Search Results
Results 501 - 550 of 2121
< 6 7 8 9 10 11 12 13 14 15 16 >
Yongzhu Jin - - 2006
In order to develop a chiral stationary phase (CSP), which has even higher separation ability than the corresponding commercially available crown ether based CSP (OA-8000 having a pseudo-18-crown-6 ether with an OMe group as a selector), chemically bonded type CSP having a phenolic OH group on a crown ring was ...
Gioia M G - - 2006
The use of 2,7-dimethyl-3,8-dinitrodipyrazolo[1,5-a:1',5'-d]pyrazine-4,9-dione as pre-column reagent for LC analysis of amino acids is proposed. The compound reacts (30 min at 68 degrees C in presence of 0.04 M triethylamine in a dimethylsulfoxide-water mixture) with primary and secondary amino function and the stable resulting adducts can be chromatographed under reversed-phase ...
Gao Rong - - 2007
A novel HPLC-UV method was developed for the simultaneous determination of two major active components in Yinhuang injection, chlorogenic acid and baicalin, in rat plasma. Extracted from the plasma samples with methanol-acetonitrile (3:1, v/v), the two compounds were successfully separated using a C18 column with a gradient elution composed of ...
Drandarov Konstantin - - 2006
The first purely chemical method for automated no-carrier-added synthesis of [1-(11)C]-labeled d(R)- and l(S)-2-hydroxypropanoic acid (lactic acid) was developed for experimental neurophysiology studies and position emission tomography (PET) diagnosis. Starting from sodium 1-hydroxyethanesulfonate and [(11)C]HCN (trapped as [(11)C]KCN) the intermediate dl-(R,S)-[1-(11)C]-2-hydroxypropanenitrile was prepared. Its rapid acid hydrolysis gave dl-(R,S)-[1-(11)C]lactic acid, ...
Berkecz Róbert - - 2006
Direct reversed-phase high-performance liquid chromatographic methods were developed for the separation of enantiomers of 14 unnatural beta-amino acids, including several beta-3-homo-amino acids on a chiral stationary phase containing (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid bonded to 3-aminopropyl silica gel as chiral selector. The effects of the organic and the acidic modifiers and the mobile ...
Wójcik Lena - - 2006
Perfluorinated carboxylic acids (PFCAs) belong to anthropogenic fluoroorganic compounds that have been detected in the natural environment and living organisms including humans. A capillary zone electrophoretic method with indirect UV detection using 2,4-dinitrobenzoic acid (2,4-DNBA) as a chromophore probe has been developed for analysis of PFCAs (C6-C12) in water. Optimal ...
Wu Yu-Tse - - 2006
Salvianolic acid B is an herbal ingredient isolated from Salvia miltiorrhiza. The aim of this study was to apply an automated blood sampling system coupled to a simple liquid chromatographic system to determine the bioavailability of salvianolic acid B in stress-free rats. The plasma sample (25 microl) was vortex-mixed with ...
Yang Wen-Chu - - 2006
A new strategy for amino acid analysis is reported involving derivatization with an N-hydroxysuccinimide ester of N-alkylnicotinic acid (Cn-NA-NHS) followed by reversed-phase chromatography and electrospray ionization mass spectrometry (RPC-MS). Detection sensitivity increased as the N-alkyl chain length of the nicotinic acid derivatizing agent was increased from 1 to 4. N-Acylation ...
Liu Yueqi - - 2006
A novel chiral stationary phase based on chitosan covalently bonded onto silica gels has been prepared and used for the separation of various alpha-amino acid enantiomers as well as alpha-hydroxycarboxylic acid enantiomers by chiral ligand-exchange chromatography with copper(II) as a complexing ion. The methanol content and copper(II) ion concentration in ...
Carlavilla Davinia - - 2006
The formation of D-amino acids (D-aa's) in many fermented foods depends, among other factors, on the particular fermentation conditions, the action and autolysis of the microorganisms involved. In this sense, the analysis of chiral amino acids is an interesting analytical strategy for food scientists, since these compounds can be used ...
