By Michael Breslav on Thursday, January 8, 2004 - 01:57 pm:
I am using best C18 stationary phases available (kromasil) to isolate poor resolved impurities at <0.5% level. I end up with HPLC pure material but large volumes of diluted solutions. After concentration by freeze-drying, NMR people often see a significant amount of unknown compound that gives two quartets at ca. 5 ppm in the NMR spectrum. Can this be a sign of leaking stationary phase? Any suggestions on how to minimize product contamination?
By MG on Tuesday, January 13, 2004 - 08:14 am:
I can't comment on the NMR data, but another possibility is that you have a coeluting impurity with no UV chromophore.