Dear forum members,
US Pharmacopoeia describes methods determining volatile impurities in drug substances (Method I, IV and V).
Method IV is headspace method. Here, the sample is dissolved in water, heated to 80įC, and an aliquot of a headspace injected. This method is applied to water-soluble substances like Vitamin C.
Can I use this method also for non-water soluble substances? For example, I have a problem with Vitamin E and Lecythin.
According to their specifications I should use Method IV. I canít find any information in monographs concerning Vitamin E and Lecythin about solvents which I should use instead of water. For Lecythin I use solution DMSO:Water (5:2). DMSO improves dissolving of Lecithin but on the other hand it decreases the sensitivity of the method. If I use only DMSO, I will not see peaks of benzene and chloroform on the chromatogram. The solution of DMSO:Water (5:2) is good enough to receive satisfactory LOQ but Lecythin is still not dissolved enough.
By Anonymous on Sunday, March 14, 2004 - 11:49 pm:
I want to advise you that benzene is out of the list of OVI impurities in the USP edition 26.