title: Use of 18O3-clodronate as an internal standard for the quantitative analysis of clodronate in human plasma by gas chromatography/electron ionisation mass spectrometry.
abstract: A sensitive and specific method for the quantitative determination of clodronate in human plasma is presented. The drug was extracted from plasma by anion-exchange chromatography and derivatised to the tetra-tert-butyldimethylsilyl derivative. 18O3-Clodronate was prepared from unlabeled clodronate and used as an internal standard. Gas chromatography/mass spectrometry (GC/MS) under electron ionisation conditions was used for quantitative measurement of the drug, using m/z 643.16 and 651.17 for target and internal standard, respectively. Calibration graphs were linear within the range of 10-1280 ng/mL plasma. Intra-day precision was 1.8% (10 ng/mL), 0.5% (40 ng/mL), 1.0% (120 ng/mL), 0.5% (200 ng/mL), 0.5% (400 ng/mL) and 2.7% (800 ng/mL) and inter-day variability was found to be 0.7% (10 ng/mL), 1.6% (40 ng/mL), 1.3% (120 ng/mL), 2.3% (200 ng/mL), 2.5% (400 ng/mL) and 1.2% (800 ng/mL). Intra-day accuracy showed deviations of 0.8% (10 ng/mL), 0.8% (40 ng/mL), 0.9% (120 ng/mL), 0.9% (200 ng/mL), 1.9% (400 ng/mL) and 0.3% (800 ng/mL) and intra-day accuracy was of -1.4% (10 ng/mL), 0.0% (40 ng/mL), -0.7% (120 ng/mL), -0.4% (200 ng/mL), -1.2% (400 ng/mL) and -3.3% (800 ng/mL). The stable isotope labeled standard was found to be stable under analysis conditions.
authors.affiliation: University Children's Hospital, Division of Analytical Biochemistry and Mass Spectrometry, Auenbruggerplatz 30, A-8036 Graz, Austria. hans.leis@meduni-graz.at
authors.forename: Hans Jörg
authors.initials: HJ
authors.lastname: Leis
authors.forename: Günter
authors.initials: G
authors.lastname: Fauler
authors.forename: Werner
authors.initials: W
authors.lastname: Windischhofer
mesh_terms: D004002:Clodronic Acid / Q000097:blood*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D006801:Humans; D010103:Oxygen Isotopes; D012015:Reference Standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D010103:Oxygen Isotopes; D004002:Clodronic Acid