TLC plate in regards to polarity

[CML]

I used a "normal" phase alumina TLC plate with 20% (v/v) dichloromethane/hexanes. I found the substance that traveled the furthest to be the most polar one (though the substance is not very polar, xanthohyll). Why would this be? I was under the impression that since the plate is polar and a nonpolar solution is used, the most polar substance would move the least. (Of course it is possible I made a mistake and the spot that moved the furthest is not the most polar one, and may have been beta carotenes, but I am almost positive I am right.)

 

[gravenewworld]

What are you trying to separate and how do you know that the one that moved the furthest on the plate is xanthohyll?

 

[CML]

What are you trying to separate and how do you know that the one that moved the furthest on the plate is xanthohyll?

I did two spots, one was crude tomato paste and another was lycopene extracted from tomato paste. The TLC looked something like:



X


L
C

| |
Crude Extract

(Edit: I cannot get the TLC to look right, when I actually post. The second "|" should be above "Extract", and the "L" should also be above "Extract". All relative positions are correct)
Where I think:
X = xanthophyll more of a yellow colour
C = beta carotene more of a orange colour
L = lycopene also more of a orange colour

Due to the colour of the dots, I deduced that X is likely xanthopyll has it has a yellow pigment (similarly for the other two dots too)

 

[gravenewworld]

This is too difficult to tell what is going on without the lab procedure and a picture of your TLC plate.

 

[CML]

I will do my best to explain the procedure in as little detail as possible.
Pigments (lycopene, xanthophyll and beta caroetene) were extracted from tomato paste via a multistep liquid-liquid extraction (including a sep funnel) and a microscale chromatography. The microscale chromatography separted these pigments (all that was collected was the lycopene fractionsm the other two pigments were discarded). This fraction (along with the solution it was eluted with (10% ethyl acetate in hexanes)) was boiled in order to evaportate the 10% ethyl acetate in hexanes and therefore concentrate the lycopene.

This extract was then spotted on a normal plase alumina TLC plate along with a pre-prepared crude sample (I assume prepared in a similar manner; however, I do not know as I did not do prepare this).


As for the TLC plate, I cannot upload a picture of it, but I can try to explain it in more detail.

(solvent front)

X



C


Crude

(solvent front)




X



Extract

Where extract and Crude are actually on same TLC plate side by side.
X = xanthophyll more of a yellow colour- moved 2.92 cm
C = beta carotene more of a orange colour - moved 1.71 cm
L = lycopene also more of a orange colour - moved 1.90 cm
Solven front moved 3.40 cm
In terms of pigment colours, xanthophyll has a yellow colour, lycopene has a red/orange colour and beta carotene has a yellow orange colour

I do not see colours all that well, so of course it may be possible that the colours are wrong, but to me that is how they looked.


However, is my original idea correct, that the least polar substance should travel the furthest?

 

[CML]

Thanks for your help, but I figured the question out. Turns out that xanthophyll was NOT what traveled the furthest, and it was infact catoene.