Acetylcysteine USP methods

[MestizoJoe]

Can anyone tell me why sodium metabisulfite solution and sodium bisulfite solution are used in the diluent for the USP HPLC methods for Acetylcysteine assay? Is it simply for solution stability?

We also have an in-house method which utilizes EDTA in the diluent, perhaps instead of bisulfite?

I'm trying to leave these additives out but I don't want to affect separation.

Thanks,

[tom jupille]

They are antioxidants; probably there for sample stability.

[Kreall]

As Tom said, there are antyoxidants. They are in sample to prevent forming two majors impurity of
N-acetylcysteine - N,N-diacetylocysteine and N,S-diacetylcysteine

Moreover N-acetylcysteine its not very stable in water samples so,i f you dilluted the sample with water I suggest injecting as fast as possible.