bluuebunny/crossref_metadata_2025_split huggingface dataset:
Corrosion of Zinc in acetic acid derivatives: Glycollic, mercaptoacetic and cyanoacetic acids and glycine
Authors: Abd El‐Rahman H. A. , Gad‐Allah A. G. , Tamous H. 
Published: May 2005

AbstractThe corrosion behaviour of zinc in glycollic, mercaptoacetic and cyanoacetic acids and glycine was studied by weight loss, pH‐monitoring and polarization measurements. The rate of corrosion was found to be a first order with respect to hydrogen ion activity and strongly dependent of the acid type. The abnormal behaviour in cyanoacetic acid at < 0.5 M was attributed to the hydrolysis of the acid during the corrosion and formation of malonic acid as confirmed by FT‐IR spectroscopy. Morphological investigation of the corroded surfaces showed localized corrosion in cyanoacetic and glycollic acids which increased as the acid concentration or corrosion time increased. The FT‐IR analysis indicated also the formation of zinc glycollate and zinc thioglycollate as the corrosion products of zinc in glycollic and mercaptoacetic acids, respectively (Scheme 1a+b).
Untersuchung der Verbindungseigenschaften an laserstrahlgefügten Brillengestellen
Authors: Dorn L. , Jafari S. , Hofmann F. 
Published: May 2005

AbstractBei der Fertigung von hochwertigen Brillengestellen aus nichtrostenden Stählen gewinnt der Einsatz der Laserstrahlfügeverfahren im Vergleich zu konventionellen Verfahren zunehmend an Bedeutung. Im Rahmen einer Studie sollte festgestellt werden, welches der beiden Verfahren Löten und Schweißen die in der Praxis gestellten Anforderungen an Brillengestelle besser erfüllt. Hierzu wurden Profile aus Cr‐Ni‐Stahl, wie sie in der Praxis wegen ihrer besonderen Langzeitstabilität gegenüber Korrosion eingesetzt werden, mittels Laserstrahl gefügt. Zur Charakterisierung der metallurgischen Eigenschaften der Fügeverbindungen wurden die Qualitätsmerkmale der Proben hinsichtlich mechanischer Eigenschaften (Härte, Festigkeit und Verformbarkeit) sowie die Gefügeausbildung untersucht. Im Hinblick auf die geforderte gute Verformbarkeit der Verbindungen konnte für die geschweißten Proben ein Vorteil gegenüber dem Laserstrahllöten nachgewiesen werden.
Plasmasensorik in gepulsten PACVD‐Plasmen
Authors: Klümper‐Westkamp H. , Mehner A. , Hoffmann F. , Mayr P. 
Published: May 2005

AbstractLangmuirsonden werden seit langem als grundlegendes Plasmadiagnosesystem zur Bestimmung lokaler Plasmaparameter wie Elektronen‐ und Ionendichte, Elektronentemperatur oder Plasmapotential benutzt. Die Erfahrungen mit Langmuirsonden haben gezeigt, daß Modifikationen der Sondenoberfläche durch Verunreinigungen oder durch Beschichtung zu signifikanten Veränderungen im Sondensignal führen können [5 – 16].Durch den Einsatz dieses Sensors sollen insbesondere jene Vorgänge, die zu einer lokalen oder generellen Verschlechterung der technologischen Schichteigenschaften führen, bereits in der Phase der Schichtentstehung erkannt und durch Variation der Prozeßparameter während der Schichtabscheidung vermieden werden. Eine solche sensorkontrollierte Prozeßsteuerung könnte den industriellen Einsatz der PACVD‐Technik auf eine breitere Basis stellen, da die gewünschten technologischen Schichteigenschaften bereits während des Prozesses über eine geeignete Prozeßführung beeinflußt werden können.
Entwicklungstrends in der Scheibenbremstechnologie für Schienenfahrzeuge
Authors: Zeuner T. , Ruppert H. , Engels A. 
Published: May 2005

Developing trends in disc brake technology for rail applicationThe substitution of conventional ferrous materials by light‐alloy solutions gives the opportunity for significant reduction of the rotating masses in the bogie and by that a decrease of energy consumption. The potential of conventional Al‐cast‐alloys is not suitable to solve this. Castable MMC‐materials are a high‐promising alternative. Under economic pressure MMC‐solutions need not to be only superior but also cost effective. And due to the low ductility of those particulate reinforced materials there is a need for new concepts.Locally optimised disks consist of a ductile carrier [body] with wear resistant rubbing surfaces. This led to several prototype disk brakes manufactured by different casting processes.This paper gives an overview about the state‐of the‐art and newly developed manufacturing routes and materials, metallic and non‐ metallic, for rail disk brake application.
The use of polar modifiers in microbore supercritical fluid chromatography combined with inductively coupled plasma spectrometry
Authors: Fujimoto Chuzo , Yoshida Hiroyuki , Jinno Kiyokatsu 
Published: May 2005