Tan Guanghui - - 2006
A chiral stationary phase (CSP 1) based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid was applied to the resolution of N-(substituted benzoyl)-alpha-amino acid amides and esters. N-(Substituted benzoyl)-alpha-amino acid amides were well resolved using a mixture of acetic acid-triethylamine-acetonitrile (0.01:0.05:100, v/v/v) as an optimum mobile phase while N-(substituted benzoyl)-alpha-amino acid esters were not resolved ...
Ilisz István - - 2006
The search for new and effective chiral selectors capable of separating a wide variety of enantiomeric compounds is an ongoing process. In the past decade, macrocyclic antibiotics have proved to be an exceptionally useful class of chiral selectors for the separation of enantiomers of biological and pharmacological importance by means ...
Kubán Pavel - - 2006
The application of gradient methods in HPLC determinations with capacitively coupled contactless conductivity detection was successfully demonstrated for non-UV-absorbing amino acids as well as for small peptides as analytes. The drift in baseline which is caused by the change in the conductivity of the mobile phase during the elution could ...
Román-Leshkov Yuriy - - 2006
Furan derivatives obtained from renewable biomass resources have the potential to serve as substitutes for the petroleum-based building blocks that are currently used in the production of plastics and fine chemicals. We developed a process for the selective dehydration of fructose to 5-hydroxymethylfurfural (HMF) that operates at high fructose concentrations ...
Arribas Alberto Sánchez - - 2006
In this work we report on the successful use of a composite prepared by dispersion of multi-wall carbon nanotubes (1-5 microm length, 20-50 nm diameter) and copper microparticles within mineral oil as detector for amino acids quantification in flow injection analysis and capillary electrophoresis. The resulting electrode displays a highly ...
Xiong Xin - - 2007
A tert-butyl carbamoylated quinine-based chiral stationary phase (CSP) for direct enantiomer separation of various natural and unnatural amino acid derivatives was studied. The influence of functional groups in the amino acid side chains upon the enantioseparation is discussed with the aim of realizing contributions to their overall chiral recognition. The ...
Lin Chen-Hsing - - 2006
The separation and retention behavior of five aromatic carboxylic acid isomers was investigated by means of high-performance liquid chromatography (HPLC) using a beta-cyclodextrin bonded phase with s-triazine ring in the spacer. The influence of mobile phase pH on the retention was examined. The presence of s-triazine moiety in the spacer ...
Kakiyama Genta - - 2006
A direct method for the separation and quantification of a series of bile acid acyl glycosides using high-performance liquid chromatography coupled to an evaporative light scattering detector (HPLC-ELSD) is described. Complete separation of each of 15 bile acid acyl 24-alpha-glucosides and their 24-beta-anomers and 24-beta-galactosides was achieved by the stepwise ...
Hvattum Erlend - - 2006
Sonazoid is a new contrast agent for ultrasound imaging. The product is an aqueous suspension of perfluorobutane microbubbles coated with phospholipids obtained from hydrogenated egg phosphatidylserine (H-EPS). A normal-phase high-performance liquid chromatographic (HPLC) method with evaporative light scattering detection was developed for quantification of free fatty acids, phosphatidylserine and phosphatidic ...
Dube Simiso - - 2006
An MEKC method was developed for the separation and characterization of phenyl-isothiocyanate (PITC)-labeled amino acids derived from Gonometa rufobrunnae silkworm after microdialysis sample cleanup. The influence of the buffer and SDS concentration on the resolution of the amino acids was investigated. A buffer system consisting of 25 mM phosphate, 10 ...
Gotti Roberto - - 2006
Phanquinone (chemically: 4,7-phenanthroline-5,6-dione) was applied as an original precolumn derivatization reagent for amino acids followed by separation using MEKC with UV detection (240 nm). The derivatization reaction was carried out at 68 degrees C in the presence of aqueous phosphate buffer (pH 8.0) and it was found to be complete ...
