I'm new to the practical use of thin layer chromatography and I'm having some issues. In the example in the pictures I've been trying to get a good TLC of a mixture of glycerides. The conditions are fixed, so I'm not supposed to change those: dichloromethane as solvent and a mixture of dichloromethane and aether (90/10) as mobile phase. The visualisation is done with iodine.
So the first set would be the best, but it's not great. Visualisation is a problem. The highest arrow would indicate triglycerides, then the next two arrows would be diglycerides and at the bottom it's monoglycerides.
I think one of the problems I have is that the plate itself got stained too much in the second attempt. I'm not sure why that is, because I used the same tank and amount of iodine as before. But I've been searching for an improvement and I think I will try by adding a layer of powdered silica to the tank in combination with the iodine, which seems to have better results. The silica is then coloured by the iodine and brought into contact with the TLC-plate.
Any tips are welcome, but I have some specific questions:
- Why are there often two tails/distinctive spots for the triglycerides? I would guess this is because I often spotted twice for each sample, but on the other hand these were really in the same spot most of the time, so it doesn't make sense to me. I don't understand why these wouldn't mix when applied on the same spot.
- The origin still shows clear spots. So there's still something there that hasn't moved, right? The sample may contain surfactants. Could that be it?