# 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).

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).

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).

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).

Figure 4

### Step 5

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

### 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).

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

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