Empower Tip: Empower User Question

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

In this tip, we will answer 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?

Great question. We can solve the problem using the Compare window.

STEP 1

Highlight the channels of data, right-click, and select ‘Compare’.

STEP 2

The Compare window opens displaying an overlay of the chromatograms.

STEP 3

Click the ‘Individual Plot’ tool and a stack plot is displayed.

STEP 4

Click the ‘Alignment Markers’ tool to display the alignment markers in the chromatograms.

STEP 5

Move the ‘first marker to the first peak’ in each chromatogram and the ‘second marker to the last peak’ in each chromatogram.

STEP 6

Click the ‘Align Chromatograms’ tool to align the peaks.

STEP 7

Click the ‘Compare Main Window’ tool to display the aligned chromatograms in one window.

It’s that easy!

Final Notes

1. If you zoom in on the baseline of the chromatograms after Step 6, the resulting view in Step 7 will remain zoomed in. This will help when looking at small impurity peaks.

2. You can use either the Pro or QuickStart interface for this tip.

About the Author

Neil Lander

Neil provides internal support for Empower CDS software and is focused on developing laboratory software solutions that help organizations achieve their scientific and operational objectives.

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