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Linear Gradient Elution (linear + gradient_elution)
Selected AbstractsSimultaneous qualification and quantification of eight triterpenoids in Radix Achyranthis Bidentatae by high-performance liquid chromatography with evaporative light scattering detection and mass spectrometric detectionJOURNAL OF SEPARATION SCIENCE, JSS, Issue 6 2007Juan Li Abstract An HPLC with evaporative light scattering detection (ELSD) and ESI-MS was established for the simultaneous determination of eight triterpenoids in Radix Achyranthis Bidentatae. The optimal chromatographic conditions were achieved on a Zorbax C18 column by linear gradient elution with 0.08% v/v aqueous formic acid and ACN as the mobile phase at the flow rate of 0.8 mL/min. Temperature for the detector drift tube was set at 101°C and the nitrogen flow rate was 2.8 L/min. The identities of the analytes were accomplished by comparing retention times and mass data with those of reference compounds. The validation of the method included tests of linearity, sensitivity, repeatability, recovery, and stability. All the calibration curves of the eight triterpenoids showed good linear regression (R2 >0.997) within the test ranges. The method provides desirable repeatability with overall intra- and interday variations of less than 4.9%. The obtained recoveries varied between 93.6 and 98.1% while the RSDs were below 3.9% (n = 3). The analysis results indicate that the content of investigated triterpenoids in Radix Achyranthis Bidentatae from different locations was greatly diverse, and the triterpenoids could be used as chemical markers for the discrimination of genuine and ungenuine crude drugs. [source] Analysis of phenolic acids in honeys of different floral origin by solid-pase extraction and high-performance liquid chromatographyPHYTOCHEMICAL ANALYSIS, Issue 1 2007Burya Dimitrova Abstract The determination of 18 aromatic and arylaliphatic carboxylic acids in honey from different floral origin using solid-phase extraction (SPE) and reversed-phase high performance liquid chromatography (RP-HPLC) is reported. The behaviour of the solutes on SPE cartridges was predicted from preliminary calculations involving the pKa constants of the carboxylic groups, the n -octanol:water partition coefficients and the distribution coefficients at different pH values of the conditioning and washing solvents. The proposed SPE isolation and pre-concentration of the acids was achieved on reversed-phase Bond Elut C18 cartridges using an acetonitrile:tetrahydrofuran (1:1, v/v) elution system. RP-HPLC separations were performed on a Spherisorb ODS-2 column using linear gradient elution with a mobile phase composed of 20 mm phosphate buffer (pH 2.92) and methanol, and with UV detection. The reported SPE and RP-HPLC methods were applied to the analysis of 49 authentic honey samples from various floral sources and the results indicate that they may serve with respect to the quantitative control of a number of phenolic acids in plant-derived foods and medicinal plants. Copyright © 2006 John Wiley & Sons, Ltd. [source] Simultaneous quantitative determination of cyclosporine A and its three main metabolites (AM1, AM4N and AM9) in human blood by liquid chromatography/mass spectrometry using a rapid sample processing methodRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 5 2006Nozomu Koseki We have developed a sensitive and specific liquid chromatography/mass spectrometry (LC/MS) method for the simultaneous determination of cyclosporine A (CsA) and its three main metabolites (AM1, AM4N and AM9) in human blood. Following protein precipitation, supernatant was directly injected into the LC/MS system. Chromatographic separation was accomplished on a Symmetry C8 (4.6,×,75,mm, 3.5,µm) column with a linear gradient elution prior to detection by atmospheric pressure chemical ionization (APCI) MS using selected ion monitoring (SIM) in positive mode. This method can be applied to single mass equipment. The analytical range for each analyte was set at 1,2500,ng/mL using 100,µL of blood sample. The analytical method was fully validated according to FDA guidance. Intra-day mean accuracy and precision were 95.2,113.5% and 0.9,8.9%, respectively. Inter-day mean accuracy and precision were 95.8,107.0% and 1.5,10.7%, respectively. In blood all analytes were stable during three freeze/thaw cycles, for 24,h at room temperature and for 12 months at or below ,15°C. Stability was also confirmed in processed samples for 24,h at 10°C and for 6 months at 4°C in methanol. In addition, we confirmed the method could avoid matrix effects from transplant subjects' samples. This LC/MS technique provided an excellent method for simultaneous quantitative determination of CsA and its three metabolites for evaluation of their pharmacokinetic profiles. Copyright © 2006 John Wiley & Sons, Ltd. [source] Simultaneous determination of quinolone antibacterials in bovine milk by liquid chromatography,mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 11 2008Alberto Zafra-Gómez Abstract A new liquid chromatography,mass spectrometry (LC,MS) method has been