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Results 251 - 300 of 2120
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Bannore Yogita C - - 2008
This study has shown for the first time the suitability of CE with a partially aqueous electrolyte system for the analysis of free fatty acids (FFAs) in small portions of single peanut seeds. The partially aqueous electrolyte system consisted of 40 mM Tris, 2.5 mM adenosine-5'-monophosphate (AMP) and 7 mM ...
Ren Sheng-fang - - 2008
RP-HPLC was applied to analyze active polypeptides in Arca subcrenata, and the optimal condition for separation was also set up: temperature: 30 degrees C; wavelength: 280 nm; flow rate: 1.0 ml/min; Solvent A consisted of 80% acetonitrile and 0.1% trifluoroacetic acid (TFA) and solvent B contained 0.1% TFA. In this ...
Lin Zian - - 2008
A pressurized CEC (pCEC) coupled with on-column chemiluminescence (CL) detection was developed for direct determination of amino acids, which was based on the principle of an enhanced effect of Cu(II)-amino acid complexes on the CL reaction between luminol and hydrogen peroxide in alkaline solution. The effects of some important factors ...
Pesek Joseph J - - 2008
A pentyl (C5) stationary phase is synthesized on a hydride surface using both 100 and 300 A silica particles. The aqueous normal phase properties of these new phases are evaluated using amino acids at high concentrations of ACN in the mobile phase containing 0.1% formic acid. The RP properties of ...
Nilsson Ulrika - - 2008
A new method, involving SPE and HPLC/UV diode-array detection (DAD), was developed for the quantification of colophonium components in different consumer products, such as cosmetics. Colophonium is a common cause of contact dermatitis since its components can oxidize into allergens on exposure to air. Three different resin acids were used ...
Yang Weichun W Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602, - - 2008
Developments in biology are increasing demands for rapid, inexpensive, and sensitive biomolecular analysis. In this study, polymer microdevices with monolithic columns and electrophoretic channels were used for biological separations. Glycidyl methacrylate-co-ethylene dimethacrylate monolithic columns were formed within poly(methyl methacrylate) microchannels by in situ photopolymerization. Flow experiments in these columns demonstrated ...
Pesek Joseph J - - 2008
A novel silica hydride-based stationary phase was used to evaluate the retention behavior in the aqueous normal-phase (ANP) mode of standards representing three classes of metabolites. The effects on retention behavior of amino acids, carbohydrates and small organic acids were examined by altering the column temperature, and by adding different ...
Wang Yi - - 2008
A novel chip-based flow injection analysis (FIA) system has been developed for automatic, rapid and selective determination of dopamine (DA) in the presence of ascorbic acid (AA). The system is composed of a polycarbonate (PC) microfluidic chip with an electrochemical detector (ED), a gravity pump, and an automatic sample loading ...
Denoroy Luc - - 2008
A new in-capillary derivatization method with naphtalene-2,3-dicarboxyaldehyde (NDA)/CN(-) has been developed for capillary electrophoresis with laser-induced fluorescence detection of brain microdialysate amino acids. Samples are sandwiched between two plugs of reagent mixture at the capillary inlet and subsequently separated. Highest derivatization yields are obtained by using a reagent to sample ...
Garscha Ulrike - - 2008
Hydroperoxides of 18:2n-6 and 20:4n-6 were obtained by autoxidation and photooxidation. The enantiomers were separated as free acids (Reprosil Chiral-NR column, eluted with hexane containing 1-1.2% alcoholic modifier) and analyzed by on line UV detection (234 nm) and liquid chromatography-MS/MS/MS of carboxylate anions (A(-)-->(A(-)-18)-->full scan) in an ion trap. The ...
Korös A - - 2008
A high-performance liquid chromatographic method (HPLC) with combined diode array and fluorescence detection of amino acids and amines in various cheese samples is described. The proposal is based on acidic deproteinization, derivatization and gradient optimization studies, resulting in the identification and quantification of 21 amino acids and 9 amines from ...
