Quantitative determination of naltrexone and naltrexone prodrugs by electron-capture gas-liquid chromatography

An electron-capture gas chromatographic method has been applied to the determination of eleven ester and ether derivatives of naltrexone believed to act as prodrugs. Standard analytical curves are presented for all prodrugs and quantitation is shown to be possible from 10 ng to 1.5 microgram of each compound. Ester derivatives of naltrexone are hydrolyzed to naltrexone prior to analysis as the perfluoroalkyl esters. Analysis of synthetic mixtures of these with naltrexone demonstrated that quantitation by difference measurements is possible with naltrexone-derivative ratios from 4:1 to 1:10. Ether derivatives are analyzed without hydrolysis. This method is applicable to biological fluids as well as aqueous solutions.