bluuebunny/crossref_metadata_2025 huggingface dataset:
Berechnung der Umformeigenspannungen beim Fließpressen und Vergleich mit experimentellen Ergebnissen
Authors: Zucko M. , Pöhlandt K. , Pyzalla A. , Reimers W. , Kockelmann H.
Published: May 2005

Die beim Fließpressen erzeugten Eigenspannungen I. Art werden durch eine Simulation des Umformprozesses mit der Finite‐Elemente‐Methode berechnet. Zur experimentellen Bestimmung der Eigenspannungen werden die Röntgenbeugung, die Neutronen‐beugung und das Bohrlochverfahren eingesetzt. Die Ergebnisse der Simulation und der Versuche stimmen qualitativ, die experimentellen Verfahren untereinander auch quantitativ überein. Sie ermöglichen es, den Einfluß der Variation unterschiedlicher Umformparameter auf den Eigenspannungszustand aufzuzeigen. Damit sind die Voraussetzungen für eine Erzeugnisoptimierung hinsichtlich des Eigenspannungszustandes gegeben.
Delaminationsverhalten von langfaserverstärkten thermoplastischen UD‐Verbunden hergestellt aus unterschiedlichen Hybridgarnstrukturen
Authors: Bunzel U. , Schneider K. , Lauke B.
Published: May 2005

Zur Charakterisierung der Widerstandsfähigkeit gegen Delamination und Rißfortschritt wurde an thermoplastischen UD‐Verbunden, die aus unterschiedlichen Hybridgarnstrukturen hergestellt worden sind, die Druckscherfestigkeit sowie interlaminare Bruch‐zähigkeit mittels „Double Cantilever Beam”︁‐Test (DCB), „Single Edge Notched”︁‐Test (SEN) und „Notched Bending”︁‐Test (NBT) für Mode I‐Belastung und dem „End Notched Flexure”︁‐Test (ENF) für Mode II‐Belastung untersucht. Die Hybridgarnstrukturen unterscheiden sich ihrer Herstellugstechnologie entsprechend in der Anordnung der Verstärkungs‐und thermoplastischen Matrixfilamente im Garn. In die Untersuchungen einbezogen wurden außerdem Verbunde mit unterschiedlicher Grenzschichtgestaltung. Ermittelt wurden die kritischen Energiefreisetzungstraten Gc bzw. die kritischen Spannungsintensitätsfaktoren Kc und für Mode I‐Belastung die entsprechenden Rißausbreitungskurven, die die interlaminare Rißausbreitung charakterisieren. Die besten Ergebnisse wurden mit der lufttexturierten Hybridgarnstruktur erreicht.
Schutzsysteme für Verschraubungselemente in Kontakt mit Leichtmetall
Authors: Reinhold B. , Klose S. G. , Kopp J.
Published: May 2005

Es wird ein Überblick über die derzeit im Kraftfahrzeugbau verwendeten Verschraubungselemente für Leichtmetallegierungen gegeben. Dabei werden konstruktive Auslegungen, Werkstoffauswahl und Beschichtungskonzepte für Magnesium‐ und Aluminiumlegierungen vorgestellt. Die spezielle Problematik der Kontaktkorrosion wird anhand elektrochemischer Messungen f ür verschiedene Beschichtungssysteme im Verbau mit Magnesium diskutiert. Bisherige Felderfahrungen im Automobilbereich fließen jeweils in die Betrachtungen mit ein.
Deposition of PVD Coatings on different geometries and local characterization for reliable properties
Authors: Friedrich Chr. , Berg G. , Senf J. , Broszeit E.
Published: May 2005

Although the characteristics of PVD coatings in research and development papers are very promising, in the field of tribology the industrial application of these coating types is restricted to special market segments up to now: the deposition of hard coatings is state of the art on tools, whereas PVD coated machine components are quite rare.

This is caused by the coatings profile of properties, the various surroundings and the demands for application reliability. The last aspect is the main topic of this contribution. Reliability is especially important for machine components, because tools may fail after relative short life time compared to machine parts. Besides this tools and the corresponding production equipment are designed for fast tool replacement in contrast to other machines, which should work without standstill and with a minimum of maintenance.

