Using the Compare Window in Empower - Tip222

OBJECTIVE or GOAL

Tip #222: Empower User Question: Aligning chromatograms using the Compare window in Empower

This tip answers an Empower user question regarding aligning peaks between chromatograms where the retention times have shifted. 

Q: It is not unusual to have a small amount of retention time shifts from injection to injection. How can I be sure that the peaks from chromatogram to chromatogram are the same so that I can track them with this shift in retention time?
A: This can be solved using the Compare window. 
 

ENVIRONMENT

• Empower

PROCEDURE

1. Highlight the channels of data, right click, and select ‘Compare’
   
2. The Compare window opens displaying an overlay of the chromatograms
   
3. Click the ‘Individual Plot’ tool and a stack plot is displayed 
   
4. Click the ‘Alignment Markers’ tool to display the alignment markers in the chromatograms
   
5. Move the ‘first marker to the first peak’ in each chromatogram and the ‘second marker to the last peak’ in each chromatogram
   
6. Click the ‘Align Chromatograms’ tool to align the peaks
   
7. Click the ‘Compare Main Window’ tool to display the aligned chromatograms in one window
   

ADDITIONAL INFORMATION

If you zoom in on the baseline of the chromatograms after Step 6, the resulting view in Step 7 remains zoomed in. This will help when looking at small impurity peaks. 
Use either the Pro or QuickStart interface for this tip.