[wee1998]

I was tried a lot of HPLC methods for changing the extraction solvent, mobile phase and pH for the assay of folic acid in multivitamin and minerals caspule. The resolution of the folic acid peak was good and not tailing. But the main problem was the percentage content of folic acid is only 80% for all the 5 batches manufactured during NOV 2007. I analysed back on MAC 2008 for all the 5 batches the percentage content of folic acid dropped to 50%. I take one  previous released batch JAN 2008 initial analysed result was 110% and dropped to 80% on MAC 2008. Why the folic acid degrade so fast in the caspule form? Or the method got problem?

[Arkcon]

I'd look very carefully at your integration method, before I'd suspect the folic acid was degrading.  Folic acid is notorious for tailing badly, even on a brand new column, with the best methods, so you may be missing some.

[coquim]

Hi! look, that Arkon says it´s true, Folic Acid has always a bad tailing, however with correct method the resolution must be good. First off, tell us what other vitamins ar you testing it with Folic (for example i was testing with B-15 last month and the retention was exactly the same for both and also b-6) and if you can of course, tell us what kind of mobile phase are you using and the extracting procedure. You must be careful at this time whit folic, you can extract folic at higher ph, and have careful with other vitamins at the same time.
 Bye