Retention time shift for one analyte

This could be due to a matrix affect of the sample.

Thank you for your reply Ron. The standard matrix is a solvent, diethyl ether. My sample matrix may have dirt particles or flux, and if it does, it does not appear in the chromatography. Do you think that ambient temperature in the lab would affect the chromatography? My recommended operating temperature range is 68F-80F. My instrument is not fitted with an exhaust flue to move hot exhaust from the lab area, also, my lab is not temperature controlled. There are hot days when my lab heats up to about 92F. Just curious. Also to remember that all of the compounds save one or two have very high vapor pressures and so low boiling points. Would elevated ambient temperature wreak havoc with my chromatography? Any additional insight is helpful.

Thanks for you reply Ron.

Hi Ron,

What can you tell me about Retention time Low Bound and Retention Time High Bound settings?  I believe it is under "Calibration settings" in Chem Station my version B.04.03.[16]. Thanks for any help.

Sorry I don't know OpenLab software. I added a tag for OpenLab to increase visibility for the software.

Hello, 

In B.04.03 ChemStation the size of the default RT windows used for your compounds is set in Calibration>Calibration Settings. You can either set an absolute window size of X minutes or you can set a relative RT window which would be the size of a certain percentage of a compound's RT. 

To see the actual start and end times of a compound's RT window, these values can be displayed in the calibration table. You can do this by going to Calibration>Calibration Table Options>Identification Details. In this view of the Cal Table there will be a 'To' and a 'From' column displayed with the information you are looking for. 

The typical workflow for updating retention times is to do so automatically with calibration calibration standards by using the update RT column in the sequence table. This workflow will use the default RT window size as defined in Calibration>Calibration Settings though. If you require more control over the RT window limits then what you proposed should work. You would just need to make sure that you are making the RT window changes to the correct method (e.g. if you have unique folder creation turned on the default processing method in Data Analysis is the sequence method. If you make changes to the sequence method, you will need to update the master method with those changes for them to apply to future runs). 

Thanks for your reply ryoboyle,

When I am setting limits for retention time range, should I be running a calibration too? Or am I able to modify my limits, say, before a sample run for the day, save my method, and my limits will be followed for that particular sample run? Please let me know when you get a chance!

Thanks for your reply ryoboyle,

When I am setting limits for retention time range, should I be running a calibration too? Or am I able to modify my limits, say, before a sample run for the day, save my method, and my limits will be followed for that particular sample run? Please let me know when you get a chance!

The typical workflow for updating retention times is to do so automatically with calibration calibration standards by using the update RT column in the sequence table. This workflow will use the default RT window size as defined in Calibration>Calibration Settings though. If you require more control over the RT window limits then what you proposed should work. You would just need to make sure that you are making the RT window changes to the correct method (e.g. if you have unique folder creation turned on the default processing method in Data Analysis is the sequence method. If you make changes to the sequence method, you will need to update the master method with those changes for them to apply to future runs).