Standards polydextran

The second method assumes that the molecular weight calibration curve is linear on a semilog plot and should be employed where universal calibration is not practical as with aqueous SEC. Several variants of these methods involving different molecular weight data for the standards are discussed. The proposed methods have been evaluated using aqueous SEC and polydextran standards and nonaqueous SEC with polyvinylchloride standards. 

Methods based on universal calibration will be illustrated using nonaqueous SEC and broad MWD PVC standards. The and of these standards is known. Methods based on the linear molecular weight calibration will be illustrated using aqueous SEC and broad MTO polydextran standards for which M and My are known. 

Polydextran standards employed in this investigation are listed in Table IV. 

Figure 4. Molecular weight calibration curves for polydextran obtaimd u g linear calibration and two broad M WD standards and by plotting Mrm ( / Mif Mw) vs, peak retention volume ((%) Mrms, (---------) M(v) = 0,37 X exp(—OJ v))...

Table V. Results of Case Study 2 - Linear Calibration with Two Broad MWD Polydextran Standards with Known Mj and...

Figure 13.4. Apparent MWs of HS from different environments as determined by SEC [compiled from the data reported by Perminova et al. (2003)]. Bars represent a range of weight-averaged molecular weights determined for different groups of humic materials. Two black dots represent two IHSS standards Suwannee River FA and HA. SEC chromatograms were obtained with column-packing Toyopearl HW-50S using 0.028 M phosphate buffer at pH 6.8 as a mobile phase. Two different sets of standards were used to calibrate the column polystyrene sulfonates (PSS) and polydextrans the upper MW scale corresponds to dextran calibration and the bottom one—to PSS calibration.

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