particle size (dso) were determined by the laser diffraction method (FRITSCH Model ANALYSETTE 22, Idar-Obeistein, Germany). One gram of the sample was suspended with 10 ml bi-disdUed water, then the produced suspension (produced with hand shaking) was employed for measuring size analysis. The specific surface area (Sbet) as well as the pore volume of the powders was determined by BET method using a surface area analyzer (Autosoib-1, Quantachrome Instruments, USA). 

It follows that individual measuring methods depend upon particle definition. Particle definitions might include such details as number, length, surface area, mass, and volume, as a result of which one has the choice of using various counting methods - microscopy, image analyzers, laser diffraction, as well as sieving and air classification methods. 

The most common tests involve analytical data such as particle size, particle size distribution, and particle shape. The standard method for more granular materials and coarser powders is sieve analysis [153], whereas for fine materials laser diffraction is well established [154]. If the particle shape and particle shape distribution are of special interest, optical systans are preferred, in which a multitude of single particles are detected by a camera and pictures of the particles may be analyzed [155],... 

Mica products are usually analyzed by screening to determine particle distributions. Specifications typically include minimum and maximum values for the amount of mica passing or retained on screens of varying mesh sizes. Another value often used for a material specification is loose bulk density. Laser particle size analysis is also being used to some extent to define mica products. One should remember that most other minerals are measured by an instrument called a sedigraph, which measures the size of particles based on their settling rate. This procedure can be used with very small low-aspect ratio minerals such as calcium carbonate, talc, silica, very small particle size mica, and aluminum trihydrate but cannot be used for analysis of most mica products. Sedigraph particle size values for very small mica products are about one-half to one-third of the values obtained by laser diffraction. 

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