Molecular weight calibration curve coefficients

For all four sets of PEO standards the coefficient of determination (R ) for the linear calibration curves for the four linear columns in water and in water/methanol are better than 0.99, except for the PL PEO standards and the TSK GM-PWxl column in water/methanol. The coefficient of determination for the TSK GM-PWxl column in general is not as good as the other three linear columns. The coefficient of determination for the TSK PEO standards showed the least dependency on columns and mobile phases. The TSK GM-PWxl column has a lower exclusion limit in the high molecular weight range than TSK GM-PW, Shodex SB-806, and SB-806MHQ columns. 

Table 5.4.13 Molecular weight, ion pseudo-molecular, correlation coefficient and calibration curves of BAs analysed (reprinted from [32])...

Bile Acid Molecular Weight [M-H] Ion Correlation Coefficient (r) Calibration Curve Equation... 

Results and Discussion. The 2-ethyl polyaniline concentration in the silica gel film was determined by constructing a Beer s law calibration curve from solutions of known concentration. Assuming an average molecular weight of 5000, the 2-Et PANi concentration in the silica gel was found to be 9.6 x 10 4 M. The refractive indices of CS2 and 2-Et PANi SiC>2 were estimated to be 1.6 and 1.4 at 1.06 im, respectively. The emeraldine base doped silica gel was found to have low losses due to scatter, and exhibited good transparency at 1.06 im. Spectrophotometric measurements at 1.06 fim yielded absorption coefficients of 0.1 cm-1 (> 99% T over 1 mm pathlength) for the CS2 reference and 4 cm 1 (96% T over 1 mm pathlength) for the 2-Et PANi doped silica film. 

Supports for SEC of proteins are designed to be neutral and very hydrophilic to avoid disruption of protein structure and interaction of the solutes with the support by ionic or hydrophobic mechanisms. The base matrix can be either silica or polymer efforts are made to totally mask its properties with a carbohydratelike stationary phase. The pore structure is critical to successful SEC. Not only must the total pore volume (F,) be adequate for separation, the pore diameter must be consistent and nearly homogeneous for attainment of maximum resolution between molecules with relatively small differences in molecular size (radius of gyration or molecular weight). A twofold difference in size is usually required for separation by SEC. Pore homogeneity can be assessed from the slope of the calibration curve of the logarithm of the molecular weight versus the retention time or the partition coefficient (Kd) = (F - Fq)/F , where F is... 

Fig. 2. Fibrin zymography of PA standards. (A) Fibrin zymogram demonstrating electrophoretic migration of uPA (45-kDa), tPA (70-kDa), and higher molecular weight tPA/PAI-1 complex (110-kDa). Fibrin indicator gels were stained with amido black (see Section 3.5). Samples 1-5 correspond to PAs and PAIs of various compositions as described (R4, R5). (B) Calibration curve obtained with PA standards. Linear regression analysis was performed and correlation coefficient (r) is shown (r = 1.000, perfect correlation).

As a result of eqs. (9-13), each PS molecular weight standard can be converted through use of Mark-Houwink coefficients from PS and CTC into a corresponding CTC molecular weight. These CTC molecular weights form the basis of a new calibration curve... 

If the Mark-Houwink coefficients for the polymer-solvent system are known, then the IVD measured by SEC-viscornetry can be converted into the molecular weight distribution using the Mark-Houwink relation. This should give greater precision in the measurement of molecular weight distribution than SEC-vi scorn etry with universal calibration, because the IVD measurement is much less sensitive to experimental conditions than a calibration curve. 

As described in Chapter 1, a calibration curve constructed for polystyrene can be used to determine the molecular weight of a second polymer if the Mark-Houwink coefficients of the two polymers in the solvent used for SEC analysis are known. The Mark-Houwink coefficients for cellulose in a variety of solvents have been tabulated (138). 

Although Dt varies with the polymer-solvent system, it is independent of molecular weight in a given system, at least for random-coil homopolymers. The separation of differing-molecular-weight components is therefore based solely on differences in D, which means that the principles of universal calibration that are relevant to SEC are also applicable to ThFFF. Thus, a calibration curve made with one polymer-solvent system can be applied to other systems, provided the values of the thermal diffusion coefficient associated with each polymer-solvent system are available. Fortunately, accurate values of Dj can be obtained from the combination of ThFFF with any technique that measures D, such as dynamic light scattering ... 

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