Liquid-liquid extraction using 96-well plate format in conjunction with liquid chromatography/tandem mass spectrometry for quantitative determinationof methylphenidate (Ritalin (R)) in human plasma

Methylphenidate (MPH; Ritalin(R): methyl-alpha-phenyl-2-piperidinacetate hy drochloride) is utilized for the treatment of attention deficit hyperactivi ty disorder (ADHD) and narcolepsy. Recently, we described a rapid enantiose lective liquid chromatography/tandem mass spectrometry (LC/MS/MS) method fo r 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 at tained for the human plasma assay. The present paper describes a high-throu ghput sample preparation procedure in conjunction with racemic LC/MS/MS ana lysis for MPH with a LLOQ of 50 pg/mL, A semi-automated robotics method usi ng liquid-liquid extraction (LLE) in a 96-well plate format was developed a nd validated. The correlation coefficients were greater than or equal to 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 ap proach were comparable to those obtained using the manual sample preparatio n technique reported previously (vide supra). The current method can easily be adapted to the enantioselective LC/MS/MS assay of MPH. The assay was si mple, fast, specific, and exhibited excellent ruggedness. Copyright (C) 200 0 John Wiley & Sons, Ltd.