Abstract Capillary electrophoresis was applied to the analysis of a mixture of triazine herbicides of environmental interest. Micellar electrokinetic capillary chromatography (MECC) proved to be satisfactory for the separation of triazines, providing high efficiency in short analysis times. Several...
A system for interfacing electrochemical detection with micellar electrokinetic capillary chromatography is demonstrated. This system couples the separation column to a short length of the same column material together with a section of porous graphite tubing which forms an electrically conductive joint. The joint is immersed in a buffer reservoir together with the ground electrode of the high-power source (15 kV). The reservoir is electrically insulated from the electrochemical cell containing the carbon fibre detector. This configuration effectively separates the detector from the high separation potential applied. Amperometric detection with micellar solutions is demonstrated for a mixture of B6 vitamers on a 50 μm I.D. column. A detection limit of ca. 4 fmol is obtained. The linear dynamic range of the calibration plot is slightly over two orders of magnitude (from ca. 1 to 200 ppm). © 1991 ...
Micellar electrokinetic chromatography (MEKC), is a chromatography technique, used in analytical chemistry. It is a modification of capillary electrophoresis (CE), where the samples are separated by differential partitioning between micelles (pseudo-stationary phase) and a surrounding aqueous buffer solution (mobile phase). The basic set-up and detection methods used for MEKC are the same as those used in CE. The difference is that the solution contains a surfactant at a concentration that is greater than the critical micelle concentration (CMC). Above this concentration, surfactant monomers are in equilibrium with micelles. In most applications, MEKC is performed in open capillaries under alkaline conditions to generate a strong electroosmotic flow. Sodium dodecyl sulfate (SDS) is the most commonly used surfactant in MEKC applications. The anionic character of the sulfate groups of SDS cause the surfactant and micelles to have electrophoretic mobility that is counter to the direction of the ...
The research presented in this dissertation involves the synthesis, modification, characterization, and the application of polymeric surfactants in micellar electrokinetic chromatography (MEKC). Sodium undecenoyl-L-Leucinate (L-SUL) was synthesized and modified by use of alkali metal counterions, alcohols, and Triton X-102. Characterization of the modified poly-L-SUL was performed in order to elucidate the structural changes on the surfactants by use of four techniques. While surface tensiometry was used for the determination of the critical micelle concentration (cmc), fluorescence measurements were used for the determination of the polarity of the modified polymeric surfactants. The information about the size of the polymeric surfactants was obtained by use of pulsed field gradient-NMR (PFG-NMR). A superior chromatographic performance in MEKC was demonstrated by the modified polymeric surfactants as compared to the non-modified polymeric surfactants. A correlation between the polarity and the ...
A cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) technique has been developed for enantioseparation of vinpocetine using an inexpensive 2-hydroxypropyl-β-CD (HP-β-CD) as the chiral selector (CS). The best chiral separation was achieved using 40 mM HP-β-CD as the CS in 50 mM phosphate buffer (pH 7.0) consisting of 40 mM sodium dodecyl sulfate (SDS) at a separation temperature and separation voltage of 25°C and 25 kV, respectively. To the authors best knowledge, this is the first CD-MEKC study able to successfully separate the four stereoisomer of vinpocetine in separation time of 9.5 min and resolution of 1.04-3.87. Chirality, 2012. © 2012 Wiley Periodicals, Inc. ...
Capillary zone electrophoresis and micellar electrokinetic chromatography, with taurodeoxycholate as micellar agent, of protein kinase A peptide substrates ...
Ge, L., Tan, S.N., Yong, J.W.H., Hua, L., Ong, E.S. (2008). Separation of cytokinin isomers with a partial filling-micellar electrokinetic chromatography-mass spectrometry approach. Electrophoresis 29 (10) : 2024-2032. [email protected] Repository. https://doi.org/10.1002/elps. ...
Journal of Analytical Methods in Chemistry is a peer-reviewed, Open Access journal that publishes original research articles as well as review articles reporting methods and instrumentation in chemical analysis, and their application to real-world problems.
A free platform for explaining your research in plain language, and managing how you communicate around it - so you can understand how best to increase its impact.
