Adjusting retention times in Data Analysis (Chemstation)

Discussions about GC and other "gas phase" separation techniques.

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So I know you can use RTL to adjust head pressure and get the same retention times as before after doing column maintenance (trimming), but is there any way to adjust the retention times from a data file you load in the Data Analysis? Like shift all these peaks by %? I know you can do this in MSD Chemstation, but it doesn't appear there's a way in Chemstation CDS (C.01.07)?

Thanks!
I likely don't understand exactly.

We used to adjust the retention times in the Calibration Table, then Save, then Reprocess. Is that what you mean?
I don't know about Chemstation CDS (C.01.07). But maybe this will jog some memory for someone else. In Chemstation... Read about the Global Update Dialog Box and other Global dialogues in the Chemstation help...
Snip... and Paste...
Global Update Dialog Box
When you select Initial Calibration / Global Update, the Global Update dialog box lets you change the following parameters for the entire quantitation database.

Shift Retention Times
Prompts you to shift the times by a constant x minutes or scale them by x percent. Put an m after the number to specify a constant shift (in minutes) or a % after the number to specify a percentage shift. For example, if all compounds are now eluting 2 minutes later than the expected retention time, enter 2m as the retention time shift. Shift Retention Times affects the Retention Time Information in the compound database.

Set Extraction Windows
Prompts you to resize by x percent or by x minutes. Resize Extraction Windows affects the Retention Time Information in the compound database.

Set Curve Fit Type
Prompts you to select a curve fit. Affects the Calibration Information.

Set Identification Method
Prompts you to select an identification method for the target ions in the extraction window. Although globally done here, it is much more likely done compound by compound in the database. See also Quantitation Parameters.

Set Subtraction Method
Lets you specify the method for calculating qualifier ion ratios: Average of first and last; lower of first or last; no subtraction; extended area quantitation (use only with quantitation by peak area). See also Target Compound Identification.

Set Other (via command)
Lets you use commands to make global changes to other parameters. For example, to change the units of concentration to "ug/L" for all compounds, enter Amt_Units$="ug/L" and press OK. The units of concentration for all compounds in the quantitation database are then updated.

Any quantitation database variable can be updated in a similar manner. GETCOMPOUND and GETRESULT contain a list of applicable variables.
LALman wrote:
I don't know about Chemstation CDS (C.01.07). But maybe this will jog some memory for someone else. In Chemstation... Read about the Global Update Dialog Box and other Global dialogues in the Chemstation help...
Snip... and Paste...
Global Update Dialog Box
When you select Initial Calibration / Global Update, the Global Update dialog box lets you change the following parameters for the entire quantitation database.

Shift Retention Times
Prompts you to shift the times by a constant x minutes or scale them by x percent. Put an m after the number to specify a constant shift (in minutes) or a % after the number to specify a percentage shift. For example, if all compounds are now eluting 2 minutes later than the expected retention time, enter 2m as the retention time shift. Shift Retention Times affects the Retention Time Information in the compound database.

Set Extraction Windows
Prompts you to resize by x percent or by x minutes. Resize Extraction Windows affects the Retention Time Information in the compound database.

Set Curve Fit Type
Prompts you to select a curve fit. Affects the Calibration Information.

Set Identification Method
Prompts you to select an identification method for the target ions in the extraction window. Although globally done here, it is much more likely done compound by compound in the database. See also Quantitation Parameters.

Set Subtraction Method
Lets you specify the method for calculating qualifier ion ratios: Average of first and last; lower of first or last; no subtraction; extended area quantitation (use only with quantitation by peak area). See also Target Compound Identification.

Set Other (via command)
Lets you use commands to make global changes to other parameters. For example, to change the units of concentration to "ug/L" for all compounds, enter Amt_Units$="ug/L" and press OK. The units of concentration for all compounds in the quantitation database are then updated.

Any quantitation database variable can be updated in a similar manner. GETCOMPOUND and GETRESULT contain a list of applicable variables.


Sadly I think those commands are only in the MSDChemstation/Enviroquant versions. When we used the A.xx.xx versions of Chemstation on our HPLCs I always opened the data with the MSDChemstation to do the quantitation simply because the Chemstation version was a pain to work with. We always used the MSDChemstation for control and data analysis on all of our GCs even if they are not attached to a MS. I think CDS is just the newer version of the old Chemstation and probably lacks the tools for easy RT updates.
The past is there to guide us into the future, not to dwell in.
Yes, that is correct - in MSD Chemstation only. What we were hoping for was to be able to shift retention times proportionally on already run data files (so they match up previous ones from before column maintenance).
Can you import the data files to a computer with MSDChemstation? I know the older Chemstation files were compatible, but not sure about the new ones.
The past is there to guide us into the future, not to dwell in.
To determine whether the latest version of MSDChemstation can import your specific data files, you should consult the documentation and support resources provided by Agilent or contact their technical support directly.
shell shockers
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