Empower Tip: Creating, Searching, and Restoring UV libraries

In this tip, we will learn how to do a manual search in the UV library we created. Often, we may want to simply identify a peak in a chromatogram. This is done by taking the apex spectrum of the peak and having Empower compare it to the spectra in the library to find a possible match.

STEP 1 Select ‘Load Library’ from the Library menu, select the library you want to use, and Click ‘Load’.

The spectra from the library are loaded into the Spectra table. To distinguish the library spectra from the peak spectra, add the following fields to the table: ‘Name’ and ‘Library Name’. Any spectra with a name are in the library.

Select a peak spectrum you want to identify by deselecting all but the spectrum of interest using the ‘Select’ field in the Spectra table.

Select ‘Match against library (library name)’ from the Library menu. Click the ‘Library Match’ tab under the Spectrum Review window to view the results. Notice that the best match is to ‘Acetaminophen’ and the second-best match is to ‘Phenacetin’. The match to Phenacetin doesn’t make sense since these compounds elute at very different retention times.

Select ‘Match Parameters’ from the Library menu. Enable the ‘Retention Time Presearch Qualifier’ so that the retention time of the peak spectrum and the retention time of the spectrum in the library need to be close before Empower considers the library spectrum a possible match. The default is 10%.

Repeating the search yields only one possible match to ‘Acetaminophen’.

It’s that easy!