Question

Why does the malachite green dye elute first? What physical properties does it have that affect it’s interaction with alumina and how are those different from crystal violet?

Answer 1

MG is less polar

Step-by-step explanation:

The structures of crystal violet (CV) and malachite green (MG) are shown in Figures 1 and 2, respectively.

The obvious difference is that CV has an extra dimethylamino group (polar).

Alumina is a polar adsorbent, so it retains the more polar substances more strongly and they are eluted last.

MG is less polar than CV, so it is retained less strongly and is eluted first.