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Reversed-phase C18 Column (reversed-phase + c18_column)
Selected AbstractsIonic liquids as mobile phase additives for high-performance liquid chromatography separation of phenoxy acid herbicides and phenolsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 23-24 2009Xialin Hu Abstract In this present study, 1-butyl-3-methylimidazolium chloride ([C4MIM]Cl), 1-octyl-3-methylimidazolium chloride ([C8MIM]Cl), and 1-decyl-3-methylimidazolium chloride ([C10MIM]Cl) were adopted as mobile phase additives in the high performance liquid chromatography (HPLC) to simultaneously separate phenoxy acid herbicides and phenols at neutral pH. It was found that by using 20,mM of [C4MIM]Cl, baseline separation and good chromatograms for all the acid compounds were obtained on a normal reversed-phase C18 column. The retention time of the target acid compounds shortened with the increase of the alkyl chain length and the concentrations of ionic liquids, probably due to the delocalization of the positive charge on the imidazolium cation, the repulsion between chlorine ions of ionic liquids and the acid compounds, as well as the stereo-hindrance effect. The mechanism with ionic liquids as mobile additives for the separation of acid compounds was discussed. [source] Separation and determination of small amounts of sulfur in technical thiophanate-methyl by reversed-phase high-performance liquid chromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 9-10 2003R. Nageswara Rao Abstract A simple and rapid reversed phase high-performance liquid chromatographic method for separation and determination of elemental sulfur in technical thiophanate-methyl using a reversed-phase C18 column and methanol-water-tetrahydrofuran (90 : 8 : 2 v/v/v) as eluent with UV detection at 254 nm has been developed and validated with respect to accuracy, precision, specificity, linearity range, and limits of detection and quantification. The method was found to be suitable not only for detection but also determination of elemental sulfur at levels of 5×10,9 g. [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] Structural characterization and identification of ecdysteroids from Sida rhombifolia L. in positive electrospray ionization by tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 16 2008Yan-Hong Wang Seven ecdysteroids isolated from Sida rhombifolia L. were studied by electrospray ionization multi-stage tandem mass spectrometry (ESI-MSn) in the positive ion mode using an ion trap analyzer and high-performance liquid chromatography coupled with a diode-array detector (HPLC/DAD). The HPLC experiments were performed by means of a reversed-phase C18 column and a binary mobile phase system consisting of water (containing 0.05% formic acid) and acetonitrile (containing 0.05% formic acid) under gradient elution conditions. According to mass spectral features and the substitution at C-2, C-20, C-24 and C-25, ecdysteroids in S. rhombifolia were classified into three sub-groups. Structural identification of these three sub-groups of ecdysteroids was established by LC/multi-stage ion trap mass spectrometry on-line or off-line. The fragmentation patterns of ecdysteroids yielded ions of successive loss of 1,4 water molecules. Furthermore, ions corresponding to the complete loss of the side chain at C-17 will help to identify the sub-groups of ecdysteroids in addition to containing a hydroxyl moiety at one of the above-mentioned positions. Based on the HPLC retention behavior, the diagnostic UV spectra and the molecular structural information provided by ESI-MSn spectra, a total of nine naturally occurring ecdysteroids were identified, of these two are identified for the first time in S. rhombifolia. Copyright © 2008 John Wiley & Sons, Ltd. [source] Characterization of isoquinoline alkaloids, diterpenoids and steroids in the Chinese herb Jin-Guo-Lan (Tinospora sagittata and Tinospora capillipes) by high-performance liquid chromatography/electrospray ionization with multistage mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 15 2006Yufeng Zhang This study sought to determine the primary components (isoquinoline alkaloids, diterpenoids and steroids) in crude extracts of the Chinese herb Jin-Guo-Lan, prepared from the roots of Tinospora sagittata and T. capillipes, by liquid chromatography/electrospray ionization multistage mass spectrometry coupled with diode-array detection (LC-DAD/ESI-MSn). After separation on a reversed-phase C18 column using gradient elution, positive and negative ESI-MS experiments were performed. In positive ion mode, the three types of compounds showed