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Injection Time (injection + time)
Selected AbstractsUse of chemometric methodology in optimizing conditions for competitive binding partial filling affinity capillary electrophoresisELECTROPHORESIS, Issue 16 2008Ruth E. Montes Abstract This work expands the knowledge of the use of chemometric response surface methodology (RSM) in optimizing conditions for competitive binding partial filling ACE (PFACE). Specifically, RSM in the form of a Box,Behnken design was implemented in flow-through PFACE (FTPFACE) to effectively predict the significance of injection time, voltage, and neutral ligand (neutral arylsulfonamide) concentration, [Lo], on protein,neutral ligand binding. Statistical analysis results were used to create a model for response surface prediction via contour and surface plots at a given maximum response (,RMTR) to reach a targeted Kb,=,2.50×106,M,1. The adequacy of the model was then validated by experimental runs at the optimal predicted solution (injection time,=,2.3,min, voltage,=,11.6,kV, [Lo],=,1.4,,M). The achieved results greatly extend the usefulness of chemometrics in ACE and provide a valuable statistical tool for the study of other receptor,ligand combinations. [source] Implementation of chemometric methodology in ACE: Predictive investigation of protein,ligand bindingELECTROPHORESIS, Issue 16 2007Grady Hanrahan Abstract An ACE predictive investigation of protein,ligand binding using a highly effective chemometric response surface design technique is presented. Here, Kd was estimated using one noninteracting standard which relates to changes in the electrophoretic mobility of carbonic anhydrase B (CAB, EC 4.2.1.1) on complexation with the ligand 4-carboxybenzenesulfonamide (CBSA) present in the electrophoresis buffer. Experimental factors including injection time, capillary length, and applied voltage were selected and tested at three levels in a Box,Behnken design. Statistical analysis results were used to create a mathematical model for response surface prediction via contour and surface plots at a given target response (Kd,=,1.19×10,6,M). As expected, there were a number of predicted solutions that reached our target response based on the significance of each factor at appropriate levels. The adequacy of the model was validated by experimental runs with the predicted model solution (capillary length,=,47,cm, voltage,=,11,kV, injection time,=,0.01,min) presented in detail as an example. [source] Study on the enhancement of Ru(bpy)32+ electrochemiluminescence by nanogold and its application for pentoxyverine detectionELECTROPHORESIS, Issue 23 2005Yingju Liu Abstract In this work, CE separation with end-column Ru(bpy)32+ ECL detection for the quantitative determination of pentoxyverine was firstly performed. The experimental conditions, such as the applied potential, injection voltage, injection time, and the pH of separation buffer, were discussed in detail. Gold nanoparticles were found to enhance the ECL intensity at an appropriate volume ratio of nanogold with Ru(bpy)32+ but without changing their nanoproperties proved by transmission electron microscopy (TEM) and UV-vis spectra. The detection limits with or without nanogold were 6,nM and 0.6,,M, respectively. Successful separation of pentoxyverine, chlorpheniramine, and lidocaine was achieved. This method was also applied to monitor drug binding with HSA, and the binding constant for pentoxyverine was estimated as 1.8×103/M. [source] Combination of cationic surfactant-assisted solid-phase extraction with field-amplified sample stacking for highly sensitive analysis of chlorinated acid herbicides by capillary zone electrophoresisELECTROPHORESIS, Issue 18 2005Yan Xu Abstract This report describes a novel online field-amplified sample stacking (FASS) procedure to analyze 16 chlorinated acid herbicides. By using a poly(vinyl alcohol) (PVA)-coated capillary to reduce electroosmotic flow and introducing a methanol,water plug before sample loading, the sample injection time could be very long without loss of sample and separation efficiency. Under the optimized condition, the FASS procedure could provide great sensitivity enhancement (5000,10,000-fold) and satisfactory reproducibility (relative standard deviations of migration times less than 2.4%, relative standard deviations of peak areas less than 8.0%). Combined with cationic surfactant-assisted solid-phase extraction (CSA-SPE), the limit of detection of the herbicides ranged from 0.269 to 20.3,ppt, which are two orders lower than those of the US Environmental Protection Agency standard method 515.1. The CSA-SPE-FASS-CE method was successfully applied to the analysis of local pond water. [source] Dynamic analyte introduction and focusing in plastic microfluidic devices for proteomic analysisELECTROPHORESIS, Issue 1-2 2003Yan Li Abstract Isoelectric focusing (IEF) separations, in general, involve the use of the entire channel filled with a solution mixture containing protein/peptide analytes and carrier