Tip #55: Deriving Channels in Empower (Part 8)

Welcome back to Get Empowered! In our last tip-of-the-week blog for Empower Software, we reviewed Deriving Channels when working with 3D PDA chromatography data in Empower.

• 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).
• Tip 51: Subtract a 2D baseline from 3D PDA data by Deriving a Channel (part 4).
• Tip 52: Derive MaxPlot from 3D PDA data (part 5)
• Tip 53: Derive TotalPlot from 3D PDA data (part 6)
• Tip 54: Derive RatioPlot from 3D PDA data (part 7)

In this tip, we will discuss another option for Deriving Channels when working with photodiode array (PDA) data, called Timed Wavelength.

Have you ever had a sample where each component had a different lambda max and it was difficult to pick one wavelength to use for quantitation?

We learned in Tip 52 that MaxPlot plots each point in time at the maximum absorbance across the collected wavelength range. From a method development viewpoint, this gives us a quick and easy way to see the lambda max for each component. However, MaxPlot is typically not used for quantitative purposes.

Timed Wavelength creates a channel that specifies a wavelength at specified starting times. This maximizes sensitivity and allows us to perform quantitation for all components regardless of the differences in lambda max. (It is analogous to wavelength programming in the instrument method for a UV detector, except this being done post-run.)

Let me show you how it is done.

Step 1

We begin by bringing a channel of PDA data into Review and deriving MaxPlot using the Extract Choices drop-down list (Figure 1). We see three peaks each with a different lambda max – 257, 289, and 244 nm.

Figure 1

Step 2

Go to the Method Set window and Derive a Channel, selecting Timed Wavelength (Figure 2).

Figure 2

Step 3

Enter the time and the wavelength to be displayed for each component (Figure 3).

Figure 3

Step 4

Save the Derived Channel and select a generic processing method (Figure 4).

Figure 4

Step 5

Return to the main window and apply the Method Set. The Timed Wavelength chromatogram is displayed (Figure 5).

Figure 5

It’s that easy!

Final note: This procedure can be followed using the QuickStart or Pro interface.

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Next week in Empower Tip #56: Deriving Channels in Empower (part 9).

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