title: Semi-automated liquid--liquid back-extraction in a 96-well format to decrease sample preparation time for the determination of dextromethorphan and dextrorphan in human plasma.
abstract: A semi-automated, 96-well based liquid-liquid back-extraction (LLE) procedure was developed and used for sample preparation of dextromethorphan (DEX), an active ingredient in many over-the-counter cough formulations, and dextrorphan (DOR), an active metabolite of DEX, in human plasma. The plasma extracts were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS-MS). The analytes were isolated from human plasma using an initial ether extraction, followed by a back extraction from the ether into a small volume of acidified water. The acidified water isolated from the back extraction was analyzed directly by LC-MS-MS, eliminating the need for a dry down step. A liquid handling system was utilized for all aspects of liquid transfers during the LLE procedure including the transfer of samples from individual tubes into a 96-well format, preparation of standards, addition of internal standard and the addition and transfer of the extraction solvents. The semi-automated, 96-well based LLE procedure reduced sample preparation time by a factor of four versus a comparable manually performed LLE procedure.
authors.affiliation: Procter and Gamble Pharmaceuticals, 8700 Mason-Montgomery Road, Mason, OH 45040, USA.
authors.forename: Renee D
authors.initials: RD
authors.lastname: Bolden
authors.forename: Steven H
authors.initials: SH
authors.lastname: Hoke
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Eichhold
authors.forename: David L
authors.initials: DL
authors.lastname: McCauley-Myers
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: Wehmeyer
mesh_terms: D001331:Automation; D002138:Calibration; D002853:Chromatography, Liquid / Q000379:methods*; D003915:Dextromethorphan / Q000097:blood* / Q000493:pharmacokinetics; D003917:Dextrorphan / Q000097:blood* / Q000493:pharmacokinetics; D006801:Humans; D015203:Reproducibility of Results; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D003917:Dextrorphan; D003915:Dextromethorphan