Get Empowered: Review Window and the Processing Method | Tip #38

By October 11, 2017


Tip #38: Working with Misidentified Peaks Due to Retention Time Shifts (Part 3)

Welcome back to Get Empowered! In the last tip-of-the-week blog for Empower Software, we explored  working with peaks that have been misidentified due to retention time shifts.

This time, let’s use the Retention Time (RT) Reference peak in the Processing Method. Use of the RT Reference temporarily adjusts the expected retention time of a chromatographic peak. As long as Empower identifies the retention time reference peak, it will identify the peak of interest properly.

Step 1

Let’s start by bringing data into review, in this case a standard and a sample. Open the Processing Method and integrate/calibrate the standard followed by integrate/quantitate for the sample (Figure 1).

 

Empower Tips: Integrate/calibrate standard/integrate/quantitate sample | figure 1

Figure 1

Step 2

We see that the third peak in the sample is not identified properly and has a retention time of 8.033 minutes (Figure 2).

Empower Tips: Third peak in sample/not identified properly | figure 2

Figure 2

Step 3

Open the Processing Method and select the Components tab. Note that the expected retention time for this peak is 8.166 +0.091 minutes, which is a range of 8.075 to 8.257 minutes (Figure 3).

Empower Tips: Select components tab | figure 3

Figure 3

Step 4

Click inside of the RT Reference field on row 3 and select a retention time reference peak, in this case peak 2 (Figure 4).

Empower Tips: RT Reference field/Select retention time reference peak | figure 4

Figure 4

Step 5

Return to the main window and click quantitate. Now the third peak is identified properly (Figure 5).

Empower Tips: Main window and click quantitate | figure 5

Figure 5

Step 6

How does this work? Empower uses the following calculation to temporarily adjust the expected retention time for peak 3:

(RT of RT Ref Peak in Sample / RT of RT Ref Peak in Standard) x RT of peak of interest in the standard.

Substituting in the real numbers: (4.842 / 4.889) x 8.146 = 8.068.  The temporary expected retention time for the peak is 8.068 +0.091 minutes or a range of 7.977 to 8.159 minutes. So now the peak at 8.033 minutes falls within the range and is identified properly.

 

It’s that easy!

I learned how to work with misidentified peaks due to retention time shifts in Empower! #EmpowerTips Click To Tweet

Final note:

  1. This procedure can be followed using the QuickStart or Pro interface.
  2. The RT Reference peak should be in every chromatogram and well separated from all other peaks so that you can increase its retention time window (see Tip #36).

Please rate this Empower Tip of the Week


 

Next week in Empower Tip #39: Working with misidentified peaks due to retention time shifts (Part 4)

 

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