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Phase Containing (phase + containing)

Distribution by Scientific Domains
Chemistry88%

Kinds of Phase Containing

  • mobile phase containing
    		•

    Selected Abstracts

    Multi-walled carbon nanotube composites with polyacrylate prepared for open-tubular capillary electrochromatography

    ELECTROPHORESIS, Issue 19 2010
    Jian-Lian Chen
    Abstract A new phase containing immobilized carbon nanotubes (CNTs) was synthesized by in situ polymerization of acid-treated multi-walled CNTs using butylmethacrylate (BMA) as the monomer and ethylene dimethacrylate as the crosslinker on a silanized capillary, forming a porous-layered open-tubular column for CEC. Incorporation of CNT nanomaterials into a polymer matrix could increase the phase ratio and take advantage of the easy preparation of an OT-CEC column. The completed BMA-CNT column was characterized by SEM, ATR-IR, and EOF measurements, varying the pH and the added volume organic modifier. In the multi-walled CNTs structure, carboxylate groups were the major ionizable ligands on the phase surface exerting the EOF having electroosmotic mobility, 4.0×104,cm2,V,1,S,1, in the phosphate buffer at pH 2.8 and RSD values (n=5), 3.2, 4.1, and 4.3%, for three replicate capillaries at pH 7.6. Application of the BMA-CNT column in CEC separations of various samples, including nucleobases, nucleosides, flavonoids, and phenolic acids, proved satisfactory upon optimization of the running buffers. Their optima were found in the borate buffers at pH 9.0/50,mM, pH 9.5/10,mM/50% v/v ACN, and pH 9.5/30,mM/10% v/v methanol, respectively. The separations could also be used to assess the relative contributions of electrophoresis and chromatography to the CEC mechanism by calculating the corresponding velocity and retention factors. Discussions about interactions between the probe solutes and the bonded phase included the ,,, interactions, electrostatic repulsion, and hydrogen bonding. Furthermore, a reversed-phase mode was discovered to be involved in the chromatographic retention. [source]

    HPLC enantioseparation of ,2 -homoamino acids using crown ether-based chiral stationary phase

    JOURNAL OF SEPARATION SCIENCE, JSS, Issue 7 2009
    Róbert Berkecz
    Abstract RP high-performance liquid chromatographic methods were developed for the enantioseparation of eleven unusual ,2 -homoamino acids. The underivatized analytes were separated on a chiral stationary phase containing (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid as chiral selector. The effects of organic (alcoholic) and acidic modifiers, the mobile phase composition and temperature on the separation were investigated. The structures of the substituents in the ,-position of the analytes substantially influenced the retention and resolution. The elution sequence was determined in some cases: the S enantiomers eluted before the R enantiomers. [source]

    Development and validation of a stereoselective HPLC method for the determination of the in vitro transport of nateglinide enantiomers in rat intestine

    JOURNAL OF SEPARATION SCIENCE, JSS, Issue 12 2007
    Srinivas Maddi
    Abstract A simple stereoselective high performance liquid chromatographic method was developed for the determination of the in vitro transport of the enantiomers of nateglinide (N -(trans -4-isopropylcyclohexyl-carbonyl)-phenylalanine) in the rat intestine using a Chiralcel OJ-RH column (150×4.0 mm, 5 ,m). The effects of the mobile phase composition, pH, the flow rate, and the temperature on the chromatographic separation were investigated. The enantioseparation was achieved at 33°C using a mobile phase containing 100 mM potassium dihydrogen phosphate, pH 2.5, and ACN (32:68 v/v) delivered at a flow rate of 1 mL/min. The analytes were monitored at 210 nm and linearity (r >0.99) was obtained for a concentration range of 0.5,50 ,g/mL. The LOD and LOQ were 0.2 and 0.5 ,g/mL for the R -enantiomer and 0.2 and 0.8 ,g/mL for the S -enantiomer, respectively. Both, the intra- and interday accuracy and precision of the calibration curves were determined. The method was successfully applied to estimate the in vitro passage of the enantiomers and the racemate of nateglinide in duodenum, jejunum, and ileum of rats. Generally, higher concentrations of nateglinide and the S -enantiomer were observed when the racemate was administered compared to administration of the individual enantiomers of nateglinide. [source]

