TLC Rf Values for LSD and Friends

[Kapitan]

Does anyone have any information about thin layer chromatography "Rf" values for LSD and/or ALD-52, under any conditions? A vendor I've done business with a few times is trying to sell a batch of blotter as ALD, and I am (I think justifiably) skeptical. I don't have access to a mass spec at the moment, but I was wondering if I could tell the difference with TLC.

I apologize in advance if this is a stupid question

 

[atrollappears]

How do you expect to get the chemical onto a TLC plate?

 

[Kapitan]

I was thinking I would just extract a blotter or two with methanol or acetone, evaporate to concentrate, and then spot with a capillary tube.

 

[Kapitan]

As far as I know, for TLC to be a valid way of testing, the molarity of both solutions must be the same. That is, the Rf values of a compound will differ depending on the molarity solution spotted on the TLC plate. Unless you have the actual mass of lsd and ald-52 it might be difficult. The blotters are likely to be 25X-NBOMe.

That's interesting, I've never heard that before. I'm pretty sure that Rf only depends on the identities of the mobile and stationary phases, and the molecule.

For the purpose of this discussion, let's just assume that the blotter is not DOX or NBOMe or whavever else I might get ripped off with

 

[skillet]

It doesn't depend on concentration, not noticeably at least. I guess the Rf values of the two will be pretty close, I'm not sure you could be accurate enough to tell without some LSD as a reference.

 

[Kapitan]

It doesn't depend on concentration, not noticeably at least. I guess the Rf values of the two will be pretty close, I'm not sure you could be accurate enough to tell without some LSD as a reference.

I was worried about that. I guess I'll just have to get some other acid and spot them next to each other, or even in the same spot and just look for two bands. Thanks for your input

 

[Iodjini_dk]

Maybe you should convert them to freebase as well or at least add a little base to the eluent. Charged molecules have strong interactions with the stationary phase (I assume youre using silicon dioxide TLC plates). Chromatography of the protonated species will probably end up in some long smear instead of well-defined spots.

And you definitely need some LSD as a reference. IME Rf values can vary a lot depending on exact eluent composition, chamber atmosphere, temperature etc.

 

[skillet]

Best way to do it is to put 3 spots - reference on one side, mixture in the middle and the other compound on the other side. So the developed plate looks something like:

__________

     o  o
  o  o


  .  .  .
__________

You'll have to use base in the eluent with silica plates, and with such small amounts converting to freebase probably isn't necessary. I'd make a 10% solution of conc. aqueous ammonia in methanol (9mL MeOH:1mL ammonia) and start with 5% of that solution in DCM/chloroform.

 

[nuke]

it's probably easier to just do reverse phase tlc than to convert to the freebase. I would guess if lsd were n-acylated you would see a pretty different rf with the right solvent system. Tlc rf values are concentration independent unless you overload like crazy.