4. In TLC lab when you separated spinach pigments’, most sections found 45:55 ac

Question

4. In TLC lab when you separated spinach pigments’, most sections found 45:55 acetone:hexanes mobile phase composition to give the best results. In column chromatography, the best mobile phase turned out to be 40:60 or 35:65 acetone:hexanes. What is the reason that the exact mobile phase composition from TLC does not give the best separation in column chromatography? Explain (4 pts) 5. Why is it important to keep the solvent level above the stationary phase? What would happen if one lets the solvent get much lower than the silica stationary phase? (4 pts)

Explanation / Answer

4.

The stationary phase used in TLC plate is different than the stationary phase used in column chromatography.

Hence, the solvent system optimized for TLC will be different than the solvent system optimized for column chromatography.

5.

When the solvent level is below the stationary phase, the compound loaded on the stationary phase will not evenly spread out. It will have some effect on the separation of components as it will not be uniformly adsorbed on the stationary phase.

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