Question

A student received two vials labeled A and B, containing three distinct organic compounds in un specified Predict the results of each of the following common TLC mistakes and explain the reasons why each would result in failure: a. The solvent is allowed to travel all the way to the top of the plate. b. A student uses a pen instead of pencil to mark the initial spot locations. c. A beaker is used instead of a TLC chamber, and no folded filter paper is placed inside.

Answer 1

a. The solvent is allowed to travel all the way to the top of the plate

If solvent goes either way to top of the plate then all the 3 compound will come to middle of TLC. Hence we can not determine the compounds.

b. A student uses a pen instead of pencil to mark the initial spot locations.

If he uses pen

i) TLC will absorb ink from pen which will elute along with solvent and compound. then can not see your compound.

ii) it will break silica layer in TLC then sovent elution will not be uniform

c. A beaker is used instead of a TLC chamber, and no folded filter paper is placed inside.

Mixture of solvent wil evaporate according to it's boiling point. then solvent ratio will vary which will not give correct Rf value