Capillary electrokinetic chromatography is generally recognized as a versatile and robust capillary electromigration technique for the separation of enantiomers. In this mode, one or more chiral selectors are added to the background electrolyte acting as pseudostationary phases. Within the various chiral selectors that have been applied to enantioseparations in capillary electrokinetic chromatography, cyclodextrins are by far the most often used selectors because of their versatility, structural variety and commercial availability. This is reflected in the large number of applications of cyclodextrins to analytical enantioseparations that have been reported between January 2012 and July 2016, the period of time covered by this review. Many of these applications cover aspects of life sciences such as drug analysis, bioanalysis or food analysis. Despite the large number of commercially available cyclodextrins, new derivatives have been developed in order to achieve altered enantioselectivities or ...
The use of auxiliary separation mechanisms to manipulate the separation selectivity of metal complexes and organometallic species is reviewed. Auxiliary separation mechanisms included in the review are micellar electrokinetic capillary chromatography, ion-pairing and ion-exchange electrokinetic chromatography. This paper discusses how these secondary mechanisms can be effectively employed to tailor separation selectivity.. ...
Studies of the capillary zone electrophoresis (CZE) and micellar electrokinetic capillary chromatography (MEKC) behaviour of 1,4-benzodiazepines have seen application in subject areas such as the development of pharmaceuticals, therapeutic drug monitoring and forensic toxicology. In the development of pharmaceuticals, pK(a) determinations by CZE can be used in preclinical studies whereas analytical data on the detection and determination of 1,4-benzodiazepines is of value primarily in raw material/formulation assay and in the analysis of body fluids in clinical studies. The capillary electrophoresis (CE) techniques, which generally have inferior limits of detection (LOD) to rival techniques such as gas chromatography (GC) and high-performance liquid chromatography (HPLC), are particularly applicable in forensic toxicology where reasonably high concentrations of these drugs can be encountered. It is anticipated that, with the interfacing of CZE: and capillary electrochromatography (CEC) with mass ...
TY - JOUR. T1 - COMPARISON OF DIFFERENT TECHNIQUES FOR THE ANALYSIS OF METALLOTHIONEIN ISOFORMS BY CAPILLARY ELECTROPHORESIS. AU - RICHARDS, M P AU - BEATTIE, J H PY - 1995/7/7. Y1 - 1995/7/7. N2 - We have investigated free-solution capillary electrophoresis (FSCE) and micellar electrokinetic capillary chromatography (MECC) separations of metallothionein (MT) isoforms conducted in uncoated and surface-modified fused-silica capillaries. At alkaline pH, FSCE rapidly resolves isoforms belonging to the MT-1 and MT-2 charge classes. At acidic pH, additional resolution of MT isoforms is achieved. The use of high-ionic-strength (0.5 M) phosphate buffers can result in high peak efficiencies and increased resolution for some MT isoforms. Interior capillary surface coatings such as polyamine and linear polyacrylamide polymers permit separation of MT isoforms with enhanced resolution through their effects on electroosmotic flow (EOF) and protein-wall interactions. Improvements in MT isoform resolution can ...
Capillary electrophoresis (CE) comprises a family of related separation techniques in which an electric field is used to achieve the separation of components in a mixture. One of the key features of CE is the simplicity of the instrumentation required, and today, these techniques have become powerful analytical tools for high efficiency separation, and the identification of a variety of ionic and neutral compounds.. Moreover, the versatility of CE operational modes (capillary zone electrophoresis, micellar electrokinetic capillary chromatography, capillary electrochromatography, capillary isoelectric focusing, isotachophoresis, non-aqueous capillary electrophoresis, etc.) and detection systems (ultraviolet, fluorescence, amperometric, mass spectrometry…) make CE useful for applications in many fields such as environmental, food, pharmaceutical, and forensic analysis. The typcial drawback of CE techniques, based on their low sensitivity when dealing with conventional UV-detection, due to their ...
In order to adopt a general workflow for complex biological matrices with respect to a new blood-brain barrier (BBB) model, a micellar electrokinetic chromatography method has been developed. The cells forming the BBB have been cultivated in a special cell growth medium in which six drugs (acetaminophen, caffeine, carbamazepine, cimetidine, indometacin and propranolol) have been dissolved and tested for their penetration properties. The results showed good to very good accordance to the reference values. Samples were directly injected onto the capillary without any pretreatment (fused silica capillary, id: 50 μm, L: 48 cm, l: 40 cm). After method development, separations were carried out using a 60 mM borate buffer containing 200 mM of SDS at 30 kV, leading to an analysis time of less than 10 min. Between two runs the capillary was rinsed with a mixture of equal parts of running buffer and isopropanol (70% v/v), which proved to be very effective to remove matrix compounds. An appropriate choice ...
