Home About us Contact
|
Home About us Contact | ||
|
|
||
kV Voltage (kv + voltage)
Selected AbstractsDetermination of vigabatrin in human plasma by means of CE with LIF detectionELECTROPHORESIS, Issue 19 2007Alessandro Musenga Abstract A method has been developed for the quantitation of the antiepileptic drug vigabatrin (VGB) in human plasma. It is based on CE with LIF detection. The effect of the pH of the buffer and of N -methylglucamine (GLC) as BGE constituent was investigated. The final BGE consisted of 50,mM borate buffer, pH,9.0, with 100,mM GLC and enabled separation within 12,min at 20,kV voltage. An SPE procedure was used for the pretreatment of biological samples, based on mixed-mode lipophilic-cation exchange cartridges, followed by a derivatization step with 6-carboxyfluorescein- N -succinimidyl ester (CFSE). Fluorescence was excited by an Ar-ion laser (,exc,=,488,nm). Linearity was observed in the 10,120,,g/mL plasma concentration range. Extraction yield was >96%, precision (expressed as RSD) <6.7% and accuracy (recovery) was between 97.0 and 101.6%. The method has been successfully applied to the analysis of VGB in plasma of epileptic patients undergoing therapy with the drug. [source] In vivo simultaneous monitoring of ,-aminobutyric acid, glutamate, and L -aspartate using brain microdialysis and capillary electrophoresis with laser-induced fluorescence detection: Analytical developments and in vitro/in vivo validationsELECTROPHORESIS, Issue 18 2003Valérie Sauvinet Abstract ,-Aminobutyric acid (GABA), glutamate (Glu), and L -aspartate (L -Asp) are three major amino acid neurotransmitters in the central nervous system. In this work, a method for the separation of these three neurotransmitters in brain microdialysis samples using a commercially available capillary electrophoresis (CE) system has been developed. Molecules were tagged on their primary amine function with the fluorogene agent naphthalene-2,3-dicarboxaldehyde (NDA), and, after separation by micellar electrokinetic chromatography, were detected by laser-induced fluorescence using a 442 nm helium-cadmium laser. The separation conditions for the analysis of derivatized neurotransmitters in standard solutions and microdialysates have been optimized, and this method has been validated on both pharmacological and analytical basis. The separation of GABA, Glu, and L -Asp takes less than 10 min by using a 75 mmol/L borate buffer, pH 9.2, containing 70 mmol/L SDS and 10 mmol/L hydroxypropyl-,-cyclodextrin and +,25 kV voltage. The detection limits were 3, 15 nmol/L and, 5 nmol/L for GABA, Glu, and L -Asp, respectively. Moreover, submicroliter samples can be analyzed. This method allows a simple, rapid and accurate measurement of the three amino acid neurotransmitters for the in vivo brain monitoring using microdialysis sampling. [source] Enantioseparation of nuarimol by affinity electrokinetic chromatography-partial filling technique using human serum albumin as chiral selectorJOURNAL OF SEPARATION SCIENCE, JSS, Issue 18 2008Maria Amparo Martínez-Gómez Abstract The present paper deals with the enantiomeric separation of nuarimol enantiomers by affinity EKC-partial filling technique using HSA as chiral selector. Firstly, a study of nuarimol interactions with HSA by CE-frontal analysis was performed. The binding parameters obtained for the first site of interaction were n1 = 0.84; K1 = 9.7 ± 0.3×103 M,1 and the protein binding percentage of nuarimol at physiological concentration of HSA was 75.2 ± 0.2%. Due to the moderate affinity of nuarimol towards HSA the possibility of using this protein as chiral selector for the separation of nuarimol using the partial filling technique was evaluated. A multivariate optimization approach of the most critical experimental variables in enantioresolution, running pH, HSA concentration and plug length was carried out. Separation of nuarimol enantiomers was obtained under the following selected conditions: electrophoretic buffer composed of 50 mM Tris at pH 7.3; 160 ,M HSA solution applied at 50 mbar for 156 s as chiral selector; nuarimol solutions in the range of 2,8×10,4 M injected hydrodynamically at 30 mbar for 2 s and the electrophoretic runs performed at 30°C applying 15 kV voltage. Resolution, accuracy, reproducibility speed and cost of the proposed method make it suitable for quality control of the enantiomeric composition of nuarimol in formulations and for further toxicological studies. The results showed a different affinity between nuarimol enantiomers towards HSA. [source] Rapid speciation of iron by on-line coupling of short column capillary electrophoresis and inductively coupled plasma mass spectrometry with the collision cell techniqueJOURNAL OF SEPARATION SCIENCE, JSS, Issue 6 2007Bao-Hui Li Abstract A method for rapid speciation analysis of iron was developed by on-line coupling of short