Tip #51: Deriving Channels in Empower (Part 4)

Welcome back to Get Empowered! In our last tip-of-the-week blog for Empower Software, we did a quick year-in-review. This week we continue our series on Deriving Channels in Empower CDS.

• Tip 47: Smooth a chromatogram by Deriving a Channel (part 1)
• Tip 48: Correct for the time offset between detectors connected in series by Deriving a Channel (part 2)
• Tip 49: Subtract a baseline from a 2D chromatogram by Deriving a Channel (part 3).

Now let’s learn how to subtract a 2D baseline from 3D PDA data (part 4).

In Tip 49, I had a related question that I will answer with this tip!

Question: How do I subtract a baseline at a particular wavelength from my PDA data using Empower Software? We need to first save the blank as 2D data at the wavelength of interest, and the rest is easy.

Let me show you how it’s done.

Step 1

We begin by bringing a sample set into Review, extract the wavelength of interest, and observe the baseline of one of the injections. We see the rise in the baseline due to the gradient (Figure 1).

Figure 1

Step 2

First, we need to give the blank injection a label either in the Sample Set method prior to acquiring the data, or post run in Alter Sample (Figure 2).

Figure 2

Step 3

Select the blank injection and from the File menu select Save Chromatogram (Figure 3).

Figure 3

Step 4

Similar to what we did in Tip 49, Derive a Channel and on the First (Only) Channel tab select PDA: Single Wavelength from the Channel drop-down list (Figure 4).

Figure 4

Step 5

Enter the wavelength. In this example, it is 215 (Figure 5).

Figure 5

Step 6

On the Second Channel tab, select subtraction from the Operator drop-down list and then type 215.0nm (this is how Empower names the 2D data as per step 3) into the Channel field. Do not select anything from the Channel drop down list (Figure 6).

Figure 6

Step 7

Check the From injection labeled box and enter the label for the blank injection (Figure 7).

Figure 7

Step 8

Click OK, give the new Derived Channel a name, and select the Processing Method in the Channel table within the Method Set (Figure 8).

Figure 8

Step 9

Apply the Method Set to the same injection as in step 1 and zoom in on the corrected baseline (Figure 9).

Figure 9

It’s that easy!

What about subtracting a 3D baseline across the collected wavelength range? Stay tuned for a future tip for the answer to that one.

Final notes:

1. I would only recommend using this procedure if the baseline is very reproducible.
2. This procedure can be followed using the QuickStart or Pro interface.

Please rate this Empower Tip of the Week

Next week in Empower Tip #52: Deriving Channels in Empower (part 5).

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