Simultaneous determination of fenfluramine and phentermine in urine using gas chromatography mass spectrometry with pentafluoropropionic anhydride derivatization

Fenfluramine and phentermine ('fen-phen') are stimulants used primarily for weight loss that have a causative association with serious health problems . Though voluntarily removed from the market by their manufacturers and the FDA in September of 1997, both drugs occasionally reappear in the clinical and forensic setting from individuals who retained old prescriptions, tran sported the drugs from foreign countries, or 'stockpiled' the medications i mmediately before their removal from the market. The authors describe an an alytical method for simultaneous detection of fenfluramine, phentermine, an d the internal standard, N-propylamphetamine, in urine using pentafluoropro pionic anhydride derivatization. Detection using and mass spectrometry is d escribed. Baseline resolution of the analytes was achieved in the presence of four other common sympathomimetic amines. The increased molecular weight s, better peak profiles, and characteristic fragments containing portions o f both derivatizing agent and parent compound aid in the unambiguous identi fication of these analytes.