Empower Tip: Empower CDS User Question

In this tip for Empower Chromatography Data System (CDS), we will answer an another Empower CDS user question.

Q: How do you subtract a blank baseline from chromatograms in a Sample Set when working with both 2D and 3D chromatography?

This short series will demonstrate how to subtract baselines.

Let’s get started with 2D chromatography.

We start with a chromatogram collected from a UV detector at 225nm.

Zooming in on the baseline, we see that it rises due to the gradient.

This is further illustrated by looking at the blank injection. [figures 3]

Now let’s subtract the baseline from the chromatogram.

Enter a label in the Label field in the Sample Set Method. This can be done either before or after the data has been collected in Alter Sample. It is not necessary to use the Blank field. That field is used when calculating USP, EP, and JP signal-to-noise ratio using a blank injection.

Derive a channel in the Method Set and on the First (Only) Channel tab select the channel you are working with.

On the Second Channel tab, select subtraction from the Operator list, select the channel, and check the box ‘From Injection Labeled’. Enter the label for the injection in the field to the right, click ‘OK’ and give the derived channel a name.

The Method Set now displays the derived channel in the channel table with the Processing Method.

Once the Sample Set has been processed, you see a straight line for the blank as the blank subtracted from itself produces a straight line.

Zooming in on the baseline of the chromatogram we looked at in Step 2, you see the baseline is now flat.

It’s that easy!