( te for different flowrates (using diffe...)Practical Aspects of Evaluation of Chromatographic Data in Size Exclusion Chromatography

te for different flowrates (using different pump, leaking pump head seals etc.), however will not compensate for fluctuating flowrate by faulty valves, air bubles (causing in fact some offset of time axis). The same concentration of marker, well resolved from system peak disturbances, must be used or otherwise the marker RT concetration or matrix dependence can cause an additional error instead of the expected improvement.

Conclusion
To produce not only precise but also accurate molecular weight data by GPC/SEC, besides the proper instrumentation and methods, the data processing must not be neglected. In this note, we tried to point out the common sources of problems in use of chromatography software for evaluation of GPC/SEC data.

Fig. 1. Effect of baseline setting
Integration of polymer peak with too high threshold (B01), valey to valey (B02) or baseline peak separation (B03) is compared with respect to resulting differences in MW distribution and averages.

Fig. 2 Effect of calibration curve fit
Even with practically linear calibration column set, significant differences in results especially in extrapolated regions occur by using different regression line polynom degree.

Fig. 3 Effect of flow rate correction
The results without and with flow rate are demonstrated on the same chromatogram scaled +/- 5% original size on time axis.

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