SIMON, Brigitta; HANCU, Gabriel and GYERESI, Árpád. Application of capillary electrophoresis to the simultaneous determination and stability study of four extensively used penicillin derivatives. Braz. J. Pharm. Sci. [online]. 2014, vol.50, n.3, pp.521-527. ISSN 1984-8250. http://dx.doi.org/10.1590/S1984-82502014000300010.. The applicability of capillary electrophoresis for the analysis of four extensively used penicillin derivatives (benzylpenicillin, ampicillin, amoxicillin, oxacilllin) has been studied. Because of structural similarities, the electrophoretic behavior of these derivatives is very similar; consequently an efficient separation using the conventional capillary zone electrophoresis is hard to be achieved. Their simultaneous separation was solved by using micellar electrokinetic capillary chromatography, the separation being based on the differential partition of the analytes between the micellar and aqueous phase. Using a buffer solution containing 25 mM sodium tetraborate and ...
Abstract A method for the determination of histamine, 2-phenylethylamine, tryptamine, putrescine, cadaverine, spermidine and spermine in fish using micellar electrokinetic capillary chromatography (MECC) was developed. Seven biogenic amines (BAs) were extracted from a sample with 6% perchloric acid, then derivatized with benzoyl chloride. 0.02 mol/L borate buffer (pH 9.2) containing 0.06 mol/L sodium deoxycholate-methanol (95∶5, v/v)was used as a running buffer. The detection wavelength was set at 214 nm. The separation was achieved within 12 min. Good linearities were observed from the calibration plots in the concentration ranges. The detection limit of histamine was 15 μg/g and those of the other amines were 5 μg/g. The developed method was successfully employed for the simultaneous determination of 7 BAs in fish sample with satisfactory results. ...
A method for simultaneous determination of polyamines and catecholamines in cell extracts by micellar electrokinetic capillary chromatography with UV detection at 254 nm was established at the first time. The polyamines (putrescine, spermidine and spermine) and catecholamines (dopamine, serotonin, norepinephrine and epinephrine) were extracted from PC-12 cells and were derivatized with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate. Different derivatization conditions such as temperature, ratio of derivatization reagents and incubation time were investigated to find the best reaction condition which gave the highest detection sensitivity for polyamines and catecholamines. The influence of running buffer and additives on the separation such as pH, sodium dodecyl sulfate (SDS) concentrations and various additives was also investigated. Separation was achieved within 20 min with good repeatability in a 100 mM boric acid buffer containing 10 mM SDS and 10 mM 18-crown-6 at a pH of 9.5. The detection limit
Rapid determination of acyclovir in plasma and cerebrospinal fluid by micellar electrokinetic chromatography with direct sample injection. 500 mg acyclovir.Commande En Ligne Valtrex (valacyclovir) 500 Mg and Pharmacie de garde Zovirax (Acyclovir) 200 mg, Valtrex (Valacyclovir) 500 mg Canada, Acyclovir Acheter Sans.Star spare parts common rail diesel injection pump and pump injector, petrol injection and repair kits, diesel fuel filters and bearings, caterpillar, lucas, delphi.. I came to your La Saint Valentin à l hôtel Atrium: Hotel Arles,. Both the Dow andthe S&P_ 500 closed at all-time highs on Friday - for the secondday in a row.buy valacyclovir 500 mg And cold sores pain lower back amoxicillin allergic reaction in baby buy valacyclovir 500 mg does have shelf life. Is still available dose.Cialis in pakistan price, The cost of cialis and viagra. Purchase acyclovir online! Trazodone online purchase? Kamagra uk prices, Nexium overnight!.Stability of cidofovir in 0.9% sodium chloride and in ...
A double-injection micellar electrokinetic chromatography (DIMEKC) method for the identification of Æ - caprolactam and melamine deliberately added to povidone (polyvin..
