Recently we attempted to purify a molecule that moved rapidly on silica TLC plates even at 100% hexane. We did not have alumina TLC plates; therefore, we ran a pipet column using alumina and obtained satisfactory preliminary results. We plan to scale up next week. What makes alumina more suitable for separating compounds of low polarity? I have searched through a few practical organic chemistry books, but so far I have not found a good discussion of this question.

Silica has more surface area per gram than alumina does, suggesting to me that one may need a larger amount of alumina than silica for a given mass of starting material. What other practical differences are there?