Formation of Oxazolidine Derivatives by Reaction with Ephedrines and Aldehyde Impurities in Ethyl Acetate.

Ethyl acetate potentially contains formaldehyde and acetaldehyde as impurities. Ephedrines (ephedrine and pseudoephedrine) react with these aldehydes to give oxazolidines. The purpose of this study is to elucidate the effects of aldehydes in ethyl acetate on the analysis of ephedrines by gas chromatography/mass spectrometry (GC/MS). Ephedrines dissolved in a basic solution were extracted with five lots of ethyl acetate; then, injected into a GC/MS system. Acetaldehyde in ethyl acetate was determined by headspace GC/MS. Acetaldehyde-free ethyl acetate, prepared by washing with sodium bisulfite solution, was also subjected to ephedrine extraction and acetaldehyde determination. Four of the five ethyl acetate lots produced 3,4-dimethyl-5-phenyloxazolidines (formaldehyde adducts of ephedrines) and 2,3,4-trimethyl-5-phenyloxazolidines (acetaldehyde adducts of ephedrines). Acetaldehyde was detected in the range of 23-89 μL/L in four lots of ethyl acetate and not detected in one lot, and the detection of acetaldehyde was associated with oxazolidine formation. Washing with sodium bisulfite solution removed ~90% of acetaldehyde and prevented oxazolidine formation. The study indicated that ephedrines reacted with aldehydes in ethyl acetate to produce oxazolidines and washing with sodium bisulfite solution prevented it. It is necessary to exercise caution when using ethyl acetate to extract ephedrines.