title: Determination of methadone and its metabolites by high performance liquid chromatography following solid-phase extraction in rat plasma.
abstract: This paper describes a rapid, quantitative liquid chromatographic analysis and extraction of methadone and its two major metabolites from rat plasma, using difenoxin as the internal standard. Using a C18 column, resolution of all sample components and the internal standard is achieved with a mobile phase of 25:75 acetonitrile-0.08% diethylamine in 1000 mL water, pH 2.3, at a flow rate of 1.5 mL/min. The injection volume is 100 microL. Standards are linear over the range 25-100 ng, with a lower limit of detection for methadone of 0.25 ng. Within- and between-run coefficients of variation (CV) are 1.24% and 2.94%, respectively. Extraction of methadone and its metabolites from rat plasma uses a solid-phase extraction technique that is highly efficient. Extraction efficiencies of 90.3%, 99.6%, 85.9% and 93.8% were achieved for methadone, its primary and secondary metabolites, and difenoxin, respectively.
authors: Department of Pharmacology, Victorian College of Pharmacy, Monash University, Parkville, Australia.
authors: T L
authors: TL
authors: Pierce
authors: A G
authors: AG
authors: Murray
authors: W
authors: W
authors: Hope
mesh_terms: D000818:Animals; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004157:Diphenoxylate / Q000031:analogs & derivatives / Q000097:blood; D008691:Methadone / Q000097:blood* / Q000378:metabolism*; D051381:Rats
chemical_list: C100010:difenoxin; D004157:Diphenoxylate; D008691:Methadone