Isocratic Mobile Phase (isocratic + mobile_phase)

Distribution by Scientific Domains

Terms modified by Isocratic Mobile Phase

  • isocratic mobile phase consisting

  • Selected Abstracts


    Rapid simultaneous determination of codeine and morphine in plasma using LC-ESI-MS/MS: Application to a clinical pharmacokinetic study

    JOURNAL OF SEPARATION SCIENCE, JSS, Issue 2 2009
    Qiongfeng Liao
    Abstract A rapid and sensitive high-performance LC-MS/MS method was developed and validated for the simultaneous quantification of codeine and its metabolite morphine in human plasma using donepezil as an internal standard (IS). Following a single liquid-liquid extraction with ethyl acetate, the analytes were separated using an isocratic mobile phase on a C18 column and analyzed by MS/MS in the selected reaction monitoring mode using the respective [M+H]+ ions, mass-to-charge ratio (m/z) 300/165 for codeine, m/z 286/165 for morphine and m/z 380/91 for IS. The method exhibited a linear dynamic range of 0.2,100/0.5,250 ng/mL for codeine/morphine in human plasma, respectively. The lower LOQs were 0.2 and 0.5 ng/mL for codeine and its metabolite morphine using 0.5 mL of human plasma. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. A run time of 2.0 min for each sample made it possible to analyze more than 300 human plasma samples per day. The validated LC-MS/MS method was applied to a pharmacokinetic study in which healthy Chinese volunteers each received a single oral dose of 30 mg codeine phosphate. [source]


    Rapid comprehensive amino acid analysis by liquid chromatography/tandem mass spectrometry: comparison to cation exchange with post-column ninhydrin detection

    RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 22 2008
    Dennis J. Dietzen
    Ion-exchange chromatography with ninhydrin detection remains the gold standard for detecting inborn errors of amino acid catabolism and transport. Disadvantages of such analysis include long chromatography times and interference from other ninhydrin-positive compounds. The aim of this project was to develop a more rapid and specific technique using liquid chromatography/tandem mass spectrometry (LC/MS/MS). Optimal fragmentation patterns for 32 amino acids were determined on a triple quadrupole mass spectrometer following butylation. Chromatographic characteristics of each of the amino acids were determined using C8 reversed-phase chromatography with 20% acetonitrile/0.1% formic acid as isocratic mobile phase. Quantitation using eleven deuterated internal standards was compared to cation exchange and ninhydrin detection on a Beckman 7300 system. Following methanol extraction and butylation, determination of 32 amino acids required 20,min. The dynamic range of each amino acid was generally 1,1000,mol/L. Imprecision ranged from 7 to 23% (CV) over 6 months and recovery ranged from 88,125%. Deming regression with the Beckman 7300 yielded slopes from 0.4,1.2, intercepts from ,21 to 65,mol/L, correlation coefficients from 0.84,0.99 and Syx from 2,125,mol/L. Isobaric amino acids were separated by chromatography (e.g. leucine, isoleucine) or by unique fragmentation (e.g., alanine, , -alanine). LC/MS/MS is comparable to traditional LC-ninhydrin detection. Mass spectral detection shortens analysis times and reduces potential for interference in detecting inborn metabolic errors. Copyright 2008 John Wiley & Sons, Ltd. [source]


    Development of a liquid chromatography/tandem mass spectrometry assay for the quantification of rabeprazole in human plasma

    RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 16 2005
    Jinchang Huang
    A simple and sensitive liquid chromatography/tandem mass spectrometry method, employing electrospray ionization, has been developed and validated to quantify rabeprazole in human plasma using omeprazole as the internal standard. The method was validated to demonstrate the specificity, lower limit of quantification, accuracy, and precision of measurements. Selected reaction monitoring was specific for rabeprazole and omeprazole (the internal standard, IS); no endogenous materials interfered with the analysis of rabeprazole and IS from blank plasma. The assay was linear over the concentration range 0.2,200,ng/mL using a 2,L aliquot of plasma. The correlation coefficients for the calibration curves ranged from 0.9988,0.9994. The intra- and inter-day precision, calculated from quality control samples, were less than 6.65%. A mixture of methanol and water (50:50) was used as the isocratic mobile phase, with 0.1% of formic acid in water, that did not affect the stability of rabeprazole or IS. A simple sample preparation method of protein precipitation with methanol was chosen. The method was employed in a pharmacokinetic study after oral administration of 20,mg rabeprazole to 24 healthy volunteers. Copyright 2005 John Wiley & Sons, Ltd. [source]


    HPLC determination of irbesartan in human plasma: its application to pharmacokinetic studies

