Empower Tip: Working with GPC Data

In this tip, we will discuss Axial Dispersion with GPC Data.

Here’s some background information:

Axial dispersion is the broadening of a GPC peak which is caused by the chromatographic system and most of that comes from using columns with large particles, such as 20 micron. This results in modified molecular weight moments and molecular weight distribution for a broad peak. Monodisperse polymer standards are used to calculate system band broadening. Once we know the system band broadening value, we can use axial dispersion in the Processing Method which results in an estimation of true molecular weight moments and molecular weight distribution for a broad peak. (Please refer to Empower On-Line help for additional information on this topic.)

Bring a narrow standard into Review and open a Processing Method which is used for Relative Calibration.

Integrate the chromatogram.

From the Process menu, select ‘Quantitate Standard’.

Calculate the average System Sigma (this could be done with a Simple Custom Field).

Modify the Processing Method on the Axial Dispersion tab to include the Axial Dispersion Correction and enter the value from Step 4 into the Sigma (ml) field.

Save all changes to the Processing Method and process the Sample Set in the normal fashion.

Results now reflect the use of Axial Dispersion.

A simple report table displays the difference in the results with and without the Axial Dispersion correction.

It’s that easy!