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mM SDS (mm + sd)
Selected AbstractsSimultaneous determination of nine endogenous steroids in human urine by polymeric-mixed micelle capillary electrophoresisELECTROPHORESIS, Issue 19 2010Sabrina Flor Abstract A new CE system based on the use of polymeric-mixed micelles (cholic acid, SDS and the poloxamine Tetronic® 1107) was developed for the simultaneous determination of nine steroids in human urine. This method allows the baseline separation and quantitation of cortisol, androstenedione, estriol, dehydroepiandrosterone sulfate, testosterone, dehydroepiandrosterone, estrone, progesterone and estradiol in less than 25,min showing to be sensitive enough to detect low concentrations of these steroids in urine samples (5,45,ng/mL). The optimized electrophoretic conditions were performed using a 50,cm×75,,m capillary, 18,kV, 25°C, with 44,mM cholic acid, 10,mM SDS, 0.05%,w/v tetronic® 1107, 2.5%,v/v methanol, 2.5%,v/v tetrahydrofuran in 5,mM borate , 5,mM phosphate buffer (pH=8.0) as a background electrolyte and a dual 210/254 UV-detection. The method can simultaneously determine 0.1,120,,g/mL, which corresponds to 5,6000,ng/mL of steroids in 2,mL urine. The recoveries ranged between 82.4 and 101.5%. Due to its simplicity, speed, accuracy and reliability, the proposed method could be a potential alternative to the traditional methodologies used with clinical purposes. [source] SPE and large-volume sample stacking in MEKC for determination of doxycycline in biological fluids: Comparison of direct injection to SPE-MEKCELECTROPHORESIS, Issue 21 2008Rade Injac Abstract A novel and simple method has been developed for the determination of doxycycline (DOX) in biological fluids. The method is based on SPE, large-volume sample stacking (LVSS) and MEKC with UV-DAD detection. Six SPE cartridges have been used in investigation for sample clean up and pre-concentration (Supelco® LC-8, LC-18, LC-SCX, and LC-WCX, as well as StrataÔ-X and X-C). DOX was determined on a 56,cm (effective length 50,cm)×50,,m id fused-silica capillary. The BGE was 20,mM borate buffer, pH 9.3, containing 80,mM SDS and 7.5%,v/v of methanol (30,s×50,mbar), and the temperature and voltage were 25°C and 30,kV, respectively. The analytical wavelength was set at 210,nm. Under optimized conditions it is possible to determine DOX in human serum, urine, semen, tears and saliva with recovery of 97.5% (RSD 2.5%). The method was shown to be sensitive (LOD is 1,,g/L) and precise (intra-day RSD 0.2 and 2.4%; inter-days 0.4 and 3.5% for migration time and peak area, respectively). Results for developed SPE-LVSS-MEKC were compared with LVSS-MEKC method with direct sample injection. The new LVSS-MEKC method is presented as a useful technique for rapid determination without extraction procedure of DOX in human urine and serum, using 80,mM of SDS, 10%,v/v of methanol and 40,mM borate buffer (pH 9.3; 30,s×50,mbar; 25°C; 30,kV; 350,nm), but not for the other biological fluids, according to lower sensitivity of the method and because of the sample composition. [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] Determination of biogenic amines in HeLa cell lysate by 6-oxy-(N -succinimidyl acetate)-9-(2',methoxycarbonyl) fluorescein and micellar electrokinetic capillary chromatography with laser-induced fluorescence detectionELECTROPHORESIS, Issue 4 2006Liwei Cao Abstract An MEKC-LIF method using 6-oxy-(N -succinimidyl acetate)-9-(2'-methoxy-carbonyl) fluorescein (SAMF) newly synthesized in our lab as a labeling reagent for the separation and determination of eight typical biogenic amines was proposed. After careful study of the derivatization condition such as pH value, reagent concentration, temperature, and reaction time, derivatization reaction was accomplished as quickly as 10,min with stable yield. Optimal separation of SAMF-labeled amines was achieved with a running buffer (pH,9.3) containing 30,mM boric acid, 25,mM SDS, and 20%,v/v ACN. The proposed method allowed biogenic amines to be determined with LODs as low as 0.25,2.5,nmol/L and RSD values from 0.4 to 4.5%. The present method has been successfully used to monitor biogenic amines in HeLa cells and fish samples. This study exploits the potential of MEKC-LIF with SAMF labeling as a tool for monitoring biogenic amines involved in complex physiological and behavioral processes in various matrices. [source] Analytical potential of 6-oxy-(N -succinimidyl acetate)-9-(2'-methoxycarbonyl) fluorescein for the determination of amino compounds by capillary electrophoresis with laser-induced fluorescence detectionELECTROPHORESIS, Issue 10 2005Liwei Cao Abstract The analytical potential of a fluorescein analogue, 6-oxy-(N -succinimidyl acetate)-9-(2'-methoxycarbonyl) fluorescein (SAMF), for the first time synthesized in our laboratory, as a labeling reagent for the labeling and determination of amino compounds by capillary electrophoresis (CE) with laser-induced fluorescence (LIF) detection was investigated. Biogenic monoamines and amino acids were chosen as model analytes to evaluate the analytical possibilities of this approach. The derivatization conditions and separation parameters for the biogenic amines were optimized in detail. The derivatization was performed at 30°C for 6 min in boric acid buffer (pH 8.0). The derivatives were baseline-separated in 15 min with 25 mM boric acid running buffer (pH 9.0), containing 24 mM SDS and 12.5% v/v acetonitrile. The concentration detection limit for biogenic amines reaches 8×10,11 mol·L,1 (signal-to-noise ratio = 3). The application of CE in the analysis of the SAMF-derivatized amino acids was also exploited. The optimal running buffer for amino acids suggested that weak acidic background electrolyte offered better separation than the basic one. The proposed method was applied to the determination of biogenic amines in three different beer samples with satisfying recoveries varying from 92.8% to 104.8%. Finally, comparison of several fluorescein-based probes for amino compounds was discussed. With good labeling reaction, excellent photostability, pH-independent fluorescence (pH 4,9), and the resultant widely suited running buffer pH, SAMF has a great prospect in the determination of amino compounds in CE. [source] Analysis of lamotrigine and its metabolites in human plasma and urine by micellar electrokinetic capillary chromatographyELECTROPHORESIS, Issue 4-5 2005Vincenzo Pucci Abstract A reliable micellar electrokinetic capillary chromatographic method was developed and validated for the determination of lamotrigine and its metabolites in human plasma and urine. The variation of different parameters, such as pH of the background electrolyte (BGE) and Sodium dodecyl sulfate (SDS) concentration, were evaluated in order to find optimal conditions. Best separation of the analytes was achieved using a BGE composed of 10 mM borate and 50 mM SDS, pH 9.5; melatonin was selected as the internal standard. Isolation of lamotrigine and its metabolites from plasma and urine was accomplished with an original solid-phase extraction procedure using hydrophilic-lypophilic balance cartridges. Good absolute recovery data and satisfactory precision values were obtained. The calibration plots for lamotrigine and its metabolites were linear over the 1,20 ,g/mL concentration range. Sensitivity was satisfactory; the limits of detection and quantitation of lamotrigine were 500 ng/mL and 1 ,g/mL, respectively. The application of the method to real plasma samples from epileptic patients under therapy with lamotrigine gave good results in terms of accuracy and selectivity, and in agreement with those obtained with an high-performance liquid chromatography (HPLC) method.* [source] Determination of the chiral and achiral related substances of methotrexate by cyclodextrin-modified micellar electrokinetic chromatographyELECTROPHORESIS, Issue 16 2004Roberto Gotti Abstract A cyclodextrin-modified micellar electrokinetic chromatographic (CD-MEKC) method for the determination of the most important potential impurities of methotrexate (MTX): 2,4-diamino-6-(hydroxymethyl)pteridine, aminopterine hydrate, 4-[N -(2-amino-4-hydroxy-6-pteridinylmethyl)- N -methylamino] benzoic acid, 4-[N -(2,4-diamino-6-pteridinylmethyl)- N -methylamino] benzoic acid, and the distomer D -MTX is presented. The MEKC separation of these compounds was optimized by applying a step-by-step approach. The addition of ,-CD to a conventional MEKC system, based on sodium dodecyl sulfate (SDS) as surfactant, showed to be essential for the enantioresolution of racemic MTX as well as for the separation of the achiral impurities. To achieve high-resolution factor between the peaks adjacent to the main component (L -MTX), as required in the analysis of related impurities, the separation conditions were stressed; in particular, the addition of methanol to the CD-MEKC