Characteristics of coated systems must be guaranteed in practice theory and laboratory experiments have to show what is possible. On the one hand reproduction of the deposition process must be guaranteed to enter application fields with high demands for reliability, on the other hand characterization of coated systems must be standardized with admissible deviations for communication between coaters and users. These aspects are important for decisions concerning the use of coating substrate systems in tribology besides the topics of technical function.

The present investigation shows main reasons for deviations in results of PVD coatings.
Colouring process for ferritic stainless steel alloy in NaNO3‐KNO3 eutectic melt
Authors: Ali H. A. Abdel‐Hakim , Gwad S. A. Abdel , Masri A. N. Al , Baraka A. M.
Published: May 2005

The colouring process of the ferritic stainless steel alloy (15.03 Cr) was carried out in pure NaNO3‐KNO3 eutectic melt and in presence of Na2O2, NaCl and their mixtures at different temperatures (673–873 K) under open‐circuit and galvanostatic anodic polarization conditions. Coloured oxide films can be formed and the colours greatly depend on the thickness which in turn depends on the composition of the molten bath and its temperature. The more attractive, bright, adherent and uniform coloured films can be formed at temperatures of 673, 723 and 773 K in the nitrate melt containing Na2O2 and mixtures of 0.5 M NaCl with Na2O2 additions. The corrosion tests, carried out on the coloured oxide films in 0.1 M HCl solution, show that the corrosion resistance of the coloured films greatly depends on the previous operating conditions of the colouring process such as composition of molten bath and its temperature.
Development of a new creep specimen for medium and high temperature tests
Authors: Skrotzki B. , Neuking K. , Mayr Ch. , Eggeler G.
Published: May 2005

A new creep sample geometry is presented which has round heads instead of threads to connect to the grips. This reduces high temperature adhesion problems considerably. In addition, the production of samples from materials which are difficult to machine or which requires expensive machining techniques is made easier using this geometry. The successful use of the sample is demonstrated by means of two examples.
Verwendung von statistischen Grundlagen für die Lebensdauervorhersage bei schwingender Beanspruchung
Authors: Gudladt H.‐J. , Bazaios I.
Published: May 2005

Zur experimentellen Lebensdauervorhersage an bauteilnahen Proben werden Schwingfestigkeitsuntersuchungen üblicherweise aus Zeit‐ und Kostengründen mit einer relativ kleinen Anzahl von Proben durchgeführt. Andererseits ist auf einem vorgegebenen Lastniveau grundsätzlich mit einer Streuung der Versuchsergebnisse, d. h. der Anrißlastspielzahl Nibzw. der Lastspielzahl bis zum Bruch Nf, Zu rechnen. Um Lebensdauervorhersagen auf statistischer Grundlage durchführen zu können, muß beim Merkmalswert Nfin Betracht gezogen werden, daß die Rißausbreitung im Gegensatz zur Rißbildung in vielen Fällen deterministisch bestimmbar ist. Es ist daher abzuschätzen, in wie weit dieser Beitrag die Streuung der Gesamtlebensdauer beeinflußt. Desweiteren wurde bislang vorausgesetzt, daß der Versagensmechanismus immer auf dem selben Schädigungstyp beruht. In diesem Fall kann die Lebensdauer z. B. mit einer zweiparametrigen Weibull‐Verteilung durch Angabe des Streu‐und Lageparameters statistisch beschrieben werden. Bei der Verwendung einer geeigneten Dichtefunktion lassen sich die Schwingspielzahlen über die Ausfallwahrscheinlichkeiten auftragen. Im Fall von Al‐Basislegierungen hat sich gezeigt, daß diese Auftragung keinen linearen Zusammenhang mehr aufweist, was dafür sprechen könnte, daß mindestens zwei unterschiedliche Defektsorten die Anrißbildung im Bauteil einleiten. Dies konnte für AlMgSi‐Bleche anhand von Bruchflächenanalysen direkt nachgewiesen werden. Dazu wurden Ermüdungsrisse klassiert, die sich entweder an den Probenkanten oder direkt an Kratzern der Walzhaut bildeten. Die zwei Ereignisse ließen sich bei sonst gleichbleibenden Versuchsbedingungen in einzelne Weibull‐Verteilungen zerlegen. Damit läßt sich im Fall von bauteilnahen Proben die Lebensdauer für kleine Ausfallwahrscheinlichkeiten genauer abschätzen als dies bislang der Fall ist.
Spannung‐Dehnung‐Hysteresismessungen an zyklisch beanspruchtem unidirektional SiC‐kurzfaserverstärktem Alkali‐Kalk‐Silicatglas
Authors: Marchetti K. , Roeder E. , Eifler D.
Published: May 2005

