COLUMN CLEANING/PEAK SPLITTING

[Harry]

Hi,

Is it advisable to backflush the column with 50/50 DMSO/DMF to clean the C18 column? If yes then what exactly these solvents is doing? What other solvents should be used in cleaning the C18 column?

Can some body help me out with the problem of peak splitting with increase in back pressure for C18 column? waht may be causes and remedies for the same?

[Consumer Products Guy]

OK, I'll assume your column manufacturer stats that it's OK to backflush your column (usually: if frits at both ends are same size). It sounds like your inlet frit may be partially blocked by some gunk not soluble in your mobile phase, that can cause both peak splitting and higher pressures. First, I'd reverse-flush with 95% of the organic which you're now using before I'd try any DMF or DMSO. I'm also assuming that you have a brand-new back-up column in the drawer so you can get your results if the clean-up doesn't work. And, remember, your labor to reverse-flush, then return to original configuration and equilibrate before running samples is downtime as well, and not free.

[Harry]

OK, but what should I assume when problem comes in brand new column only after 50 injections?

[HW Mueller]

You may assume that you injected gunk. I have seen worse problems after one injection.

[Rafael Chust]

Just as a quite bad graphic example: some years ago I had a customer who injected some petroleum-derived wax directly into a GC-MSD from HP.

The MSD was directly to scrap, as the service guys were unable to clean it!