Negative ion chemical ionization for the determination of methylphenidate in human plasma by stable isotope dilution gas chromatography/mass spectrometry.
A sensitive and specific method for the determination of methylphenidate in human plasma is presented. Methylphenidate was extracted from plasma by solvent extraction with hexane at pH 9.3 and derivatized to its heptafluorobutyrate derivative. The derivative was measured by gas chromatography/negative ion chemical ionization mass spectrometry without any further purification. Using this detection mode, a diagnostically useful fragment ion at m/z 369 was obtained at high relative abundance. (18)O(2)-labelled methylphenidate was used as an internal standard and its rapid and facile preparation from the unlabeled compound is described. Calibration graphs were linear within the range 0.14-18.25 ng ml(-1). The inter-assay precision was 8.7% (0.14 ng ml(-1)) and 3.1% (4.56 ng ml(-1)) and the intra-assay variability was 1.3% (0.14 ng ml(-1)) and 0.4% (4.56 ng ml(-1)). Accuracy determinations showed deviations of +0.7% (0.14 ng ml(-1)) and -2.5% (4.56 ng ml(-1)). The method is rugged, rapid and robust and has been applied to the batch analysis of methylphenidate during pharmacokinetic profiling of the drug.
Leis
H J
HJ
University Children's Hospital, Department of Analytical Biochemistry and Mass Spectrometry, Auenbruggerplatz 30, A-8036 Graz, Austria. hans.leis@kfunigraz.ac.at
Fauler
G
G
Raspotnig
G
G
Windischhofer
W
W
D000697:Central Nervous System Stimulants / Q000097:blood* / Q000493:pharmacokinetics; D004300:Doping in Sports; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D007202:Indicators and Reagents; D008774:Methylphenidate / Q000097:blood* / Q000493:pharmacokinetics; D011786:Quality Control; D015203:Reproducibility of Results; D012997:Solvents; D015813:Substance Abuse Detection / Q000379:methods
D000697:Central Nervous System Stimulants; D007202:Indicators and Reagents; D012997:Solvents; D008774:Methylphenidate