Category Archives: retention time
Internal Standard Retention Time and Peak Width Diagnostic Chart
This a useful and simple report that is best viewed in Excel.
Click here to download the zip file:
Internal Standard Retention Time and Peak Width At Half Height
Place in the folder: C:\TraceFinderData\4.0\Templates\ReportTemplates
The chart shows the Retention Time and the Chromatographic Peak Width at Half Height, in a line chart over the entire batch. It should show you the performance of the internal standard and the reliability of the chromatographic conditions. A moving retention time and/or a widening of the chromatographic peak may indicate issues with the columns or mobile phase. This is useful in determining the health of the system and variability of the assay over time.
The Chromatographic Peak Width can be attained by setting the conditions in the detection portion of the method as shown below. You can change the width measurement to be any desired value. Default is 50% of peak height, though 25% may better gauge peak fronting or tailing.
The report is currently set up to show 59 samples from the data table. If your data set is typically large or smaller you can adjust the ending row in the series section of the chart dialog. Simply open the editor for this report, double click on the chart and the dialog will open as shown below. Expand the section for the Data Source/Series and enter your typical ending row. Any empty cells will not be charted.
Retention Time Reference Compounds Used For Correcting Chromtographic Drift
TraceFinder has an option to allow the user to set a reference compound to assist in corrections of retention time drift.
The feature is the same implementation that has been a part of the Xcalibur feature set for over 20 years and is well characterized. The user simply selects a checkbox in the RT Reference compound column of the Method – Identification tab. This sets the compound for use in linking other compounds to its found RT.
To set a compound to use a RT reference compound, simply select a RT Reference from a dropdown selector in the same definition grid.
The typical use of this feature is to set your Internal Standards as RT Reference Compounds and then link the nearby eluting components to the Reference Compound. Also, the IS retention time peak detection window is set a little larger than the target components to allow for detection if a large RT drift occurs.
When the RT reference is detected the difference, whether + or – in time are adjusted in the connected compounds. This new RT is specific to each compound in each sample. Therefore it is not reflected as a change in the method because the method is set as a batch level setting. The compound using the RT reference must have an original expected retention time to be adjusted, it cannot be left as zero for this feature to work.