Chromatography Forum

We have used two similar columns in one GC. All parameter are the same in one run, but when calibrate with defined standard, the response factor for two chancel are different so much (i.e. one is .77 and another is 1.4). one of columns installed recently. Is it related to new column or detectors should be checked? both coulmn are CP-SIL 5CB 25m,0.32 d, 0.5u film

Assuming you are using FID (you did not state the detector) either your two injectors have a different discrimination when you split the sample, or the detectors have a different response to the analytes.

While it may be possible that one column or injector may degrade or absorb one of the analytes that possibility also exists, but may not be likely. With so little information offered it is impossible to offer much in response.

best wishes,

Rod

both detectors are FID and both liner of injector are new ones

Several questions:

1) Are all parts of the systems identical (same part numbers) including inlet liners, FID jets, and such. Also same gas supplies?
2) Are all conditions the same from gas pressures at the back of the instrument to integration conditions?
3) when was the last maintanance of inlets and detectors of each instrument - including replacement of jets, liners, septa, etc? Leak checking for helium leaks from ferrules etc? (you noted new liners in the post above - both the same kind I assume?)
4) can you overlay the chromatograms on top of each other and demonstrate the same retention times and peak shapes?

If everything is equal so far, you can swap the column between instruments and see if the problem moves with the column.

Note that simple things like differenes in placement of the column in the inlet or in the detector can have an effect on instrument sensitivity. Other things like age of electronic components can also have an effect.