[Babcock_Hall]

We need to purify a thiol for the first time.  It is in the form of a diethyl ester bearing a phosphonate group.  Obviously, we need to be mindful of the possibility of oxidation and work quickly.  Are there any other problems that we might encounter, such as streaking?  It occurs to me that an additive such as 0.5% HOAc might be helpful, but I am not sure.

[rolnor]

I don't think it so critical, are you afraid of disulfide formation? If you are going to alkylate it, you can do this on the raw product, then purify the sulfide i guess.

[Babcock_Hall]

Yes, disulfide formation was on my mind.  In water, it happens more quickly at higher pH (more thiolate), but perhaps disulfide formation is slow under the conditions of chromatography.