Calibration methodology

In the model simulations, the settling and decanting phase were characterized by a reactive point-settler model. The simulations were carried out using matlab 6.5 simulation platform. A systematic model calibration methodology as described in Fig. 2 was applied to the SBR. Fig. 3. shows the simulation results from the calibrated model. The model predicted the dynamics of the SBR with good accuracy. 

L. K. Kostanski, D. M. Keller, and A. E. Hamielec. Size-Exclusion Chromatography A Review of Calibration Methodologies. J. Biochem. Biophys. Meth., 58(2004) 159-186. 

SEC calibration methods can be generally categorized into techniques which employ a series of narrow MWD standards and those which employ one (or more) broad MWD standards (2). Calibration techniques which utilize polydisperse, broad MWD standards have been found to be particularly useful when narrow MWD standards are not available or universal calibration methodology is impractical as for example with most water-soluble polymers or polymer/solvent/temperature combinations for which appropriate Mark-Houwlnk constants are not known or readily available. 

A direct consequence of the development of hydrodynamic volume theory In SEC has been the universal calibration method as introduced by Benoit (17). Universal calibration methodology is based upon the fact that retention in SEC can be described as a function of the hydrodynamic volume of polymer molecules. 

Usually the function [Cn) M] (intrinsic viscosity times molecular weight) is used to represent hydrodynamic volume which is plotted versus elution volume. For such a plot the calibration curves of many polymers fall on the same line irrespective of polymer chemical type. Universal calibration methodology usually requires knowledge of Mark-Houwink constants for the polymer/ temperature/solvent system under study. 

Universal calibration methodology has been successfully applied to PVC and many other chemical types of polymers (22). However, availability of Mark-Houwlnk constants can limit the utility of universal calibration. In these cases, the use of a linear, polydlsperse standard calibration method Is a viable alternative for generation of a molecular weight calibration curve. 

Optimization of Linear Calibration Methodology. The accuracy of linear calibration methods for utilization of polydisperse calibration standards depends upon (1) how well the column set approximates true linearity over the molecular weight calibration range and (2) the extent to which instrumental band broadening affects the elution volume profile of the polydisperse standard. 

Instrumental band broadening or axial dispersion can cause calibration errors when employing polydisperse standards. Correction of the polydisperse standard calibration data for instrumental band broadening will minimize the effect on molecular weight analyses of polymer samples. However, as previously demonstrated in this report, when low dispersion SEC columns are employed instrumental band broadening is minimized and the effect on use of linear calibration methodology is negligible. 

In comparing the linear calibration method to a universal calibration method for PVC polymers, the universal calibration method appeared to be slightly more accurate suggesting that universal calibration methodology be applied whenever possible. In cases where universal calibration can not be utilized, the linear calibration method provides a viable alternative. 

The linear calibration method has utility for characterization of water-soluble polymers due to the constraints imposed in aqueous SEC towards universal calibration methodology. A cursory evaluation of the linear calibration method for aqueous SEC indicates the method can be used with a high degree of accuracy to calculate molecular weight distribution values. 

The sample fluid could be any neat liquid or a sample of polymer solution. Under favorable conditions, a single viscosity determination on a polymer solution at high dilution can provide a direct measure of the polymer intrinsic viscosity, without the need of polymer concentration extrapolation. With this viscometer used as a continuous viscosity detector for SEC, it is possible to achieve SEC molecluar weight calibration by way of the universal SEC calibration methodology without the need of molecular weight standards for the unknown polymers. 

Sources of error in this approach arise from both experimental and theoretical grounds. Modern theories of SEC retention mechanism are based on the assumption that the size exclusion process uniquely determines the elution volume, and yet the possibility of reversible adsorption is difficult to dismiss and, where it occurs, errors in the interpretation may easily result. As a warning for the application of universal calibration methodology, Cas-sassa (29) indicates in a later paper that the quantity rj M is not a truly... 

If measurements need to be made at a variety of heating rates during the day, recalibration each time can be a significant inconvenience. One approach to overcome this is to calibrate at 0°C/min. At first this may seem odd, but it does have some advantages. First, it means that experiments can be made at any heating rate, and then a correction may be applied to the data to take into account the heating rate used. This calibration methodology also benefits isothermal experiments (for example, in kinetic studies) as the isothermal temperatures are exactly calibrated as well. 

In the context of two-dye fluorescence, the calibration methodology is identical except that one must now assess the temperature dependence of each dye. This calibration is accomplished by applying the procedure outlined above to the temperature-sensitive and temperature-insensitive... 

The temperature of the dye is then varied slightly and a new ensemble of images is acquired at this new temperature. This procedure is repeated until image ensembles have been acquired at several known temperatures over the range expected in a given experiment. This procedure allows one to construct a calibration curve of intensity ratio (or equivalently quantum-efficiency ratio) versus temperature. In the context of two-dye fluorescence, the calibration methodology is identical except that one must now assess the temperature dependence of both dyes. 

The electrical properties of a soil are measured using a radiofrequency voltage applied to soil electrical probes driven into the soils and soil aggregates to be tested, in a prescribed pattern and depth. Certain algorithms of these properties are related to wet density and water content. This correlation between electrical measurements and density and water content is accomplished using a calibration methodology. In the calibration methodology, density and... 

In practice, even if careful optimization of the ETV program is carried out, matrix effects cannot be fully eliminated in many cases, especially when very demanding samples (e.g., solids) are considered. In these cases, calibration methodologies being able to deal with these matrix effects are needed. As for any other sample introduction system used in combination with ICPMS,... 

FIGURE 28.5 Overview of lane oil thickness calibration methodology. 

Successful application of NIRS greatly depends on the robustness, specificity, selectivity and transferability of the calibration. In particular, it is highly desirable to be able to support a plant analyser from a laboratory instrument. Sampling-based optical artefacts and the optical characteristics of each instrument, including mechanical and photometric errors, impair transferability of data between instruments. Collaborative NIRS projects with transfer between instruments of calibration files, equations and spectra have been described [245] and interlaboratory collaborative studies of NIRS calibration methodology (for moisture analysis) have been carried out [246]. Blanco et al. [247] have compared various calibration methods in NIR diffuse reflectance spectroscopy. An absolute procedure for instrument calibration and standardisation has been presented [248]. A cloning procedure and... 

Plank, D. M. Sussman, M. A. Intracellular Ca measurements in live cells by rapid line scan confocal microscopy simplified calibration methodology. Methods Cell Sci. 2003, 25, 123-133. 

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