Empower Tip: Helpful Empower Tools

In this tip, we will learn about using relative retention time to identify peaks rather than absolute retention times if the variation in retention time becomes excessive.

We start with a standard containing four components, all identified properly.

In the sample chromatogram, peak #3 has shifted and is not identified. The peak type is Unknown. The peak table also shows that peak #3 is missing. Notice the peak at 8.033 minutes, however, Empower has not identified it.

Select a Retention Time Reference peak from the RT Reference field in the Components tab of the Processing Method.

Working with the chromatogram for the standard, click Calibrate and unhide RRT~ in the Peaks table. RRT~ is calculated as RT of Peak of interest/RT of RT Reference peak.

STEP 5:

Make the following modifications on the Components tab of the Processing Method:

Remove the retention time for the peak

Enter the RRT value in the field for the peak

This is the calculation for the temporary retention time used for peak identification. This does not change anything in the Components tab of the Processing Method. Substituting in the real numbers: 1.666 x 4.842 = 8.067 +/- 0.091.

The temporary expected retention time for the peak is 8.067 +/- 0.091 minutes. Now the peak at 8.033 minutes falls within the new retention time window and is identified properly.

It’s that easy!