ampholytes for the creation of a pH gradient. Thus, the preparative capabilities of IEF are inherently greater than most microfluidics-based electrokinetic separation techniques. To further increase sample loading and therefore the concentrations of focused analytes, a dynamic approach, which is based on electrokinetic injection of proteins/peptides from solution reservoirs, is demonstrated in this study. The proteins/peptides continuously migrate into the plastic microchannel and encounter a pH gradient established by carrier ampholytes originally present in the channel for focusing and separation. Dynamic sample introduction and analyte focusing in plastic microfluidic devices can be directly controlled by various electrokinetic conditions, including the injection time and the applied electric field strength. Differences in the sample loading are contributed by electrokinetic injection bias and are affected by the individual analyte's electrophoretic mobility. Under the influence of 30 min electrokinetic injection at constant electric field strength of 500 V/cm, the sample loading is enhanced by approximately 10,100 fold in comparison with conventional IEF. [source] Adversarial models for priority-based networks,NETWORKS: AN INTERNATIONAL JOURNAL, Issue 1 2005C. Ŕlvarez Abstract In this article, we propose several variations of the adversarial queueing model and address stability issues of networks and protocols in those proposed models. The first such variation is the priority model, which is directed at static network topologies and takes into account the case in which packets can have different priorities. Those priorities are assigned by an adversary at injection time. A second variation, the variable priority model, is an extension of the priority model in which the adversary may dynamically change the priority of packets at each time step. Two more variations, namely the failure model and the reliable model, are proposed to cope with dynamic networks. In the failure and reliable models the adversary controls, under different constraints, the failures that the links of the topology might suffer. Concerning stability of networks in the proposed adversarial models, we show that the set of universally stable networks in the adversarial model remains the same in the priority, variable priority, failure, and reliable models. From the point of view of protocols (or queueing policies), we show that several protocols that are universally stable in the adversarial queueing model remain so in the priority, failure, and reliable models. However, we show that the longest-in-system (LIS) protocol, which is universally stable in the adversarial queueing model, is not universally stable in any of the other models we propose. Moreover, we show that no queueing policy is universally stable in the variable priority model. Finally, we analyze the problem of deciding stability of a given network under a fixed protocol. We provide a characterization of the networks that are stable under first-in-first-out (FIFO) and LIS in the failure model (and therefore in the reliable and priority models). This characterization allows us to show that the stability problem under FIFO and LIS in the failure model can be solved in polynomial time. © 2004 Wiley Periodicals, Inc. NETWORKS, Vol. 45(1), 23,35 2005 [source] Potential determination of aminated pesticides and metabolites by cyclodextrin capillary electrophoresis,laser-induced fluorescence using FITC as labellingPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 2 2005Miguel Navarrete-Casas Abstract We describe a detailed study on the possibility of analyzing aminated pesticides and metabolites using pre-column derivatization with fluorescein isothiocyanate (FITC) and their subsequent separation and detection by cyclodextrin capillary electrophoresis,laser-induced fluorescence (CE-LIF) detection. Different variables affecting the derivatization reaction (pH, FITC concentration, reaction time and temperature) and those related with the separation itself (buffer concentration, addition of various organic modifiers, pH, applied voltage and injection time) were studied. The limit of detection obtained was between 0.45 and 3.48 µg litre,1 showing a relative standard deviation between 0.26 and 2.08% at a concentration level of 50 µg litre,1. Copyright © 2004 Society of Chemical Industry [source] Study of the Cathode Potential in a Sputtering Discharge by Pulsing the Reactive Gas: Case of a W Target in an Ar-O2 AtmospherePLASMA PROCESSES AND POLYMERS, Issue 1 2007Nuno M.G. Parreira Abstract The process we used was d.c. magnetron sputtering, and we studied both the conventional process, using a constant flow of oxygen, and the process in which we pulsed the reactive gas. Square regulation signal with different pulsing periods (T) and oxygen injection time (ton) was used in the reactive gas pulsing (RGP), while the partial argon pressure was kept constant for all depositions. The oxygen flow rate during the injection time was sufficient to switch the process