Linear calibration methods

Dow 1683 polystyrene standard was utilized as a broad MWD standard in the linear calibration method due to its distribution symmetry and particular lack of significant tail at the low end of its MWD. 

NBS 706 broad distribution polystyrene, NBS 705 narrow distribution polystyrene, and NBS 1478 narrow distribution polystyrene reference materials were used as samples in the evaluation of the proposed linear calibration method in this study. These reference materials have the following reported values ... 

Dextrans were employed to evaluate the linear calibration method for utility in aqueous SEC. The dextrans were obtained from Pharmacia Chemical Co. (Upsala, Sweden) of the following molecular weights ... 

The blend of T-70 and T-40 dextran materials was utilized as a polydisperse calibration standard for the linear calibration method and the T-40 dextran standard was used as a sample for evaluation. Concentrations of 0.15% W/V were injected for each dextran material chromatographed. 

Dextran polymers were used to evaluate the utility of the linear, polydisperse calibration method for water-soluble polymer characterization. A blend of T-40 and T-70 dextran standards was used as a polydisperse calibration standard. Table VIII displays the report from the linear calibration method using this standard. Nine Iterations of the search algorithm were required for convergence to the true and Mn values of the standard. As can be seen in the report, the elution volume profile of the standard contained 72 area/time slices upon which calibration calculations were based. The slice width was set at 10 seconds/siIce. Figure 5 shows a plot of the calibration curve generated from the linear calibration method utilizing the dextran standard,... 

Due to the fact that application of universal calibration is not always practical in aqueous SEC, a linear calibration method using a single polydisperse standard has a high degree of viability for characterization of water-soluble polymers. Although few water-soluble polymers with characterized MWD moments are commercially available, in many Instances an in-house polydisperse standard can be generated by measuring Mn and M, of one lot of polymer of the same chemical type as that under study. 

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. 

Conclusion. A linear calibration method based upon that of Balke... 

The linear calibration method provides an equivalent molecular weight calibration curve to a peak position method of calibration using a series of polystyrene standards. 

Based upon studies with the NBS standard reference materials, the linear calibration method appears to give equivalent accuracy compared to a peak position method irrespective of sample disperslty provided that the sample elute over the elution volume range covered by the polydlsperse standard and low dispersion SEC column are utilized. 

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. 

Keywords Traceability Linear calibration Method validation... 

Effective Linear Calibration Method without Peak Broadening Correction... 

The researchers used HPLC and gradient elution, combined with a linear calibration method with substances of known K w values, to relate retention time to hydrophobicity. Their findings are summarized in the accompanying figures. 

For the linear calibration methods, the regression vector, b, is estimated directly from R and c where... 

The global linear models calculated by PCR are PLS are not always the best strategy for calibration. Global models span the variance of all the samples in the calibration set. If the data are nonlinear, then the linear PCR and PLS methods do not efficiently model the data. One option is to employ nonlinear calibration methods. The second option is to employ linear calibration methods on small subsets of the data. 

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