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HPLC Determination (hplc + determination)
Selected AbstractsSupported liquid membranes in hollow fiber liquid-phase microextraction (LPME) , Practical considerations in the three-phase modeJOURNAL OF SEPARATION SCIENCE, JSS, Issue 9 2007Kari Folde Bårdstu Abstract In this work, three-phase liquid-phase microextraction (LPME) based on a supported liquid membrane (SLM) sustained in the wall of a hollow fiber was investigated with special focus on optimization of the experimental procedures in terms of recovery and repeatability. Recovery data for doxepin, amitriptyline, clomipramine, and mianserin were in the range of 67.8,79.8%. Within-day repeatability data for the four basic drugs were in the range of 4.1,7.7%. No single factor was found to be responsible for these variations, and the variability was caused by several factors related to the LPME extractions as well as to the final HPLC determination. Although the volume of the SLM varied within 0.4,3.1% RSD depending on the preparation procedure, and the volume of the acceptor solution varied within 4.8% RSD, both recoveries and repeatability were found to be relative insensitive to these variations. Thus, the handling of microliters of liquid in LPME was not a very critical factor, and the preparation of the SLM was accomplished in several different ways with comparable performance. Reuse of hollow fibers was found to suffer from matrix effects due to built-up of analytes in the SLM, whereas washing of the hollow fibers in acetone was beneficial in terms of recovery, especially for the extraction of the most hydrophobic substances. Several of the organic solvents used in the literature as SLM suffered from poor long-term stability, but silicone oil AR 20 (polyphenyl-methylsiloxane), 2-nitrophenyl octyl ether (NPOE), and dodecyl acetate (DDA) all extracted with unaltered performance even after 60 days of storage at room temperature. [source] Comparison of two sample clean-up methodologies for the determination of polycyclic aromatic hydrocarbons in edible oilsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 17 2003Alejandro Barranco Abstract An off-line high-performance normal-phase liquid chromatography procedure with a silica column followed by reversed-phase high-performance liquid chromatography (HPLC) with fluorescence detection for the determination of polycyclic aromatic hydrocarbons (PAHs) in edible oils is reported. The method was validated using certified reference materials and compared with a standardized method widely used in the food industry, consisting in low pressure column chromatography with alumina as stationary phase followed by reversed phase HPLC determination. The limits of detection were lower than 1 ng/g and good selectivity was achieved for both methods. There were no significant differences in accuracies and precisions obtained for each approach. The advantages and disadvantages of the two methods are discussed. [source] Ultrasonic extraction and HPLC determination of anthraquinones, aloe-emodine, emodine, rheine, chrysophanol and physcione, in roots of Polygoni multifloriPHYTOCHEMICAL ANALYSIS, Issue 4 2009Yue Jiao Abstract Introduction Polygoni multiflori, one of traditional Chinese herbal medicines for the treatment of various diseases commonly associated with aging, is known to contain active anthraquinone ingredients. However, the content of the anthraquinones varies among P. multiflori samples with collection season and sites. Thus, simple, reliable and accurate analytical methods for determining of anthraquinones in P. multiflori products are needed for the quality control and pharmacological studies. Objective To develop an HPLC method for the simultaneous determination of five anthraquinones, aloe-emodine, rheine, emodine, chrysophanol and physcione, in the roots of P. multiflori. Methodology Anthraquinones were extracted from the roots of P. multiflori using aqueous alcohol solutions or hot water under ultrasonication. Separation and quantitation of anthraquinones was accomplished using a reversed-phase C18 column with the mobile phase of methanol,water,phosphoric acid (600:400:1), and the detection wavelength of 254 nm. Results Seventy per cent aqueous ethanol showed the highest extraction efficiency for anthraquinones from roots of P. multiflori when compared with four other extraction solvents tested. All calibration curves were linear over the concentration range tested with the square of correlation coefficients >0.999. The detection limits (S/N = 3) were 0.89, 1.1, 1.6, 1.7 and 2.0 ng for chrysophanol, aloe-emodine, rheine, emodine and physcione, respectively. Emodine and physcione were found in the samples tested at concentrations of 0.341 and 0.197 mg/g, respectively. Conclusion The described HPLC methods are simple, accurate and selective techniques for