Fuguet Elisabet - - 2008
The performance of the most common and also some other less common CE buffers has been tested for the pKa determination of several types of compounds (pyridine, amines, and phenols). The selected buffers cover a pH ranging from 3.7 to 11.8. Whereas some buffers, like acetic acid/acetate, BisTrisH+/BisTris, TrisH+/Tris, CHES/CHES-, ...
Graça Gonçalo - - 2008
The metabolic profiling of human amniotic fluid (HAF) is of potential interest for the diagnosis of disorders in the mother or the fetus. In order to build a comprehensive metabolite database for HAF, hyphenated NMR has been used, for the first time, for systematic HAF profiling. Experiments were carried out ...
Kaspar Hannelore - - 2008
A gas chromatography-mass spectrometry (GC-MS) method was developed for the quantitative analysis of free amino acids as their propyl chloroformate derivatives in biological fluids. Derivatization with propyl chloroformate is carried out directly in the biological samples without prior protein precipitation or solid-phase extraction of the amino acids, thereby allowing automation ...
Kühn K-D - - 2008
The quality control of gentamicin in different antibiotic carriers, using MEKC as stability-indicating method is described. Baseline separations of gentamicin C1, C1a, C2, C2a and C2b and, furthermore the impurities and degradation products garamin (GARA), 2-deoxy-streptamine (DSA) and sisomicin (SISO) were achieved with a background electrolyte containing 20mM deoxycholic acid, ...
Yu Fang - - 2009
Thermal lensing (TL) permits ultra-sensitive measurements of optical absorption of analytes in very small liquid volumes. We report the construction and use of a TL detector based on pulsed ultraviolet (UV) laser excitation (266 nm). We applied this detector to quantitate amino acids using capillary electrophoresis (CE) as a means ...
Deng Li - - 2008
An HPLC-based method for separation of isomers of monoacylglycerols (MAGs) was established using an enantioselective column, Chiralcel OF. Three MAG isomers, i.e. sn-1-MAG, sn-2-MAG and sn-3-MAG, having the same acyl groups were baseline separated with resolution factor of more than 1.2 between adjacent peaks. In addition, mixtures of enantiomer pairs ...
Liu Kaiying - - 2008
A capillary array electrophoresis (CAE) with confocal rotary scanner for high-throughput carboxytetramethylrhodamine succinimidyl ester (TAMRA)-labeled amino acid (AA) analysis is presented. Performance of the CAE setup was evaluated with AA samples. Up to 128 capillaries could be detected in parallel. For the first time, the device was applied to separate ...
Bhushan Ravi - - 2008
Ten chiral dichloro- and monochloro-s-triazines were prepared by the nucleophilic displacement of chlorine atom(s) in s-triazine chloride and its 6-methoxy derivative with different amino acid amides. Dichloro-s-triazines (DCTs) were used as CDRs for derivatization of alpha-amino acids under basic conditions at room temperature (30 degrees C) while derivatization with monochloro-s-triazine ...
Ramautar Rawi - - 2008
A capillary electrophoresis-time of flight-mass spectrometry (CE-TOF-MS) method for the analysis of amino acids in human urine was developed. Capillaries noncovalently coated with a bilayer of Polybrene (PB) and poly(vinyl sulfonate) (PVS) provided a considerable EOF at low pH, thus facilitating the fast separation of amino acids using a BGE ...
Thiele Björn - - 2008
A method has been developed for quantification of 20 amino acids as well as 13 (15)N-labeled amino acids in barley plants. The amino acids were extracted from plant tissues using aqueous HCl-ethanol and directly analyzed without further purification. Analysis of the underivatized amino acids was performed by liquid chromatography (LC)-electrospray ...
Guillaume Yves-Claude - - 2008
In a previous paper [C. Andre, M. Thomassin, A. Umrayami, L. Ismaili, B. Refouvelet, Y.C. Guillaume, Talanta 71 (2007) 1817] a novel cyclic hexapeptide molecule dissolved in the mobile phase was evaluated as a chiral selector (CS) for the enantiomer separation of a series of dansyl amino and arylalkanoic acids ...
