[Babcock_Hall]

I thought I would collect a couple of tips that I found recently in a couple of threads.  Please feel free to add.

Kriggy wrote "b) dry loading is my go-to technique since I dont have to try to dissolve my compounds in mobile phase which they might not be soluble (especially if you work with hexane:EA). As rolnor already said, there are adapters with filters that work well but simple splashguard / bumptrap or whatever you call it with cotton in the connection between the trap and your flask works well. Usually, low boiling solvents like DCM or MeOH are used. Evaporate to dryness, to the state of dry silica."  Whenever there is a substantial fraction of hexanes, we are now automatically using dry loading.  Adapters with fritted glass help keep the silica from going where it should not.

clarkstill wrote, “I used to put a long pipette on my fumehood compressed air line and use it to evaporate any solvent on the inner walls of the column before adding the dry-loaded sample - then all the silica remains dry and doesn’t stick.”  This sounds like a neat trick, and we will try it next time.

[rolnor]

Nice with some tips! Whenever you evaporate these guards with a filter eliminates splashing, you can buy these now, I think our group invented them. We custom ordered these from Werner-glas in -94 something, they were not available from glassware-vendors back then.

[Babcock_Hall]

Someone mentioned to me that it can be helpful in some cases to dry load onto celite (diatomaceous earth).  Has anyone done this, and what are the advantages/disadvantages?

[Babcock_Hall]

We have a possibly difficult separation today, and the solvent is 25:75 ethyl acetate hexanes.  I am inclined to dry load, but I am interested in the question of dry loading and resolution.

[Guitarmaniac86]

Someone mentioned to me that it can be helpful in some cases to dry load onto celite (diatomaceous earth).  Has anyone done this, and what are the advantages/disadvantages?

I did this once and the biggest advantage is that it immediately releases the compound as soon as solvent touches it. Disadvantage is you need more of it than silica gel itself.

[rolnor]

Someone mentioned to me that it can be helpful in some cases to dry load onto celite (diatomaceous earth).  Has anyone done this, and what are the advantages/disadvantages?

I did this once and the biggest advantage is that it immediately releases the compound as soon as solvent touches it. Disadvantage is you need more of it than silica gel itself.

EtOAc/Hexane is a poor solvent, EtOAc/Toluene is similar in polarity and a powerful solvent

[Babcock_Hall]

Hi Rolnor,

When you say poor or powerful, do you mean in terms of their ability to make things soluble?