Empower Tip: Working with GPC/SEC data in Empower

In this tip we will learn how to work with GPC/SEC data in Empower.

GPC, or Gel Permeation Chromatography, is referred to when working with organic polymers and SEC, or Size Exclusion Chromatography, is referred to when working with biomolecules. In both cases this type of chromatography is the separation of compounds based on their effective size in solution.

This tip will cover the creation of a Processing Method for Relative Calibration using narrow, or monodisperse, standards. The advantages to this technique are that it is easy and accurate for polymers of the same chemical nature as the standards. The disadvantage is that narrow standards are not available for every type of polymer.

Let’s see how it’s done!

Select representative chromatograms for standards and samples and bring them into Review. Typically, relative calibration with narrow standards is done by injecting mixtures, or cocktails, of monodisperse standards. Start by adding the molecular weights into the Component Editor for each of the standard vials either in Run Samples or post run in Alter Sample.

STEP 2Create a new Processing Method with the wizard if you are new to working with GPC data. Most of the screens will be similar to developing a Processing Method with the wizard when working with LC data. There are a few differences, such as the Calibration window requires you to select the type of calibration, the calibration fit and the x-axis for the calibration curve. (If it is determined that the fit needs to be modified after a calibration curve has been generated, that can be done and will be discussed in a future tip.

STEP 3The Column Set window requires a void volume time and a total volume time. These values will depend on the column or column bank being used.

STEP 4Once you finish going through the wizard, check the integration for the standards and modify as needed so that only the peaks for the monodisperse standards are integrated.

STEP 5Select a sample and then click the Processing Method Wizard tool to modify the Processing Method for broad samples. When the Wizard opens, click the Back button a few times to get to the peak detection and integration parameters and then proceed through the wizard.

STEP 6On the Broad Unknowns and Standards window, you can enter a name for the broad peak. If you have more than one peak, you can assign a name to each peak.

STEP 7Save all the changes to the Processing Method and exit out of the wizard. Check the integration on the chromatograms for the broad samples and modify them as needed.

STEP 8Alternatively, you could develop a Processing Method without the wizard. For peak detection and integration, the Integration tab has parameters for both narrow and broad peaks.

STEP 9You can go to the Calibration tab to set the calibration parameters including V0 and Vt. Finally, the Slicing tab allows you to name the broad peak(s).

It’s that easy!