Location:
General tab page
Use Prev. Retention Time (Peak Table) Report Variable
Type:
Check box
Dimension:
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Value Ranges:
Marked/not marked
Use recently detected ret. times of last sample/standard
Set reference time to Last value/Average of last n values/Global average
Defaults:
Not marked
Last sample
Last value
Related Parameters:
Description:
This QNT File parameter (General tab page) defines whether the retention time stored in the peak table (nominal time) is used by default to identify a peak or whether the actual retention time of a peak in the last sample is used. Thus, many types of drift phenomena can be compensated; for example, evaporation of volatile components in pre-mixed solvents or column age.
If the peak is not found in this sample, the chronologically previous sample in the sequence is searched, etc. (The chronological order is important and not the order in the sample list.)
If you have chosen this option, you may select whether you want to use the retention times of the last unknown sample (Sample) or of the last Standard.
Click Options to define whether you want to use the last retention time (Last value), the average of the last x retention times (Average of last x values), or the average of all retention times (Global average).
Function:
If the Use Recently Detected Ret.Time check box is selected, Chromeleon always stores the last actual retention time of the peak and positions the Window specified in the peak table around this actual value, not around the nominal value stated in the peak table.
This allows positive identification of peaks even if the retention time changes due to column trends, and thus, if the peak leaves the defined retention time window.
Example:
The first sample of a sequence containing 10 samples is processed in an automatic batch. Based on the retention times stated in the peak table and the selected window values; for example, 0.2G, four peaks are identified in the first sample (A, B, C, and D). Each one of these peaks may have an actual retention time that deviates from the nominal retention time. Chromeleon stores these actual values and uses them as the basis for positioning the time window in the second sample. If single peaks are then identified in the second sample, the "stored" actual values are replaced by the current actual values. The time window is repositioned accordingly. If, for example, the retention time of peak A from the first sample (1 min) is delayed by 10 s in each sample, the peak will be appear at 1 min + 9 x 10 s = 150 s or 2.5 min in the tenth sample. As the time window is also moved by 10 s with each sample, peak A can be clearly identified in the tenth sample, although the peak is no longer within the originally specified time window (48 s to 1 min 12 s).
Note:
Only retention times of identified peaks are corrected!
