[Fluorine]

I want to run my own column and I have a few questions. I've done it before in class so I have an idea of how it works but the finer details I don't know. This is only for me to learn skills and gain more experience. I'm not asking from an academic/professional setting so if I can get away with using lesser quality/used that's fine.

- What are the main differences in silica and aluminum oxide as the stationary phase? In other words, is either used for specific type of compounds or can they be used interchangeably? Are there any other commonly available options for citizen chemists?

- Do they need to be "chromatography grade" and/or specific size or will the regular powder or "activated" forms work?

- If I get a used bottle of either do they need to be oven dried or will I be OK as is?

Thanks!

[Doc Oc]

1) Standard silica is considered mildly acidic, while aluminum oxide is considered basic (more basic than silica is acidic, if you ask me).  I've never used aluminum oxide, but some of my colleagues did to isolate things like amines (which drag like a mofo on silica).  I spiked my solvent with a little triethylamine and ran amines on standard silica, so there are ways around everything.  I'm not aware of other media, unless we start talking about things like size exclusion or ion exchange chromatography.

2) You can use a low grade silica for a flash column, though if you have close running spots a higher grade can really help the separation.  If this is something you're doing purely for self interest, get a lower grade.  Higher grades cost more, and the prices increase very quickly.  We use 60-200 um particle size and it's a good general starting point.  This is the brand we currently use:
http://www.silicycle.com/products/siliaflash-irregular-silica-gels/r10040b

3) I've never dried silica, even in very humid climates, and it's always worked fine.

[Fluorine]

That was very helpful, thank you so much.