Im Hinblick auf die technische Anwendung faserverstärkter Gläser ist die Kenntnis des Ermüdungsverhaltens dieser Werkstoffe eine unabdingbare Voraussetzung. Hierzu wurden AR‐Glasproben sowie SiC‐kurzfaserverstärkte AR‐Glas‐Verbundproben durch Strangpressen hergestellt und in spannungskontrollierten 3‐Punkt‐Biegeversuchen im Schwellbereich schwingend beansprucht. Die Charakterisierung des zyklischen Verformungsverhaltens und die Bewertung der Versagensmechanismen in Abhängigkeit von Beanspruchungsamplitude, Beanspruchungsdauer und Faservolumengehalt erfolgte mit Hilfe des Hysteresismeßverfahrens sowie lichtmikroskopischer Strukturuntersuchungen an den Probenoberflächen. Ausgewählte Versuchsergebnisse werden vorgestellt und diskutiert.
Anrißlebensdauervorhersagemethode für beliebige mehrachsige Beanspruchungen mit kontinuierlicher Schädigungserfassung
Authors: Ott W. , Nowack H. , Trautmann K.‐H.
Published: May 2005

Das Problem der Anrißlebensdauervorhersage bei beliebigen proportionalen und nicht‐proportionalen mehrachsigen Schwingbeanspruchungen im Zeitfestigkeitsbereich ist immer noch nicht befriedigend gelöst. In der vorliegenden Arbeit wird eine neue Methode vorgeschlagen, mit der an hochfesten mittelspannungsempfindlichen Aluminiumlegierungen positive Ergebnisse erzielt wurden. Diese Methode benutzt die plastische Arbeit, die in jedem Punkt eines mittels der elastisch‐plastischen FE‐Methode dargestellten Prüfkörpers während der mehrachsigen schwingbelastunginkrementell akkumuliert wird, als Indikator für die auftretende Ermüdungsschädigung. Eine neue Formulierung berücksichtigt zusätzlich die momentane Mittelspannungen. Aus Anwendersicht ist die vorgeschlagene Methode vorteilhaft, weil besondere ermüdungsbezogene Beanspruchungsereignisse, wie z. B. geschlossene Hystereseschleifen, nicht definiert und „gezählt”︁ werden müssen.
Bewertung des Einflusses von Eigen‐ und Mittelspannungen auf die Dauerfestigkeit des Stahls 42CrMo4 im vergüteten Zustand
Authors: Bomas H. , Linkewitz T. , Mayr P.
Published: May 2005

Seit langem ist die qualitative Wirkung von Mittel‐ und Eigenspannungen auf die Dauerfestigkeit von Stählen bekannt. Die quantitative Beschreibung der Wirkung der Eigenspannungen erscheint jedoch unzureichend, da die Besonderheiten des Eigenspannungszustandes wie Nichtstabilität während der Belastung, Mehrachsigkeit, starke Gradienten sowie gelegentliche große Unterschiede zwischen Oberfläche und Volumen in den gängigen Konzepten nicht berücksichtigt werden. Es werden Untersuchungen zur Dauerfestigkeit eines vergüteten Stahls vorgestellt, auf die verschiedene Konzepte zur Bewertung von Eigen‐ und Mittelspannungen angewandt werden. Hierbei zeigt sich, daß auf die Unterscheidung zwischen Eigenspannungs‐ und Mittelspannungsempfindlichkeit verzichtet werden kann, wenn das Bewertungskonzept die oben genannten Charakteristika der Eigenspannungen berücksichtigt.
Gefüge und Korrosionsverhalten eines stickstofflegierten rostfreien Stahls
Authors: Herzbach L. C. , Schmidt H. , Windler M.
Published: May 2005

