Empower Tip: Empower User Question Answered

In this tip, we will answer a question from an Empower User.

QUESTION:

How can I view the second derivative of a chromatogram?

This is one of the great questions I received during an Empower: Ask Me Anything webinar.

Let’s see how it’s done!

We begin by bringing an injection into Review, open and apply the Method set.

Go to the Method set and derive a channel, and on the First (Only) Tab select the channel from the Channel drop down list.

On the Filter/Offset tab select Second from the Derivative drop down list.

Click OK, save the derived channel with a name and add it to the Method set along with a Processing Method.

Return to the Main Window, apply the Method set and click the Overlay tool.

It is very difficult to see the overlay and we can improve the display by going into the properties of the chromatogram and set the overlay to Make Stack Plot. (Optionally, you can clear the integration from the Edit menu.)

If you want to get a closer look at the second derivative you can zoom in on it much like you would on a chromatogram.

It’s that easy!

Important Note:

The Aspartame peak has a USP Tailing value of 1.26 and the Benzoate peak has a USP Tailing value of 1.12, hence less tailing. Note the shape of the second derivative for both peaks. If a peak is perfectly symmetrical, the lift off and touch down points in the second derivative would be of equal amplitude.