Chromatography Forum

Good afternoon, I have a big problem with the chromatograph of the laboratory and, please, need help.

It is a gas chromatograph HP 68980 Series (GC ChemStation) and just go to work and I've found with broken capillary column. We have substituted but the method does not recognize the compounds which have preeterminados, as it is logical retention times have changed.
Can you tell me if there is a list of retention times for compounds according to the column you use?. Compounds which are determined: ethyl acetate, acetaldehyde, dieteilacetal, methanol, n-propanol, isobutanol, and ethyl lactate isoamilicos, employing an internal standard (ISTD: 4-methyl-2-pentanol).

Could you help me out for the new method, please?

Thank you very much.

Good afternoon, I have a big problem with the chromatograph of the laboratory and, please, need help.

It is a gas chromatograph HP 68980 Series (GC ChemStation) and just go to work and I've found with broken capillary column. We have substituted but the method does not recognize the compounds which have preeterminados, as it is logical retention times have changed.

Logically, when the column was replaced with another of the same type and parameters retention times should stay more or less unchanged.

Can you tell me if there is a list of retention times for compounds according to the column you use?. ...

Yes. Such list is called "calibration table" and it is saved with method file.

The important parameters in replacing a capillary GC column are: length, internal diameter, stationary phase, and film thickness.

If you have a packed GC column, it is: length, internal diameter, stationary phase, % loading of the stationary phase, support material and mesh of the support.

If a significant portion of the old column was removed by trimming the end from the column, this is important as well.

If you have changed to a column with the same stationary phase, the retention order will remain the same.

Chemstation can identify peaks based upon absolute retention time or based on relative retention time, depending on the method you set up. It sounds like you have a method looking for absolute retention times. If you go into the method and look at the 'Compound Details', you can set one peak as the reference (usually an internal standard) and then set the other peak retention times relative to the reference. It's frustrating to get it set up, but once you have it done, it's pretty reliable. Check the Chemstation Manuals, under 'Peak Identification' for more detailed information.