Das Korrosionsverhalten eines stickstofflegierten rostfreien Stahles wird durch potentiodynamische anodische Polarisation in physiologischer NaCl‐Lösung untersucht. Der Gefügezustand geschmiedeter Proben wird mikroskopisch und durch Härtemessungen ermittelt. Der Stahl weist ein globulares austenitisches Gefüge auf, in der Zone starker Schmiedeverformung sind die Körner gestreckt. Es liegen Ausscheidungen vor, in denen Chrom und Molybdän angereichert sind. Der Stahl zeigt Durchbruchspotentiale zwischen 200 und 1170 mV vs. SCE, die meisten Werte liegen über 500 mV. Die Durchbruchspotentiale fallen mit zunehmendem Streckungsgrad der Körner und zunehmender Härte ab. Die Ausscheidungen sind Initialpunkte für loch‐ und kraterförmigen Materialabtrag.
Corrosion Inhibition of mild steel in aqueous solution containing H2S by some naturally occurring substances
Authors: Barakat Y. F. , Hassan A. M. , Baraka A. M.
Published: May 2005

The corrosion inhibition of mild steel by some naturally occuring substance was evaluated in absence and presence of 600 and 1200 mg H2S/l in 3% NaCl aqueous solution and pH of 3 and temperature of 25 °C. These naturally occurring substance included the water extracts, coumarines and fatty matters extracts of some Egyptian plants. These plants included:

(1) Nigella Sativa (Family Ranunculacease) (Extract (1), 2) Coriandrum Sativum (Family Umbelliferea) (Extract II), 3) Ricinus communis (Family Euphorbiaceae) (Extract III). The galvanostatic anodic and cathodic polarization measurements were used for studying the corrosion behavior of mild steel and evaluation of the percentage inhibition of the undertesting extracts of these three plants and also preparation of fatty matters and coumarin fractions were mentioned.
Entwicklung metallorganisch basierter Keramiken
Authors: Gadow R. , Kienzle A.
Published: May 2005

Ausgangspunkt des Polymer‐Pyrolyse‐Verfahrens stellen hochreine monomere Precursor dar, die über Additions‐ oder Kondensationsreaktionen polymerisiert und durch Pyrolyse unter Schutzgasatmosphäre in amorphe Keramiken überführt werden. Durch Tempern bei erhöhter Temperatur können die Keramiken zur Kristallisation gebracht werden. Die Pyrolyse von Polysilanen und Polycarbosilanen ergibt Si‐C‐Keramiken, Polysiloxane werden in Si‐C‐O‐Keramiken und Polysilazane bzw. Polysilylcarbodiimide in Si‐C‐N‐ oder Si3N4‐Keramiken umgewandelt. Durch Kombination verschiedener Precursormaterialien lassen sich über die Polymer‐Pyrolyse‐Route Multikomponentenkeramiken außerordentlicher Homogenität und mit vielfältigen Eigenschaften herstellen. Die erreichbaren keramischen Ausbeuten liegen je nach Precursorsystem bei bis zu 90%. Die beschriebenen Keramiken finden Anwendungen in Form monolithischer Formkörper, als Fasern oder faserverstärkte Verbundwerkstoffe oder als über Dip‐Coating hergestellte Schichten.
Anforderungen und Bewertung dünner Schichten im tribologischen Einsatz
Authors: Friedrich C. , Berg G. , Senf J. , Broszeit E. , Kioos K.‐H.
Published: May 2005

