Get Empowered: Review Window and the Processing Method | Tip #39

By October 17, 2017

Tip #39: Working with Misidentified Peaks Due to Retention Time Shifts (Part 4)

Welcome back to Get Empowered! In the last Empower tip-of-the-week blog for Empower Software, we explored (Part 3) for working with chromatography peaks that have been misidentified due to retention time shifts. This week we will explore the final approach to deal with this issue.

Here, we use the Update Retention Time (RT) function in the Processing Method. The Update RT function adjusts the retention time for the peak in the calibration curve, thereby adjusting the retention time Empower uses to match unknown peaks. Sound complicated? It’s actually quite easy to use.

Step 1

Let’s start by bringing a sample set into Review, in this case there are three standards with three injections each (Figure 1).

Empower Tips: Sample set into Review | figure 1

Figure 1

Step 2

Open the Processing Method, integrate the chromatograms for the standards, and observe the retention time fluctuation for peak 1 (Figure 2).

Empower Tips: Processing method/integrate the chromatograms | figure 2

Figure 2

Step 3

Open the Processing Method and select the Components tab. By default the Update RT function is set to Never, which means it is turned off (Figure 3).

Empower Tips: Processing Method/Select the Components tab | figure 3

Figure 3

Step 4

Click the down arrow to view the choices (Figure 4).

Empower Tips: Down arrow/View the choices | figure 4

Figure 4

Step 5

Which one should you pick? If the retention times for your peaks are moving in one direction with each injection (increasing or decreasing), then Replace or Replace Standards will help. If the retention times for your peaks are fluctuating around an average value, then Average or Average Standards will help. Since the retention time of peak 1 is hovering around an average of 2.461, select Average Standards (Figure 5).

Empower Tips: Retention times/Select average standards | figure 5

Figure 5

Step 6

What does this do? The expected retention time for the peak is set in the components table and does not change. Every time you inject a standard, Empower Software calculates an average retention time for the peak, which can be seen in the Calibration Curve window (Figure 6)

Empower Tips: Calibration Curve window | figure 6

Figure 6

Step 7

Even though the retention time of the peak is moving around, it is identified properly for all standards. If you are interested in the math behind this please refer to Empower Online Help (Figure 7) or view the Empower 3 Data Acquisition and Processing Theory Guide (Chapter 4).

Empower Tips: Updating Retention Time/Online Help | figure 7

Figure 7

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:

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

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