A methodology for the determination of tomato phenolic acids and flavonoids has been developed combining MEKC and DAD detection. The influence on polyphenol separation of pH and background electrolyte, BGE (borax, acetonitrile, methanol and SDS concentrations), was studied and optimized using response surface methodology and weighted desirability function. Separation of polyphenols was achieved within 20 min at 15 °C using 11.3 mM borax and 11.2 mM SDS adjusted to pH 8.5 as BGE. Validation was performed using standards and tomato extracts. Recoveries ranged from 77 to 106%. Acceptable repeatabilities were obtained for peak area (%RSD ,3.1% and ,3.7%) and migration times (%RSD ,0.2% and ,1.4%) for intra- and inter-day respectively. Detection limits ranged between 0.8 and 3.8 mg kg−1. Five and seven of these polyphenols were determined in samples of tomato and related species. This methodology will be valuable tool in breeding programs, analyzing a large number of samples. [-] ...
A capacitively coupled contactless conductivity detection (CCD) system has been applied for the detection of neutral synthetic polymers in capillary size-exclusion electrokinetic chromatography (SEEC). Polystyrene standards, that were used as a model compounds, were separated on a capillary column packed with porous 10 μm silica particles with an electrokinetically driven mobile phase, and detected by CCD and UV detection simultaneously. Mass-calibration curves for polystyrene were constructed. Satisfactory results were obtained for the linearity, the run-to-run repeatability (,0.2% for the relative retention and ,4% for the peak area) and the robustness of the detector. One of the major issues in this preliminary study was to investigate the origin of the peaks observed for the polystyrene standards. The effect of the molar mass of the polystyrenes on the sensitivity was small. Therefore, the signals obtained could not be explained as the result of an increased viscosity and a decreased ...
A field-amplified sample injection-micellar electrokinetic chromatography (FASI-MEKC) method for the determination of 14 benzophenones (BPs) in a food simulant used in migration studies of food packaging materials was developed, allowing almost baseline separation in less than 21 min. The use of a 10 mM sodium dodecyl sulfate (SDS) solution as sample matrix was mandatory to achieve FASI enhancement of the analyzed BPs. A 21- to 784-fold sensitivity enhancement was achieved with FASI-MEKC, obtaining limits of detection down to 5.1-68.4 µg/L, with acceptable run-to-run precisions (RSD values lower than 22.3%) and accuracy (relative errors lower than 21.0%). Method performance was evaluated by quantifying BPs in the food simulant spiked at 500 µg/L (bellow the established specific migration limit for BP (600 µg/L) by EU legislation). For a 95% confidence level, no statistical differences were observed between found and spiked concentrations (probability at the confidence level, p value, of 0.55),
Partial filling-micellar electrokinetic chromatography optimizationstudies of ibuprofen, codeine and degradation products, and coupling tomass spectrometry: Part II. ...
Zhan, Q., Gusev, A., & Hercules, D. M. (1999). A novel interface for on-line coupling of liquid capillary chromatography with matrix-assisted laser desorption/ionization detection. Rapid Communications in Mass Spectrometry, 13(22), 2278-2283 ...
The arrangement of the glucose units in the three different forms of cyclodextrin are shown in figure 26. The mouth of the torus-shaped cyclodextrin molecule has a larger circumference than at the base and is linked to secondary hydroxyl groups of the C2 and C3 atoms of each glucose unit (see figure 27). The primary hydroxyl groups are located at the base of the torus on the C6 atoms. As these hydroxyl groups are free to rotate, they partially block the base aperture. The size of the cavity increases with increasing number of glucose units (figure 26).The secondary hydroxyl groups can be reacted with appropriate reagents to introduce additional and different interactive character to the cyclodextrin molecule. The strong chiral selectivity of the cyclodextrins structures is thought to arise from the many chiral centers they contain (e.g., b-cyclodextrin has 35 stereogenic centers). The cyclodextrins are probably the most effective chirally selective stationary phases presently available for the ...
It is clear that the column radius is the critical property of the system, significantly effecting both the column efficiency and the analysis time. It is also seen that the contribution to dispersion from longitudinal diffusion is the same for both columns and so the striking difference between the performance of the two columns depends solely on the effect of the column radius on the resistance to mass transfer terms. This is clearly illustrated by the large difference in slopes of the two linear curves for the resistance to mass transfer shown in figure 17.. ...
