How to Work with GPC/SEC data in Empower Software (Part 5) - Tip128

OBJECTIVE or GOAL

Welcome back to Get Empowered! In the last Empower tip-of-the-week post for Empower Chromatography Data Software, we learned about doing universal calibration using Mark-Houwink constants (Tip #127).

In this week’s tip, we are going to 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 get started.

ENVIRONMENT

• Empower

PROCEDURE

1. We begin by looking at a result for a broad unknown which was determined from via Relative Calibration using narrow standards (Tip #125). In the Results window, from the Options menu, select Save as Named Distribution. Enter a name and click ‘OK’.

2. Bring the channel for the broad unknown into Alter Sample, change the Sample Type to Broad Standard and click ‘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.

3. Here we use the Processing Method developed when using Relative Calibration to process the broad standard and a broad unknown. The calibration curve has 100 points.

4. The results for the broad unknown are displayed.

How will these results compare to the original results generated with a Relative Calibration using narrow standards? Please message me with the answer. (click to message)

It’s that easy!

ADDITIONAL INFORMATION

• Broad standard cumulative matching percent calibration corrects for observed differences in total band spreading between results generated using high speed versus traditional GPC methods.
• This procedure can be followed using the QuickStart or Pro interface.