Hello,
I'm taking a chem class at my local college in the USA and I am doing an honors project with chromatography.
I'm having trouble getting my project to work correctly.
The project includes a glass column, with small grained silica sand. My goal is to separate out both chlorophyll and beta carotene from spinach. On my first trial I found that the silica had too large a grain size (mesh of fine granular) and went to a much finer grain size. The second trial with the finer grain size (mesh of 240, a very silty size) would not allow the solution to pass through the frit at all. Which has got both my instructor and myself, frustrated and stumped. He looked through his old notes from his time in school and couldn't find any notes on the proper size for the silica.
My question at this point would be if you know what size grained silica would be ideal. Fine granular is too large, and 240 mesh is too fine.
I hope my description is complete enough for my query.
Thank you for your time and attention to my inquiry.
Please email me directly with your responses.
Again, thank you.

What you need is silica with a mesh size range (e.g., 100/200 mesh, which consists of particles which pass through a 100 mesh screen and are retained by a 200 mesh screen). It's been a long time, but if memory serves, 100/200 should be about right. 240 mesh material is getting down into a few tens of microns in particle size; you need a pressurized system for this.

Good luck!