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Coefficients Greater (coefficient + greater)

Distribution by Scientific Domains
Chemistry85%

Kinds of Coefficients Greater

  • correlation coefficient greater
    		•

    Selected Abstracts

    Separation of Escherichia coli 055:B5 lipopolysaccharide and detoxified lipopolysaccharide by high-performance capillary electrophoresis

    ELECTROPHORESIS, Issue 17 2003
    Nicola Volpi
    Abstract A rapid, highly sensitive and reproducible high-performance capillary electrophoresis (HPCE) method (electrokinetic chromatography with sodium dodecyl sulfate) is described for the determination of the lipopolysaccharide (LPS) and detoxified LPS (D-LPS), produced by both alkaline treatment in anhydrous conditions and mild acid hydrolysis, from Escherichia coli 055:B5 bacteria. LPS and D-LPS are separated and readily determined within 25 min on an uncoated fused-silica capillary using normal polarity at 20 kV and detection at 200 nm. A linear relationship (correlation coefficient greater than about 0.97) was found for the LPS and the two D-LPS species over a wide range of concentrations, from approximately 120 to 360 ng, with a detection sensitivity less than about 100 ng. Furthermore, HPCE was able to separate several molecular species mainly due to the presence of populations with O -specific polysaccharides of distinct and increasing mean chain lengths. This approach could be of great importance for the quantitative determination of LPS and D-LPS during the purification and preparation processes, also considering the importance of D-LPS in the preparation of human vaccines, and for the qualitative evaluation of the heterogeneity of LPS and the O -polysaccharide components. [source]

    Sensitivity improvement of circular dichroism detection in HPLC by using a low-pass electronic noise filter: Application to the enantiomeric determination purity of a basic drug

    CHIRALITY, Issue 2 2007
    Marie Lorin
    Abstract The quality control of chiral drugs requires the determination of their enantiomeric purity. Nowadays, circular dichroism (CD) spectroscopy is gaining increasing importance in pharmaceutical analysis because of the commercially available CD detector in liquid chromatography. The separation of the two enantiomers of a basic drug (efaroxan) was achieved by high performance liquid chromatography using an amylose-derivated column with both UV and CD detections. A baseline-resolved separation (resolution: 5) was obtained after optimization of the mobile phase composition with hexane-ethanol-diethylamine (90:10:0.05; v/v/v). The use of a commercial low-pass electronic noise filter of the CD signal has improved the signal-to-noise ratio by a factor twelve and allowed the quantitation of each enantiomer in the 1.25,300 ,g ml,1 concentration range. The CD linear calibration curve, expressed in terms of stereoisomer height ratio versus concentration ratio, was plotted over the 0.4,6% range. A correlation coefficient greater than 0.999 was obtained by least-squares regression and the limit of detection for the distomer/eutomer ratio was estimated at 0.14%. Although the method validation showed good repeatability on the retention times (RSD < 0.9%), on the peak height ratios (RSD < 8.7%) of each enantiomer only up to 99.2% enantiomeric purity was achieved. Chirality, 2006. © 2006 Wiley-Liss, Inc. [source]

    Lack of appreciable species differences in nonspecific microsomal binding

    JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 8 2010
    Ying Zhang
    Abstract Species differences in microsomal binding were evaluated for 43 drug molecules in human, monkey, dog and rat liver microsomes, using a fixed concentration of microsomal protein. The dataset included 32 named drugs and 11 proprietary compounds encompassing a broad spectrum of physicochemical properties (11 acids, 24 bases, 8 neutral, c,log,D ,1 to 7, MW 200 to 700 and free fraction <0.001 to 1). Free fractions (fu,mic) in monkey, dog, rat and human microsomes were highly correlated, with linear regression correlation coefficients greater than 0.97. The average fold-difference in fu,mic between monkey, dog, or rat, and human was 1.6-, 1.3-, and 1.5-fold, respectively. Species differences in fu,mic were also assessed for a range of microsomal protein concentrations (0.2,2,mg/mL) for midazolam, clomipramine, astemizole, and tamoxifen, drugs with low to high microsomal binding. The mean fold species-difference in fu,mic for midazolam, clomipramine, astemizole, and tamoxifen was 1.1-, 1.2-, 1.3-, and 2.0-fold, respectively, and was independent of normalized microsomal protein concentration. For a fixed concentration of microsomal protein, greater than 76% and 90% of drugs examined in this study had preclinical species fu,mic within 1.5- and 2-fold, respectively, of experimentally measured human values. © 2010 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:3620,3627, 2010 [source]

    Development of a method for the direct analysis of peptide AM336 in monkey cerebrospinal fluid using liquid chromatography/electrospray ionization mass spectrometry with a mixed-function column

    RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 21 2003
    Wei Bu
    A liquid chromatography/mass spectrometry (LC/MS) analytical procedure, using a single column for sample clean-up, enrichment and separation, has been developed for the determination of the peptide AM336 in monkey cerebrospinal fluid (CSF). CSF samples were injected and analyzed using a polymer-coated mixed-function high-performance liquid chromatography (HPLC) column with gradient elution and application of a timed valve-switching event. The mass spectrometer was operated in the positive electrospray ionization (ESI+) mode with single ion recording (SIR) at m/z 920. The method was validated, yielding calibration curves with correlation coefficients greater than 0.9892. Assay precision and accuracy were evaluated by direct injection of AM336-fortified CSF samples at three concentration levels. Analyzed concentrations ranged from 99.93 to 113.1% of their respective theoretical concentrations with coefficients of variation below 9.0%. An evaluation of the signal-to-noise (S/N) ratio for a 200 ng/mL calibration standard, considered to be the lower limit of quantitation (LLOQ), resulted in an estimated limit of detection (LOD) of 31.2,ng/mL. Preliminary data suggest the possibility of using this method to analyze AM336 also in plasma samples, pending the successful outcome of additional investigations. Copyright © 2003 John Wiley & Sons, Ltd. [source]

    Determination of a novel paclitaxel derivative (NPD-103) in human plasma by ultra-performance liquid chromatography,tandem mass spectrometry

    BIOMEDICAL CHROMATOGRAPHY, Issue 5 2009
    Shuang-Qing Zhang
    Abstract A sensitive and specific ultra-performance liquid chromatography,tandem mass spectrometry (UPLC-MS-MS) method for quantification of a newly developed anticancer agent NPD-103 has been established. An aliquot of human plasma sample (200 µL) was spiked with 13C-labeled paclitaxel (internal standard) and extracted with 1.3 mL of tert -butyl methyl ether. NPD-103 was quantitated on a C18 column with methanol,0.1% formic acid (75:25, v/v) as mobile phase using UPLC-MS-MS operating in positive electrospray ionization mode with a total run time of 3.0 min. For NPD-103 at the concentrations of 1.0, 5.0 and 10.0 µg/mL in human plasma, the absolute extraction recoveries were 95.58, 102.43 and 97.77%, respectively. The linear quantification range of the method was 0.1,20.0 µg/mL in human plasma with linear correlation coefficients greater than 0.999. The intra- and inter-day accuracy for NPD-103 at 1.0, 5.0 and 10.0 µg/mL levels in human plasma fell into the ranges of 95.29,100.00% and 91.04,94.21%, and the intra- and inter-day precisions were in the ranges of 8.96,11.79% and 7.25,10.63%, respectively. This assay is applied to determination of half-life of NPD-103 in human plasma. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Determination of a novel epothilone D analog (AV-EPO-106) in human plasma using ultra-performance liquid chromatography,tandem mass spectrometry

    BIOMEDICAL CHROMATOGRAPHY, Issue 3 2009
    Shuang-Qing Zhang
    Abstract A novel ultra-performance liquid chromatography,tandem mass spectrometry (UPLC-MS-MS) method has been established for the determination of a newly synthesized epothilone D analog (AV-EPO-106) in human plasma. The plasma samples were prepared by liquid,liquid extraction with cold tert -butyl methyl ether. The chromatographic separation was achieved within 5 min on a C18 column with water,methanol (10:90, v/v) as mobile phase at a flow-rate of 0.8 mL/min. Mass transition of m/z 568.2 to 386.1 was measured for AV-EPO-106 in positive atmospheric pressure chemical ionization mode. A detailed validation of the method was performed as per the USFDA guidelines. For AV-EPO-106 at the concentrations of 1.0, 5.0 and 10.0 µg/mL in human plasma, the absolute extraction recoveries were 86.17, 85.24 and 85.69%, respectively. The linear quantification range of the method was 0.10,20.0 µg/mL in human plasma with linear correlation coefficients greater than 0.999. The intra-day and inter-day accuracy for AV-EPO-106 at the levels of 1.0, 5.0 and 10.0 µg/mL in human plasma fell in the ranges of 98.25,100.47 and 94.19,97.25%, and the intra- and inter-day precision were in the ranges of 4.75,6.30% and 8.89,10.45%, respectively. The method was successfully applied to quantify AV-EPO-106 in human plasma to determine the half-life of this compound in human plasma. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Validation of a simple HPLC method for assay of haplamine and its metabolites in plasma suitable for pharmacokinetic application in rats

    BIOMEDICAL CHROMATOGRAPHY, Issue 2 2008
    Sompheary Ea
    Abstract A simple HPLC method with ultraviolet detection has been developed and validated for the simultaneous determination of haplamine and its metabolites (trans/cis -3,4-dihydroxyhaplamine) in rat. A liquid,liquid extraction was used to extract the compounds from rat plasma. The analysis was performed on a C18 Nucleosil Nautilus column. The mobile phase consisted of water (A) and a mixture of methanol and acetonitrile (85:15; v/v) (B) used in gradient mode (38,40% B for 10 min, 40,58% B for 49 min, 58,38% B for 1 min, and 38% for 5 min) pumped at 1 mL/min. The calibration curves showed good linearity with correlation coefficients greater than 0.999 for the analytes in the investigated concentration range. The lower limit of detection was 0.007, 0.008 and 0.009 µg/mL and the lower limit of quantification was 0.014, 0.017 and 0.018 µg/mL for haplamine, and trans/cis -3,4-dihydroxyhaplamine, respectively. The method was applied to a preliminary pharmacokinetic study in rats. This method proved to meet fully the standards required of experimental pharmacokinetic studies and should be used in further preclinical investigation. Copyright © 2007 John Wiley & Sons, Ltd. [source]