In TLC, why do you spot multiple times? Select one or more correct answers.

A. To fill the capillary almost instantly by capillary action.
B. So the developing chamber solvent does not evaporate.
C. The higher compound concentration facilitates visualization.
D. To acheive a high concentration of sample in a small spot.

THERE IS MORE THAN ONE ANSWER CORRECT HERE. I KNOW IT IS D, BUT THERE IS ONE MORE CORRECT ANSWER. WHAT IS IT? THANKS!

I'm not an expert on TLC but the way I see it it can't be A or B. Capillaries are not involved and multiple spotting has nothing to do (at least I don't think so) with the solvent evaporation. I didn't pick C earlier because that applies only to "VISIBLE" components and TLC is good for separating components, too, that are not visible (for example amino acids). However, if there is an answer in addition to D it must be C.

thanks :] it is correct. D and C are the answers

To determine the second correct answer in addition to option D, let's analyze the options provided:

A. To fill the capillary almost instantly by capillary action.
B. So the developing chamber solvent does not evaporate.
C. The higher compound concentration facilitates visualization.
D. To achieve a high concentration of sample in a small spot.

Option D, "To achieve a high concentration of the sample in a small spot," is correct because one purpose of spotting multiple times in Thin Layer Chromatography (TLC) is to enhance the spot size, concentration, and visibility of the sample.

Now, let's consider the remaining options:

A. To fill the capillary almost instantly by capillary action.
B. So the developing chamber solvent does not evaporate.
C. The higher compound concentration facilitates visualization.

Option A, "To fill the capillary almost instantly by capillary action," is not a reason for spotting multiple times in TLC. Capillary action occurs due to the attraction between the solvent and the stationary phase (silica gel or adsorbent) on the TLC plate, and it helps the solvent move up the plate to separate the components of the mixture.

Option B, "So the developing chamber solvent does not evaporate," is not a reason for spotting multiple times in TLC. The primary function of spotting multiple times is to increase the amount and concentration of the sample, rather than preventing the solvent from evaporating.

Finally, option C, "The higher compound concentration facilitates visualization," is the second correct answer. By spotting the sample multiple times, the concentration of the compound increases in the small spot, enhancing its visibility when developing and analyzing the TLC plate.

Therefore, the correct answers are D. To achieve a high concentration of the sample in a small spot and C. The higher compound concentration facilitates visualization.