separation and quantification of anthraquinones in roots of P. multiflori and other plant samples. Copyright © 2009 John Wiley & Sons, Ltd. [source] Evaluation of detection methods for the reversed-phase HPLC determination of 3,,4,,5,-trimethoxyflavone in different phytopharmaceutical products and in human serumPHYTOCHEMICAL ANALYSIS, Issue 2 2001Christian W. Huck Abstract Quantitative determination of the major compound, 3,,4,,5,-trimethoxyflavone (1), in plant extracts, in tablets of Flos and of Radix Primulae veris and in human serum has been accomplished using reversed-phase HPLC with UV, fluorescence and mass spectrometric (MS) detection. Compared to UV detection, fluorescence detection showed greater selectivity, was 10-fold more sensitive and allowed the determination of 1 in human serum after sample pre-treatment by solid-phase extraction. MS detection of 1 using electrospray ionisation (ESI) interface could be improved by substituting trifluoroacetic acid with the more polar and less conductive additive acetic acid, giving rise to a 230-fold improvement in analyte detectability at the cost of an increase of only 45% in the peak width of the eluting peak at its half height. Further optimisation of the acetic acid concentration showed the highest signal intensity at 1.25% for HPLC-atmospheric pressure chemical ionisation (APCI)-MS and at 0.75% for HPLC-ESI-MS. The optimised MS method proved to be extremely selective, 50 times more sensitive than UV detection and 5 times more sensitive than fluorescence detection. Furthermore, fragment-ion spectra produced by collision induced dissociation-MS have been used as "fingerprints" for identifying compounds in the highly complex mixtures examine. Copyright © 2001 John Wiley & Sons, Ltd. [source] HPLC determination of irbesartan in human plasma: its application to pharmacokinetic studiesBIOMEDICAL CHROMATOGRAPHY, Issue 6 2009Soo 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 µm) at 40°C. 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] HPLC determination of acidic d -amino acids and their N -methyl derivatives in biological tissuesBIOMEDICAL CHROMATOGRAPHY, Issue 6 2009Mara Tsesarskaia Abstract d -Aspartate (d -Asp) and N -methyl- d -aspartate (NMDA) occur in the neuroendocrine systems of vertebrates and invertebrates, where they play a role in hormone release and synthesis, neurotransmission, and memory and learning. N -methyl- d -glutamate (NMDG) has also been detected in marine bivalves. Several methods have been used to detect these amino acids, but they require pretreatment of tissue samples with o -phthaldialdehyde (OPA) to remove primary amino acids that interfere with the detection of NMDA and NMDG. We report here a one-step derivatization procedure with the chiral reagent N-, -(5-fluoro-2,4-dinitrophenyl)-(d or l)-valine amide, FDNP-Val-NH2, a close analog of Marfey's reagent but with better resolution and higher molar absorptivity. The diastereomers formed were separated by HPLC on an ODS-Hypersil column eluted with TFA/water,TFA/MeCN. UV absorption at 340 nm permitted detection levels as low as 5,10 pmol. d -Asp, NMDA and NMDG peaks were not obscured by other primary or secondary amino acids; hence pretreatment of tissues with OPA was not required. This method is highly reliable and fast (less than 40 min HPLC run). Using this method, we detected d -Asp, NMDA and NMDG in several biological tissues (octopus brain, optical lobe and bucchal mass; foot and mantle of the mollusk Scapharca broughtonii), confirming the results of other researchers. Copyright © 2009 John Wiley & Sons, Ltd. [source] HPLC determination of safflor yellow A and three active isoflavones from TCM Naodesheng in rat plasma and tissues and its application to pharmacokinetic studiesBIOMEDICAL CHROMATOGRAPHY, Issue 6 2007Zhiguo Yu Abstract A high-performance liquid chromatographic method was developed for the simultaneous determination and pharmacokinetic studies of safflor yellow A, puerarin, 3,-methoxyl-puerarin, and puerarinapioside in the plasma and tissues of rats that had been administered with the traditional Chinese medicine (TCM) preparation Naodesheng via the caudal vein. Samples taken from rats were subjected to protein precipitation with acetone. Separation of these four compounds was accomplished on a Kromisil C18 stationary phase using a mobile phase of acetonitrile,0.1% phosphoric acid,tetrahydrofuran (8:92:2, v/v/v) at a flow-rate of 1.0 mL/min. The detection wavelength was set at 250 nm. The calibration curves of the four components were linear in the given concentration ranges. The intra- and inter-day precisions in plasma and tissues were less than 15% and the extraction recoveries were higher than 60%. The lower limits of quantitation of four components were low enough to determine the four components. These four components all exhibited kinetics that fitted