Dong Shuqing - - 2008
A carbon paste electrode modified with multiwall carbon nanotubes and copper(I) oxide (MWCNT-Cu(2)O CPME) was fabricated, and the electrochemical behaviors of 19 kinds of natural amino acids at this modified electrode were studied. The experimental results showed that the various kinds of amino acids without any derivatization displayed obvious oxidation ...
Gbabode Gabin - - 2008
The pentadecanoic acid-heptadecanoic acid (C(15)H(29)OOH-C(17)H(33)OOH) binary system is dealt with in this article. Combined thermal analysis and X-ray powder diffraction experiments are performed to characterize the polymorphism of the pure compounds and of their mixed samples. In particular, modern methods of crystal structure resolution from powder data (direct space methods) ...
Brunelli Claudio - - 2008
The separation of neutral, acidic, and basic pharmaceuticals with diverse physicochemical properties by packed column supercritical fluid chromatography (pSFC) on a 2-ethylpyridine column (25 cmx4.6 mm id, 3 mum particles) is presented. The optimization strategy involved separations at 100% methanol (MeOH) and at 50% MeOH/50% ACN while keeping the peak ...
Huang Yu-Fen - - 2008
This manuscript describes dynamic coating of capillaries with poly(L-lysine) (PLL) and silica nanoparticles (SiO2 NPs) and use of the as-prepared capillaries for the separation of biogenic amines and acids by CE in conjunction with LIF detection. The directions of EOF are controlled by varying the outmost layer of the capillaries ...
Takegawa Yasuhiro - - 2008
Capillary zwitterionic-type hydrophilic interaction chromatography (ZIC-HILIC)/ESI-MS has been applied to the Glu-C digest of recombinant human erythropoietin (rhEPO) expressed in Chinese hamster ovary (CHO) cells. N-Glycopeptides (105) and O-glycopeptides (8) were detected in a single run of the capillary ZIC-HILIC/ESI-MS analysis. Among them, N-acetyl-neuraminic acids (Neu5Ac) of N- and O-glycans ...
Simionato Ana V Colnaghi - - 2008
In this work, a CE equipment, online hyphenated to an IT MS analyzer by a linear sheath liquid interface promoting ESI, was used to develop a method for quantitative determination of amino acids. Under appropriate conditions (BGE composition, 0.8% HCOOH, 20% CH3OH; sheath liquid composition, 0.8% HCOOH, 60% methanol; V ...
Kazarian Artaches A - - 2008
This study explores the use of pH stacking in conjunction with 5-aminofluorescein as a derivatization agent for the sensitive analysis of simple sugars such as glucose, lactose and maltotriose by capillary electrophoresis (CE). The derivatization agent was selected on the basis of its extremely high molar absorptivity, its compatibility with ...
Hill Lauren A - - 2008
A sequential injection analysis procedure with dual-reagent chemiluminescence detection was applied to the screening of street drug seizure samples for the presence of heroin. The chemiluminescence reagents (acidic potassium permanganate and tris(2,2'-bipyridine)ruthenium(III)) were aspirated from either side of a sample aliquot that was sufficiently large to prevent interdispersion of the ...
Mohammad A - - 2008
A new method for separation of several amino acids using mobile phases (MPs) containing mixed micelles as well as 1-butanol and aprotic organic solvents as modifying additives has been developed. The effect of experimental factors (the ratio of MP components, nature of stationary phase) on separation of amino acids is ...
Choi Hee Jung - - 2008
Two chiral stationary phases (CSPs) based on optically active (3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6 covalently bonded to silica gel were utilized for the first time for the resolution of racemic beta-amino acids using high performance liquid chromatography. All of the 10 beta-amino acids tested were resolved on the CSP containing residual silanol-protecting n-octyl groups, ...