    BIOMEDICAL CHROMATOGRAPHY, Issue 6 2009
    Soo Kyung Bae
    Abstract A simple and rapid HPLC method using fluorescence detection was developed for determination of irbesartan in human plasma. Sample preparation was accomplished through a simple deproteinization procedure with 0.4 mL of acetonitrile containing 800 ng/mL of losartan (internal standard), and to a 0.1 mL plasma sample. Chromatographic separation was performed on a Zorbax Xclipse XDB C18 column (150 4.6 mm, i.d., 5 m) at 40C. An isocratic mobile phase, acetonitrile:0.1% formic acid (37:63, v/v), was run at a flow-rate of 1.0 mL/min, and the column eluent was monitored using a fluorescence detector set at excitation and emission wavelengths of 250 and 370 nm, respectively. The retention times of irbesartan and losartan were 4.4 and 5.9 min, respectively. This assay was linear over a concentration range of 10,5000 ng/mL with a lower limit of quantification of 10 ng/mL. The coefficient of variation for this assay precision was less than 8.48%, and the accuracy exceeded 94.4%. The mean relative recoveries of irbesartan and losartan were 98.4 and 99.1%, respectively. This method was successfully applied for pharmacokinetic study after oral administration of irbesartan (300 mg) to 23 Korean healthy male volunteers. Copyright 2009 John Wiley & Sons, Ltd. [source]


    Sensitive liquid chromatography tandem mass spectrometry method for the quantification of sitagliptin, a DPP-4 inhibitor, in human plasma using liquid,liquid extraction

    BIOMEDICAL CHROMATOGRAPHY, Issue 2 2008
    Ramakrishna Nirogi
    Abstract A sensitive high-performance liquid chromatography,positive ion electrospray tandem mass spectrometry method was developed and validated for the quantification of sitagliptin, a DPP-4 inhibitor, in human plasma. Following liquid,liquid extraction, the analytes were separated using an isocratic mobile phase on a reverse-phase column and analyzed by MS/MS in the multiple reaction monitoring mode using the respective [M + H]+ ions, m/z 408,235 for sitagliptin and m/z 310,148 for the internal standard. The assay exhibited a linear dynamic range of 0.1,250 ng/mL for sitagliptin in human plasma. The lower limit of quantification was 0.1 ng/mL with a relative standard deviation of less than 6%. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. A run time of 2.0 min for each sample made it possible to analyze more than 300 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic studies. Copyright 2007 John Wiley & Sons, Ltd. [source]


    Quantification of tenatoprazole in rat plasma by HPLC: validation and its application to pharmacokinetic studies

    BIOMEDICAL CHROMATOGRAPHY, Issue 12 2007
    Ramakrishna Nirogi
    Abstract A simple, reliable HPLC method with UV detection (295 nm) in rat plasma was developed and validated for quantification of tenatoprazole, a novel proton pump inhibitor, which is in clinical trials. Following a single-step liquid,liquid extraction, the analyte and internal standard were separated using an isocratic mobile phase on a reverse phase C18 column. The lower limit of quantitation was 20 ng/mL, with a relative standard deviation of less than 10%. A linear dynamic range of 20,6000 ng/mL was established. This HPLC method was validated with between-batch and within-batch precision of 2.9,6.3 and 1.4,5.8%, respectively. The between-batch and within-batch accuracy was 95.1,104.1 and 92.4,101.0%, respectively. This validated method is simple and repeatable enough to be used in pharmacokinetic studies. Copyright 2007 John Wiley & Sons, Ltd. [source]


    A validated new method for nevirapine quantitation in human plasma via high-performance liquid chromatography

    BIOMEDICAL CHROMATOGRAPHY, Issue 1 2006
    Courtney F. Silverthorn
    Abstract A fully validated and clinically relevant assay was developed for the assessment of nevirapine concentrations in neonate blood plasma samples. Solid-phase extraction with an acid,base wash series was used to prepare subject samples for analysis. Samples were separated by high performance liquid chromatography and detected at 280 nm on a C8 reverse-phase column in an isocratic mobile phase. The retention times of nevirapine and its internal standard were 5.0 and 6.9 min, respectively. The method was validated by assessment of accuracy and precision (statistical values <15%), specificity, and stability. The assay was linear in the range 25,10,000 ng[sol ]mL (r2 > 0.996) and the average recovery was 93% (n = 18). The lower limit of quantification (relative standard deviation <20%) was determined to be 25 ng[sol ]mL for 50 L of plasma, allowing detection of as little as 1.25 ng of nevirapine in a sample. This value represents an increase in sensitivity of up to 30-fold over previously published methods. Copyright 2005 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 2004
    Wilson 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 m) 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]


    Determination of the ,avone tricin in human plasma by high-performance liquid chromatography

    BIOMEDICAL CHROMATOGRAPHY, Issue 7 2003
    Hong Cai
    Abstract Tricin is a ,avone constituent of brown rice and rice bran, which interferes potently with the survival of human-derived breast and colon cancer cells in vitro. A speci,c and simple high-performance liquid chromatographic (HPLC) method was developed for the determination of tricin in human plasma with UV,visible detection. HPLC separation on Hypersil-BDS C18 (4.6 250 mm) was carried out with an isocratic mobile phase of 52% methanol in 0.1 m ammonium acetate, pH 5.10, containing 0.27 mm disodium ethylenediamine tetraacetic acid and detection at 355 nm. The retention times of tricin and quercetin (internal standard) were 14.2 and 7.8 min, respectively. The assay was linear in the range 1,100 g/mL (r2 , 0.995). Tricin in plasma was ef,ciently extracted with 0.1 m acetic acid in acetone, and the recoveries were in the range 92.6,102.8% (n = 6) with relative standard deviation below 10% for three concentrations of tricin, 5, 10 and 100 g/mL. The lower limit of quantitation (relative standard deviation <20%) was 1 g/mL. Copyright 2003 John Wiley & Sons, Ltd. [source]