Particle counting methods

Computer-assisted molecular modeling package, 10 331-333 Computer-assisted tomography (CAT), sodium iodide in, 22 827 Computer-automated image analysis, as a particle counting method, 18 146-149 Computer-controlled viscometers, 21 732 Computer controller, closed loop fuel metering system, 10 57 Computer control loop, components of, 20 677-678... 

Takeuchi et al. (1996) have confirmed the mucoadhesive properties of polymer-coated liposomes with a simple particle counting method in vitro. This mucoadhe-sion test was carried out using intestines isolated from male Wistar rats. The intestines were washed with saline solution, filled with a liposomal suspension that was diluted 100-fold with a buffer solution (pH 7.4, 6.5, 5.6 or 1.2) or saline... 

The a-particle counting method has been widely used in U-Th disequilibrium series studies (Vdovenko and Dubasov, 1974 Ivanovich and Harmon, 1992). However, recent developments in TIMS have greatly improved the analytical precision and sample size requirements (Chen et al., 1986 Edwards et al., 1987). Certain samples that could not be dated with a counting can now be measured precisely. The use of electrostatic filters or deceleration lenses has greatly improved the abundance sensitivity of TIMS (Cohen et al., 1992), so that ratios of 10 5-10-6 for 230Th/232Th can now be accurately measured. 

Figure 11. Schematic diagram shows the incremental decreases in box size used for the particle counting method for the determination of the microscopic fractal dimension Df.

Frojmovic MM, Milton JG, Gear AL. Platelet aggregation measured in vitro by microscopic and electronic particle counting. Methods Enzymol 1989 169 134-147. 

Particle-counting methods count particles present in ambient air and do not require the subject to be exposed to any test aerosol. The most commonly used method is condensation nuclei counting (CNC) in which a vapour, usually isopropyl alcohol, is condensed onto particles to grow them to a size that can be seen and counted, by a laser and/or a light-scattering system. 

Particle Counting Methods. In order to calculate adhesion numbers and evaluate the effects of different factors on adhesion, methods must be available for counting the particles present on different substrates. All of the existing methods for particle counting can be classed arbitrarily as either visual or automatic. 

The container must be transparent to permit inspection of the content If this is not the case (opaque container) an alternative particle counting method has to be applied (see Sect 32.12). 

Two general methods have evolved. One uses a stirred tank system, while the other depends on the measurement of particle size or surface area change via particle counting or image analysis techniques. 

Radioactivity of uranium can be measured by alpha counters. The metal is digested in nitric acid. Alpha activity is measured by a counting instrument, such as an alpha scintillation counter or gas-flow proportional counter. Uranium may be separated from the other radioactive substances by radiochemical methods. The metal or its compound(s) is first dissolved. Uranium is coprecipitated with ferric hydroxide. Precipitate is dissolved in an acid and the solution passed through an anion exchange column. Uranium is eluted with dilute hydrochloric acid. The solution is evaporated to near dryness. Uranium is converted to its nitrate and alpha activity is counted. Alternatively, uranium is separated and electrodeposited onto a stainless steel disk and alpha particles counted by alpha pulse height analysis using a silicon surface barrier detector, a semiconductor particle-type detector. 

Pharmacopeial count limits for particulates in parenteral solutions is given in Table 39. The limit depends on the method used for the determination and also on the volume of the sample. Two different procedures for the determination are generally proposed light obscuration particle count test (LO) and microscopic particle count test (M), since neither is applicable to all kinds of samples. 

Note The limits are related to the method used for the determination LO = light obscuration particle count test, M = microscopic particle count test, IP = International Pharmacopeia. 

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. 

C3. Cambiaso, C. L., Riccomi, H. A., Sindic, C. J. M., and Masson, P. L., Particle counting immunoassay (PCIA). II. Automated determination of circulating immune complexes by inhibition of the agglutination activity of rheumatoid sera. J. Immunol. Methods 23, 29-50 (1978). 

A cleanliness classification in accordance with the latest revision of ISO 14644 is generally inadequate by itself to describe a facility used for pharmaceutical processes. The presence of viable particles (living organisms) within the particle count achieved by applying methods described in the standard may affect the product within the facility. A measure of both viable and nonviable particles is required to provide sufficient information upon which to base a decision regarding the suitability of the clean room for its intended purpose. 

An alternative method to filtration has been considered in order to reduce the large particles and agglomerates. Li and co-workers [41] investigated a novel slurry conditioner to reduce the oversized particle count present in CMP slurries. This study focused on the correlation between the oversized particle counts in STI CMP slurries and their influence on the wafers after polishing. A representative oversized particle count reduction after the treatment with the conditioner is shown in Fig. 13.30. 

---