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Short Analysis Times (short + analysis_time)
Selected AbstractsDetermination of oxalate in beer by zone electrophoresis on a chip with conductivity detectionJOURNAL OF SEPARATION SCIENCE, JSS, Issue 8 2003Marián Masár Abstract The use of a poly(methylmethacrylate) capillary electrophoresis chip, provided with a high sample load capacity separation system (a 8500 nL separation channel combined with a 500 nL sample injection channel) and a pair of on-chip conductivity detectors, for zone electrophoresis (ZE) determination of oxalate in beer was studied. Hydrodynamic and electroosmotic flows of the solution in the separation compartment of the chip were suppressed and electrophoresis was a dominant transport process in the separations performed on the chip. A low pH of the carrier electrolyte (3.8), implemented by aspartic acid and bis-tris propane, provided an adequate selectivity in the separation of oxalate from anionic beer constituents and, at the same time, also a sufficient sensitivity in its conductivity detection. Under our working conditions, this anion could be detected at a 0.5 ,mol/L concentration also in samples containing chloride (a major anionic constituent of beer) at a 1800 higher concentration. Such a favorable analyte/matrix concentration ratio made possible accurate and reproducible [typically, 2,5% relative standard deviation (RSD) values of the peak areas of the analyte in dependence on its concentration in the sample] determination of oxalate in 500 nL volumes of 20,50-fold diluted beer samples. Short analysis times (about 200 s), minimum sample preparation, and reproducible migration times of this analyte (0.5,1.0% RSD values) were characteristic for ZE on the chip. [source] Development of off-line and on-line capillary electrophoresis methods for the screening and characterization of adenosine kinase inhibitors and substratesELECTROPHORESIS, Issue 12 2006Jamshed Iqbal Abstract Fast and convenient CE assays were developed for the screening of adenosine kinase,(AK) inhibitors and substrates. In the first method, the enzymatic reaction was performed in a test tube and the samples were subsequently injected into the capillary by pressure and detected by their UV absorbance at 260,nm. An MEKC method using borate buffer (pH,9.5) containing 100,mM SDS (method,A) was suitable for separating alternative substrates (nucleosides). For the CE determination of AMP formed as a product of the AK reaction, a phosphate buffer (pH,7.5 or 8.5) was used and a constant current (95,,A) was applied (method,B). The methods employing a fused-silica capillary and normal polarity mode provided good resolution of substrates and products of the enzymatic reaction and a short analysis time of less than 10,min. To further optimize and miniaturize the AK assays, the enzymatic reaction was performed directly in the capillary, prior to separation and quantitation of the product employing electrophoretically mediated microanalysis (EMMA, method,C). After hydrodynamic injection of a plug of reaction buffer (20,mM Tris-HCl, 0.2,mM MgCl2, pH,7.4), followed by a plug containing the enzyme, and subsequent injection of a plug of reaction buffer containing 1,mM,ATP, 100,,M adenosine, and 20,,M,UMP as an internal standard,(I.S.), as well as various concentrations of an inhibitor, the reaction was initiated by the application of 5,kV separation voltage (negative polarity) for 0.20,min to let the plugs interpenetrate. The voltage was turned off for 5,min (zero-potential amplification) and again turned on at a constant current of ,60,,A to elute the products within 7,min. The method employing a polyacrylamide-coated capillary of 20,cm effective length and reverse polarity mode provided good resolution of substrates and products. Dose,response curves and calculated Ki values for standard antagonists obtained by CE were in excellent agreement with data obtained by the standard radioactive assay. [source] Poly(N -vinylimidazole)-grafted capillary for electrophoresis prepared by surface-initiated atom transfer radical polymerizationJOURNAL OF SEPARATION SCIENCE, JSS, Issue 17-18 2010Jing Li Abstract A CE method for poly(N -vinylimidazole) (PVI)-grafted capillaries by the surface-initiated atom transfer radical polymerization has been developed. The coating was prepared with N -vinylimidazole as the monomer, 2-bromo-2-methyl- N -[3-(triethoxysilyl) propyl] propanamide (BTPAm) as the initiator and CuCl/CuCl2/2,2,-bipyridine as the catalyst and ligand. The direction and magnitude of EOF in the PVI-grafted capillary were investigated in a pH range of 3.0,9.0. The results indicated that the EOF could be modulated by varying the pH value of the buffer and an anodic EOF was obtained at pH values below 6.5. A significant improvement in reproducibility and reduction of EOF appeared on the PVI-grafted capillary when compared with the uncoated capillary. Furthermore, the polymer coated capillaries were applied to the separations of the inorganic anions, organic acids and basic proteins and baseline separations were achieved with short analysis time and high reproducibility. [source] GC-FID/MS method for the impurity profiling of synthetic d-allethrinJOURNAL OF SEPARATION SCIENCE, JSS, Issue 1-2 2004Matteo Bragieri Abstract A GC/FID/MS method was developed for the identification and quantification of d-alle thrin (DA) and its major impurities in commercial samples. Optimisation of the experimental