title: High-performance liquid chromatography-mass spectrometry for the quantification of nortriptyline and 10-hydroxynortriptyline in plasma.
abstract: A highly sensitive and selective method for the quantification of nortriptyline and its major 10-hydroxy metabolite in plasma is described. The method is based on liquid-liquid extraction in combination with acid dehydration of the 10-hydroxy metabolite to the less polar 10,11-dehydronortriptyline. Deuterium labelled internal standards ([2H4]NT and [2H3]10-OH-NT) were used and the compounds were separated by reversed-phase HPLC and detected using atmospheric pressure chemical ionisation and mass spectrometry. The limit of quantification was 0.8 ng/ml for both compounds. A 1-ml volume of plasma was used for analysis in the concentration range 0.8-32 ng/ml. The within- and between-day coefficients of variation were 11% in the low, 1.6 ng/ml range, and 7% at 8 ng ml/ml. Using this method it was possible to quantify plasma concentrations for 168 h following a single oral dose of 25 mg of nortriptyline with good accuracy and precision.
authors.affiliation: Department of Medical Laboratory Sciences and Technology, Huddinge University Hospital, Sweden.
authors.forename: G
authors.initials: G
authors.lastname: Tybring
authors.forename: J
authors.initials: J
authors.lastname: Nordin
authors.forename: J
authors.initials: J
authors.lastname: Widén
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D003903:Deuterium; D006801:Humans; D007700:Kinetics; D013058:Mass Spectrometry / Q000379:methods*; D008832:Microchemistry; D009661:Nortriptyline / Q000031:analogs & derivatives* / Q000097:blood* / Q000493:pharmacokinetics; D011786:Quality Control; D012680:Sensitivity and Specificity
chemical_list: C013567:10-hydroxynortriptyline; D003903:Deuterium; D009661:Nortriptyline