title: Quantitative liquid chromatography-mass spectrometry determination of isatin in urine using automated on-line extraction.
abstract: Here we describe a simple, fast and sensitive liquid chromatography/mass spectrometry method with automated on-line extraction to quantify isatin, an endogenous monoamine oxidase, and atrial natriuretic peptide inhibitor, in urine. After derivatisation of isatin to isatinoxime with hydroxylamine hydrochloride and zinc sulfate precipitation, samples were loaded on the extraction column, washed and, after activation of the column-switching valve, backflushed onto the analytical column. Using electrospray ionisation, [M+H]+ ions could be detected in the selected ion monitoring mode. The assay was linear from 5 to 5000 ng/ml (r2>0.99) and analytical recovery was >80%. Inter-assay precision for the quality control samples was less than 3% and inter-assay accuracy was within +/- 5%.
authors.affiliation: Department of Biopharmaceutical Sciences, University of California, San Francisco 94143-0446, USA.
authors.forename: Matthias
authors.initials: M
authors.lastname: Unger
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Jacobsen
authors.forename: Ulrike
authors.initials: U
authors.lastname: Holzgrabe
authors.forename: Leslie Z
authors.initials: LZ
authors.lastname: Benet
mesh_terms: D002138:Calibration; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D006801:Humans; D007510:Isatin / Q000652:urine*; D008996:Monoamine Oxidase Inhibitors / Q000652:urine*; D015203:Reproducibility of Results; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: D008996:Monoamine Oxidase Inhibitors; D007510:Isatin