conditions was carried out considering such important requirements as resolution, reproducibility, detection limits of 0.1% (m/m) for the impurities, and short analysis time. Under the optimised final conditions the method was validated for specificity, precision (CV% = 0.133 at 2.10 mg/mL and CV% = 0.035 at 3.00 mg/mL), linearity (0,3.00 ,g injected), limits of detection (0.09 ng injected) and quantitation (0.28 ng injected), and robustness. The DA related impurities were identified by using a GC/MS method with ion trap mass detection and also by comparison with synthesised standards. The most abundant impurities were crysolactone, allethrolone, chrysanthemic acid, and chloro-derivatives of DA. [source] Chiral separation of the plant lignan matairesinol by capillary electrophoresis,ELECTROPHORESIS, Issue 17 2008Ulrike Müller Abstract Lignans are dimeric phenylpropanoid compounds in plants that enjoy increasing medicinal interest because of their phytoestrogen activity. Lignans are chiral compounds and for most natural occurring lignans, chirality is not known. Separation of racemic matairesinol by CE in a non-coated silica capillary with carboxymethyl-,-cyclodextrin as chiral selector in phosphate buffer was successful. Electrolyte and selector concentrations and pH were systematically optimized in order to obtain baseline separation and short analysis times. Matairesinol from safflower fruit was determined as (,)-enantiomer. Quantitation results for matairesinol with the optimized method after calibration with authentic lignan were very similar to those by HPLC. The limit of detection is 2,,g/mL sample by DAD detection. [source] Simultaneous determination of digoxin and digitoxin by micellar electrokinetic chromatography and application to drug formulationsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 18 2003Hsiu-Hui Tseng Abstract A simple micellar electrokinetic chromatographic method is described for simultaneous determination of digoxin and digitoxin. The simultaneous analysis of digoxin and digitoxin was performed in Tris buffer (10 mM; pH 9) with 90 mM sodium dodecyl sulfate and 10% isopropyl alcohol as an anionic surfactant and organic modifier. Under these conditions, good separation with high efficiency is achieved in short analysis times. Several parameters affecting the separation of the drugs were studied, including the pH and concentrations of the Tris buffer and sodium dodecyl sulfate. The linear range of the method for the determination of digoxin and digitoxin was over 0.01,0.3 mg/mL; the detection limit (signal to noise ratio = 3; injection 3.5 kPa 3 s) was 4 and 6 ,g/mL, respectively. Application of the proposed method to the determination of digoxin in commercial tablets and in injections proved to be feasible. [source] Highly automated and fast determination of raffinose family oligosaccharides in Lupinus seeds using pressurized liquid extraction and high-performance anion-exchange chromatography with pulsed amperometric detectionJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 11 2008David Bansleben Abstract BACKGROUND: Taking into account several requirements for the determination of raffinose family oligosaccharides (RFOs) from Lupinus seeds,e.g., conducting plant breeding projects or food product development,a reasonable combination of efficient automated sample preparation and reliable analysis need to be developed and validated. RESULTS: In this regard pressurized liquid extraction was applied to extract the RFOs from ground and defatted lupin flour. Compared to many other publications, no further pretreatment, such as protein precipitation, was necessary to obtain satisfactory results applying ion chromatography with pulsed amperometric detection. The oligosaccharide content for the examined Lupinus albus samples were in the range 5.19,9.25 g kg,1 and for Lupinus angustifolius RFOs 3.49,4.75 g kg,1. Stachyose has always been the main component followed by raffinose and verbascose. CONCLUSION: The developed sample preparation and analytical method is suited to quantify raffinose, stachyose, verbascose and the disaccharide sucrose and, owing to a high degree of automation for sample preparation and relatively short analysis times by pretty peak separation, particularly high sample numbers can be accomplished. Copyright © 2008 Society of Chemical Industry [source] Simultaneous determination of 1H,1H and 1H,13C residual dipolar couplings in a chiral liquid crystal solvent using a natural abundance HSQC experimentMAGNETIC RESONANCE IN CHEMISTRY, Issue 7 2005Vasilios M. Marathias Abstract A high-resolution, phase-sensitive, natural abundance F2 -coupled 1H,13C HSQC (F2HSQC) NMR experiment was developed to measure simultaneously both nDHH and 1DCH residual dipolar couplings (RDCs) of small molecules present in a chiral polypeptide liquid crystal solvent system composed of poly-,-benzyl- L -glutamate (PBLG) in CDCl3. Because this is an indirect-detection NMR experiment, the relatively small amount of sample (7.5 mg in this study) and short acquisition times (5 h) that are required make this HSQC experiment well suited for samples that are either limited in solubility or in quantity or require short analysis times. The F2HSQC experiment can be performed without any specialized equipment or sample modification and can enhance our ability to measure RDCs accurately and rapidly in polypeptide liquid crystal solvents. Copyright © 2005 John Wiley & Sons, Ltd. [source] | ||||||||||