a two-compartment model in rats. The elimination half-life was 1.19 h for safflor yellow A, 2.69 h for puerarin, 2.94 h for 3,-methoxyl-puerarin, and 0.87 h for puerarinapioside, respectively. Following administration of a single injection of Naodesheng, the concentration (C) of the four components in the tissues showed Ckidney > Clung, Cliver > Cspleen, Cstomach, Cheart, approximately. The method is a reliable tool for performing studies of safflor yellow A and three puerarin isoflavones in different biological material. Copyright © 2007 John Wiley & Sons, Ltd. [source] HPLC determination and pharmacokinetic studies of salvianolic acid B in rat plasma after oral administration of Radix Salviae Miltiorrhizae extractBIOMEDICAL CHROMATOGRAPHY, Issue 1 2005Jinlan Zhang Abstract A precise and reproducible HPLC method has been established and validated for determination of salvianolic acid B (SalB) in rat plasma after oral administration of Radix Salviae Miltiorrhizae extract. Liquid,liquid extraction was adopted for the sample preparation. Separation was accomplished on a C18 column with a linear gradient elution consisting of acetonitrile and aqueous phosphoric acid. Ultraviolet detection was at 280 nm. The method was validated over the concentration range 10.8,259.4 µg/mL using 1 mL of plasma. The assay was linear over this concentration range with a coef,cient of variation less than 7%. The extraction recovery of SalB was within the range 71,83% with RSD 11%. The mean recovery of the internal standard was 84% (n = 6) with RSD of 5.6%. This method is suitable to determine SalB in plasma and to investigate the pharmacokinetics of SalB. Copyright © 2004 John Wiley & Sons, Ltd. [source] 5,7-dihydroxytryptamine lesions enhance and serotonergic grafts normalize the evoked overflow of acetylcholine in rat hippocampal slicesEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2002Anja Birthelmer Abstract Adult rats were subjected to intracerebroventricular injections of 5,7-dihydroxytryptamine (5,7-DHT; 150 µg) and, 15 days later, to intrahippocampal grafts of fetal raphe cell suspensions. About 11 months later, we assessed baseline and electrically evoked release of tritium ([3H]) in hippocampal slices, preloaded with tritiated ([3H])choline or [3H]serotonin (5-HT), in the presence or absence of the 5-HT1B receptor agonist CP-93,129 and the 5-HT receptor antagonist methiothepine. HPLC determinations of monoamine concentrations were also performed. The lesions reduced the concentration of 5-HT (,90%) and the accumulation (,80%) as well as the evoked release (,90%) of [3H]5-HT. They also decreased the inhibitory effects of CP-93,129 on the evoked release of [3H]5-HT. Most interestingly, they facilitated the evoked release of [3H]acetylcholine (+20%). In slices from rats subjected to lesions and grafts, the responsiveness of the serotonergic autoreceptors (presumably located on the terminals of the grafted neurons) and the release of acetylcholine were close to normal. These results confirm that grafts rich in serotonergic neurons may partially compensate for the dramatic effects of 5,7-DHT lesions on serotonergic hippocampal functions. The lesion-induced reduction of the 5-HT1B autoreceptor-mediated inhibition of evoked 5-HT release may be an adaptation enhancing serotonergic transmission in the (few) remaining terminals. The facilitated release of acetylcholine is probably caused by a reduced serotonergic tone on the inhibitory 5-HT1B heteroreceptors of the cholinergic terminals. When related to data in the literature, this facilitation may be of particular interest in terms of transmitter-based strategies developed to tackle cognitive symptoms related to neurodegenerative diseases. [source] HPLC determinations of enantiomeric ratiosCHIRALITY, Issue 1 2007Peter Wipf Abstract Evaporative light-scattering detection (ELSD) is widely applied in the HPLC analysis of organic compounds lacking a UV chromophore. However, this detection method is generally unsuitable for determination of enantiomeric ratios (er). The er calculated from a UV trace and an ELS trace of the same compound differs significantly. Because of the nonlinear concentration response of the ELS detector, a compound with an er of 95:5 appears to be enantiomerically pure by ELS detection. It is possible to obtain a calibration curve and to calculate a correction factor, but this procedure is time consuming and therefore not very practical for routine analyses. In contrast, a charged aerosol detector allows a very accurate determination of the enantiomeric ratios. Like the ELS detection, the CA detection is independent of the chromophore properties of the substrate. Therefore, we recommend the use of CA instead of ELS detection for determination of the enantiomeric ratios of non-UV active compounds. Chirality, 2006. © 2006 Wiley-Liss, Inc. [source] | ||||||||||