Originally Posted by SkyHighLer
At the beginning of the video you show the label of a bottle of silica gel:
"Analtech Catalog #B12050
Silica gel 60 Angstrom pore size
Is the preferred mesh/micron size for filtering cannabinoids 200-400/37-74?
I found these two, and placed standing orders on each (Amazon doesn't charge you until it ships.)
Attached screen shots of the product information sheets for the above, and the silica gel HiMedia catalog page.
This stuff is expensive, what's the best deal??
I cannot give a specific answer to this.
There are many different products because there are many different opinions.
Generally silica gel is either considered normal phase or reverse phase. I use normal phase gel. Silica gel sold as "C18" is reverse phase. It is spendy stuff but is legendary for organic seperations of difficult compounds. On reverse phase gel the solvent system goes from polar like methanol to non-polar like hexane instead of the other way around of non-polar to polar (hence, reverse phase).
I use standard phase gel. The pore sizes listed and such obviously impact the product but my experience is with just the standard off the shelf stuff at 35-75 microns. There is no "best way" really but since so much data about the use of silica gel is out there I chose to run with standard stuff.
At my hobby level of seperation I have a hard time visualizing any real difference between slightly different grades of standard gel. The finer you get the slower it goes so can be better seperation. Coarse grades elute faster with poorer seperation. However in the hands of a skilled operator each grade can and is used in a highly effective manner.
Every single thing in chromatography will impact each and every seperation. Type of gel, solvents used, rate through column used (vacuum), packing technique, gel type, column width and depth, wet vs. dry loading, and so on. The idea is to select a method that you can repeat PRECISELY on each and every run. This is a core concept. With each run mental notes are taken and a strategy is formed to make the next run better by tuning just one aspect of your setup. Then repeat. Chromatography is easy and pretty cheap but it is very delicate. You are placing a "stain" onto a gel that almost does not wah off. Then you are trying to wash it off one layer at a time, so to speak with the goal to eventually wash it all through.
With hexane and extract alone, the extract WlLL NOT budge through even the top layer of silica gel. I use this phenomena to my advantage. I run much heavier loads than dry loading can accomodate through my column so I "wet load" the sample onto the gel now. This means that I disolve the extract in the minimum hexane need to disolve it. Then I can easily transfer that onto my column without any rush to get the column going becaue it all stays on top.
Then, to get it going and to start the run, I take a pipette and squirt about ½ ml of Ethyl Acetate onto the mix. EA is the polar solvent in this scenario and once even a drop of polar solvent hits it then the comound will begin to move through the column and gradient elution then proceds like normal.
It takes just a teeny tiny bit of the polar solvent to get the stain moving. Add too much and the whole stain washes through all at once. Add too little and the stain just begins to spread out and diffuse with time and seperating it then becomes impossible. So the "dance" you play is a delicate balancing act.
You may pick a gel type and solvent system that turns out to be the industry standard and may work better than any other known procedure. We actually have an opportunity as hobbyists/entrepenuers here. Since all research money is hogtied by prohibition there is no available research online about how to do this with 420 extracts. We get to be pioneers with this. This is why I post. Once a knowledge base of years is built then there will be definitive answers to your questions but for now I suggest being confident in what you do know, make a choice, and then do the grunt work and see what you need to adjust to make it all work
That is the essence of chromatography.
Good luck and post often.