in thin-layer chromatography, why is it important to use a very small amount of sample when spotting the plate

Answer 1

If you make a large spot, the bottom of it will start to move before the top. You need the whole spot to start moving at the same time. A large spot leads to what is called streaking. Instead of neat spots, the chromatogram shows comet-like streaks.

Answer 2

Thin layer chromatography(TLC) is a technique to find the dyes in a specimen.It is used in forensics to identify a certain piece of clothing be cause paint or dyes differ in chemical composition, even the ones that are supposed to be completely similar. This usually does narrow the range to a much smaller amount.