Get Empowered: Review Window and the Processing Method | Tip #64, Deriving Channels

By April 11, 2018

Tip #64: Deriving Channels in Empower (Part 17)

Welcome back to Get Empowered! In our last tip-of-the-week blog for Empower Software, we reviewed Deriving Channels when working with 3D MS 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)
  • Tip 55: Derive Timed Wavelength from 3D PDS data (part 8)
  • Tip 56: Derive Single Mass from 3D MS data (part 9)
  • Tip 57: Derive TIC plot from 3D MS data (part 10)
  • Tip 58: Improve noisy TIC plot Derived from 3D MS data (part 11)
  • Tip 59: Derive MaxPlot from 3D MS data (part 12)
  • Tip 60: Derive Total Plot for 3D MS data (part 13)
  • Tip 61: Derive Timed Mass for 3D MS data (part 14)
  • Tip 62: Create a Formula Based Derived Channel (part 15)
  • Tip 63: Create a mirror image of a chromatogram (part 16)

In this tip, we will learn how to look at the second derivative of a chromatogram.

Many of you use the Apex Track peak detection and integration algorithm. Apex Track detects peaks from the second derivative of the chromatogram and a number of you have asked, “How do I look at the second derivative of my chromatogram?” Looking at the second derivative can make it easier to identify coeluting peaks.

Let me show you how it is done.

Step 1

We begin by bringing an injection into Review, open and apply the Method Set (Figure 1).

Empower Tips: Open and apply the Method Set | Figure 1

Figure 1

Step 2

Derive a Channel and on the First (Only) Channel tab, select the channel from the Channel drop-down list (Figure 2).

Empower Tip: Select the channel from the Channel drop down list | Figure 2

Figure 2

Step 3

On the Filter/Offset tab, select Second from the Derivative drop-down list (Figure 3).

Empoer Tip: Select Second from the Derivative drop down list | Figure 3

Figure 3

Step 4

Click OK, save the Derived Channel with a name, and add it to the Method Set along with a Processing Method (Figure 4).

Empower Tip: Save the Derived Channel / add it to the Method Set | Figure 4

Figure 4

Step 5

Return to the Main Window, apply the Method Set, and click the Overlay tool (Figure 5).

Empower Tip: Apply the Method Set / click the Overlay tool | Figure 5

Figure 5

Step 6

It is very difficult to see the overlay. We can improve the display by going into the properties of the chromatogram and set the overlay to Make Stack Plot (Figure 6). (Optionally, you can clear the integration from the Edit menu.)

Empower Tip: Set the overlay to Make Stack Plot | Figure 6

Figure 6

Step 7

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 (Figure 7).

Empower Tip: Zoom in to take a closer look at the second derivative | Figure 7

Figure 7


It’s that easy!

Final Notes:

  1. 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.
  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 #65: Deriving Channels in Empower (part 18).


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