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Hello!

I'm having some trouble understanding what exactly are mobile and stationary phases for the three tests above. I know it's a great way to view the polarities of compounds and NOT isolate them, but I don't understand what it means for a mobile or stationary phase to be polar/nonpolar and the significance of what that means. Would anyone be willing to help me out?

Thanks for the question!

Essentially, the mobile phase is what moves down through the column and the stationary phase is what's not moving (instead, it's sort of bound to the column). You can use these techniques to separate compounds based on each compound's affinity for a given phase. If a compound wants to interact with the stationary phase, then it'll take much longer for it to elute. If a compound doesn't want to interact with the stationary phase, then it'll elute more quickly.

Typically, in "normal-phase" chromatography, the stationary phase is a highly polar substance (like silica) and the mobile phase is a non-polar substance. "Reverse-phase" is just the opposite: the stationary phase is non-polar and the mobile phase is polar.

Chromatography can be used to separate compounds based on polarity/intermolecular interaction differences.

I hope this is helpful and good luck!