    Optimization of the separation conditions of tetracyclines on a preselected reversed-phase column with embedded urea group

    JOURNAL OF SEPARATION SCIENCE, JSS, Issue 7 2006
    Leila Kallel
    Abstract The use of a C12 stationary phase with embedded polar group has been investigated for the separation of seven tetracyclines. The influence of pH, organic modifier, buffer, and temperature on the peak shape and analyte separation was discussed. It appears that all the chromatographic conditions had a great effect on both the resolution and peak shape whereas the elution order was not affected. The baseline separation with symmetrical peaks of the seven tetracyclines can be obtained with a mobile phase containing either 5 mM phosphate buffer pH 2.5/ACN (84 : 16 v/v) or 5 mM perchlorate buffer pH 2.5/ACN (75 : 25 v/v) at a temperature not exceeding 20°C. This study reveals that the retention mechanism is ion-pairing. [source]

    Ion-pair mediated transport of angiotensin, neurotensin, and their metabolites in liquid phase microextraction under acidic conditions

    JOURNAL OF SEPARATION SCIENCE, JSS, Issue 11 2005
    J. Léon E. Reubsaet
    Abstract This paper discusses the behaviour of angiotensin 1 and neurotensin together with their metabolites in a three-phase liquid phase microextraction under acidic conditions. Variations in donor phase, organic phase, and acceptor phase are studied with extraction recovery as response variable. It is proved that for all peptides the transport across the organic phase is mediated by heptane-1-sulphonic acid. n -Octanol gave overall best results as organic phase. A donor phase volume of 1.0 mL was chosen as a compromise between optimal recovery and robustness of the LPME device. The optimal pH of the donor phase (using acceptor phase of pH 2) was found to be different for the peptides, which opens opportunities for selective sample preparation. Decreasing the acceptor phase pH to 1.0 resulted in increased extraction recoveries. On using 1.0 mL of donor phase containing 50 mM heptane-1-sulphonic acid pH 3, n -octanol as organic phase immobilized in the pores of the fibre, and 20 ,L of acceptor phase containing 0.1 mol/L HCl, extraction recoveries up to 82% (enrichment factor = 41) were achieved. To our knowledge this is the first report on liquid phase microextraction of angiotensins and neurotensins. [source]

    Varietal differences in terpene composition of blackcurrant (Ribes nigrum L) berries by solid phase microextraction/gas chromatography

    JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 13 2002
    Maria Luisa Ruiz del Castillo
    Abstract Relative amounts of volatile terpenes in berries of 10 different blackcurrant (Ribes nigrum L) cultivars were examined by solid phase microextraction/gas chromatography (SPME/GC). The optimisation of a variety of parameters affecting SPME enabled relative standard deviations from three replicates ranging from 2 to 12% to be achieved. Differences between cultivars in the proportions rather than in the qualitative composition of volatile terpenes were found, and the proportions of some terpenes were especially variable. Furthermore, the enantiomeric ratios of the chiral terpenes were determined for the first time in blackcurrant berries by GC using a column with a stationary phase containing permethylated cyclodextrin (Chirasil-,-Dex). The enantiomeric compositions of the majority of the chiral terpenes varied within a reasonably narrow range. However, the levels of two monoterpene alcohols, terpinen-4-ol and linalool, exhibited considerable variations amongst cultivars. © 2002 Society of Chemical Industry [source]

    Photostability studies for micellar liquid chromatographic determination of nifedipine in serum and urine samples