developed and validated for the simultaneous determination of eight quinolone antibacterials for veterinary use in processed bovine milk samples. The quinolones studied included marbofloxacin, ciprofloxacin, danofloxacin, enrofloxacin, sarafloxacin, difloxacin, oxolinic acid and flumequine. Also, a new sample-treatment procedure was used for extraction and preconcentration of these compounds. It involved defatting by centrifugation, protein precipitation by adding a mixture of glacial acetic acid,acetonitrile and removing acetonitrile with dichloromethane; finally, the acidified aqueous layer was evaporated to dryness in a speed vac system, resuspended in the mobile phase and filtered prior to LC injection. The mobile phase was composed of a formic acid aqueous solution 0.1% (v/v) and acetonitrile, with an initial composition of water,acetonitrile 95: 5 (v/v) and using linear gradient elution. Norfloxacin was used as internal standard. The limits of quantification found (2,7 ng g,1) were in all cases lower than the maximum residue limits tolerated by the European Union for these compounds in milk. Copyright © 2008 John Wiley & Sons, Ltd. [source] Simultaneous determination and pharmacokinetic study of oxymatrine and matrine in beagle dog plasma after oral administration of Kushen formula granule, oxymatrine and matrine by LC-MS/MSBIOMEDICAL CHROMATOGRAPHY, Issue 8 2007Yiqi Wang Abstract A rapid, specific and sensitive LC-MS/MS method was developed for the determination of oxymatrine (OMT) and matrine (MT) in beagle dog plasma. The method was applied to study the pharmacokinetics of OMT and MT after oral administration of OMT, MT and Kushen formula granule (KFG) containing equivalent amounts of OMT and MT in a three-period crossover design. The analysis was carried out on an Acquity UPLCÔ BEH C18 column by linear gradient elution with 0.01% acetic acid,water,methanol as mobile phase. Detection was by positive ion electrospray ionization (ESI) mass spectrometry with multiple-reaction monitoring (MRM). Linear calibration curves were both obtained over the concentration range 15,2000 ng/mL, with a limit of quantification of 15 ng/mL. The matrix effect was minimized. The intra- and inter-day precisions (RSDs) were less than 12.4 and 14.7%, respectively, and the accuracy (RE) was from ,2.1 to 2.7%. The validated method was used to determine the concentration,time profiles of OMT and MT. The results indicated that the absorption of OMT and MT after oral administration of KFG was significantly greater than that after oral administration of pure components. Copyright © 2007 John Wiley & Sons, Ltd. [source] Preparation of Immobilized Metal Affinity Chromatographic Packings by Immobilization of Carboxymethylated Asparate (CM-Asp) Based on Monodisperse Hydrophilic Non-porous Beads and Their ApplicationCHINESE JOURNAL OF CHEMISTRY, Issue 7 2010Bolin Gong Abstract The hydrophilic immobilized metal affinity chromatographic packing was prepared by immobilization of carboxymethylated asparate (CM-Asp) as chelating ligand and Ni2+ as center ion on the base of monodispersed, 3.0 µm non-porous monodisperse poly(glycidylmethacrylate- co -ethylenedimethacrylate) (PGMA/EDMA) particles. The retention behavior of proteins and the effect of pH on the retention in the range from 4.0 to 9.0 were investigated on both the naked and metal ion chelated columns. Four proteins were quickly separated in 2.0 min with linear gradient elution at a flow rate of 3.0 mL·min,1 by using the synthesized Ni2+ -CM-Asp-PGMA/EDMA packings. The separation time was shorter than other immobilized metal affinity chromatography reported in the literature. The Ni2+ -CM-Asp-PGMA/EDMA column was further investigated for the rapid separation and purification of copper-zinc superoxide dismutase (Cu,Zn-SOD) from the blood of pig in 3.0 min with only one step. The results obtained were satisfactory. [source] Preparation of Immobilized Metal Affinity Chromatographic Packings Based on Monodisperse Hydrophilic Non-porous Beads and Their ApplicationCHINESE JOURNAL OF CHEMISTRY, Issue 5 2008Chun-Miao BO Abstract Three hydrophilic immobilized metal affinity chromatographic packings for HPLC have been synthesized by chemical modification of 3.0 µm monodisperse non-porous poly(glycidyl methacrylate- co -ethylenedimethacrylate) (PGMA/EDMA) beads. The retention behavior of proteins on the metal ion chelated columns loaded with copper(II), nickel(II) and zin(II) ion was studied. The effect of pH on the protein retention was investigated on both the naked and metal ion chelated columns in the range from 4.0 to 9.0. Four proteins were quickly separated in 3.0 min with linear gradient elution at a flow rate of 3.0 mL/min by using the synthesized Ni2+ -IDA (iminodiacetic acid) packings. The separation time was shorter than other immobilized metal affinity chromatography reported in the literature. Purification of lysozyme from egg white and trypsin on the commercially available trypsin was performed on the naked-IDA and Cu2+ -IDA columns, respectively. The purities of the purified trypsin and lysozyme were more than 92% and 95%, respectively. [source] | ||||||||||