Chromatography Forum

I am currently in the progress of trying to develop a stability-indicating method and am running into quite a few issues. I only found 1 paper in literature for povidone iodine.

Mobile Phase: 700 mL MeOH + 300 mL H2O + 10 g Potassium Iodide - Tried at pH 3.0 and 7.8
** Best consistency from injection to injection using pH 3.0.

Columns Tried : Luna C18, Luna C18(2), Luna C8, Spherisorb C18, Spherisorb ODS2, Spherisorb S5 CN, Inertsil ODS2, Inertsil ODS3, Zorbax SB-C8 (All are 5um, 250 x 4.6)
Best Peak shape: Luna C18 (Tailing 1.9 - to close to limit)
Best Tailing: Inertsil ODS3 (Tailing 1.0 - fronting of peak)


Flowrate: 1.0 mL/min

Column Temps tried at 10, 30, and 50 C.
* 10 C gives best tailing.


Issues: Either have good peak shape but bad tailing, good tailing but bad peak shape, or not reproducible from injection to injection.

Any suggestions you have will be very much appreciated.

Are you trying to measure the vinyl pyrrolidone or the iodine associated with it?

If both, I might be inclined to try to measure them separately. First, I'd reduce the iodine to iodide with thiosulfate and assay via IEX with UV detection at ~226-nm. I had pretty good luck years ago measuring total iodine this way with a Waters IC-Pak Anions HC column and a modified borate-gluconate mobile phase.

With the vinyl pyrrolidone, depending upon the degree of polymerization I'd try either a wide pore reversed phase with a perfluoroalkyl acid ion pairing agent (TFA, HFBA) or an aqueous GPC column. For detection, I'd either use low UV or ELSD if available.

I hope this helps a bit.

Cheers!

CJ