system resulted in a very effective choice. Under the optimized final conditions (100 mM SDS and 45 mM ,-CD in a mixture of 50 mM borate buffer, pH 9.30-methanol (75:25 v/v)), the method was validated showing a general adequate accuracy (93,106% recovery) in the determination of L -MTX related substances at the impurity level of 0.12% w/w with a relative standard deviation (RSD)% lower than 8% (n = 4). The method was successfully applied to the analysis of pharmaceuticals (tablets and injections) which showed to contain the distomer D -MTX as major impurity and aminopterine hydrate as a further related substance in the commercial tablets. [source] Micellar and aqueous-organic liquid chromatography using sub-2,,m packings for fast separation of natural phenolic compoundsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 13 2010Jun Cao Abstract The objective of the present work was to investigate the chromatographic behavior of natural phenolic compounds in micellar and aqueous-organic LC using a short column packed with 1.8,,m particles. Firstly, the effect of ACN and SDS on elution strength and selectivity was examined by isocratic submicellar (0,30% ACN/5% 1-butanol/1,6,mM SDS) and micellar (0,30% ACN/5% 1-butanol/40,60,mM SDS) systems. The varied concentrations of two modifiers in the mobile phases revealed different eluting power. Then, the application of organic modifier gradient was discussed in both submicellar and micellar LC using mobile phases of 4,mM SDS/5% 1-butanol or 50,mM SDS/5% 1-butanol containing ACN gradient from 0 to 30%, respectively. For micellar system, the separation was found to be better in gradient than isocratic elution. Additionally, the sensitivity of aqueous-organic LC was examined. The mobile phase was a mixture of ACN and water employing gradient elution at a flow rate of 0.5,mL/min, with analysis time below 9,min. It was found that separation efficiency was significantly better compared with micellar LC. Besides, the aqueous-organic LC has been applied to separation of various phenolic compounds in Yangwei granule or Radix Astragali samples. [source] Determination of montelukast sodium by capillary electrophoresisJOURNAL OF SEPARATION SCIENCE, JSS, Issue 6-7 2008Yuliya Shakalisava Abstract This work verifies the potential of CE in the analysis of significant impurities of montelukast sodium , an active ingredient for the treatment of bronchial asthma. Using 20 mM borate buffer pH 9.2 with 10 mM SDS and 10 mM (2-hydroxypropyl)-,-CD (2HP-,-CD) it was possible to separate montelukast and several impurities, including its cis -isomer, after exposure to light and oxygen. The obtained method surpasses a chromatographic method for montelukast sodium in terms of time of analysis (9 min of CE analysis vs. 35 min HPLC) and efficiency (CE offered over 900 000 theoretical plates for montelukast). Good repeatability of the method was supported by the low % RSD for the migration time of montelukast (0.53%). For the first time, the capillary electrophoretic method was employed for temporal study of the degradation of montelukast. The results showed that degradation of montelukast and the formation of the cis -isomer mainly occurred during the first 2 days of exposure, and occurred to a higher degree when there was no contact with the air (oxygen) in the exposed sample. [source] Comparison of two capillary electrophoresis online stacking modes by analysis of polycyclic aromatic hydrocarbons in airborne particulatesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 13 2006Guan-Qun Song Abstract Naphthalene, fluorene, pyrene, anthracene, phenanthrene, and chrysene were successfully separated by CD-modified MEKC (CD-MEKC) using 20 mM borate (pH 9.0) containing 90 mM SDS and 75 mM ,-CD. Two online stacking methods, i. e., sweeping and field-enhanced sample injection (FESI), were explored to enhance the detection sensitivity. The influences of some crucial parameters in sweeping and FESI procedures were investigated. For FESI method, a plug of water and low-conductivity sample matrix was used to increase the stacking efficiency. Compared with the sweeping method, FESI can increase the sensitivity in the range of 10,20-fold. The proposed method was used for the analysis of polycyclic aromatic hydrocarbons in airborne particulates. [source] Micellar electrokinetic capillary chromatography determination of zinc bacitracin and nystatin in animal feedJOURNAL OF SEPARATION SCIENCE, JSS, Issue 