Tips & Tricks: GPC/SEC Increase Resolution and Separation Range

February 4, 2011

The Column

The Column, The Column-02-04-2011, Volume 7, Issue 2

The precision and accuracy of the results depends, amongst other parameters, on the selection of the proper separation columns.

GPC/SEC is used to separate, identify and characterize macromolecules with respect to their molar mass averages and molar mass distribution (MMD). The precision and accuracy of the results depends, amongst other parameters, on the selection of the proper separation columns.

A proper column selection in GPC/SEC always includes finding a compromise between separation range, analytical quality, analysis time and solvent consumption. A wide separation range is required for highest versatility and applicability, a good resolution is required for the in-depth analysis, especially for a detailed MMD. Analysis time and solvent consumption are important especially for quality control in high temperature GPC and when expensive solvents are used.

The dependence of GPC/SEC column characteristics and experimental parameters on the resolution is quite complex. Column material particle size and packing quality, pore size and pore size distribution, solvent viscosity, temperature and flow-rate, as well as sample concentration and other factors influence the mass transfer and, therefore, the resolution.

A measure for the resolution can either be the plate count, N, or (recommended for GPC/SEC) the specific resolution, Rsp. For the specific resolution the peak standard deviation (which is proportional to the peak width) and the slope of the calibration curve are required.

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