Chromatography Forum

Dear all,

I'm having a problem with a ciprofloxacin analysis (USP Method).

Before, I had success on System Suitability Test with a Waters Symmetry column (C18, 4,6 x 250 mm - 5µ) but these column were retired and I'm not approving my SST Test with no one column.

I Can't approve resolution and theoretical plates parameters.

My mobile phase is a 0,025 M phosphoric acid, pH adjusted with triethylamine to a pH 3. After this I prepare a mix with phosphoric acid and acetonitrile (87:13).

What may be happening?

Thak you!

Best regards,

Fred

You still can do your SST with a new Symmetry column. Symmetry columns are extremely reproducible from batch to batch and column to column.
Or you take "old" chromatograms and recalculate resolution and N.
Good luck.

I agree with Gerhard. If it used to work with the Symmetry, I'd stick with that column. Did you try to revive the old columns with some sort of strong solvent wash? With only 13% ACN in your mobile phase, all sort of junk may have been accumulated on the column, resulting in poor performance.