Chromatography Forum

I have a student who would like to run samples from a given reaction where the samples will contain salts such as NaCl, LiCl, LiOH, AlCl3 (plus some HCl); we'd be using a RP C18 column with either MeOH:H2O or MeCN:H2O (unsure of % yet).

If we flush the column and system with MeOH:H2O 10:90 at the end of running samples for the day, would that be enough to flush out any of the salts that would remain?

I'm mostly concerned about AlCl3 since I don't have much experience with it, although I would expect it to be converted to a hydrate in water.


Thanks

Honestly, I would not worry about it too much. If the salt concentration is very high or the pH is extreme (<1 or >12), consider a dilution (and potentially buffering) or desalting step and make sure that the mobile phase contains at least some water at the beginning of the run to avoid precipitation. Methanol is better at dissolving salts than ACN in general.

I am very often analyzing samples containing large amounts of salts and have not had issues that flushing the system and cleaning the inlet (GC) or MS inlet (LC-MS) hasn't solved.

If you are using LC-MS, you should consider diverting the first 2 column volumes away from the MS so that the unretained salts are not making it to the MS.

I have recently injected samples containing ~1 wt% aluminum sulfate on an LC-MS system WITHOUT diverting the flow and have not seen any ill-effects.


And yes, AlCL3 will decompose upon contact with water.

Thank you!