Close The Infona portal uses cookies, i.e. strings of text saved by a browser on the users device. The portal can access those files and use them to remember the users data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser. ...
Liposome and micelle electrokinetic chromatography (EKC) were used to determine retention factors (k) that are directly related to partition coefficients (K) and the phase ratio (φ) as: k = K*φ. Linear solvation energy relationship (LSER) models were used to elucidate the contributions of solute partitioning into liposomes. In addition, an LSER model for both MEKC and LEKC was used to determine partition coefficients for solutes without observed partition coefficients. The observed partition coefficients and those determined from LSER were then used to predict partition coefficients with the group contribution approach (GCA) and the fragmental constant approach (FCA) from solute structure. In the GCA, a relatively small number of key monosubstituted aromatic and aliphatic solutes are used to determine the substituent constants of functional groups. These substituent constants as well as the contributions from aromatic and aliphatic carbon plus hydrogen are used to predict partition ...
Berezkin, V.G.; Popova, T.P.; Shiryayeva, V.Ye.; Nomura, N., Gas-chromatographic separation of monoalkylphenols on polar and non-polar phases by means of capillary chromatography, Pet. Chem. USSR (Engl. Transl.), 1997, 37, 2, 161-167. 16 matching species were found. For each matching species the following will be displayed: ...
Polyprotic molecular weight = 1003.19 for mass spectrometry analysis • Near-infrared (NIR) fluorescent dye • Solubility: Water or DMSO • Carboxylic acid available for covalent attachment • Supplied as polysodium salt • Used as a contrast agent by itself or for making optical probes for NIR fluorescence imaging. ...
How is the column strength affected by its slenderness?. The column slenderness is defined in terms of its slenderness ratio kLu/r, where the term kLu is called the effective length and the factor k modifies the actual column length to account for end restraints other than pinned. The value of the effective length factor k varies between 0.5 and 2.0, depending of the buckled shape of the column for different end conditions. The parameter r is the radius of gyration of the cross section.. In practice, columns are rarely found as isolated members, but they are part of rigid frames together with other structural members such as beams. When the frame is laterally braced, the joint translation is prevented by shear walls, attachment to adjoining structures, etc, and such a column is called Non-sway, as opposed to a Sway column, where the lateral stability is dependent of the stiffness of the members of the frame.. When a slender column is axially loaded, it tends to buckle, which creates a deflection ...
How is the column strength affected by its slenderness?. The column slenderness is defined in terms of its slenderness ratio kLu/r, where the term kLu is called the effective length and the factor k modifies the actual column length to account for end restraints other than pinned. The value of the effective length factor k varies between 0.5 and 2.0, depending of the buckled shape of the column for different end conditions. The parameter r is the radius of gyration of the cross section.. In practice, columns are rarely found as isolated members, but they are part of rigid frames together with other structural members such as beams. When the frame is laterally braced, the joint translation is prevented by shear walls, attachment to adjoining structures, etc, and such a column is called Non-sway, as opposed to a Sway column, where the lateral stability is dependent of the stiffness of the members of the frame.. When a slender column is axially loaded, it tends to buckle, which creates a deflection ...
Capillary electrophoresis (CE) is a family of electrokinetic separation methods performed in submillimeter diameter capillaries and in micro- and nanofluidic channels. Very often, CE refers to capillary zone electrophoresis (CZE), but other electrophoretic techniques including capillary gel electrophoresis (CGE), capillary isoelectric focusing (CIEF), capillary isotachophoresis and micellar electrokinetic chromatography (MEKC) belong also to this class of methods. In CE methods, analytes migrate through electrolyte solutions under the influence of an electric field. Analytes can be separated according to ionic mobility and/or partitioning into an alternate phase via non-covalent interactions. Additionally, analytes may be concentrated or "focused" by means of gradients in conductivity and pH. The instrumentation needed to perform capillary electrophoresis is relatively simple. A basic schematic of a capillary electrophoresis system is shown in figure 1. The systems main components are a sample ...