very different characteristic ions: strong [M]+ or [M+H]+ ions were observed for isoquinoline alkaloids; [M+NH4]+ and/or [M+HCO2]+ for diterpenoids; [M+HnH2O]+ (n=1,3) for steroids. These adduct ions and/or fragments were used to deduce the mass and categories of known and unknown components in crude extracts, and their structures were further confirmed by ESI-MSn in positive ion mode. Moreover, UV absorption peaks obtained from DAD provided useful functional group information to aid the MSn -based identification. As a result, 11 compounds were unambiguously identified by comparing with standard compounds and 13 compounds were tentatively identified or deduced according to their MSn data. Two of these compounds (13-hydroxycolumbamine and 13-hydroxyjatrorrhizine) were found to be new compounds and another one (13-hydroxypalmatine) was detected for the first time as a natural product. In addition, a [M·CH3H2O].+ ion in MS2 of [M]+ after in-source collision-induced dissociation was used to differentiate positional isomers of protoberberine alkaloids, columbamine and jatrorrhizine. Although the roots of T. sagittata and T. capillipes contain almost identical compounds, the content of the compounds in them is dramatically different, suggesting the necessity for further comparison of the bioactivities of the two species. Copyright © 2006 John Wiley & Sons, Ltd. [source] Development and validation of a high-performance liquid chromatography method for the simultaneous determination of aspirin and folic acid from nano-particulate systemsBIOMEDICAL CHROMATOGRAPHY, Issue 9 2010Abhishek Chaudhary Abstract Attention has shifted from the treatment of colorectal cancer (CRC) to chemoprevention using aspirin and folic acid as agents capable of preventing the onset of colon cancer. However, no sensitive analytical method exists to simultaneously quantify the two drugs when released from polymer-based nanoparticles. Thus, a rapid, highly sensitive method of high-performance liquid chromatography analysis to simultaneously detect low quantities of aspirin (hydrolyzed to salicylic acid, the active moiety) and folic acid released from biodegradable polylactide-co-glycolide (PLGA) copolymer nanoparticles was developed. Analysis was done on a reversed-phase C18 column using a photodiode array detector at wavelengths of 233,nm (salicylic acid) and 277,nm (folic acid). The mobile phase consisted of acetonitrile,0.1% trifluoroacetic acid mixture programmed for a 30,min gradient elution analysis. In the range of 0.1,100,,g/mL, the assay showed good linearity for salicylic acid (R2 = 0.9996) and folic acid (R2 = 0.9998). The method demonstrated good reproducibility, intra- and inter-day precision and accuracy (99.67, 100.1%) and low values of detection (0.03, 0.01,,g/mL) and quantitation (0.1 and 0.05,,g/mL) for salicylic acid and folic acid, respectively. The suitability of the method was demonstrated by simultaneously determining salicylic acid and folic acid released from PLGA nanoparticles. Copyright © 2009 John Wiley & Sons, Ltd. [source] Measurement of fexofenadine concentration in micro-sample human plasma by a rapid and sensitive LC-MS/MS employing protein precipitation: application to a clinical pharmacokinetic studyBIOMEDICAL CHROMATOGRAPHY, Issue 3 2010Daqing Guo Abstract A simple, rapid and sensitive liquid chromatography/positive ion electro-spray tandem mass spectrometry method (LC-MS/MS) was developed and validated for the quantification of fexofenadine with 100,,L human plasma employing glipizide as internal standard (IS). Protein precipitation was used in the sample preparation procedure. Chromatographic separation was achieved on a reversed-phase C18 column (5,,m, 100 × 2.1,mm) with methanol,:,buffer (containing 10,mmol/L ammonium acetate and 0.1% formic acid; 70,:,30, v/v) as mobile phase. The total chromatographic runtime was approximately 3.0,min with retention time for fexofenadine and IS at approximately 1.9 and 2.1,min, respectively. Detection of fexofenadine and IS was achieved by LC-MS/MS in positive ion mode using 502.1 , 466.2 and 446.0 , 321.1 transitions, respectively. The method was proved to be accurate and precise at linearity range of 1,600,ng/mL with a correlation coefficient (r) of ,0.9976. The validated method was applied to a pharmacokinetic study in human volunteers following oral administration of 60 or 120,mg fexofenadine formulations, successfully. Copyright © 2009 John Wiley & Sons, Ltd. [source] Identification of key metabolites of tectorigenin in rat urine by HPLC-MSnBIOMEDICAL CHROMATOGRAPHY, Issue 2 2009Wei-Dong Zhang Abstract This is a report about the identification