title: Ion-pair extraction and liquid chromatographic analysis of morphine in rat brain and plasma.
abstract: A highly efficient and reproducible two-step liquid-liquid ion-pair extraction technique for the isolation of morphine from biological samples is described. A rapid normal phase high-performance liquid chromatographic procedure coupled with amperometric electrochemical detection has also been developed for subsequent quantification of morphine. Extraction involves the disruption of brain tissue or plasma in methanol, centrifugation, evaporation and reconstitution in ethyl acetate containing 10 mM di-(2-ethylhexyl) phosphoric acid, a liquid cation-exchanger, and back-extraction into 170 mM orthophosphoric acid. An acidic eluent consisting of acetonitrile-76 mM orthophosphoric acid-ammonia buffer (pH 3.0) (15:85, v/v) in combination with a strong cation-exchange column allows complete separation of morphine and the internal standard, nalbuphine. The limit of detection for morphine is 1.3 ng on-column.
authors.affiliation: School of Pharmacology, Victorian College of Pharmacy, Monash University, Royal Parade, Parkville, Australia.
authors.forename: P J
authors.initials: PJ
authors.lastname: Borg
authors.forename: B R
authors.initials: BR
authors.lastname: Sitaram
authors.forename: D A
authors.initials: DA
authors.lastname: Taylor
mesh_terms: D000818:Animals; D001923:Brain Chemistry; D002851:Chromatography, High Pressure Liquid / Q000379:methods* / Q000592:standards / Q000706:statistics & numerical data; D007700:Kinetics; D008297:Male; D009020:Morphine / Q000032:analysis* / Q000097:blood*; D010755:Organophosphates; D010756:Phosphoric Acids; D051381:Rats; D017208:Rats, Wistar; D012997:Solvents
chemical_list: D010755:Organophosphates; D010756:Phosphoric Acids; D012997:Solvents; C007377:di-2-(ethylhexyl)phosphoric acid; D009020:Morphine; C030242:phosphoric acid