9 2006Rade Injac Abstract An MEKC procedure was developed for the separation of zinc bacitracin (Zn-BC) and nystatin (NYS) in mixtures and in animal feedstuff. The running buffer was 15 mM borate/19 mM phosphate, pH 8.2, containing 20 mM SDS and 10% v/v methanol. Samples were run at 25°C, the applied voltage was 25 kV, and an additional pressure of 5 mbar was applied. Both analytes were detected by UV simultaneously at 215 nm, Zn-BC alone at 192 and 254 nm, and NYS alone at 305 nm. The method was shown to be specific, accurate (recoveries were 100.0 ± 0.6% and 100.1 ± 0.6% for Zn-BC and NYS, respectively), linear over the tested range (correlation coefficients 0.9991 and 0.9994), and precise (RSD below 1.3% for both analytes). The method was applied to determine Zn-BC and NYS as additives in animal feed. [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] Determination of the purity of ampicillin by micellar electrokinetic chromatography and reversed phase liquid chromatography on a monolithic silica columnJOURNAL OF SEPARATION SCIENCE, JSS, Issue 7-8 2004Milada Dole, alová Abstract A micellar electrokinetic chromatographic (MEKC) method and a fast reversed-phase liquid chromatographic one have been developed for determining the purity of ampicillin. MEKC separation of ampicillin and its related substances was performed with the use of an untreated fused-silica capillary and 40 mM phosphate-borate buffer, pH 7.5 containing 75 mM SDS. The HPLC method employed a monolithic silica C18 column and a mobile phase composed of phosphate buffer, pH 5.2 and ACN, the flow rate being 4.0 mL/min. Both methods were successfully validated. Linearity, relative response factors, limits of quantitation, intermediate precision, and accuracy were evaluated. The methods proved to be fast, reliable, and sufficiently sensitive and, accordingly, well-suited for control of purity of ampicillin substance, injections, and capsules. A combination of both methods can be very useful in the confirmation of impurity profiles. [source] Determination of diterpenoid triepoxides in Tripterygium wilfordii by micellar electrokinetic capillary chromatographyPHYTOCHEMICAL ANALYSIS, Issue 3 2003Xiurong Song Abstract A micellar electrokinetic capillary chromatographic (MEKC) method has been established for the identification and determination of diterpenoid triepoxides in the Chinese herb Tripterygium wilfordii Hook F. and its preparations. Studies of the influence of boric acid and borax buffer concentration and pH, and of sodium dodecylsulphate (SDS) concentration have been carried out, and the optimum separation for the triepoxides was achieved using 20,mM boric acid and 10,mM borax with 20,mM SDS as the running buffer. MEKC was found to exhibit good accuracy, precision and repeatability. The sensitivity of the assay was sufficient to monitor the three active components in T. wilfordii and its preparations. Copyright © 2003 John Wiley & Sons, Ltd. [source] Quantitation of oxcarbazepine and its metabolites in human plasma by micellar electrokinetic chromatographyBIOMEDICAL CHROMATOGRAPHY, Issue 4 2003Vincenzo Pucci Abstract A reliable micellar electrokinetic chromatographic method for the determination of oxcarbazepine and its two main metabolites, 10-hydroxycarbamazepine and 10,11- trans -dihydroxy-10,11-dihydroxycarbamazepine, in human plasma was developed. The separation and determination of the analytes was achieved using a system consisting of 60,mM SDS in phosphate buffer (30,mM, pH 8.0), to which 20% (v/v) methanol was added. Separation was carried out in an uncoated fused-silica capillary with a separation voltage of 25,kV and currents typically less than 40,µA. Spectrophotometric detection was at 205,nm. Isolation of oxcarbazepine and its metabolites from plasma was accomplished by a solid-phase extraction procedure. The mean extraction yield of the analytes from plasma was higher than 94%. The linear correlation coefficients were better than 0.994 for all analytes. The limit of detection was 0.05,µg/mL, the limit of quantitation 0.15,µg/mL. The repeatability for the spiked blank plasma samples was lower than 1.9% and the intermediate precision lower than 2.1%, both expressed as RSD%. The results obtained analysing real plasma samples from epileptic patients under therapy with Tolep® were satisfactory in terms of precision, accuracy and detectability. Copyright© 2003 John Wiley & Sons, Ltd. [source] | ||||||||||