GC-MS detection and characterization of thebaine as a urinary marker of opium use

The differentiation between legal and illegal opiate product use through the detection of marker compounds in urine is one of the most important subjects in forensic toxicology. Thebaine, an opium alkaloid, can be detected by gas chromatography-mass spectrometry (GC-MS) and has been suggested as a good marker of poppy seed use in differentiation from that of illicit heroin. In the present study, thebaine was targeted as a urinary marker of opium use because it is a major constituent of opium. Although thebaine lacks the conventional functional group, it was found to form a trimethylsilyl (TMS) derivative. This has made it possible to simultaneously detect thebaine together with morphine and codeine in the same urine sample to confirm opium use, thus saving time and cost of analysis while using less material. The TMS derivatization was found to enhance the stability and chromatographic properties of thebaine and to increase the sensitivity of its detection about 50-fold in comparison with that of the underivatized compound. Using the present method, thebaine was analyzed for a number of actual urine samples obtained from users of opium, illicit heroin, or codeine preparation. The results showed that thebaine is a useful opium-use marker subject to its oral administration.