Detection of drugs at low concentration is required in a variety of biological and medical situations, in order to avoid harmful side effects posed by some drug residues. The book details the instrumentation, detection, and application of nano chromatography (that is, any chromatographic and capillary electrophoretic method dealing with the detection of a sample at nano gram per liter or lower) and capillary electrophoresis in the analyses of biological and environmental samples. Methods discussed include: Nano Gas Chromatography, Nano Capillary Electrophoresis, Nano Chiral Chromatography, Micellar Electrokinetic Chromatography, Supercritical Fluid Chromatography, and Nano High Performance Liquid Chromatography.. ...
Nanoparticles were used as a pseudostationary phase in capillary electrochromatography (CEC) electrospray ionisation-mass spectrometry (ESI-MS) for separation of both neutral analytes by a reversed phase mechanism, as well as for cationic analytes by a cation exchange mechanism. Nanoparticles suspended in electrolyte, were injected as a plug prior to the sample using a partial filling technique (PF), or used as electrolyte in a continuous full filling (CFF) technique. An orthogonal ESI probe was used to hinder the nanoparticles from entering the mass spectrometer and to allow detection of analytes co-eluting with concentrated nanoparticle slurries. Two types of nanoparticles were synthesised and used, both of them having a hydrophobic core and a hydrophilic surface. The hydrophobic core gave the nanoparticles reversed phase properties and the hydrophilic surface promoted the formation of stable slurries of nanoparticles in electrolytes with a low concentration of organic modifier. The surface of ...
Enantioseparation has attracted considerable attention in biological science and pharmaceutical industry because of the different physiological activity and pharmacological effects of different enantiomers (1). Amongst many analytical techniques, capillary electrophoresis (CE) is a relatively new separation technique that provides rapid analysis with high efficiency and resolution due to the use of electric field and a variety of selective modes (2). Cyclodextrins are the most commonly utilized chiral selectors added into the background electrolyte to perform enantioseparation. Besides neutral CDs derivatives, the synthesis and application of charged CDs derivatives have become attractive due to their good water solubility and excellent enantiorecognition abilities towards counter-charged racemic analytes (3,4). Previously, our group has developed a series of positive changed single isomer CD selectors which afforded good enantioseparation abilities to anionic and ampholytic acids by CE (5,6,7). ...
High-speed capillary electrochromatography was developed on both short and long packed columns with 2 mu m non-porous ODS as the stationary phase. Factors that affect the analysis time of samples, such as voltage, electrolyte concentration, pH and organic modifier concentration in the mobile phase, were studied systematically. Fast analysis of aromatic compounds within 13 seconds was realized with column efficiency of 573,000 plates/m and a R.S.D.% of the retention times of all components in 8 consecutive injections below 1.0%. which demonstrated the high efficiency and high reproducibility of such a technique. In addition, DNPH derived aldehydes and ketones in both standards and environmental samples were separated with high speed ...
article{350485, author = {Lynen, Frederic and BUICA, A and De Villiers, Andr{\e} and CROUCH, A and Sandra, Patrick}, issn = {1615-9306}, journal = {JOURNAL OF SEPARATION SCIENCE}, language = {eng}, number = {13}, pages = {1539--1549}, publisher = {WILEY-V C H VERLAG GMBH}, title = {An efficient slurry packing procedure for the preparation of columns applicable in capillary electrochromatography and capillary electrochromatography-electrospray-mass spectrometry}, volume = {28}, year = {2005 ...
On-Column Ion-Exchange Preconcentration of Inorganic Anions in Open Tubular Capillary Electrochromatography with Elution Using Transient-Isotachophoretic Gradients. 3. Implementation and Method Development
Characterization of nanocrystals is crucial for the development of many chemical methods based on this technology. For this, there are several techniques, mainly microscopic, and recently capillary electrophoretic techniques, that have been proposed. In our laboratory, we examined several capillary electrophoretic methodologies: zone (CZE), micellar (MEKC), microemulsion (MEEKC), non-aqueous (NACE) and polymer based (CGE). For the separation of water soluble CdSe nanocrystals, CZE, MEKC and CGE were found to be suitable
Close The Infona portal uses cookies, i.e. strings of text saved by a browser on the users device. The portal can access those files and use them to remember the users data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser. ...