of key metabolites of tectorigenin in rat urine using high-performance liquid chromatography,electrospray ionization ion trap tandem mass spectrometric method (HPLC-ESI-MSn). Six healthy rats were administered a single dose (80 mg/kg) of tectorigenin by oral gavage. Urine was sampled for 0,24 h and centrifuged at 12,000 rpm for 10 min to obtain the supernatants, then the supernatants were purified by solid-phase extraction with a C18 cartridge. The chromatographic separation was carried out on a reversed-phase C18 column with a gradient elution program whereas acetonitrile,0.1% formic acid water was used as mobile phase. Mass spectra were acquired in negative ionization mode and a data-dependant scan was used for the identification of the key metabolites of tectorigenin in the urine samples. As a result, four phase II metabolites and the parent drug tectorigenin were found and identified in rat urine for the first time. Copyright © 2008 John Wiley & Sons, Ltd. [source] Automated analysis of fluvoxamine in rat plasma using a column-switching system and ion-pair high-performance liquid chromatographyBIOMEDICAL CHROMATOGRAPHY, Issue 12 2008Shicheng Liu Abstract We have established a robust, fully automated analytical method for the analysis of fluvoxamine in rat plasma using a column-switching ion-pair high-performance chromatography system. The plasma sample was injected onto a precolumn packed with Shim-pack MAYI-ODS (50 µm), where the drug was automatically purified and enriched by on-line solid-phase extraction. After elution of the plasma proteins, the analyte was back-flushed from the precolumn and then separated isocratically on a reversed-phase C18 column (L-column ODS) with a mobile phase (acetonitrile,0.1% phosphoric acid, 36:64, v/v) containing 2 mm sodium 1-octanesulfonate. The analyte was monitored by a UV detector at a wavelength of 254 nm. The calibration line for fluvoxamine showed good linearity in the range of 5,5000 ng/mL (r > 0.999) with the limit of quantification of 5 ng/mL (RSD = 6.51%). Accuracy ranged from ,2.94 to 4.82%, and the within- and between-day precision of the assay was better than 8% across the calibration range. The analytical sensitivity and accuracy of this assay is suitable for characterization of the pharmacokinetics of orally-administered fluvoxamine in rats. Copyright © 2008 John Wiley & Sons, Ltd. [source] Determination of oleanolic acid, ursolic acid and amygdalin in the flower of Eriobotrya japonica Lindl. by HPLCBIOMEDICAL CHROMATOGRAPHY, Issue 7 2007Chunhua Zhou Abstract Simple and accurate HPLC methods were developed for the determination of oleanolic acid (OA), ursolic acid (UA) and amygdalin in loquat (Eriobotrya japonica Lindl.) flower, which is commonly used for the treatment of various diseases as a traditional Chinese medicine. HPLC assay was performed on a reversed-phase C18 column and all three compounds were detected at 210 nm with a flow rate of 1.0 mL/min. The mobile phase consisted of methanol (A) and 0.03 mol/L phosphate buffer (pH 2.8) (B) with a ratio of 88:12 (A:B, v/v) for simultaneous detection of OA and UA, and 25:75 (A:B, v/v) for detection of amygdalin. The established methods showed good precision and accuracy with overall intra-day and inter-day variation of 0.99,3.55 and 1.05,4.05%, respectively, and overall recoveries of 97.37,99.32% for the three compounds. Application of these methods to determine the OA, UA and amygdalin contents in loquat flower showed that cultivar had a minor effect on the contents of all three compounds, with average amounts of 0.38,0.51 mg OA/g dry weight (DW), 2.15,2.68 mg UA/g DW and 1.23,1.56 mg amygdalin/g DW among five loquat cultivars tested. However, developmental stages and flower tissues showed significant effect on the contents of all three bioactive components. Copyright © 2007 John Wiley & Sons, Ltd. [source] A high-performance liquid chromatographic method for saikosaponin a quantification in rat plasmaBIOMEDICAL CHROMATOGRAPHY, Issue 5 2007Yi-hong Tang Abstract A high-performance liquid chromatographic method with UV detection has been developed for the determination of saikosaponin a in rat plasma. Saikosaponin a and internal standard jujuboside A were isolated from plasma samples by solid-phase extraction. The chromatographic separation was achieved on a reversed-phase C18 column with the mobile phase of acetonitrile,water (35:65, v/v) at a flow rate of 1 mL/min and UV detection was set at 205 nm. The standard curve for saikosaponin a was linear over the concentration range 0.25,10 µg/mL and the limit of detection was 0.05 µg/mL. The absolute recovery was greater than 