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Tetraborate Buffer (tetraborate + buffer)
Selected AbstractsInvestigation of the stereodynamics of tris-(, -diimine),transition metal complexes by enantioselective dynamic MEKCELECTROPHORESIS, Issue 2 2009Sabrina Bremer Abstract Enantiomerization of octahedral tris(, -diimine),transition metal complexes was investigated by enantioselective dynamic MEKC. Varying both the transition metal ion (Fe2+, Fe3+, and Ni2+) and the bidentate diimine ligand (1,10-phenanthroline and 2,2,-bipyridyl), the enantiomer separations were performed either in a 100,mM sodium tetraborate buffer (pH 9.3) or in a 100,mM sodium tetraborate/sodium dihydrogenphosphate buffer (pH 8.0) both containing sodium cholate as chiral surfactant. The unified equation of dynamic chromatography was employed to determine apparent reaction rate constants from the electropherograms showing distinct plateau formation. Apparent activation parameters ,H, and ,S, were calculated from temperature-dependent measurements between 10.0 and 35.0°C in 2.5,K steps. It was found that the nature of the central metal ion and the ligand strongly influence the enantiomerization barrier. Surprisingly, complexes containing the 2,2,-bipyridyl ligand show highly negative activation entropies between ,103 and ,116,J (K,mol),1 while the activation entropy of tris(1,10-phenanthroline) complexes is positive indicating a different mechanism of interconversion. Furthermore, it was found that the Ni2+ complexes are stereostable under the conditions investigated here making them a lucent target as enantioselective catalysts. [source] Determination of uranium, iron, copper, and nickel from ore samples by MEKC using N,N,-ethylene bis(salicylaldimine) as complexing reagentELECTROPHORESIS, Issue 3 2008Muhammed Aslam Mirza Abstract An analytical procedure has been developed for the separation of dioxouranium(VI), iron(III), copper(II), nickel(II), cobalt(II), cobalt(III), palladium(II), and thorium(IV) by MEKC using N,N,-ethylene bis(salicylaldimine) (H2SA2en) as a complexing reagent with total runtime <4.5,min. SDS was used as micellar medium at pH,8 with sodium tetraborate buffer (0.1,M). An uncoated fused-silica capillary with an effective length of 50,cm×75,,m id was used with an applied voltage of 30,kV with photodiode array detection at 231,nm. Linear calibrations were obtained within 0.111,1000,,g/mL of each element with LODs within 37,325,ng/mL. The developed method was tested for analysis of uranium ore samples indicating its presence within 103,1789,,g/g with RSD within 0.79,1.87%. Likewise copper, nickel, and iron in their combined matrix were also simultaneously determined with RSD 0.4,1.6% (n,=,6). [source] Enhanced separation of purine and pyrimidine bases using carboxylic multiwalled carbon nanotubes as additive in capillary zone electrophoresisELECTROPHORESIS, Issue 16 2006Xin Xiong Abstract This paper describes the enhanced separation of adenine (A), hypoxanthine (HX), 8-azaadenine (8-AA), thymine (T), cytosine (C), uracil (U) and guanine (G) by CZE dispersing carboxylic multiwalled carbon nanotubes (c-MWNTs) into the running buffer. The effect of important factors such as c-MWNT nanoparticle concentration, the acidity and concentration of running buffer, and separation voltage were investigated to acquire the optimum conditions. The seven purine and pyrimidine bases could be well separated within 16,min in a 35,cm effective length fused-silica capillary at a separation voltage of +8.0,kV in a 23,mM tetraborate buffer (pH,9.2) containing 8.0×10,5,g/mL c-MWNTs. Under the optimal conditions, the linear ranges were of 2,250,,g/mL for A (R2,=,0.995), 3,200,,g/mL for U (R2,=,0.990) and G (R2,=,0.992), 3,250,,g/mL for T (R2,=,0.998), 2,200,,g/mL for C (R2,=,0.985) and 4,200,,g/mL for HX (R2,=,0.988) and 8-AA (R2,=,0.990). The detection limits were 0.9,,g/mL for A (S/N,=,3), 2.4,,g/mL for U, 2.0,,g/mL for T, 1.5,,g/mL for C, 2.5,,g/mL for G and 3.0,,g/mL for HX and 8-AA. The proposed method was successfully applied for determining five purine and pyrimidine bases in yeast RNA. [source] Method development and validation for the analysis of didanosine using micellar electrokinetic capillary chromatographyELECTROPHORESIS, Issue 21 2005Swapna Mallampati Abstract A selective MEKC method was developed for the analysis of didanosine in bulk