Empower Tip: Peak Identification

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

In this tip, we will learn how to use Update RT.

The Processing Method is developed with a standard and the peaks are named accordingly in the first injection of the standard.

in the second injection, the third peak is not identified. We know the third peak is Benzoate

Possible solution: the Update RT field on the component tab of the Processing Method can be used in the following way:

This function does not replace the Retention Times entered into the component table of the Processing Method. It updates for peak identification purposes only.

Replace and Replace Standards should be used when Retention Time shifts are consistent (either increasing or decreasing) and there are no extra peaks that could be misidentified.

Average and Average Standards should be used when Retention Times fluctuate around a mean value and there are no extra peaks that could be misidentified.

The updated Retention Time will appear in the Calibration window. With the Update RT set to Never, the function is turned off. If you look at injection 1 side-by-side with the Calibration window, you see the expected Retention Time, as per the component tab, is 8.140 minutes and the time in the Calibration window is 8.140 minutes.

Set the Update RT to Average standards. Since there are three injections of the standard, Empower will use the following formulae to update the expected Retention Time for the peak:

For injection 1 - (RTct+RTinj1)/2=Average#1

For injection 2 - (2x(Average#1)+RTinj2)/3=Average#2

For injection 3 - (3x(Average#2)+RTinj3)/4=Average#3

Where RTct is the Retention Time of the component from the component tab and Rtinj# is the Retention Time of the component from the current injection.

STEP 6For injection 1, the Retention Time of the peak is 8.150, therefore, the calculation for expected Retention Time is (8.140 +8.150)/2 which equals 8.145 minutes. That can be seen in the Calibration window in the Time field.

STEP 7For injection 2, the Retention Time is 8.141667, therefore the calculation for expected Retention Time is (2x(8.145)+8.141667)/3 which equals 8.144 minutes. That can be seen in the Calibration window in the Time field.

Important Note: If you had selected Average instead of Average Stds, the averaging process for the expected Retention Time would continue thru all the sample injections.

It’s that easy!