Castro-Puyana María - - 2008
CE with UV detection was used for the first time to determine the enantioselective adsorption of the short-chain tricarboxylic acid, 3-carboxy adipic acid, on minerals as a mean of investigating plausible mechanisms for the origin of biochemical homochirality on Earth. The use of vancomycine as chiral selector in the separation ...
Liu De-Ling - - 2008
The capability of detecting biomarkers, such as amino acids, in chemically complex field samples is essential to establishing the knowledge required to search for chemical signatures of life in future planetary explorations. However, due to the complexities of in situ investigations, it is important to establish a new analytical scheme ...
Du Xiao-Lan - - 2008
A novel fluorescent derivatization reagent for carboxylic acids, 6-oxy-(acetyl ethylenediamine) fluorescein (AEF), was well designed, synthesized, and applied to HPLC. The derivatization reaction with 12 fatty acids, including n-valeric acid (C5), n-hexanoic acid (C6), n-heptanoic acid (C7), n-octanoic acid (C8), n-nonanoic acid (C9), n-decanoic acid (C10), lauric acid (C12), myristic ...
Poitevin Martine - - 2008
The use of quasi-isoelectric anolytes and catholytes has been investigated to improve CIEF performances. Narrow pH cuts of carrier ampholytes (NC) have been compared to more conventional couples of anolytes/catholytes (phosphoric acid/sodium hydroxide and glutamic acid/lysine). First, a CIEF setup that consists in a bare silica capillary and 70:30 water/glycerol ...
Liang Xingguo - - 2008
Two diastereomers were produced by the introduction of azobenzene-tethering prochiral linker (2,2-bis(hydroxymethyl)propionic acid) in the modified ODN, which had been used for the photoregulation of DNA functions. We found that this modified ODN with sequence 5'-...pNpXpN...-3' (p = phosphate; N = nucleoside; X = azobenzene residue) could be digested to ...
Shi Baoxian - - 2008
A rapid and sensitive method was developed for the analysis of amino acids by microchip electrophoresis with Hg-lamp excitation fluorescence detection. Fluorescein-isothiocyanate (FITC) was chosen to estimate the sensitivity of this system, and the detection limit (S/N = 3) with FITC was 1.7 nM, which showed that the system was ...
Preinerstorfer Beatrix - - 2008
Silica monoliths modified with trans-(1S,2S)-2-(N-4-allyloxy-3,5-dichlorobenzoyl)amino cyclohexanesulfonic acid were tested for enantioselective separations of various chiral bases by aqueous and nonaqueous CEC as well as nano-HPLC. The optimization of the immobilization procedure showed that an intermediate selector (SO) coverage, as does result from a single static immobilization cycle in the capillary ...
Poplewska Izabela - - 2008
The relationship between adsorption equilibria of two amino acids, i.e., l,d-threonine and l,d-methionine on the teicoplanin chiral selector and their phase behavior has been analyzed. The experimental and numerical methods have been proposed to determine activity coefficients of amino acids in different solvent systems. The procedure was based on the ...
Lee Su Jin - - 2008
Racemic vigabatrin, an anticonvulsant drug used for the treatment of epilepsy, and its analogue gamma-amino acids were resolved without derivatization on liquid chromatographic chiral stationary phases (CSPs) based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid. Between the two CSPs which contain 3 methylene-unit or 11 methylene-unit spacer group, the latter was found to be ...
