Empower Tip: Peak Identification

In this tip for Empower Chromatography Data System (CDS), we will continue our series on peak identification.

In this tip, we will learn how to use Retention Time (RT) Reference peaks.

The Processing Method is developed with a standard and the peaks are named accordingly.

We run a sample and see that there is a peak at 8.033 minutes which has a Peak Type Unknown. Peaks 3 and 4 display ‘Peak Type Missing’.

In this example, the peak at 8.033 minutes is Peak 3. The expected retention time is 8.146 + 0.058, therefore it is not identified properly. This means that the peak needs to fall in the range of 8.088 – 8.204 to be identified properly.

Make Peak 2 the RT Reference peak in the RT Reference field on the Components tab of the Processing Method.

Empower makes the following calculation:

(RT of RT Ref Peak in Sample/RT of RT Ref Peak in Standard) x RT of peak of interest in the standard, where RT = Retention Time.

Substituting in the real numbers: (4.842/4.889) x 8.146 = 8.068

Now the expected range for the peak is 8.068 + 0.058 which translates into 8.010 – 8.126 and the peak is identified properly.

STEP 6Now you have the option to identify the peak via the Relative RT Reference value rather than absolute retention time.

Important things to keep in mind when using RT Reference peaks:

1. The RT Reference peak must be in every chromatogram.

2. This is applicable to chromatograms where the peaks are close together or the RT Windows must be kept small.

3. This adjusted retention time is for peak identification purposes only; it does not affect the calibration curve.

4. You can add the RT Reference used field to the peaks table in review and the report to quickly identify the RT Reference peak used without having to go back to the Processing Method.

It’s that easy!