Method transfer from old GC-HS model (6890 / G1530A) to new model 7890A

Hi Team,

We have GC-HS method developed on the old model of GC-HS (i.e. 6890/G1530A) and now we need to use the same method on the new model of GC-HS(7890A).

In the old instrument there was an option to manually control the flow through HS to get the required split vent flow. But with the new systems HS flow is controlled through GC and to achieve the required split vent flow we might need to optimize the method with some trial and error way.

Is there is any equivalency calculation available with you when we change the method from old GC to the new GC so that we can save some time which will go in method optimization to achieve the required split vent flow. 

Will be waiting for your response.

Thank you.



  • Hi .  

    This is a great question!

    If you calculate the split ratio you were using on the 6890 GC system based on the actual flow you measured going out the split vent (requires a flow meter) and the column flow, then you can request that same split ratio on the 7890 GC.  Please note, this assumes you have the Headspace Sampler (it would be helpful if you specified the model) connected to the 7890 GC such that you have cut into the GC’s inlet weldment so that the GC inlet Electronic Pneumatic Control (EPC) is providing all of the carrier flow through the Headspace Sampler and to the inlet.

  • hi Kristen,

    Thank you so much for your response.

    It was really very helpful.

    I have one more question in the same context..

    Do the Agilent 7890 GC models have any limitation with respect to the split ratio as compared to the old models of the system.

    Can we set up the split ration to 1:2 for the new systems.

    Thank you,



  • Hi , glad my response helped.  

    The inlet split ratio is calculated by: column flow + split vent flow / column flow.

    To answer your question about split ratio limitations, details about the particular system setup need to be known, most notably, the dimensions of the configured column and the requested column flow, since this information is key to the split ratio calculation.

    In the context of a headspace‑GC connection, typically a split ratio of 5:1 is used to help keep the total flow up so the transfer of the headspace’s sample loop contents are done reasonably fast.  A split ratio of 2:1 should work under typical conditions, but it does depend on the system setup.

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