Use of solid-phase microextraction (SPME) for the determination of methadone and EDDP in human hair by GC–MS
Introduction
The analysis of drugs in hair is of particular interest because it can provide information about long-term use and is useful for many purposes including criminal investigations and monitoring the compliance on drug maintenance programmes.
Immunological methods are normally used for the screening of drugs in hair, and their results must be confirmed by more sensitive and specific methods.
Various methods have been applied to the determination of methadone in hair: radioimmunoassay [1], [2], high-performance liquid chromatography [3], capillary electrophoresis [4], and gas chromatography–mass spectrometry (GC–MS) [5], [6], [7]. Confirmation analysis generally consists of a pretreatment of the sample, and hair hydrolysis followed by liquid–liquid or a solid-phase extraction.
Solid-phase microextraction (SPME) is a new technique of extraction with many advantages: small sample volume, simplicity, quickness and solvent-free. It is mainly applied to environmental analysis, but is also useful for the extraction of drugs from biological samples [8].
Strano-Rossi and Chiarotti [9] demonstrated the suitability of SPME for the determination of methadone in hair samples. Recently, we proposed the use of SPME for the determination of methadone and its main metabolite (EDDP) in plasma, in a comparative study with the classical liquid–liquid extraction [10].
In the present work the use of SPME in the determination of methadone and EDDP in hair by GC–MS is described. The method was applied to the analysis of real hair samples from eight patients of a methadone maintenance programme (MMP).
Section snippets
Hair samples
Drug-free black hair, taken from a laboratory volunteer, was used for preparation of standards and calibrators. Hair samples from eight patients of a MMP from the Autonomic Community of Galicia (Spain) were analyzed.
Chemicals and reagents
Methadone hydrochloride and methadone-d3 hydrochloride were obtained from Sigma (St. Louis, MO); 2-ethylene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) perchlorate and EDDP-d3 perchlorate were obtained from Radian (Austin, TX). Methanol, borax and sodium chloride (analytical grade),
Analytical method
The gas chromatographic method used in this work was efficient to separate methadone and EDDP. The retention times (RT) were 7.21 min for EDDP-d3, 7.24 min for EDDP, 8.69 min for methadone-d3 and 8.72 min for methadone, as can be seen in Fig. 1 that shows the extracted ion chromatogram from patient 6.
No carry-over with the desorption time of 5 min at 250°C and no degradation of the fibre were observed after at least 90 runs.
The standard calibration curves were obtained in a triple run. Simple
Conclusion
This work describes the application of solid-phase microextraction (SPME) for the determination of methadone and EDDP in hair by GC–MS. The method was successfully applied to the analysis of hair samples from patients of a methadone maintenance programme.
The microextraction was performed directly on a small aliquot of the enzymatic hydrolysis liquid, commonly used for the screening techniques for drugs in hair, allowing the use of the remaining sample for confirmation analysis of other drugs,
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