Empower Tip: Working with GPC/SEC data in Empower

In this tip we will learn about using a Processing Method for relative calibration and broad standards.

The advantages to this technique are that it is easy and accurate for polymers of the same chemical nature as the standards. The disadvantages are broad standards are not available for every type of polymer and a single broad standard covers a limited molecular weight range.

Let’s see how it’s done!

Within Alter Sample, select the Broad Standard and click the Amounts tool. Select the Moments tab and enter the Mn, Mw, Mz and Mz+1. These values should be available from the supplier of the standard or can be determined experimentally.

STEP 2The Processing Method developed in Tip 437 can be used in this case. Once the data has been processed, review the results for the broad standard in Review. The Mn, Mw, Mz and Mz+1 are the same as entered in Step 1.

STEP 3In this case the calibration curve has 10 points. The standard was injected twice, and we entered the four moments giving us eight points plus Empower determines the Mp for each injection as well for a total of ten points.

STEP 4Here is a sample with its corresponding results based on the new calibration curve.

STEP 5We see the slice table and distribution plot for the sample.

STEP 6Finally, here is an overlay of the distribution plots for the same sample where we used the narrow standards versus the broad standard to generate the calibration curve. The differences in the numbers are to be expected as the calibration curves generated in each case are different.

It’s that easy!

Final Note

You can use a combination of a broad standard and narrow standards to extend the range of the calibration curve. In this case you may want to add Relative Weighting in the Component Editor as seen in figure 1. This weights the curve towards the broad standard or the narrow standards. The default value is 1 for all.