to compound sputtering mode, while the oxygen flow was stopped in the rest of period to allow cleaning of target. Sputtering experiments have shown that the instability phenomena, typical of the reactive sputtering process and known as the "hysteresis effect", are relatively weak due to the small reactivity of tungsten. The influence of the pulsing period and of the oxygen injection time on the deposition parameters is discussed in relation to the poisoning effect. It has been shown that d.c. magnetron sputtering with the oxygen pulsing is a suitable method to prepare tungsten oxide films. This process is very stable, leads to multilayered W-O coatings, and the deposition rates are slightly lower than those of obtained during the conventional process. [source] A comparison of seven filling to packing switchover methods for injection moldingPOLYMER ENGINEERING & SCIENCE, Issue 10 2010David O. Kazmer The effectiveness of seven methods for controlling switchover from the filling to packing stage were investigated, including: (1) screw position, (2) injection time, (3) machine pressure, (4) nozzle pressure, (5) runner pressure near the sprue, (6) cavity pressure near the gate, and (7) cavity temperature at the end of flow. The activation threshold for each of the seven switchover methods was iteratively determined so as to produce similar part weights relative to a standard process. A design of experiments was implemented for each of the seven switchover methods that perturbs the process settings by an amount equal to six standard deviations of the standard process so as to replicate the expected long-term process variation. The results suggest that conventional switchover methods (e.g., screw position) had lower short-term variation, but other methods were more robust with respect to rejecting long-term process variation. The merits of different dimensional measurements for quality control are also discussed relative to the society of the plastics industry (SPI) standard tolerances. POLYM. ENG. SCI., 50:2031,2043, 2010. © 2010 Society of Plastics Engineers [source] On-line preconcentration and quantitative analysis of peptide hormone of brain and intestine using on-column transient isotachophoresis coupled with capillary electrophoresis/electrospray ionization mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 23 2008Shifei Xia A new approach was described to achieve very sensitive analysis of peptide hormone of brain and intestine by capillary electrophoresis coupled with a transient isotachophoresis (tITP) preconcentration method. The system used was electrospray ionization mass spectrometry (ESI-MS) as detector and equipped with a sheath flow configuration. The effects of sample matrix, pH and concentration of leading electrolyte (LE), sample injection time, and ESI-MS instrumental parameters on the efficiency of the sample stacking were investigated in detail. Under the optimized conditions, lower than micromole (0.01,µM) concentrations of the peptides were easily detected. Compared to traditional hydrodynamic injection methods, about 40,230-fold increase in detection sensitivity was obtained by this technique. A distinguishing feature of the described approach is that the background electrolyte can serve as terminating electrolyte (TE), which simplifies the process of the experiments. The method was further evaluated by the analysis of low concentration active peptide mixtures spiked in hypothalamus tissue of the rat. Copyright © 2008 John Wiley & Sons, Ltd. [source] Initial investigation on the use of waterjets to place amendments in the subsurfaceREMEDIATION, Issue 1 2005John W. Cable Quasi-passive in situ remediation technologies, such as the use of permeable reactive barriers to treat contaminated groundwater or applications of granular activated carbon to treat polychlorinated biphenyl (PCB)-contaminated, near-surface sediments, are proven or promising technologies that may be limited in application due to the traditional construction techniques normally used for placement in the environment. High-pressure waterjets have traditionally been used to excavate material during mining operations or to cut rock or other durable material. Waterjets have the potential to place amendments in the subsurface at depths greater than those that can be obtained using traditional construction techniques. Likewise, waterjets may have less negative impact on near-surface utilities and/or sensitive ecological systems. Laboratory experiments were performed to characterize the placement of two solid amendments in a simulated saturated aquifer. A second set of experiments was performed to characterize the effectiveness of waterjets for placing a third amendment in simulated intertidal sediments. The laboratory work focused on characterizing the nature of the waterjet penetration of the aquifer matrix and the saturated sediments, as well as the corresponding waterjet parameters of pressure, nozzle size, and injection time. The laboratory results suggest that field trials may be appropriate