Sample prep for NP

[avitan]

There is some substance that appears as dihydrochloride salt. I want to inject it in my normal phase system, that includes hexane as main mobile phase component. Substance will be decomposed in water solution or any kind of alcohol, so I can't to turn it into base form with regular means. (TEA also doesn't work)

Can somebody suggest the way to put this substance in hexane (or in mixture hexane with polar solvent)

P.S. It can be dissolved in DMSO, but I still don't have a clue how to transfer it into a-polar phase.

Thanks in advance....

[tom jupille]

First of all, if the solubility in your mobile phase is too low, the chromatography won't work.

Assuming there is as least some solubility in the mobile phase, in what else is the salt (even slightly) soluble?

[Mark Tracy]

Just a few speculations...
Try a non-protic semipolar solvent: N-methylpyrrolidone, sulfolane, tetrahydrofuran, or dioxolane.

Ion-pair it with sodium dodecylsulfate which is moderately soluble in hexane and chlorinated solvents.

Try an amine solvent: pyridine or triethylamine

When I was in grad school, I had a similar problem with a substance that was acidic enough to catalyze its own hydrolysis. When neutralized with sodium bicarbonate, it was stable enough to get an NMR.

[avitan]

First of all, if the solubility in your mobile phase is too low, the chromatography won't work.

That's why i'm searching the way to turn into base.

Assuming there is as least some solubility in the mobile phase, in what else is the salt (even slightly) soluble?

Well, I'm pretty sure, that if i'll turn this salt into base form, its' solubility in my mobile phase will be just fine (some base-form homologues were succefully dissolved)...

It can be dissolved as is in DMSO, but it doesn't solves the problem - have to transfer substance into something that will be miscible in hexane.

[avitan]

Just a few speculations...
Try a non-protic semipolar solvent: N-methylpyrrolidone, sulfolane, tetrahydrofuran, or dioxolane.

Ion-pair it with sodium dodecylsulfate which is moderately soluble in hexane and chlorinated solvents.

Try an amine solvent: pyridine or triethylamine

When I was in grad school, I had a similar problem with a substance that was acidic enough to catalyze its own hydrolysis. When neutralized with sodium bicarbonate, it was stable enough to get an NMR.

Thanks, Mark, for interesting suggestion. I'll certanly try something from above. *TEA,THF doesn't work *

[tom jupille]

avitan, sorry I misunderstood your post. I thought you wanted to keep it in the hydrochloride form and do NP.

I'd second Mark's suggestion about converting it to a more hydrophobic salt.

[avitan]

avitan, sorry I misunderstood your post. I thought you wanted to keep it in the hydrochloride form and do NP.

I'd second Mark's suggestion about converting it to a more hydrophobic salt.

That's OK, thanks