Bhushan Ravi - - 2008
Five new chiral derivatizing reagents 5-hydrazino-2,4-dinitrophenyl-l-alaninamide (HDNP-l-Ala-NH2), 5-hydrazino-2,4-dinitrophenyl-l-phenylalaninamide (HDNP-l-Phe-NH2), 5-hydrazino-2,4-dinitrophenyl-l-valinamide (HDNP-l-Val-NH2), 5-hydrazino-2,4-dinitrophenyl-l-leucinamide (HDNP-l-Leu-NH2) and 5-hydrazino-2,4-dinitrophenyl-l-phenylglycinamide (HDNP-d-Phg-NH2) were synthesized by straightforward two-step synthesis starting from 1,5-difluoro-2,4-dinitrobenzene. Nucleophilic substitution of one fluorine atom in DFDNB with different amino acid amides yielded Marfey's reagent (5-fluoro-2,4-dinitrophenyl-l-alaninamide) and its structural variants (5-fluoro-2,4-dinitrophenyl-l-phenylalaninamide, 5-fluoro-2,4-dinitrophenyl-l-valinamide, 5-fluoro-2,4-dinitrophenyl-l-leucinamide and ...
Hyun Myung Ho - - 2008
A doubly tethered chiral stationary phase (CSP) prepared by bonding (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid to doubly tethered primary aminoalkyl silica gel was used for the resolution of various beta-amino acids. All the beta-amino acids tested were resolved quite well, the separation (alpha) and the resolution factors (RS) being in the ranges 1.34-2.09 ...
Wu Yue - - 2008
In order to accomplish the analysis of peptides and proteins by capillary electrophoresis, Lupamin, a high-molecular-weight linear polyvinylamine (PVAm) polymer, was introduced to modify the inner wall of fused-silica capillaries by physical absorption. Thanks to the high density of positively charged amino groups in Lupamin under acidic conditions, not only ...
Sardella Roccaldo - - 2008
A tert-butylcarbamoylquinine-based chiral stationary phase (Chiralpak QN-AX) has been employed for the enantiomer separation of underivatized chiral acidic amino acids, viz. 4-carboxyphenylalanine (4-CPHE), 1-aminoindan-1,5-dicarboxylic acid (AIDA), 2-(5-carboxy-3-methyl-2-thienyl)glycine (3-MATIDA), 2-(4-carboxy-5-methyl-2-thienyl)glycine (5-MATIDA), and 2-(2'-carboxy-3'-phenylcyclopropyl)glycine (PCCG). Some of the acidic amino acids have potential activity on the central nervous system and are thus ...
Akoto Lawrence - - 2008
Comprehensive two-dimensional gas chromatography (GC x GC) with time-of-flight mass spectrometry detection is used to profile the fatty acid composition of whole/intact aquatic microorganisms such as the common fresh water green algae Scenedesmus acutus and the filamentous cyanobacterium Limnothrix sp. strain MRI without any sample preparation steps. It is shown ...
Enayetul Babar Shiekh Md - - 2008
Reversible protein phosphorylation and dephosphorylation are very important activities in understanding cellular signaling networks. In this paper we described a CE-LIF-based assay method of calcineurin (CN), a protein phosphatase important in cardiac hypertrophy, in which a fluorescence-labeled 19-amino acid phosphopeptide was used as a substrate. The substrate was converted to ...
Jác Pavel - - 2008
A novel electrophoretic BGE containing tungstate as complex-forming reagent is suitable for the separation of polyphenols. Similar to molybdate-containing BGE reported earlier (cf. M. Polásek, et al.., Talanta 2006, 69, 192) addition of tungstate to BGE affects significantly migration of compounds/ligands with vicinal -OH groups due to the formation of ...
Yu Hui - - 2008
The resolution of five racemic alpha-lactams (1a-d,g) using HPLC is reported. Five different Pirkle-type stationary phases were tested. The enantiomers of alpha-lactams containing the trityl group (1a-d) were separated (selectivity factors ranging from 1.08 to 1.20) using a mobile phase of hexane/2-propanol:98/2 and a stationary phase consisting of the 3,5-dinitroaniline ...
Gong Xiao Yang - - 2008
The separation and detection of small oligopeptides in CE with contactless conductivity detection were demonstrated. A strongly acidic separation buffer (0.5 M acetic acid) was employed in order to render the species cationic. Separation of the stereoisomers was achieved in typically 10-15 min by using either dimethyl-beta-CD (DM-beta-CD), (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid ...
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