How is Acetone Used in Chromatography Calculations?

[indoubt]

chromatography...using acetone!

the protocol:

Vg = volume not accessable to solvent (volume of the gel matrix)

Vg cannot be measured directly. However, it should apparent that:
Vg = Vt - volume accessable to solvent

We can measure the volume accessable to the solvent, using a small molecule such as acetone which can be easily visualized by a UV detector.

example:
Pharmacia Superose 6 column - volume accessable to solvent = 19.5 mL (measured with acetone)
Vg = Vt - 19.5 mL = 24.4 - 19.5 mL = 4.9 mL

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hi guys!
i just find this calculation very unreasonable, since as we know Vt=Vi+Vg+Vo,
where Vt =total column volum, Vo= void volum due to EXTREMELY huge substances, Vg= volum of matrix and Vi=volum inside the beads due to EXTREMELY small substances.

my question is, how come we use acetone (small molecule) to determine both Vo and Vi, since Vg= Vt- (Vo+Vi)?


hopes for replies!

thanks!

 

[indoubt]

by the way here is the link; http://itsa.ucsf.edu/%7Ehdeacon/Stokesradius.html

 

[ravenprp]

Thank you for bringing up this concern. It is important to note that chromatography using acetone is just one method of determining Vg, and it may not be suitable for all types of columns or matrices. Other methods, such as using a small molecule like methanol or measuring the column dimensions, can also be used to determine Vg. The use of acetone is just a common and convenient method, but it is not the only way. Ultimately, the choice of method will depend on the specific column and matrix being used. It is always important to carefully consider and validate the method being used to determine Vg to ensure accurate results.