Abstract: Objective To compare morphine and codeine concentration in urines of heroin abusers and codeine users and to discuss the judgment index to distinguish between heroin abuser and codeine user. Methods The urines of heroin abusers and codeine users were collected at different time periods. After protein precipitation, the urine samples were conducted for the qualitative and quantitative analysis of morphine and codeine by UPLC-MS/MS. And the results were all statistically analyzed. Results Statistical analysis showed that morphine and codeine concentration in urines of heroin abusers and codeine users were both abnormal distributions. The probability of the heroin abuser would be more than 95% and less than 5% for the codeine user when the concentration of morphine in urine sample was more than 67 ng/mL. The probability of the codeine user would be more than 95% and less than 5% for the heroin abuser when the concentration of morphine in urine sample was less than 67 ng/mL. Conclusion The morphine concentration in urine could be used as a criterion to distinguish the heroin abuser from the codeine user, while the codeine concentration could not.

Key words: forensic toxicology, morphine, codeine, heroin, UPLC-MS/MS