{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,23]],"date-time":"2026-02-23T20:37:21Z","timestamp":1771879041452,"version":"3.50.1"},"reference-count":12,"publisher":"Wiley","issue":"1","license":[{"start":{"date-parts":[[2005,4,6]],"date-time":"2005-04-06T00:00:00Z","timestamp":1112745600000},"content-version":"vor","delay-in-days":5209,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Biomedical Chromatography"],"published-print":{"date-parts":[[1991,1]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:p>A high performance liquid chromatographic (HPLC) technique for the determination of three metabolites of theophylline, 3\u2010methylxanthine (3\u2010MX), 1\u2010methylxanthine (1\u2010MX) and 1,3\u2010dimethyluric acid (1,3\u2010DMU) in human liver microsomes is described. The analytes were extracted from human liver microsomes with methylene chloride\/isopropanol and stepwise gradient elution was employed for the resolution of peaks. The limits of quantitation were 15 ng\/mL for 3\u2010MX, 20 ng\/mL for 1\u2010MX and 20 ng\/mL for 1,3\u2010DMU. The calibration range was linear for the three metabolites and the calibration ranges were 15\u2013250 ng\/mL for 3\u2010MX, 20\u2013250 ng\/mL for 1\u2010MX and 250\u20134000 ng\/mL for 1,3\u2010DMU. The absolute recovery ranged from 63\u201384% for 3\u2010MX, 65\u201379% for 1\u2010MX and 77\u201389% for 1,3\u2010DMU over the calibration curve range. Accuracy for all three metabolites was within \u00b1 10% and adequate seletivity was demonstrated by the lack of interfering peaks in blank chromatograms. The within\u2010run and interday precision were within 10% RSD for all three metabolites tested at two concentrations. The advantage of this method over previous methods is that the use of quaternary ammonium ion pair reagents in the mobile phase has been obviated. Also, unlike a previous radiometric HPLC method, the need for radiolabelled theophylline has also been eliminated. The method was used to characterize theophylline metasbolism in human liver microsomes for immunoinhibition studies and to investigate the interaction of theophylline with selected quinolone antibiotitics.<\/jats:p>","DOI":"10.1002\/bmc.1130050109","type":"journal-article","created":{"date-parts":[[2005,5,27]],"date-time":"2005-05-27T18:57:06Z","timestamp":1117220226000},"page":"38-42","source":"Crossref","is-referenced-by-count":6,"title":["High performance liquid chromatographic determination of theophylline metabolites in human liver microsomes"],"prefix":"10.1002","volume":"5","author":[{"given":"Mohamadi A.","family":"Sarkar","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"H. Thomas","family":"Karnes","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"311","published-online":{"date-parts":[[2005,4,6]]},"reference":[{"key":"e_1_2_1_2_1","doi-asserted-by":"publisher","DOI":"10.1111\/j.1365-2125.1983.tb01475.x"},{"key":"e_1_2_1_3_1","doi-asserted-by":"crossref","first-page":"237","DOI":"10.1016\/S0090-9556(25)06689-9","volume":"15","author":"Campbell M. E.","year":"1987","journal-title":"Drug Met. Disp."},{"key":"e_1_2_1_4_1","doi-asserted-by":"publisher","DOI":"10.1002\/jps.2600760312"},{"key":"e_1_2_1_5_1","doi-asserted-by":"crossref","first-page":"213","DOI":"10.1016\/S0021-9258(19)52451-6","volume":"193","author":"Lowry O. H.","year":"1951","journal-title":"J. Biol. 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