Chromatography Forum

Hello all!

Do you guys have any experience testing purity for organic compound in potassium salt by HPLC? my colleague dissolved the potassium salt in acetonitrile and ran long scan HPLC method, however the peak shape was not quite good (multiple peaks and tailing) and the purity calculated by peak area was only 84%, whch is supposed to >99%. Please share if you know how to prepare sample in salt form for HPLC purity analysis, thanks a lot!

Xiaoyan

Without knowing details of your compound:

- Salts are generally at least somewhat soluble in water, so the initial diluent should have been an aqueous buffer, ideally with a pH significantly lower than the pKa of the drug (at least 1 pH unit; 2 units if possible); typically something like 25 mM.

If you are doing reversed-phase chromatography, run a methanol gradient using that same buffer as the "A" solvent (buffers typically have better solubility in methanol than in acetonitrile).

If you are doing HILIC, the diluent should be a 50/50 mixture of that buffer with acetonitrile. Then run a gradient gradient starting with that 50/50 mixture and *decreasing* the acetonitrile (i.e., increasing the buffer).

Thank you very much Tom! will try your suggestions.

Xiaoyan

I concur with Tom.