Fu Guo-Ni - - 2006
A fast, convenient and sensitive method of capillary zone electrophoresis (CZE) and indirect UV detection was proposed for the determination of 16 amino acids. p-Aminobenzoic acid (PAB) was selected as a background electrolyte (BGE). An isolated cell included a BGE buffer part and an electrode buffer one, which were jointed ...
Ho Yu-Hsiang - - 2006
The MEKC method is described for the quantitative analysis of 17 amino acids (AA) in pharmaceutical products. The method is based on simply derivatizing the AA with (2-naphthoxy)acetyl chloride under mild conditions. The resulting derivatives were separated by MEKC with borate buffer (35 mM; pH 9.50) including 150 mM SDS ...
de Nogales Vasco - - 2006
The acidic dissociation constants of several hydrophobic drugs, amiodarone and a series of antidepressants that show a secondary or tertiary amino group, were determined in a 50% methanol/water mixture by capillary zone electrophoresis. The electrophoretic behavior of buffers prepared from sodium acetate, tris(hydroxymethyl) aminomethane hydrochloride, sodium hydrogenphosphate, ammonium chloride, ethanolamine, ...
Carrasco-Pancorbo Alegría - - 2007
Two different families of compounds, i.e., phenolic and amino acids have been separated by capillary electrophoresis using a physically adsorbed polymer as capillary coating. The polymer used was N,N-dimethylacrylamide-ethylpyrrolidine methacrylate (DMA-EpyM) and it provided an stable coating by only flushing the capillary with a DMA-EpyM aqueous solution for 2min between ...
Tsukagoshi Kazuhiko - - 2006
Molecular recognition of mono- and disaccharides was performed making use of the interaction between their diol groups and p-iodophenylboronic acid in capillary electrophoresis (CE) with a chemiluminescence (CL) detection system. p-Iodophenylboronic acid acted as an enhancer for luminol-horseradish peroxidase-hydrogen peroxide CL reaction. p-Iodophenylboronic acid was injected as a sample into ...
Ptolemy Adam S - - 2006
Capillary electrophoresis (CE) represents a versatile platform for integrating sample pretreatment with chemical analysis because of its ability to tune analyte electromigration and band dispersion properties in discontinuous electrolyte systems. In this article, a single-step method that combines on-line sample preconcentration with in-capillary chemical derivatization is developed for rapid, sensitive, ...
Chou Wa Lok Jacky - - 2006
Acoustic wave detection of various underivatized amino acids that were hydrodynamically introduced into and electrokinetically migrated along a capillary tube has been achieved. The detection principle is based on the measurement of the ultrasonic absorption and density change of the aqueous amino acid samples as they pass by the detection ...
Qu Qishu - - 2006
A new ultraviolet (UV) labeling reagent, p-acetamidobenzenesulfonyl fluoride (PAABS-F), was designed and synthesized to label and determine the amino acids by capillary electrophoresis (CE) with diode-array detector (DAD). PAABS-F is very stable and easy to synthesize. It reacted with primary or secondary amino acids very quickly under facile conditions to ...
Sázelová Petra - - 2006
Capillary zone electrophoresis (CZE) and capillary isotachophoresis (CITP) were applied for the determination of peptide purity degree and counter-ion content in lecirelin, the synthetic analogue of luteinizing hormone-releasing hormone (LHRH). CZE analyses were carried out in acidic background electrolyte (100 mM H3PO4, 50 mM Tris, pH 2.25) in bare fused ...
Zampolli M - - 2006
The target of the in-situ research of optical activity in extraterrestrial samples stimulated an extended investigation of a GC-MS method based on the derivatization of amino acids by using a mixture of perfluorinated alcohols and perfluorinated anhydrides. Amino acids are converted to their N(O,S)-perfluoroacyl perfluoroalkyl esters in a single-step procedure, ...