COMPOSITE DESIGN SUPPORT LTD TYNE & WEAR NE31 1SR - Dissolved in 2010, Financial performance, director details, business contact information, and more…
Expanding on Jonts explanation, the frequency of vibration is strictly proportional to the speed of sound and inversely proportional to the pipes effective length (f = c/(2*Leff)). The speed of sound depends on the properties of the gas contained in the pipe and the temperature of the gas: c = const*sqrt(T(kelvin)) = const*sqrt(273+T(celsius)) For dry air, const = 20.1, so at 20 degrees celsius c = 20.1*sqrt(273 + 20) = 344 m/s A useful approximation good for a range of temperatures around zero degrees C is c = 331.3 + 0.6*T(celsius) If the pipe were cold, at say 50 degrees F (10 degrees C), the frequency would be 337.3, according to this formula. (338.1 using the more accurate sqrt formula) When warmed to a room temperature of 20 degrees C we are back to 344 m/s. So this is an increase of about 1.8% or about 3 tenths of a semi-tone (which is approx. 5.9%). You can calculate the pitch change in cents using the formula cents_change = 3986.3*log10(f2/f1) = 3986.3*log10(sqrt((273 + Tc2)/(273 + ...
Metal tubeless tire valve stem fits all cast wheels with .327in.-.339in. holes Full-length threading for various rim thicknesses Comes with metal cap, lock nut and O-ring seal 1 3/16in. effective length
Cheung, H.Y.; Ng, C.W.; Hood, D.J., 2001: Identification and quantification of base and nucleoside markers in extracts of Ganoderma lucidum, Ganoderma japonicum and Ganoderma capsules by micellar electrokinetic chromatography
Microthermometry is the most common technique used to determine the salinity of aqueous fluid inclusions but, in some cases, this technique cannot be applied. The Raman analysis of water is a good alternative. Instead of preparing fluid inclusions within minerals by the crack-and-heal method, fused-silica capillary capsules (FSCCs) were used as synthetic fluid inclusions to calibrate the Raman signal of water toward chlorinity. The preparation of FSCCs is convenient in the preparation of synthetic fluid inclusions, and the composition of the standard solutions is well controlled all along the preparation procedure. Standard fluid compositions made in FSCCs are stable over time. The treatment of Raman data is reduced to the subtraction of a straight baseline and the measurement of Raman intensity at two wavenumbers, such that it is simple and independent from the operator. The method has been tested by comparison of the results obtained from Raman spectroscopy and with phase transitions observed ...
A high-performance liquid chromatography-electrochemical detection (HPLC-ECD) method was developed to determine cyclovirobuxin D (CVB-D) levels in tablets and human blood samples. A column with a positive charge-modified C18 stationary phase, C18HCE, was selected to analyze CVB-D, because it provided a sharper and more symmetric peak for CVB-D than conventional C18 stationary phase. Two types of working electrode materials, glassy carbon (GC) and boron-doped diamond (BDD), were evaluated. BDD was found to provide better sensitivity than GC owing to its lower background current and baseline noise. Utilizing the BDD electrode, C18HCE column, and optimized mobile phase composition, the developed HPLC-ECD method showed a much better sensitivity. The limit of detection and limit of quantification of the HPLC-ECD method for CVB-D were 0.198 and 0.297 μg/L, respectively. It was approximately 12727, 11481, and 2630 times more sensitive than ultraviolet (UV), evaporative light scattering detection, and ...
The effects of alpha,beta-methylene ATP, an agent known to stimulate and then to desensitize P2-purinoceptors, on the release of endogenous norepinephrine from the electrically stimulated rat caudal artery were determined. Norepinephrine was quantified by high-performance liquid chromatography-electrochemical detection techniques. alpha,beta-Methylene ATP over the concentration range of 1 to 100 microM did not affect the release of norepinephrine evoked by stimulation for 3 min at 1 Hz. In contrast, 2-chloroadenosine, a P1 receptor agonist, and beta,gamma-methylene ATP, a P2 receptor agonist, produced a concentration-related inhibition of the release of norepinephrine presumably by activating prejunctional purinoceptors. The failure of alpha,beta-methylene ATP to inhibit transmitter release was apparently not related to the length of pretreatment with this agent because pretreatments of 0.5 to 15 min yielded similar results. These findings indicate that the ability of alpha,beta-methylene ATP to ...
Cyclodextrin-mediated enantioseparation of phenylalanine amide derivatives and amino alcohols by capillary electrophoresis-Role of complexation constants and complex mobilities ...