I have a new setup with a guard column (5 m), an analytical column (30m, 0.32 mm, 10µm) and a particle trap (2.5 m). Which values for column length should I put in the measurement program? All columns have the same I.D. ( 0.32 mm) but the different coatings (stat.phase) result in different volumes. Should I ignore this and put simply the summation of all columns for the total length, and the values of the analytical column for the I.D. film thickness?
I would add the lengths together and use the analytical column I.D. as you suggest. If anything should be changes leave the particle trap column length out of the input to the GC.
You can always inject a small amount of a not retained component ( I often use lighter gas witch is manly butane for this). The start of the emerging peak (not the apex) can be used to calculate the column parameters or to verify the assumptions in your program
What column parameter are you needing the length to calculate? If you are wanting to calculate the pressure to needed to provide a particular linear velocity, then you would use the total length.
Thank you. Yes, i need it to calculate the necessary inlet pressure. I used the total length and the inner diameter of the analytical column now and the dead time is approximately what i expected.
Alfred,
here you can find a handy tool for this kind of calculations:
http://www.chem.agilent.com/en-US/Technical-Support/Instruments-Systems/Gas-Chromatography/utilities/Pages/GCCalculators.aspx
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