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extra column volume
Posted: Sat Jun 23, 2007 7:07 pm
by project44
I would like to ask if it is possible to practicly measure the extra column volume of my chromatographic system. I have alrady tried it, without using the column. I found that the extra column volume was too high to be correct. Can anybody find a logical way of measuring these volumes in the laboratory?
Thanks for any future help
Posted: Sun Jun 24, 2007 3:25 pm
by Uwe Neue
The extra-column volume, i.e. the volume between the injector and the detector, can be measured by connecting the injector outlet tubing directly to the detector inlet tubing, and injecting a small volume of any analyte, for example acetone dissolved in mobile phase. Considering that such a volume will be rather small, it is best to do this experiment at slow flow rates with a high detector sampling rate. For a standard HPLC, I would do this at around 0.3 mL/min, and the expected value is around 100 microliter. Under these circumstances, your injection volume should be less than 2 microliter.
Posted: Sun Jun 24, 2007 8:47 pm
by project44
Thank you very much for your advice and help!
Posted: Mon Jun 25, 2007 4:28 am
by tom jupille
Another option is to leave the column in place and run a series of standards (isocratically). Plot σ^2 (σ is 1/4 of the peak baseline width) versus tr^2. The y-intercept gives an estimate of the extra-column contribution to σ^2.
Look at slide 8 from this paper for details:
http://www.lcresources.com/resources/ex ... 060223.pdf
Posted: Mon Jun 25, 2007 2:58 pm
by project44
Another option is to leave the column in place and run a series of standards (isocratically). Plot σ^2 (σ is 1/4 of the peak baseline width) versus tr^2. The y-intercept gives an estimate of the extra-column contribution to σ^2.
Look at slide 8 from this paper for details:
http://www.lcresources.com/resources/ex ... 060223.pdf
Thank you very much for your advise...I think this is a good way to demonstrate it in theory