AbstractAn interface developed for detection of microbore supercritical fluid chromatographic (SFC) effluents with an inductively coupled plasma (ICP) spectrometer is described. The effect of modifiers on chromatographic peak intensity was investigated with respect to reproducibility, nebulizing gas flow rate, and viewing height. With 8.0 mol % methanol and 7.3 mol % acetonitrile in carbon dioxide, the interface allowed the total effluent from the microbore column to be introduced into the plasma without degrading the performance of the system. The applicability and usefulness of the SFC‐ICP system are demonstrated using standard mixtures.
Direct introduction of aqueous eluents for on–line coupled liquid chromatography–capillary gas chromatography
Authors: Cortes Hernan J. , Pfeiffer Curt D. , Jewett Gary L. , Richter Bruce E. 
Published: May 2005

AbstractThe on‐line introduction of relatively large volumes of reversed‐phase (aqueous) eluents into a capillary GC column without severe distortion of components eluting at temperatures close to the solvent boiling point is described. The technique, which utilizes an uncoated inlet (retention gap), is based on complete evaporation of the solvent prior to reaching the stationary phase and introduction of components with a dispersion equivalent to that given by a micro‐LC system. Studies of the evaporation within the retention gap, accomplished by introduction of a nonvolatile dye and visual examination of the resulting band patterns, indicated minimum retention gap lengths necessary to prevent liquid solvent from reaching the capillary GC column when aqueous eluents are used. The determination of N‐Serve' (2‐chloro‐6‐[trichloro methyl]pyridine) in corn extract is described.
Supercritical fluid chromatography–supersonic jet spectroscopy: I. Microcolumns and direct expansions
Authors: Simons John K. , Sin Chung Hang , Zabriskie Norman A. , Lee Milton L. , Goates Steven R. , Fields Steven M. 
Published: May 2005

AbstractDirect supersonic expansions of the eluent from a supercritical fluid chromatograph have been investigated as a means of attaining high selectivity in laserinduced fluorescence detection of polycyclic aromatic hydrocarbons. The direct expansion method appears impractical for capillary SFC, but it works well for microbore, packed‐column supercritical fluid chromatography. Perylene and benzo[a]pyrene were selectively detected at limits of 0.5 ng and 40 ng, respectively, in standard mixtures and coal tar samples.
High‐speed gas chromatography using an on‐column thermal desorption modulator
Authors: Liu Zaiyou , Phillips John B. 
Published: May 2005

AbstractA short, narrow‐bore (50 μm) column with an on‐column thermal desorp‐ tion modulator provides a technically simple and reliable method to generate high‐ speed gas chromatograms. A thermal desorption modulator prepared on the column but operated at a lower temperature functions as a sample introduction device. The modulator portion of the column extends outside of the oven and is at room temperature. A sample stream flows continuously into the modulator and through it into the column. Retained sample is released from the modulator by an electricaliy generated temperature pulse and carried into the column as a concentration pulse analogous to a sharp injecfion. Because the modulator is part of the column, no external injector is needed, and the volume of the concentration pulse is automatically appropriate for the column diameter. A series of chromatograms can be generated from a continuously flowing sample stream by applying a series of temperature pulses to the modulator. The narrow‐bore column is highly efficient and generates chromatograms with total retention times as short as 1 s. Chromatographic efficiency reaches the column's the oretical limit at very high carrier gas linear velocity. Measured terminal band lengths are shorter than the length of the modulator because the thermal gradient between modulator and column focuses bands as they enter the column. Band durations are less than the modulator thermal pulse duration because sample substances are released from the modulator stationary phase and carried onto the column during a small part of the temperature ramp.
New nitrophenyl‐ and nitromethoxyphenyl‐substituted methylpolysiloxane stationary phases for capillary column gas chromatography
Authors: Juvancz Zoltan , Pulsipher Michael A. , Schirmer Michelle M. , Johnson R. Scott , Markides Karin E. , Bradshaw Jerald S. , Lee Milton L. 
Published: May 2005

