Location:
Peak Table tab page
Report Variable (Peak Table and Peak Results)
Dimension:
Minutes
Can be combined with:
Absolute time; Time distance/ratio to reference peak; Reference peak
Related Variables:
Description:
The retention time is used for peak identification. The Retention Time variable refers to the time (in minutes) that passed since the injection (also, refer to Dead Time).
By definition, the injection time always equals zero. Therefore, control commands issued before this time will have negative times. The advantage is that the times stated in the PGM File (file type .PGM) are compatible with the retention times, rather than being delayed by the injection time.
Peak retention times are generally interpreted as time between injection and peak maximum. However, indication of the distance to a reference peak is possible as well. As the reference peak does not need to be at the beginning of the chromatogram, such difference retention times can also have negative values. Relative retention times are time quotients in percent as to a reference peak. Another possibility is to specify the retention time when a certain relative peak area is reached.
Expected Retention Time
On the Peak Table page in the QNT Editor, the retention time can be entered either manually by the user or automatically by the system. The latter is possible via the Autogenerate Peak Table command on the Edit or context menus.
The user enters the expected retention time, while the system enters the actually detected retention time (or the retention time when a certain peak area is reached) of the actually analyzed sample.
To display the expected retention time from the Peak Table in the report, the following parameters are available:
Parameters:
Absolute Time
Output of the absolute value in minutes (default)
Text format
Output in text format: With relative retention times (difference or ratio) the name of the reference peak is also given. You can select the number of decimal places for the text format (default: 3).
Note:
If the Use Recently Detected Retention Time option (retention time correction) is enabled in the peak table, the retention times entered manually on the Peak Table page are no longer used as nominal retention times for all identified peaks. Instead, the values detected for the previously analyzed sample (its nominal times) are used. Distinguish between:
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The originally expected retention time that was entered on the Peak Table tab page.
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The nominal retention time which, in this case, corresponds to the actual retention time of the previously analyzed sample.
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The actual retention time of the actually analyzed sample.
Retention Windows are also interpreted as percentage value of the absolute retention time for both, difference, and relative retention times! Only the retention times of identified peaks are corrected!
Actual Retention Time:
How the retention times of all peaks in a chromatogram are calculated depends on the Peak Retention Time Determination setting on the General tab page of the QNT Editor. Select Use absolute greatest signal value to use the retention time of the absolute greatest signal value. Select Use relative greatest signal value over the baseline to use the retention time of the signal value that is the relatively greatest value over the baseline.
Parameters:
To display the retention time as a result in Chromeleon, use the following parameters available for the Retention Time variable in the Peak Results report category:
Detected value (Default)
Select Detected Value to display the detected (actual) Retention Time (default).
Expected value
Select Expected value to display the time when the peak was expected. In this case, all corrections ("Use Recently Detected Retention Times", modified time of the reference peak) have already been taken into account.
This variant is also available for undetected peaks.
At a specified peak %area of
Select At a specified peak %area of to display the retention time that was measured when a specified relative peak area was reached.
