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Luna C18 Column (luna + c18_column)
Selected AbstractsHigh-performance liquid chromatography determination of hydrastine and berberine in dietary supplements containing goldensealJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 7 2001Ehab A. Abourashed Abstract Goldenseal (Hydrastis canadensis L., Ranunculaceae) is an ingredient of various dietary supplements intended for enhancing general body immunity. Many goldenseal products are currently available in the United States, either alone or in combination with echinacea. In most products, the content of the main active alkaloids of goldenseal, hydrastine and berberine, is not indicated on the label. A high-performance liquid chromatography (HPLC) method has been developed for the detection and quantification of hydrastine and berberine in a number of products obtained from the United States market. The method uses a Phenomenex® Luna C18 column, a mobile phase consisting of solvent A (100 mM sodium acetate/acetic acid, pH 4.0) and solvent B (acetonitrile/methanol; 90/10, v/v). Elution was run at a flow rate of 1.0 mL/min, with a linear gradient of 80, 40% A in B over 20 min and ultraviolet detection at 290 nm. A wide range of content variation was observed for both alkaloids in the tested samples. © 2001 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 90:817,822, 2001 [source] An isocratic fluorescence HPLC assay for the monitoring of l -asparaginase activity and l -asparagine depletion in children receiving E. colil -asparaginase for the treatment of acute lymphoblastic leukaemiaBIOMEDICAL CHROMATOGRAPHY, Issue 2 2009Christa E. Nath Abstract A novel assay for the determination of l -asparaginase activity in human plasma is described that is based on the HPLC quantitation of l -aspartic acid produced during enzyme incubation. Methods for monitoring l -asparagine depletion are also described. Chromatography of l -aspartic acid, l -asparagine and l -homoserine (the internal standard) involved derivatization with o -pthaldialdehyde, then separation from other amino acids on a Phenomenex Luna C18 column using a 1 mL/min flow rate and a mobile phase consisting of di-potassium hydrogen orthophosphate propionate buffer, pH 6, with 10% methanol and 10% acetonitrile. Fluoresence detection was at excitation/emission wavelengths of 357/455 nm. Under these conditions l -aspartic acid, l -asparagine and l -homoserine had retention times of 3.5, 9.8 and 17.7 min, respectively. The l -asparaginase assay was linear from 0.1 to 10 U/mL activity and interday precision and accuracy were less than 13%. The limit of quantitation was approximately 0.03 U/mL. The assay utility was established in 12 children who received E. colil -asparaginase as treatment for acute lymphoblastic leukaemia. Copyright © 2008 John Wiley & Sons, Ltd. [source] High-performance liquid chromatography assays for desmethoxyyangonin, methysticin, kavain and their microsomal metabolitesBIOMEDICAL CHROMATOGRAPHY, Issue 1 2009Shuang Fu Abstract Three novel, simple and reproducible high-performance liquid chromatography quantitative assays with UV detection were developed and validated for three major kavalactones,desmethoxyyangonin, methysticin and kavain,in rat liver microsomes using diazepam as an internal standard; liquid,liquid extraction was used for sample preparation and analysis was performed on a Shimadzu® 10A high-performance liquid chromatography system. The analysis was carried out in reversed-phase mode with a Luna® C18 column (150 × 2.00 mm, 3 µm) at 40°C. The limit of quantitation was 0.1 µg/mL using 0.25 mL of microsomal solution. The assays were linear over the range 0.1,10 µg/mL for desmethoxyyangonin, methysticin and kavain. Quality control samples exhibited good accuracy and precision with relative standard deviations lower than 15% and recoveries between 85 and 105%. The assays exhibited satisfactory performance with high sensitivity for quantifying desmethoxyyangonin, methysticin and kavain in rat liver microsomes and were successfully used to determine the three kavalactones and their microsomal metabolites. Copyright © 2008 John Wiley & Sons, Ltd. [source] Quantitative LC/MS/MS method and in vivo pharmacokinetic studies of vitexin rhamnoside, a bioactive constituent on cardiovascular system from hawthornBIOMEDICAL CHROMATOGRAPHY, Issue 4 2007Mingjin Liang Abstract A simple and accurate liquid chromatography coupled with tandem mass spectrometry method was developed for determination and in vivo pharmacokinetic studies of vitexin rhamnoside in rat plasma. After protein precipitation using methanol, the analytes were separated by a Luna C18 column with an isocratic elution and analyzed by mass spectrometry in multiple reaction monitoring mode using the respective negative ion at m/z 577.2,293.0 for vitexin rhamnoside and m/z 593.2,413.0 for internal standard (IS) vitexin glucoside. The method was validated systematically within the concentration range 5,5000 µg/L (R > 0.996) and the lower limit of quantitation was 5 µg/L. Acceptable precision and accuracy were acquired for concentrations over the standard curve range. It was further applied to assess pharmacokinetics and bioavailability of vitexin rhamnoside after intravenous and oral administration to rats. The oral bioavailability of vitexin rhamnoside was only 3.57%, which indicated that vitexin rhamnoside had poor absorption or underwent extensive first-pass metabolism. Practical utility of this new LC/MS/MS method was confirmed in pilot pharmacokinetic studies in rats following both intravenous and oral administration. Copyright © 2007 John Wiley & Sons, Ltd. [source] Development and validation of a high-sensitivity liquid chromatography/tandem mass spectrometry (LC/MS/MS) method with chemical derivatization for the determination of ethinyl estradiol in human plasma,BIOMEDICAL CHROMATOGRAPHY, Issue 7 2004Wilson Z. Shou Abstract An ultra-sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for the analysis of oral contraceptive ethinyl estradiol (EE) was developed and validated over the curve range of 2.5,500 pg/mL using 1 mL of human plasma sample. Ethinyl estradiol and the internal standard, ethinyl estradiol tetra-deuterated (EE-d4), were extracted from the plasma matrix with methyl t -butyl ether, derivatized with dansyl chloride and then back-extracted into hexane. The hexane phase was evaporated to dryness, reconstituted and injected onto the LC/MS/MS system. The chromatographic separation was achieved on a Luna C18 column (50 × 2 mm, 5 µm) with an isocratic mobile phase of 20:80 (v/v) water:acetonitrile with 1% formic acid. The of,ine derivatization procedure introduced the easily ionizable tertiary amine function group to EE. This greatly improved analyte sensitivity in electrospray ionization and enabled us to achieve the desired lower limit of quantitation at 2.5 pg/mL. This high sensitivity method can be used for therapeutic drug monitoring or supporting bio-equivalence and drug,drug interaction studies in human subjects. Copyright © 2004 John Wiley & Sons, Ltd. [source] | ||||||||||