Hu Zhen - - 2006
A micellar electrokinetic capillary electrophoresis (MEKCE) method for the determination of cholic acid (CA), hyodeoxycholic acid (HDCA) and chenodeoxycholic acid (CDCA) in artificial Calculus Bovis and its four medicinal preparations is described. The buffer solution consisted of 40 mM disodic phosphate and 40 mM sodium dodecylsulfate (SDS) adjusted to pH ...
Lian Hongzhen - - 2007
The chromatographic fingerprints of industrial o-toluic acid, m-toluic acid and p-toluic acid have been established by HPLC-UV detection according to their impurity groups. HPLC separation of all relative substances involved in the groups was developed on a Kromasil C(18) column by using methanol-water-NH(4)Ac-HAc buffer (100mM, pH 4.70) 15/65/20 (v/v/v) as ...
Tamaya Kaori - - 2006
In single-column anion-exchange chromatography, the retention volume of some monovalent inorganic anions (Cl(-), Br(-), NO(3)(-), NCS(-) and NO(2)(-)) were observed as a function of the pH of a mobile phase at a fixed concentration of 2-phenylmalonic acid or 1,4-benzenediacetic acid used as an eluent. The experimental retention volume of such ...
Karasová Gabriela - - 2006
Five end-capped octadecyl RP stationary phases, among which one was a polar embedded stationary phase, were tested for the analysis of benzoic acid derivatives using two mobile phases with or without addition of formic acid (water pH was measured by a common approach; pH of water with addition of formic ...
Xiao Jian Bo - - 2006
A rapid revised phase high-performance liquid chromatographic (RP-HPLC) method for the determination of six organic acids in Bayer liquors is reported. Oxalic, tartaric, acetic, succinic, glutaric and butene dicarboxylic acid were separated and quantified in 10 min. First time repeatability, reproducibility and recoveries were determined out for these acids in ...
Chang Po-Ling - - 2006
This paper describes the in-column derivatization, stacking, and separation of amino acids by CE in conjunction with light-emitting diode-induced fluorescence using naphthalene-2,3-dicarboxaldehyde (NDA). According to the relative electrophoretic mobilities and the migration direction in tetraborate solution (pH 9.3), the injection order is cyanide, then amino acids, then NDA. Once poly(ethylene ...
Barrado E - - 2006
A new chromatographic modality that does not require high pressures and also allows renewal of the stationary phase as desired is reported. The technique is based on a thin layer paramagnetic stationary phase (Fe3O4-SiO2) retained on the inner wall of a minicolumn through the action of an external magnetic field, ...
Bernabé-Zafón Virginia - - 2006
The oligomers of fatty alcohol ethoxylates (FAEs) exhibit large sensitivity differences in mass spectrometry with electrospray ionisation (ESI-MS) and atmospheric pressure chemical ionization (APCI). Standards of the oligomers from m=1 to 7 ethylene oxide units (EOs) and linear alkyl chains from n=10 to 18 carbon atoms were infused to examine ...
Li Jianguo - - 2006
A novel method for highly sensitive detection of primary and secondary amino acids with selective derivatization using acetaldehyde as a new derivatization reagent was proposed by capillary electrophoresis (CE) coupled with electrogenerated chemiluminescence (ECL) of tris(2,2'-bipyridine)ruthenium(II). The precolumn derivatization of these amino acids with acetaldehyde was performed in aqueous solution ...
Zhi Wenbo - - 2006
Establishment of hydrophilic organic/salt-containing aqueous two-phase system and purification of salvianolic acid B from crude extract of S. miltiorrhiza by counter-current chromatography with said system were studied. Ethanol and n-propanol were selected to constitute biphasic systems with ammonia sulphate, sodium chloride and phosphate separately, and related system characteristics including phase ...