82%. The precision and accuracy ranged from 3.05 to 9.59% and 95.61 to 110.00%, respectively. The validated method was used to determine saikosaponin a in plasma samples in a pharmacokinetic study of saikosaponin a administered to Sprague,Dawley rats. Copyright © 2007 John Wiley & Sons, Ltd. [source] The determination of raloxifene in rat tissue using HPLCBIOMEDICAL CHROMATOGRAPHY, Issue 3 2007Zhaoyong Yang Abstract We report a rapid and reliable HPLC-UV method for determination of raloxifene, a kind of selective estrogen receptor modulator (SERM), in rat tissue. Proteins were precipitated by adding 200 µL of acetonitrile and 50 µL of methanol to 100 µL of the tissue homogenates, following vortex mixing and centrifugation. Separation was carried out on a reversed-phase C18 column (150 × 4.6 mm, 5 µm) with a mobile phase of acetonitrile:0.05 m ammonium acetate (pH 4.0 ± 0.1; 33:67, v/v) at a flow rate of 1.0 mL/min. The UV detection wavelength was set at 289 nm and the temperature of column was kept at 23°C, without interference from endogenous tissue compounds. The calibration curve was linear from 0.0125 to 10.0 µg/mL with correlation coefficient of over 0.994, while the limit of quantification was 0.008 µg/mL. The intra- and inter-day coefficients of variation were less than 10% (RSD). The recovery of assay was between 95.8 and 104.5%. Furthermore, the method was used to measure the concentration of raloxifene in rat tissue after a simple oral dose. The highest level was observed in liver, lung, spleen, then heart and kidney. The lowest level was found in brain. These results suggest that raloxifene distributes rapidly and moderately into tissues such as liver, lung and spleen. Copyright © 2007 John Wiley & Sons, Ltd. [source] Simultaneous determination of honokiol and magnolol in Magnolia officinalis by liquid chromatography with tandem mass spectrometric detectionBIOMEDICAL CHROMATOGRAPHY, Issue 10 2006Yu-Tse Wu Abstract An optimized high-performance liquid chromatographic method coupled with tandem mass spectrometric detection (LC-MS/MS) was developed for the simultaneous determination of honokiol and magnolol in Magnolia officinalis. Honokiol and magnolol were separated from the extracts using a reversed-phase C18 column with a mobile phase consisted of acetonitrile and water (75:25, v/v) at a flow-rate of 0.8 mL/min. Selected reaction monitoring (SRM) mode was used for all sample quantification by the precursor-ion/product ion pair m/z 265 , m/z 224 for honokiol and m/z 265 , m/z 247 for magnolol. Validation data showed that this method has good linearity (r2 > 0.995) over the concentration range of 0.0025,0.5 µg/mL for honokiol and magnolol, and both intra- and inter-day variability were acceptable within 15% at the lowest concentrations for this method. This proposed method provides excellent specificity, higher sensitivity and shorter run time than conventional methods and was applied successfully to determine the contents of honokiol and magnolol in M. officinalis. Copyright © 2006 John Wiley & Sons, Ltd. [source] Simultaneous determination of albi,orin and paeoni,orin in rat urine by solid-phase extraction and high-performance liquid chromatography following oral administration of Si,Wu decoctionBIOMEDICAL CHROMATOGRAPHY, Issue 10 2004Yuxin Sheng Abstract A high performance liquid chromatographic method (HPLC), together with solid phase extraction (SPE), was developed for simultaneous determination of albi,orin and paeoni,orin in rat urine after oral administration of Si,Wu decoction. The samples were pretreated with solid phase extraction using Extract-CleanÔ cartridges. Analysis of the extract was performed on a reversed-phase C18 column and a mobile phase made up of acetonitrile and 0.03% formic acid (17:83, v/v). UV detection was set at 230 nm. The assay was linear over the range 2.625,52.50 mg/mL for albi,orin and 3.875,77.50 µg/mL for paeoni,orin. The average percentage recoveries of three spiked urines were 97.01 ± 3.32 and 102.32 ± 6.97 for albi,orin and paeoni,orin, respectively. The intra-day precision (RSD) ranged from 0.21 to 1.79% at concentrations of 4.20, 10.50, 26.25 and 39.375 µg/mL of albi,orin and 0.12 to 2.92% at concentrations of 3.875, 10.85, 23.25 and 58.125 µg/mL of paeoni,orin, and inter-day precision (RSD) was from 1.02 to 1.86% for albi,orin and 0.94 to 3.30% for paeoni,orin, at the same four concentrations. This method was applied in order to analyze albi,orin and paeoni,orin in rat urine following oral administration of traditional Chinese medicinal preparation of Si,Wu decoction. Copyright © 2004 John Wiley & Sons, Ltd. [source] | ||||||||||