Question

mobile phase, length of column, solvent flow rate and stationary phase composition, which will be the easiest to change and give desired effect? why?

Answer 1

You need to specify which type of chromatography you want to do for the separation and purification.

1) it is easier to choose the length of the coulmn (different sizes) w.r.t to the amount of sample and the number of components in that sample (spots in TLC).

2) Also changing mobile phase is easier (you can select which solvents you want at which polarity you want to maintain- on the basis of TLC) which has a huge effect in separation and purification of the sample.

3) Solvent Flow rate also can be easily changed by using a Pump. It helps when two components are very close to each other in terms of polarity.

4) The stationary phase composition depends on a few factors among which Mobile phase composition plays a huge role. So, changing stationary phase is not really easy.