Empower Tip: Working with GPC/SEC data in Empower

In this tip we will learn about Cumulative Matching Percent Calibration.

The advantages to this technique are it is an easy and accurate method, calibration is precise. The disadvantages are limited number of commercially available standards, accuracy is limited by the quality of the standards and the high & low molecular weight regions are less accurate. Cumulative Matching Percent Calibration is done by running a broad unknown, determining the molecular weight distribution and saving the distribution with a name. That same broad unknown is then run as a standard and, using the saved distribution, a calibration curve consisting of 100 points is generated.

Let’s see how it’s done!

We begin by looking at a result for a broad unknown which was determined from via relative calibration using narrow standards from an earlier Empower Tip. In the Results window, from the Options menu, select Save as Named Distribution. Enter a name and click OK.

STEP 2Bring the channel for the broad unknown into Alter Sample, change the Sample Type to Broad Standard and click on the Amounts tool. Click the distribution tab, make sure you are on the Current tab and select the named distribution which was saved in Step 1.

STEP 3Use the Processing Method developed when using relative calibration to process the broad standard and a broad unknown. The calibration curve has 100 points.

STEP 4The result for the broad unknown is displayed.

It’s that easy!

Final Note

Broad standard cumulative matching percent calibration corrects for observed differences in total band spreading between results generated using high speed versus traditional GPC methods.

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Next time in Empower Tip 441 – we will continue the series on working with GPC/SEC data.