AbstractNitrophenyl‐, nitrophenylethyl‐, dinitrophenylethyl‐, and methoxynitrophen‐ ylethyl‐substituted polysiloxanes (25‐50% substitution) have been synthesized and evaluated as stationary phases in capillary column gas chromatography. Phases with 25% substitution and with ethylene spacers between the phenyl substituents and the polysiloxane backbone were found to provide high efficiencies, moderate thermal stabilities, and useful selectivities. Without flexible hydrocarbon spacers, the station‐ ary phases exhibited poor efficiencies. The 50% substituted phases generally provided narrower operational temperature ranges and lower efficiencies, and they were more difficult to immobilize by free radical crosslinking. Several methods of immobilization were evaluated, and a dynamic procedure with dicumylperoxide (DCP) was found to produce the best results for these nitrophenyl‐containing phases. The enhancements in polarity resulting from the resonances of the nitrophenyl substituent groups pro‐ vided unique selectivities for specific applications involving aromatic compounds. The dinitrophenyl‐containing phases showed, in addition, selectivity based on charge transfer complex formation.
Resolution of optical isomers of 2,3,4,6‐tetra‐O‐acetyl‐β‐D‐glucopyranosyl isothiocyanate (GITC)–derivatized DL‐amino acids by micellar electrokinetic chromatography
Authors: Nishi Hiroyuki , Fukuyama Tsukasa , Matsuo Masaaki 
Published: May 2005

AbstractResolution of isomers of 2,3,4,6‐tetra‐O‐acetyl‐β‐D‐glucopyranosyl isothiocyanate (GITC)–derivatized DL‐amino acids was accomplished using micellar electrokinetic chromatography with sodium dodecyl sulfate (SDS) solutions. These solutes were not separated by the usual capillary zone electrophoresis. Of 21 DL‐amino acids, optical resolution was recognized in 19 under the neutral and alkaline conditions; aspartic acid and glutamic acid have an additional carboxyl group. Simultaneous resolution of more than ten GITC derivatized DL‐amino acids was achieved within 40 min with the addition of 0.2 M SDS. The diastereomers of aromatic, heterocyclic, and basic DL‐amino acids were successfully separated owing to their effective solubilization into the SDS micelle, although a few peaks of the derivatives coeluted.
Analysis of cis‐platinum using a microcolumn with a β‐cyclodextrin stationary phase and electrochemical detection
Authors: Dolezel Petr , Kourilova Dana , Krejci Milos , Smolkova‐Keulemansova Eva 
Published: May 2005

AbstractA simple method for determining chemotherapeutically active cis‐platinum using a β‐cyclodextrin stationary phase on a silica gel carrier (β‐CD‐sil) is described. Retention of CDDP is considerably influenced by the content of acetonitrile in the mobile phase. With an electrochemical detector in oxidation mode, the minimal detectable amount of CDDP was determined to be 1.6 · 10−11 mol, and the minimal detectable concentration in the sample was 5 ppm (5 m̈g/mL). The method was used to determine CDDP concentration in the samples of body fluid (ascites).
Preliminary examination of the photoionization detector for microbore column supercritical fluid chromatography
Authors: Onuska Francis I. , Terry Ken A. 
Published: May 2005

AbstractA photoionization detector (PID) has been evaluated for its applications in supercritical fluid chromatography using microbore columns. The PID is a nondestructive detector which is sensitive to the concentration of the analyte. Thus, maximum sensitivity is obtained at low flow rates. The PID dynamic range in supercritical fluid chromatography is approximately 104, which is much smaller than in gas chromatography. Although the PID appears to complement the flame ionization detector (FID) in many respects, it should be considered of limited value in environmental trace analyses due to the large cell volume. The PID can be used with both conventional and microbore packed columns; however, the detector used in this study is not suitable in its present design for capillary SFC.
Preparation and separation properties of open tubular columns with immobilized Carbowax 20M for LC
Authors: Janák Karel , Horká Marie , Krejčí Miloš 
Published: May 2005

AbstractOpen tubular columns (3‐5 m × 23‐50 μm i.d.) were coated with Carbowax 20M (0.07‐0.2 μm film thickness) and immobilized with pluriisocyanates (Desmodur N or Desmodur L), a method which is simple, rapid, and reproducible. The concentration of cross‐linking agent and the preparation conditions were optimized with respect to stability and separation properties of the immobilized film under liquid chromatography (LC) conditions. Properties of columns in LC systems are strongly dependent on the degree of immobilization and slightly dependent on the type of Desmodur used as a cross‐linking agent. The degree of immobilization must exceed 90% for successful application in LC. Such columns displayed good long‐term stability, especially when immobilized with Desmodur L. Using water as the mobile phase, the LC system behaved as a reversed phase system. Capacity ratio and temperature strongly affected the separation efficiency.
Optimization of pH in the electrophoretic separation of 2‐, 3‐, and 4‐methylpyridines
Authors: Wren Stephen 
Published: May 2005