for future investigations. © 2005 Wiley Periodicals, Inc. [source] The effect of dilution and prolonged injection time on fentanyl-induced coughing,ANAESTHESIA, Issue 9 2007H. Yu Summary This study was designed to evaluate the effect of diluting fentanyl 50 ,g.ml,1 to 25 or 10 ,g.ml,1 with 0.9% saline and prolonged injection time on fentanyl-induced cough. Two hundred patients requiring general anaesthesia were randomly allocated into four groups: 50 ,g.ml,1 (Group I), 25 ,g.ml,1 (Group II), 10 ,g.ml,1 (Group III) or 10 ,g.ml,1 combined with prolonged injection (Group IV). Fentanyl 3 ,g.kg,1 was administered within 5 s in Groups I, II, and III, or over 30 s in Group IV. Occurrence of cough was significantly reduced in Group IV (2% vs 32%, 16% and 12% in Groups I, II and III, respectively, p < 0.05). There were no statistically significant differences in the severity of coughing between the four groups (p > 0.05). We conclude that dilution of fentanyl to 10 ,g.ml,1 with 0.9% saline combined with a prolonged injection time eliminates fentanyl-induced cough. [source] On-line concentration by field-enhanced sample injection with reverse migrating micelles in micellar electrokinetic capillary chromatography for the analysis of coumarins from traditional Chinese medicine and human serumBIOMEDICAL CHROMATOGRAPHY, Issue 6 2010Ting-Fu Jiang Abstract In this work, a simple, reproducible and sensitive micellar electrokinetic chromatography method was developed for the separation and determination of three coumarins, imperatorin (IM), isoimperatorin (IO) and osthole (OS) from traditional Chinese medicine and human serum. Field-enhanced sample injection with reverse migrating micelles was used for on-line concentration of the coumarins. The optimum buffer contained 50,mM H3PO4, 160,mM sodium dodecyl sulfate, 20% acetonitrile and 15% 2-propanol, and the pH of buffer was 2.0. The sample solution was diluted with water containing 5,mM sodium dodecyl sulfate and injected for 15,s with ,8,kV after injection of 2,s water plug. The effects of concentrations of sodium dodecyl sulfate and organic modifier, the sample matrix, the injection time of water plug, the injection voltage and injection time of sample on the separation and stacking efficiency were investigated. Under the optimum conditions, the analytes were well separated and by optimizing the stacking conditions, about 93, 195 and 136 fold improvement in the detection sensitivity was obtained for IM, IO and OS. The contents of three coumarins in Angelica dahurica Benth, Radix Angelicae Pubescentis and Fructus Cnidii were successfully determined with satisfactory repeatability and recovery. The possibilities of using this method for the determination of three coumarins in spiked human serum were also tested. Copyright © 2009 John Wiley & Sons, Ltd. [source] Determination of quinocide as impurity in primaquine tablets by capillary zone electrophoresisBIOMEDICAL CHROMATOGRAPHY, Issue 5 2009Abdalla A. Elbashir Abstract A capillary zone electrophoretic method has been developed and validated for the determination of the impurity quinocide (QC) in the antimalarial drug primaquine (PQ). Different buffer additives such as native cyclodextrins and crown ethers were evaluated. Promising results were obtained when either , -cyclodextrin (, -CD) or 18-crown-6 ether (18C6) were used. Their separation conditions such as type of buffer and its pH, buffer additive concentration, applied voltage capillary temperature and injection time were optimized. The use of 18C6 offers slight advantages over , -CD such as faster elution times and improved resolution. Nevertheless, migration times of less than 5 min and resolution factors (Rs) in the range of 2,4 were obtained when both additives were used. The method was validated with respect to selectivity, linearity, limits of detection and quantitation, analytical precision (intra- and inter-day variability) and repeatability. Concentrations of 2.12 and 2.71% (w/w) of QC were found in pharmaceutical preparations of PQ from two different manufacturers. A possible mechanism for the successful separation of the isomers is also discussed. Copyright © 2008 John Wiley & Sons, Ltd. [source] Subminute and sensitive determination of the neurotransmitter serotonin in urine by capillary electrophoresis with laser-induced ,uorescence detectionBIOMEDICAL CHROMATOGRAPHY, Issue 7 2004David Arráez Román Abstract In this work, a sub-minute and sensitive capillary electrophoresis with laser-induced ,uorescence (CE-LIF) method was developed for the analysis and quantitation of the neurotransmitter 5-hydroxytryptamine (5-HT) or serotonin in urine. The method involves precolumn derivatization with ,uorescein isothiocyanate isomer I (FITC) using an excitation light from an argon ion laser of 488 nm and a 520 nm band pass emission ,lter. Different variables that affect derivatization (pH, FITC concentration, reaction time and temperature) and separation (buffer concentration, pH, applied voltage and injection time) were studied. The linear