samples. Successful separation of didanosine from 13 of its potential impurities, derived from the various synthetic preparation procedures, was achieved. As CZE gave poor separation selectivity, MEKC was preferable. The use of EKC allowed achievement of the separation in a significantly shorter time than conventional HPLC. An anionic long-chain surfactant, lithium dodecyl sulfate (LiDS), was used as the pseudostationary phase and sodium tetraborate buffer as the aqueous phase. In order to obtain the optimal conditions and to test the method robustness, a central composite response surface modeling experiment was performed. The optimized electrophoretic conditions include the use of an uncoated fused-silica capillary with a total length of 40,cm and an ID of 50,,m, a BGE containing 40,mM sodium tetraborate and 110,mM LiDS at pH,8.0, an applied voltage of 18.0,kV, and the capillary temperature maintained at 15°C. The method was found to be robust. The parameters for validation such as linearity, precision, and sensitivity are also reported. Three commercial bulk samples were analyzed with this system. [source] Preliminary study on the monitoring of glutathione S-tranferase activity toward styrene oxide by electromigration methodsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 12 2005ková Abstract A new method has been developed for the monitoring of glutathione S-tranferase (GST) detoxification activity toward styrene oxide (SO). The enzymatic reaction was carried out directly in a thermostatted autosampler vial and the formation of conjugates between glutathione (GSH) and SO was monitored by sequential MEKC runs. The determinations were performed in a 50-,m fused silica capillary using 50 mM SDS in 20 mM phosphate 20 mM tetraborate buffer (pH 8.3) as a background electrolyte; separation voltage 28 kV (positive polarity), temperature of capillary 25°C, and detection at 200 nm. The method is rapid, amenable to automation, and requires only small amounts of samples, which is especially important in the case of GST isoenzyme analyses. [source] Separation of diastereomers of flavanone-7- O -glycosides by capillary electrophoresis using sulfobutyl ether-,-cyclodextrin as the selectorJOURNAL OF SEPARATION SCIENCE, JSS, Issue 9-10 2003Zeineb Aturki Abstract A method was developed for the separation of diastereomers of flavanone-7- O -glycosides by capillary electrophoresis using sulfobutyl ether-,-cyclodextrin (SBE-,-CD) in the background electrolyte. The effect of the concentration of the CD additive, buffer pH, and organic modifier on the migration times and resolution for five flavanone glycosides (naringin, hesperidin, neohesperidin, narirutin, and eriocitrin) was studied. Baseline separations of these compounds as pairs of diastereoisomers were achieved with 20 mM tetraborate buffer at pH 7 containing 5 mg/mL of SBE-,-CD and 10% (v/v) of methanol. The developed method was used for the qualitative analysis of the diastereomeric composition of the major flavanone glycosides in different citrus juices. The ability of SBE-,-CD to discriminate flavanone enantiomers was also investigated. [source] Quantitative separation of oxytocin, norfloxacin and diclofenac sodium in milk samples using capillary electrophoresisBIOMEDICAL CHROMATOGRAPHY, Issue 9 2009Amber R. Solangi Abstract A simple, sensitive and rapid method has been developed for simultaneous separation and quantification of three different drugs: oxytocin (OT), norfloxacin (NOR) and diclofenac (DIC) sodium in milk samples using capillary electrophoresis (CE) with UV detection at 220 nm. Factors affecting the separation were pH, concentration of buffer and applied voltage. Separation was obtained in less than 9 min with sodium tetraborate buffer of pH 10.0 and applied voltage 30 kV. The separation was carried out from uncoated fused silica capillary with effective length of 50 cm with 75 µm i.d. The carrier electrolyte gave reproducible separation with calibration plots linear over 0.15,4.0 µg/mL for OT, 5,1000 µg/mL for NOR and 3,125 µg/mL for DIC. The lower limits of detection (LOD) were found to be 50 ng/mL for OT, and 1 µg/mL for NOR and DIC. The method was validated for the analysis of drugs in milk samples and pharmaceutical preparations with recovery of drugs within the range 96,100% with RSD 0.9,2.8%. Copyright © 2009 John Wiley & Sons, Ltd. [source] | ||||||||||