Question

Questions regarding Thin Layer Chromatography Analysis (TLC):

1. What is the purpose of the wick?

2. Why is it important to use diluted solutions?

3. Why is it important to spot the TLC plate quickly and lightly?

4.What solvent will use to develop your TLC plates? ethyl acetate, hexanes, or some mixture of the two? Why?

5. List at least 3 common errors when performing TLC and how to fix them.

Answer 1

1)Filter paper(wick) impregnated with solvent is usually used to saturate the development chamber's air with solvent vapor so the stationary phase doesn't dry during the process.

2) lower the concentration of the loaded compound better is the separation. If the concentration of the loaded compound has been increased, it effect the separation as tailing has been occurred in the different spots due to increased concentration and RF values have not been calculated correctly. In general to get better separation and clear Rf values lower concentration (infect appropriate concentration for preparatory TLC that have to be evaluated for particular extract and solvent system) of the samples have been recommended.

3) Immediately after removing the TLC plate from the beaker, carefully draw a line along the solvent front. Be quick, because the eluent will evaporate within less than a minute

4) mixture of two will be better as first low polar solvents can be used followed by polar solvents.

5) The three most common mistakesthat cause lousy TLC results are, (1) not finding an appropriate solvent system that resolves (or separates) the sample spots during development of the TLC plate, (2) using too much or too little sample on a given sample spot, and (3) allowing the solvent in the development tank to slosh around and go above the solvent line