Question

CHEM 2010 LAB

TLC

4

PRELAB WORK

1. How would you change your technique for application or solvent system if each of these

issues was observed:

a.Large spot that trails up plate

b.Barely visible spot

C. Spot barely moves even with solvent near top of plate

d. Both compounds of mixture travel with solvent front to top with little to no

separation.

Answer 1

Hi i understand that these are pre lab assignment.

a.Large spot that trails up plate

Answer: Large spot means concentration of the sample is high, so dilute the sample and spot few times on TLC plate with nano capillary.

b.Barely visible spot

Answer: Barely visible means concentration of the sample is very low, so spot more times on TLC plate with nano capillary, or evaporate the solvent from the sample to increase the concentration. Both techniques works well.

C. Spot barely moves even with solvent near top of plate

Answer: This means compound under investigation is highly polar, so increase your TLC mobile phase proportion ratio with higher polar ratio. This means increase percentage of polar solvents such as methanol or ethyl acetate etc.

d. Both compounds of mixture travel with solvent front to top with little to no separation.

Answer: This means both compounds are less polar or non-polar. So increase gradually your TLC mobile phase proportion ratio with higher polar ratio. This means increase percentage of polar solvents such as methanol or ethyl acetate etc.

Hope this helped you!

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