AbstractThe 2‐, 3‐ and 4‐substituted methylpyridines were used to investigate the theoretical and experimental relationships between pH and separation in free solution capillary electrophoresis. Separation was improved by the use of a cationic surfactant to suppress electroosmotic flow. The electrophoretic mobilities of the 3‐ and 4‐isomers were examined and found to be linearly dependant upon calculated charge.
Polymerization of formic acid on porous glassy carbon surface
Authors: Engel Tina M. , Olesik Susan V. 
Published: May 2005

AbstractWhile using porous glassy carbon (PGC) as a stationary phase for supercritical fluid chromatography (SFC), irreversible modifications of the PGC surface were observed when using 3% formic acid in supercritical carbon dioxide mobile phase at mild operating conditions. Scanning electron microscopic and energy dispersive X‐ray spectroscopic analyses indicated the formation of a polymer coating on the PGC surface. The coating may be formed from a polymerization reaction of the formic acid modifier catalyzed by the presence of the carbon surface. Those using carbon‐based stationary phases should be aware of this reaction when using formic acid as a modifier for SFC.
Combined two‐dimensional GC/MS/matrix isolation FT‐IR with a versatile sample introduction system
Authors: Rodriguez Pedro A. , Eddy Cynthia L. , Marcott Curtis , Fey Monica L. , Anast John M. 
Published: May 2005

AbstractA versatile sample introduction system or injector/trap (I/T), described in this paper, is a stand‐alone, computer‐controlled, cryogenic concentrator with provisions for solvent venting and inert sample transfer. The I/T is designed to provide a common interface between the column and a variety of sampling modules.Modules to perform thermal desorption and pyrolysis, as well as modules for remote sampling (pre‐traps) have been developed. Large volumes of either gaseous or liquid samples can be introduced by means of pre‐traps packed with suitable substrates. Pretraps packed with Tenax TA allowed quantitative recovery of compounds as volatile as n‐decane (n‐C10) when contained in a 1‐mL volume of pentane. The introduction of a 1–mL sample makes it possible to reach a detection limit of ca. 100 ppt,ppt, ppb, ppm refer to parts‐per‐trillion (1012), billion (109), and million (106), respectively.
with an FID, for compounds with boiling points ≥n‐C9.The capability to do trace analyses with the I/T is enhanced by interfacing it to a twodimensional gas chromatograph (2D/GC) equipped with a mass‐selective detector (MSD) and a matrix isolation fourier transform infrared spectrometer (MI FT‐IR). The resulting instrumentation greatly facilitated the identification of organic compounds present at ppbconcentrations in perfume samples.
Preparation of reversed phase open tubular liquid chromatographic columns from borosilicate glass
Authors: Claire Robert L. St. , Dohmeier Daniel M. , Jorgenson James W. 
Published: May 2005

AbstractThe preparation of open tubular liquid chromatographic columns with small inner diameters (≤ 20 μm) from Pyrex 7740 borosilicate glass is described. The surface area of the inner wall of the capillary is increased by etching with a series of acidic and basic solutions. Dimethyloctadecylchlorosilane is then reacted with the column wall to create a bonded stationary phase layer. The resulting columns exhibit good retention and high efficiency. The effects of each step in the etching process are examined and the silanization reaction is optimized.
4‐(Methylsulfonyl)phenyl‐containing polysiloxane stationary phase for capillary column gas chromatography
Authors: Juvancz Zoltan , Schirmer Michelle M. , Johnson Deborah F. , Markides Karin E. , Bradshaw Jerald S. , Lee Milton L. 
Published: May 2005

AbstractA new polar polysiloxane stationary phase for capillary column gas chromatography containing 4‐(methylsulfonyl)phenyl substitution was synthesized and compared to a cyanophenylpolysiloxane, OV‐225. The sulfonylphenylpolysiloxane phase was useful and stable over a wide temperature range from 70°C to 320°C, and it exhibited similar overall polarity to OV‐225. However, because of the specific chemical properties of the 4‐(methylsulfonyl)phenyl group, this phase demonstrated unique selectivities for certain classes of compounds including basic nitrogen heterocycles and polychlorinated biphenyls.
Polymeric coatings in packed fused silica micro‐LC columns
Authors: Ghijs Marleen , Sandra Pat 
Published: May 2005

