Size calibration

Calibration curves are obtained by measuring the residence time of known-size standards (such as the monodisperse polystyrene latexes manufactured by Dow) at a given eluent ionic strength. Typically, 6-10 particle sizes in the submicron range are needed to produce an accurate curve. In addition, comparison of chromatogram peak areas for samples run through the column and bypass lines allow determination of the upper size limit for 100% recovery 

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Straight chain alkanes from Applied Science, aromatics from Fisher Scientific Company and polystyrene standards from Waters Associates were used without purification for the linear molecular size calibration of the GPC. Since the solubility of the larger alkanes in THF is very low, appproximately 0.2 -1 mg of each standard was dissolved in 50 microliters of the THF for the molecular size calibrations. 

Monodisperse spheres are not only uniquely easy to characterize, but also very rarely encountered. Polymerization under carefully controlled conditions allows the preparation of the polystyrene latex shown in Figure 1.8. Latexes of this sort are used as standards for the size calibration of optical and electron micrographs (also see Section 1.5a.3). However, in the majority of colloidal systems, the particles are neither spherical nor monodisperse, but it is often useful to define convenient effective linear dimensions that are representative of the sizes and shapes of the particles. There are many ways of doing this, and whether they are appropriate or not depends on the use of such dimensions in practice. There are excellent books devoted to this topic (see, for example, Allen 1990) and, therefore, we consider only a few examples here for the purpose of illustration. 

Spherical particles of known diameter (e.g., 5% to 20% of the diameter of the aperture in the glass tube) are used to calibrate the electrical pulse counting instrument. The particles are suspended to an appropriate concentration in electrolyte solution (see recipe). Monodisperse latex particles are commercially available, which can be used for this purpose. Particle size calibration standards can be obtained from a number of chemical suppliers or from the National Institute of Standards and Technology (e.g., NBS 1003b). Lines (1996) lists a number of standards that are appropriate for this purpose. 

An Improved disc centrifuge photosedimentometer (DCP) was developed for use in the determination of the particle size and size distribution of latices, pigments and other particulates. Separation is based on Stokes Law for the sedimentation of particles in a centrifugal force field and does not rely on the use of particle size calibrants or standards. The DCP Instrument provides accurate stable particle size analyses over a wide range of conditions while at the same time is rugged enough for heavy use in both a research and quality control environment. A stand-alone data collection, analysis and management system was developed both for routine quality control operation and for research use of the instrument. 

Since the calibration of a GPC is dependent upon the effective size in solution of the sample molecules, the type (structure) of molecules used for the calibration is important. The ideal case is to calibrate with a standard sample(s) of the material of interest. However, this is not always possible. In those instances, arbitrary standards are chosen. The arbitrary standards are used to construct a size calibration where the molecular size is calculated from the standard. For polymer analysis, these standards are often polystyrene of narrow molecular weight distribution. These standards may be purchased from a variety of suppliers. 

Size Calibration. The -Styragel columns were calibrated to transform the elution data from the time domain to the size domain using both n-alkane and polystyrene (Pressure Chemicals) standards. The n-alkane sizes are related to the carbon number by Equation 1 (7). 

Fig. 6.10-35 Screened coal-based compliance fuel after the sizing (calibration) of briquettes (Section 13.3, ref. 134)...

D. Cykana, How to size calibrate profile parts. Plast. Technol. (2011)... 

An internal calibration method based on the universal calibration concept " was used to establish a hydrodynamic-size calibration curve which gave the relationship between the retention volume (V ) and the... 

Figure 5. Hydrodynamic Size Calibration Curve Constructed Based on the Chromatogram of PAAM.

Temperature and size calibration—Temperature and size calibration of TMA are carried out using melting of pure metals (see Chapter 1, Section 1.4.5). 

Santos et al. [55, 148] studied the styrene suspension polymerization using NIRS. A dispersive NIR instrument equipped with a transflectance probe was used to monitor the reaction course and very good PLS calibration models were developed for the final average particle sizes. Calibration models were then used as references for the implementation of an in-line procedure for control of average... 

Many water treatment operators consider liquid chemicals easy to feed and handle. Chemical suppliers deliver the chemicals in sealed containers, and the feed and delivery systems are contained. Accurate feed is assured when using properly sized, calibrated, and maintained chemical metering pumps and control systems. Liquids also mix easily into the process water stream. Table 7-1 hsts some of the more common liquid chemicals used in water treatment. In addition to these, there are many liquid polyelectrolytes sometimes used in coagulation and filtration. They are not listed in the table because their properties vary depending on the specific product. 

When these calculatirns are performed for a range of particle sizes, calibration curves of phase difference versus particle size can be generated for any desired optical configuration and particle refractive index. It... 

Haematologically, for red blood cell sizing, calibration is performed against a series of specimens of normal fresh blood cells, taken into a known anticoagulant, whose mean sizes have been determined by the reference procedures of total red cell volume (centrifuged haematocrit) and total red cell count (for example as measured by an electrical sensing zone analyzer fitted with an accurate manometer and used with accurate dilution methods). The procedure may or may not be allowed to account for any plasma still trapped within the packed bed of red cells. 

ASTM F65 8-87(1992) Standard Practice for Defining Size Calibration, Resolution, and Counting Accuracy of a Liquid-Borne Particle Counter Using Near-Monodisperse Spherical Particulate Material... 

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