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Total Flow

camelia

I am faced with a bit of a puzzle I hope someone can help with.

I am using a 6890GC with EZChrom CDS to run 2 methods. Both methods are operated in split mode with a split flow of 192 mL/min, the column configured in each method is the same and both methods are operated in constant pressure mode with a nominal flow of 2.4 mL/min.

The Total Flow on one method is 197.1 mL/min but it is 196.6 mL/min on the 2nd method.

Why is there a difference in the Total Flow between the 2 methods?

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  • 0

    Hi,

     exactly what you said and like what  pointed out,the septum purge flow cannot set on GC 6890 but we can control the septum flow by reduce split vent value or split ratio ,so you can reduce split vent value in method 1 from 197.1 mL/min to 196.3 mL/min and for method 2 196.6 mL/min to 194.7 mL/ min to get 3 mL/min septum purge flow for two methods.

    you can now measure the septum flow by electronic flow meter you should got 3mL/min

    after Carefully checking you can see in method 1 air flow FID detector 350 mL/min and for method 2 air flow FID detector 400 mL/min and I think this difference led to difference in septum flow ,you can change it and see what will you get.

    Dheya

Reply
  • 0

    Hi,

     exactly what you said and like what  pointed out,the septum purge flow cannot set on GC 6890 but we can control the septum flow by reduce split vent value or split ratio ,so you can reduce split vent value in method 1 from 197.1 mL/min to 196.3 mL/min and for method 2 196.6 mL/min to 194.7 mL/ min to get 3 mL/min septum purge flow for two methods.

    you can now measure the septum flow by electronic flow meter you should got 3mL/min

    after Carefully checking you can see in method 1 air flow FID detector 350 mL/min and for method 2 air flow FID detector 400 mL/min and I think this difference led to difference in septum flow ,you can change it and see what will you get.

    Dheya

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