Povidone-Iodine Method Development

[jmmunson]

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.

[juddc]

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