Empower Tip: Creating, Searching, and Restoring UV libraries

In this tip, we will learn how to do an automated search with the UV library we created in Empower. If you have a complex chromatogram with many peaks, it is more efficient to automate the search of the peak apex spectra by adding the library search to the Processing Method.

STEP 1 Bring the data into Review and apply the Method Set. Open the Processing Method and Click ‘Purity’ tab. The Spectral Contrast parameters which were discussed in Tip 135 & Tip 136 for Peak Purity apply to library searching as well, therefore, there is no need to modify them.

Click the ‘PDA Library Search’ tab. Select the newly created library from the list on the left and enable the ‘Retention Time Presearch’. The Solvent Angle needs to be determined. Please see the On-Line Help for information on determining the Solvent Angle. Bonus Tip: you can select multiple libraries so that Empower searches across multiple libraries.

Save the changes to the Processing Method and reapply the Method Set. Go to the Main window and Click the ‘Peaks’ tab. The PDA/FLR Match1 Spectrum Name field is now populated with the name of the spectrum in the library corresponding to the best match. If the PDA Match angle is less than the PDA Threshold, it indicates a good match. (We should take advantage of the PDA Match Plot and Triple Plot before we make a conclusion) The PDA/FLR Match 1 Library Name indicates the library where the library spectrum resides.

Go to the Results window and Click the ‘PDA Match Plot’ tab. This plot overlays the peak apex spectrum with the matched library spectrum.

You can normalize the y-axis in the properties of the plot so that you can compare the shape differences between the spectra.

Click the ‘PDA Triple Plot’ tab. The lower plot displays the subtracted difference between the 2 spectra. If the spectra were the same, it would result in a straight line.

It’s that easy!