dynamic range obtained was between 0 and 188 nm with a detection limit of 16 nm with a RSD between 2 and 9%. The applicability of the proposed method was demonstrated by analysis of 5-HT in human urine, establishing a concentration of 57 nm in control urine. The method was validated by standard-addition methodology. Copyright © 2004 John Wiley & Sons, Ltd. [source] Determination of Bioactive Components in Polygonum perfoliatum L. by Capillary Electrophoresis with Electrochemical DetectionCHINESE JOURNAL OF CHEMISTRY, Issue 4 2009Shuping JIN Abstract The major bioactive components in a Chinese herb named Polygonum perfoliatum L. including ferulic acid, vanillic acid, quercetin, caffeic acid and protocatechuic acid were simultaneously determined by capillary electrophoresis with electrochemical detection (CE-ED) in this paper. The effects of working electrode potential, pH and concentration of running buffer, separation voltage, and injection time on CE-ED were investigated. Under the optimum conditions, the five analytes could be separated within 17 min at a separation voltage of 18 kV in 10 mmol· L,1 phosphate buffer (pH 9.2). A 300 µm diameter carbon disk electrode generated good responses at +0.95 V (vs. SCE) to the five analytes. The response was linear over three orders of magnitude with detection limits (S/N=3) ranging from 7.1×10,8 to 9.3×10,8 g·mL,1 for the analytes. This proposed method could be successfully applied to the analysis of the real samples with relatively simple extraction procedures and satisfactory results. [source] Analysis of Trace Ingredients in Green Tea by Capillary Electrophoresis with Amperometric DetectionCHINESE JOURNAL OF CHEMISTRY, Issue 3 2008Ping LI Abstract In this paper, four trace ingredients (rutin, gallic acid, quercetin, chlorogenic acid) in green tea were simultaneously determined by capillary electrophoresis coupled with amperometric detection (CE-AD). Effects of several important factors such as the pH and concentration of running buffer, separation voltage, injection time and detection potential were investigated to acquire the optimum conditions. Under the optimum conditions, the analytes could be separated within 20 min at a separation voltage of 18 kV in a 60 mmol/L borate buffer (pH 8.7). A 300 µm diameter carbon disk electrode generated good responses at 950 mV (vs. SCE) for all analytes. The relationship between the peak currents and concentrations of the analytes was linear over about three orders of magnitude with detection limits (S/N=3) ranging from 1.0×10,7 to 1.0×10,4 g·mL,1 for all the analytes. This proposed method demonstrated long-term stability and reproducibility with relative standard deviations less than 3% for both migration time and peak current (n=7), which could be successfully used for the determination of the analytes in green tea with satisfactory assay results. [source] Fast Determination of Clenbuterol and Salbutamol in Feed and Meat Products Based on Miniaturized Capillary Electrophoresis with Amperometric DetectionCHINESE JOURNAL OF CHEMISTRY, Issue 12 2007Qing-Cui CHU Abstract The fast separation capability of a novel miniaturized capillary electrophoresis with an amperometric detection (,CE-AD) system was demonstrated by determining clenbuterol and salbutamol in real samples. The effects of several factors such as the acidity and concentration of the running buffer, the separation voltage, the applied potential and the injection time on CE-AD were examined and optimized. Under the optimum conditions, the two , -agonists could be baseline separated within 60 s at a separation voltage of 2 kV in a 90 mmol/L H3BO3 -Na2B4O7 running buffer (pH 7.4), which was not interfered by ascorbic acid and uric acid. Highly linear response was obtained for above compounds over three orders of magnitude with detection limits ranging from 1.20×10,7 to 6.50×10,8 mol/L (S/N=3). This method was successfully used in the analysis of feed and meat products with relatively simple extraction procedures. [source] Simultaneous enantioseparation and sensitivity enhancement of basic drugs using large-volume sample stackingELECTROPHORESIS, Issue 19 2007Nerissa L. Deńola Abstract Simultaneous enantioseparation with sensitive detection of four basic drugs, namely methoxamine, metaproterenol, terbutaline and carvedilol, using a 20-,m ID capillary with native ,-CD as the chiral selector was demonstrated by the large-volume sample stacking method. The procedure included conventional sample loading either hydrodynamically or electrokinetically at longer injection times without polarity switching and EOF manipulation. In comparison to conventional injections, depending on the analyte, about several hundred- and a thousand-fold sensitivity enhancement was achieved with the hydrodynamic and the electrokinetic injections, respectively. The simple method developed was applied to the analysis of racemic analytes in serum samples and better recovery was achieved using hydrodynamic injection than electrokinetic injection. [source] | |||||||||||||