Thin Layer Chromatography to determine purity

[Bagseed]

Hello,

recently I learned how to perform TLC on some compounds for qualitative and quantitative analysis. I know that without a scanner and proper standards for calibration, I'm not going to be able to determine it exactly, but from the size of the peak and their quantity, I should be able to see how many parts there are in a drug and which one is the largest, right?

for example, I have two batches of MDMA I'd like to try it with. what's the best way to choose the mobile and the stationary phase. also, is MDMA visible under UV, because it's probably not in VIS spectrum?

any ideas on how to go about this, and if it's possible/reasonable to do?

greets

 

[sekio]

TLC doesn't make 'peaks', it makes spots. With the right solvent system you should be able to seperate various drugs and get an idea of what is in your stuff. You'd want to use a stain, even something like Marquis, rather than UV for detection.

I think without a quantitative standard for MDMA or the impurities you'll have a hard time determining % of anything, even relative. Different compounds can stain/fluoresce different amounts.

And although quantitative TLC exists I don't think it's a very accurate method to determine actual percentage purity compared to e.g. GCMS.

It's still way better than trying to judge a mixture with spot tests!

 

[Bagseed]

yeah, spots was what I meant

As I said, I know that I won't be able to produce a precise result (like mass %), especially when doing it at home, but one could tell from the amount of spots and their sizes how many different things there are in there, and get an idea of quantity by the size of the spots, right? (at least if the resolution is good enough)

I'm still not sure about which mobile and stationary phases to use. maybe something not too polar for the mobile, and silica for the stationary (rather polar/hydrophil), since MDMA is a salt. or am I mistaken?

It would be rather a fun project for personal interest...

 

[sekio]

I believe there's reports in the chemical literature on how to seperate MDMA on TLC plates. You'd have to look it up though.