Determination of methadone and its metabolites EDDP and EMDP in human hairby headspace solid-phase microextraction and gas chromatography-mass spectrometry

A simple method for analysis of methadone and its two main metabolites EDDP and EMDP in hair was developed using automatic headspace solid-phase micro extraction (HS-SPME) at a multipurpose sampler and gas chromatography - mas s spectrometry with electron impact ionization and selected ion monitoring (GC-MS-SLM). The washed hair pieces were digested in the closed headspace v ial in 1 ml 1 M NaOH containing 0.5 g NaCl and each 10 ng of the internal s tandards D-9-methadone and D-3-EDDP at 110 degrees C for 20 min. Then the H S-SPME was performed with a 65 mu m polydimethylsiloxan/ divinylbenzene fib er at the same temperature in the same vial for another 20 min followed by the desorption in the GC injection port. The calibration curves were lineal between 0.1 and 3 ng/mg (methadone and EMDP) and 10 ng/mg (EDDP) respectiv ely, at higher concentrations a negative deviation from linearity was found . The detection limits were 0.03 ng/mg (methadone) and 0.05 ng/mg (EDDP and EMDP), and the reproducibility was 9.2% for methadone and 11.2% for EDDP ( n=12). The method was applied to hair samples of 26 drug fatalities. 19 cas es were positive with 0.36-11.8 ng/mg methadone and 0.19-10.8 ng/mg EDDP. E MDP was found only in two cases with 0.18 and 0.84 ng/mg. The methadone con centration range was in agreement with previous data, but the EDDP/methadon e concentration ratios (0.19-0.67) were definitely higher than those determ ined by other methods. (C) 2000 Elsevier Science B.V. All rights reserved.