column capillary electrophoresis and inductively coupled plasma mass spectrometry. The collision cell technique was used to eliminate argon-based polyatomic interferences and a Micromist nebulizer was employed to increase the nebulization efficiency. Rapid speciation analysis of Fe(II) and Fe(III) was achieved within 1 min by short column capillary electrophoresis in a 14 cm×50 ,m id capillary at 28 kV voltage with a mixture of 15 mmol/L tris(hydroxymethyl)aminomethane + 1 mmol/L 1,10-phenanthroline + 1 mmol/L EDTA (pH 8.6) as running electrolyte. The precisions (RSD, n = 5) of migration time and peak area for Fe(II) and Fe(III) were in the range of 1.0,2.6 and 1.9,3.9%, respectively. The limits of detection (3,) of Fe(II) and Fe(III) were 10.0 and 8.3 ,g/L, respectively. [source] Analysis of aromatic and terpenic constituents of pepper extracts by capillary electrochromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 4 2007Alessandro Musenga Abstract An original method based on CEC has been developed for the determination of aromatic and terpenic compounds in extracts of spices obtained from Piper nigrum. The method is based on the use of a fused silica capillary (effective length: 23.5 cm, internal diameter: 100 ,m) packed with a C18 sorbent (packing length: 23 cm, particle size: 5 ,m). The mobile phase is a 50 mM, pH 6.0 ammonium acetate/ACN (10:90 v/v) mixture. Applying a 30 kV voltage, the following 11 compounds were separated and analysed: terpinen-4-ol, caryophyllene oxide, limonene, ,-pinene, 3-carene, ,-pinene, ,-humulene, ,-caryophyllene, ,-phellandrene, eugenol and piperine. Compound determination is carried out using a diode-array detector set at 265 and 338 nm for ,-phellandrene and piperine, respectively, and at 210 nm (reference subtraction at 282 nm) for all the other analytes. The optimised method has been validated with good results in terms of linearity, limits of quantitation, detection and precision. The CEC method was successfully applied to the analysis of essential oils and methanolic extracts of ,black', ,white' and ,green' pepper. [source] Micellar electrokinetic capillary chromatography of methylxanthines-containing beverages: discussion of the molecular species involvedJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 4 2005Alicia B Pomilio Abstract Micellar electrokinetic capillary chromatography (MECC) experimental conditions were applied to 12 samples of methylxanthine-containing infusions of different commercial brands of yerba mate, coffee, tea and cocoa as well as two cola drinks. The best resolution in this mode of automated high-performance capillary electrophoresis (HPCE) was achieved here when using 15 kV voltage in an uncoated fused-silica capillary of 45 cm length (40 cm effective length), 50 mM sodium dodecylsulfate, 90 mM pH 8.5 borate buffer and UV detection. Theobromine, caffeine and theophylline were separated, and the peak splitting due to tautomeric species was observed. Experimental conditions were controlled, keeping constant the size of the elution window in each analysis. The limit of detection was less than 1 mg l,1, the limit of quantitation was 2.5 mg l,1 and the work range was 2.5,300 mg l,1. This HPCE,MECC system has proved suitable for the analysis/quality control of xanthines in beverages for consumption. Roles of various parameters as well as distinctly charged species of each xanthine and the origin of peak splitting in this MECC system are discussed. Copyright © 2004 Society of Chemical Industry [source] PI3D processing of DLC coatings for different applicationsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2008S. A. Nikiforov Abstract DLC (a -C:H) and Si-DLC coatings have been deposited on various materials (steel, aluminium, silicon, glass, polymers) using a 1-m3 interior-antenna ICP PI3D facility with HMDSO and toluene as precursors. For conformal treatment of 3-D workpiececs, a low-voltage (0.5 - 1) kV, high repetition rate (up to 70 kHz) pulsing was applied. However, DLC formation on dielectric substrates was performed at higher (2 - 10) kV voltage using short (1 - 1.5) ,s pulses to minimize surface charging. Coating adhesion was achieved by formation of multi layer structure comprising Si-containing buffer layer, transient layer, DLC layer with gradually increasing hardness, and top hard DLC. Film hardness was (5 - 20) GPa, and the deposition rate (4 - 0.5) ,m/h. DLC surface roughness was (0.7 - 60) nm and water contact angle 70° - 110° depending on process parameters which implies various applications. Batch processing of sliding parts, cutting tools, glass moulds was performed. Double-side DLC coating on polymer web eliminated its rolling up due to the coating stress. With novel ICP antenna the DLC processing is promising for large-scale nano pattern transfer technology. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||