Alkaline alumina surface tends to retain positive charges or hydrogen bonds. Alumina pretreated with alkaline solution has anionic properties and cation exchange function. It can be retained to electron sample such as neutral amines, which is much weaker than neutral and acidic alumina. Alkaline alumina has strong hydrogen bonding, so it has obvious effect on polar cationic samples.

Acidic alumina has better retention for electron-rich compounds. Pretreated with acidic solvents, it has weak cationic properties. It is easier to retain neutral and negatively charged substances on the surface, but it can not retain positively charged substances well.