title: Liquid-liquid extraction using 96-well plate format in conjunction with liquid chromatography/tandem mass spectrometry for quantitative determination of methylphenidate (Ritalin) in human plasma.
abstract: Methylphenidate (MPH; Ritalin: methyl-alpha-phenyl-2-piperidinacetate hydrochloride) is utilized for the treatment of attention deficit hyperactivity disorder (ADHD) and narcolepsy. Recently, we described a rapid enantioselective liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for the determination of the enantiomers of MPH (Rapid Commun. Mass Spectrom. 1999; 13: 2054). A lower limit of quantification (LLOQ) of 87 pg/mL was attained for the human plasma assay. The present paper describes a high-throughput sample preparation procedure in conjunction with racemic LC/MS/MS analysis for MPH with a LLOQ of 50 pg/mL. A semi-automated robotics method using liquid-liquid extraction (LLE) in a 96-well plate format was developed and validated. The correlation coefficients were > or =0.998 for MPH indicating good fits of the regression models over the range of the calibration curve. The accuracy and precision of the semi-automated approach were comparable to those obtained using the manual sample preparation technique reported previously (vide supra). The current method can easily be adapted to the enantioselective LC/MS/MS assay of MPH. The assay was simple, fast, specific, and exhibited excellent ruggedness.
authors.affiliation: Drug Metabolism and Pharmacokinetics Department, Novartis Institute for Biomedical Research, East Hanover, NJ 07936, USA.
authors.forename: L
authors.initials: L
authors.lastname: Ramos
authors.forename: R
authors.initials: R
authors.lastname: Bakhtiar
authors.forename: F L
authors.initials: FL
authors.lastname: Tse
mesh_terms: D001289:Attention Deficit Disorder with Hyperactivity / Q000097:blood; D002138:Calibration; D002853:Chromatography, Liquid / Q000379:methods; D006801:Humans; D013058:Mass Spectrometry / Q000379:methods; D008774:Methylphenidate / Q000097:blood*; D009290:Narcolepsy / Q000097:blood; D012044:Regression Analysis; D015203:Reproducibility of Results; D012371:Robotics; D013237:Stereoisomerism
chemical_list: D008774:Methylphenidate