Forlay-Frick Peter - - 2006
Three new tetraoxa-diaza derivatives of 1,4,10,13-tetraoxa-7,16-diazacyclo-octadecane (R-1, R-2 and R-3) and three commercially available crown ethers, 18-crown-6 (18C6), (+)-18-crown-6-tetracarboxilic acid (18C6H4) and 1,4,10,13-tetraoxa-7,16-diazacyclo-octadecane, were investigated to separate the positional isomers of aminophenol, aminobenzoic acid and aminocresol. The running electrolyte, in which the crown ethers were dissolved, was a 50 mM ...
Tsukamoto Yuhki - - 2006
The isotope-labeled benzofurazan derivatization reagent for carboxylic acids, 7-(N,N-dimethylaminosulfonyl)-4-(aminoethyl)piperazino-2,1,3-benzoxadiazole (d6) [DBD-PZ-NH2 (D)] was synthesized. DBD-PZ-NH2 (D) was used for the accurate quantification of fatty acids by liquid chromatography/mass spectrometry (LC/MS). The standard fatty acids were derivatized with DBD-PZ-NH2 (D) to the stable isotope-labeled compounds for the fatty acids derivatives of ...
Hyun Myung Ho - - 2006
Preparation of liquid chromatographic chiral stationary phases (CSPs) based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid and their application are reviewed. The various methods of connecting (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid to silica gel covalently or dynamically are demonstrated. The CSPs based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid have been very successful for the resolution of various primary amino compounds ...
Zusková Iva - - 2006
The dependence of the effective electrophoretic mobility on pH of the background electrolyte was experimentally determined by capillary zone electrophoresis (CZE) for cationic forms of amino acids. The pH of the background electrolytes was in the highly acidic range, 1.6-2.6 pH units, to ensure a high degree of protonation of ...
Mori Masanobu - - 2006
Influence of acidic eluent on retention behaviors of common anions and cations by ion-exclusion/cation-exchange chromatography (ion-exclusion/CEC) were investigated on a weakly acidic cation-exchange resin in the H(+)-form with conductivity. Sensitivities of analyte ions, especially weak acid anions (F(-) and HCOO(-)), were affected with degree of background conductivity level with pK(a1) ...
Liang Lina - - 2006
Speciation analysis of selenomethylcysteine (SeMeCys), selenomethionine (SeMet) and selenocystine (SeCys) has been performed using a direct amino acid analysis method with high-performance anion-exchange chromatography (HPAEC) coupled with integrated pulsed amperometric detection (IPAD). Three selenoamino acids could be baseline-separated from 19 amino acids using gradient elution conditions for amino acids and ...
Cesla Petr - - 2006
A possibility of using capillary electrophoresis for separation of anacardic acids (6-alkylsalicylic acids) has been studied. Conventional micellar electrokinetic chromatography (MEKC) in non-coated fused silica capillaries and reversed-flow micellar electrokinetic chromatography (RF-MEKC) in capillaries coated with polydimethylacrylamide was applied for separation of anacardic acids extracted from cashew nuts. Influence of ...
Murkovic Michael - - 2006
The analysis of carbohydrates and amino acids in green coffee is of the utmost importance since these two classes of compounds act as precursors of the Maillard reaction during which the colour and aroma are formed. During the course of the Maillard reaction potentially harmful substances like acrylamide or 5-hydroxymethyl-furfural ...
Mori Masanobu - - 2006
Ion-exclusion/adsorption chromatography of dimethylsulfoxide (DMSO) and its derivatives, i.e., methanesulfinic acid (MSI), methanesulfonic acid (MSA) and sulfuric acid (SA), was developed in order to clear the decomposition mechanism of DMSO on quality-test of TiO(2)-photocatalyst in water. The separation was achieved by the adsorption effect for DMSO and ion-exclusion effect for ...
< 6 7 8 9 10 11 12 13 14 15 16 >