Tip #66: Working with Method Sets in Empower (Part 1)

Welcome back to Get Empowered! In our last tip-of-the-week blog for Empower Software, we learned how to use a derived channel function called Switch To (Tip 65).

This week we will begin a new multi-part discussion around Method Sets: How to subtract a 3D baseline from 3D PDA data (Part 1).

From time to time, I am asked if Empower can subtract a 3D baseline from 3D data such as from a PDA. If the method calls for a gradient and the gradient results in a rising baseline, it may be desirable to subtract the baseline across the wavelength range. Sound complicated? It’s very easy to do.

Let me show you how it is done.

Step 1

We begin by bringing a Sample Set into Review, open, and apply the Method Set. The mobile phase in this case is water/acetonitrile and the gradient goes from 7% acetonitrile to 20% acetonitrile in 1.5 minutes. We see the resulting rise in the baseline for the blank (Figure 1).

Figure 1

Step 2

Go to the Method Set window and enter the label for the blank injection into the PDA 3D Blank Subtraction field (Figure 2). The label comes from the Sample Set Method and, in this case, is simply B.

Figure 2

Step 3

Save the change to the Method Set, return to the Main Window, and reapply the Method Set. Notice that the baseline for the blank is a straight line, i.e., it subtracted from itself should result in a straight line (Figure 3).

Figure 3

Step 4

Select one of the standards or samples and zoom in on the baseline. Notice the flat baseline, which results from subtracting the blank baseline (Figure 4).

Figure 4

Step 5

Finally, I have included an overlay of the baseline for the sample without the subtraction (blue) and with the subtraction (black) (Figure 5).

Figure 5

It’s that easy!

Final Notes:

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

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Next week in Empower Tip #67 – Working with Method Sets (part 2).

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