    BIOMEDICAL CHROMATOGRAPHY, Issue 2 2006
    M. T. Gil-Agustí
    Abstract Nifedipine is a photosensitive compound that is converted into its 4-(2-nitrophenyl) pyridine and 4-(2-nitrosophenyl) pyridine homologue. In order to obtain the most adequate conditions for handling nifedipine solutions in the analytical laboratory, a number of studies on the decomposition of this compound were performed. A simple micellar liquid chromatographic procedure was described to determine nifedipine in different biological matrices such as serum and urine, and to control its decomposition. To perform the analysis, nifedipine was dissolved in 0.1 m SDS at pH 3 and chromatographed using a mobile phase containing 0.125 m SDS,3% pentanol, pH 3 on a C18 column and UV detection at 235 nm. The chromatographic analysis time was 8 min. The response of the drug for both biological matrices was linear in the 1,100 µg/mL range, with r2 > 0.997 at all times. Repeatability, intermediate precision (CV, %) and limits of quantification and detection (ng/mL) were 0.19, 4.3, 104 and 31 in serum and 0.81, 2.1, 136 and 41 in urine. The method developed here does not show interferences or matrix effects produced by endogenous compounds. Micellar media and mobile phases have the advantage of stabilising the compounds, thus preventing photodegradation and allowing the direct injection of biological samples. Copyright © 2005 John Wiley & Sons, Ltd. [source]

    Simultaneous determination of estramustine phosphate and its four metabolites in human plasma by liquid chromatography,ionspray mass spectrometry

    BIOMEDICAL CHROMATOGRAPHY, Issue 5 2004
    M. Breda
    Abstract A sensitive and selective method, using liquid chromatography,ionspray mass spectrometry, was developed and validated for the simultaneous determination of Estracyt (estramustine phosphate) and its four metabolites, estramustine, estromustine, estrone and estradiol, in human plasma. Deuterated internal standards were available for all analytes. The ,ve compounds were extracted from plasma by protein precipitation with acetonitrile. The chromatographic separation was performed using a Zorbax SB C18, (150 × 4.6 mm i.d., 5 µm) reversed-phase column under gradient conditions with a mobile phase containing 2 mm ammonium acetate buffer (pH 6.8) and acetonitrile. MS detection was by electrospray ionization with multiple reaction monitoring in the positive ion mode for estramustine phosphate, estromustine and estramustine, and in the negative ion mode for estrone and estradiol. The limit of quantitation was 10 ng/mL for estramustine phosphate, 3 ng/mL for estromustine, estramustine and estrone and 30 ng/mL for estradiol. Linearity was veri,ed from these LLOQs up to about 4000 ng/mL for the parent drug and 2000 ng/mL for the metabolites. Inter-day precision and accuracy values were all less than 15%. This assay was applied successfully to the routine analysis of human plasma samples collected in cancer patients administered estramustine phosphate intravenously. Copyright © 2003 John Wiley & Sons, Ltd. [source]

    Ambient-Pressure Organic Superconductors ,-(DMEDO-TSeF)2[Au(CN)4](solv.): Tc Tuning by Modification of the Solvent of Crystallization,

    CHEMISTRY - A EUROPEAN JOURNAL, Issue 27 2007
    Takashi Shirahata Dr.
    Abstract The unsymmetrical , donor dimethyl(ethylenedioxy)tetraselenafulvalene (DMEDO-TSeF) has provided six new organic superconductors with a monovalent square-planar [Au(CN)4], ion and cyclic ethers as solvent of crystallization. The six new organic superconductors ,-(DMEDO-TSeF)2[Au(CN)4](solv.) [solv.=1,3-dioxolane (DOL), 2,5-dihydrofuran (DHF), tetrahydropyran (THP), 1,3-dioxane (1,3-DOX), 3,4-dihydro-2H -pyran (DHP), or 1,4-dioxane (1,4-DOX)] are classified into two subphases ,L and ,, according to the differences in their space group symmetry. ,L -(DMEDO-TSeF)2[Au(CN)4](solv.) (solv.=DOL, DHF, THP, 1,3-DOX or DHP) crystallizes in the orthorhombic space group Pnma, and Tc of the ,L phase varies by 1.7,5.3,K according to the size and shape of the solvent of crystallization. On the other hand, ,,-(DMEDO-TSeF)2[Au(CN)4](solv.) (solv.=DOL or 1,4-DOX) crystallizes in the noncentrosymmetric monoclinic space group Cc. The ,,-phase containing 1,4-DOX shows superconductivity at 4.2,K, but the ,,-phase containing DOL does not show superconductivity down to 1.4,K. Systematic investigation of the six new organic superconductors, together with the two previously reported superconductors ,H - and ,L -(DMEDO-TSeF)2[Au(CN)4](THF), revealed that the Tc of the present system is finely tunable by utilizing the effect of the solvent of crystallization. [source]