AbstractDifferent polymer‐coated stationary phases have been evaluated in micro‐LC: Nucleosil‐100‐5‐C1‐PMSC18 (C18‐substituted polymethylsiloxane, C1‐deactivated with trimethylsilylenolate) and Nucleosil‐100‐5‐C1‐PMSCN (cyanopropyl‐substituted polymethylsiloxane, C1‐deactivated) in the reversed phase mode and Nucleosil‐100‐5‐PEG (polyethylene glycol‐coated) in the normal phase mode.Fused silica tubing of 320‐μm i.d. was slurry packed with suspensions optimized for each packing material. The micropacked columns were studied for efficiency and selectivity. The silanol activities of the polymer coated phases were compared to monomeric phases for the reversed phase mode and to silica for the normal phase mode.
Chemical analysis of bis(5‐amidino‐2‐benzimidazolyl) methane in the arthritic rat knee using microdialysis and microcolumn liquid chromatography
Authors: Claire Robert L. St. , Brouwer Kenneth R. 
Published: May 2005

AbstractMicrocolumn liquid chromatography and microdialysis were coupled together to study the distribution of an IV administered drug into the knee joint of a rat with acute arthritis. Dialysate from microdialysis probes located directly within the intraarticular region and in the surrounding muscle was delivered at a flow rate of 0.25 μL min−1 directly into a microcolumn LC system. A 0.5‐mm i.d. microcolumn and fluorescence detector were utilized. An in vitro model was developed to estimate the drug concentration in the dialysate. Differences in drug distribution between the intra and extraarticular knee regions were detected, and the potential utility of this technique in the pharmacokinetic evaluation of site‐specific drugs was demonstrated.
Examination of variables affecting the performance of isoelectric focusing in uncoated capillaries
Authors: Mazzeo Jeff R. , Krull Ira S. 
Published: May 2005

AbstractThe effects of different variables on protein separation by isoelectric focusing in uncoated capillaries were investigated. Four model proteins were used to study the effects. The variables included applied electric field, column length, % methyl cellulose, % tetramethylethylenediamine (TEMED), and buffer concentration. Methyl cellulose showed a bimodal effect on the separation performance in terms of migration time and peak width. It was determined that the optimal %TEMED and applied field depended strongly on each other. Furthermore, longer column lengths led to better resolution at constant field and % TEMED. Using a grid, the applied electric field and % TEMED were optimized concurrently at a fixed column length.
(S) ‐TroloxTM methyl ether, a powerful derivatizing reagent for the determination of the enantiomeric purity of chiral alcohols by GC and SFC with achiral columns
Authors: Walther Wiley , Vetter Walter , Netscher Thomas 
Published: May 2005

AbstractThe enantiomers of aliphatic alcohols are transformed by a new chiral reagent (S)‐Trolox methyl ether to their diastereomeric esters which are separated by capillary GC or SFC on achiral columns. The applicability of this reagent and its superiority to the hitherto known reagents are demonstrated by selected examples.
Temperature‐programmed microcolumn liquid chromatography/mass spectrometry
Authors: Yoo Jong Shin , Watson J. Throck , McGuffin Victoria L. 
Published: May 2005

AbstractA temperature‐programmed microcolumn liquid chromatography/mass spectrometry (LC/MS) system has been developed as a practical alternative to conventional solvent‐programmed LC/MS. Good reproducibility of solute retention was achieved in a specially modified oven that permitted linear temperature programming between 40 and 100°C at rates of 0.1 to 0.5°C min−1. Through theoretical modelling studies performed under isocratic and isothermal conditions, the optimum separation under temperature‐programmed conditions was rapidly and accurately predicted. This method enabled the complete resolution of saturated and unsaturated fatty acids in a fish oil dietary supplement with identification from their characteristic fragmentation patterns under electron‐impact MS conditions. The mass spectra from the LC/MS system correlated very well with those from a standard reference library to facilitate spectral searching methods.
Optimization of the eluent delivery system for micro size‐exclusion chromatography
Authors: Alexandrov Maxim L. , Belenkii Boris G. , Gotlib Vladimir A. , Kever Jeno E. 
Published: May 2005

AbstractThe problems of microcolumn size‐exclusion chromatography and its instrumentation are considered. It is shown that the reproducibility of retention times of a micro‐gel chromatograph depends on the stability of eluent delivery by a syringe micropump. It is possible to increase this stability and to suppress the relaxation processes related to the changes in hydrodynamic column resistance and in the solvent temperature in the pump chamber.In order to suppress instability when columns of 0.5‐mm inner diameters are used, the volume of the eluent delivery system should be as small as possible (Vp ⩽ 1 mL) and the system should be thermostatted at ΔT 〈P∞(α/β)δ where P ∞ is the pressure under conditions of constant pump pressure, α and β are the coefficients of thermal expansion and compressibility of the liquid, and δ is the permissible retention time error (ΔtR/tR).