How to Do Universal Calibration using Mark-Houwink Constants - Tip127

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 relative calibration with broad standards (Tip #126).

In this week’s tip, we are going to learn about doing universal calibration using Mark-Houwink constants (k and alpha). The advantages to this technique are: it is an easy and accurate method, you can use one calibration curve for different types of polymers and you can determine the intrinsic viscosity of a polymer. The disadvantage is, the accuracy depends on the accuracy of the Mark-Houwink constants.

Let’s get started.

ENVIRONMENT

• Empower

PROCEDURE

1. Bring the Sample Set into the Alter Sample window and click the Amounts tool. Change the Sample Set Type to Standards & Unknowns.

2. Click the K-Alphas tab. Enter the Ks and Alphas for the standards and samples. You can find these values in polymer handbooks and/or Google them.

3. Create a Processing Method and on the Calibration tab, select Universal for the GPC Technique.

4. After processing the Sample Set, we see the result for a sample. The calculation of Mv and [n]P (the intrinsic viscosity) are done in addition to the other molecular weight calculations.

5. The calibration curve plots Retention Time on the x-axis versus Log(Mw[n]) on the y-axis to reflect the addition of the viscosity term.

6. Click the Viscosity Law tab to view the Viscosity Law plot. This plot illustrates the relationship between viscosity and molecular weight. The slope of the plot is alpha, and the y-intercept is K.

7. Here we view a comparison of the results for a polymer processed using the Universal calibration curve versus the Relative calibration curve developed in an earlier tip.

It’s that easy!

ADDITIONAL INFORMATION

1. Intrinsic viscosity is the polymers contribution to the viscosity when it is in solution.
2. This procedure can be followed using the QuickStart or Pro interface.