Dünne Schichten für die Tribologie sind in den letzten Jahren und Jahrzehnten intensiv gefördert worden. Dementsprechend viele Einzelkenntnisse liegen daher zu diesem Thema vor. Bis heute fehlt jedoch eine handhabbare und zuverlässige Entwicklungssystematik für den praktischen Ingenieureinsatz. Die am Schluß des Beitrags angegebene Literaturquelle greift dieses Problem auf und zeigt Lösungen. Nachfolgender Beitrag stellt einen Ausschnitt daraus vor. Aus diesem Grund werden einzelne Aspekte nur beschrieben, ohne alle Einzelheiten an dieser Stelle zu belegen. Dafür steht die Quelle mit vielen detaillierten Hinweisen zur Anwendung von Hartstoffschichten und über 900 weiteren Literaturverweisen zum Thema zur Verfügung. Dort finden sich auch alle hier fehlenden Angaben zu einzelnen Parametern und Randbedingungen sowie weitere Daten und Angaben zu allen hier angesprochenen Aspekten. Auswahl‐ und Bewertungstabellen machen die Quelle zu einem nützlichen Handbuch für den Einsatz von dünnen Hartstoffschichten in Theorie und Praxis. Bei Fragen zur Beschaffung der Literaturquelle steht der Autor für nähere Auskünfte zur Verfügung.
Wälzverschleiß und ‐ermüdung von Bauteilen und Maßnahmen zu ihrer Einschränkung
Authors: Böhmer H.‐J.
Published: May 2005

Wälzbeanspruchte Teile, wie Zahnräder und Wälzlager, unterliegen ganz charakteristischen Beanspruchungen, wie sie in anderen technischen Anwendungen nicht vorkommen. Diese besonderen Bedingungen und ihre Auswirkungen auf die Beanspruchungsverhältnisse und das Werkstoffverhalten werden ausführlich beschrieben. Vor allem Ingenieuren, die weniger mit dem Themenkomplex Wälzermüdung und ‐verschleiß vertraut sind, soll eine übersichtliche und gestraffte Einführung in dieses Gebiet gegeben werden. Hierzu werden die wichtigsten Einflußgrößen auf das verhalten wälzbeanspruchter Bauteile, der Ablauf einer eventuellen Schadensinitiierung und die Erscheinungsbilder verschiedener Ausfallsursachen dargestellt. An Beispielen wird gezeigt, wie sich aus der Analyse der Schädigungsabläufe Abhilfemaßnahmen herleiten lassen. Die Literaturhinweise sind so gewählt, daß sich der interessierte Leser in die einzelnen Themengebiete selbständig weiter vertiefen kann.
Supercritical fluid extraction combined with microcolumn liquid chromatography for the analysis of polymer additives
Authors: Hirata Y. , Okamoto Y.
Published: May 2005

Polymer additives were extracted with supercritical carbon dioxide and collected in a microtrap. The collected samples were separated by microcolumn liquid chromatography. Polymer samples down to the sub‐milligram level were handled without loss of extract. Information about the distribution of additives was also obtained.
Capillary zone electrophoresis with laser fluorescence detection of marine toxins
Authors: Wright Bob W. , Ross Gerald A. , Smith Richard D.
Published: May 2005

Capillary zone electrophoresis (CZE) was applied to the characterization of highly polar marine toxins that can be difficult to address using traditional chromatographic methods. Separation efficiencies of nearly 400,000 the oretical plates were obtained in just over 10 min. Laser fluorescence detection provided attomole detection limits of parts per trillion solutions.
Scanning ultraviolet detection in capillary supercritical fluid chromatography
Authors: Weinberger Scot R. , Bornhop Danyl J.
Published: May 2005

A rapid‐scanning ultraviolet‐visible (UV‐vis) detector was interfaced successfully with capillary supercritical fluid chromatography (SFC). The pseudo on‐column detection approach was used to produce a detector dead volume of less than 60 nL. High sensitivity (low picogram detection limits), a large linear dynamic range (greater than three orders of magnitude in concentration), and full spectral scanning were achieved. Many of the limitations commonly encountered when in corporating a photodiode array (PDA) into a capillary‐based separation scheme were overcome. An SFC separation of several pesticides and caffeine illustrate the utility of the detector‐SFC system.
Microcolumn supercritical fluid chromatography with on‐line Fourier transform infrared detection
Authors: Raynor Mark W. , Clifford Anthony A. , Bartle Keith D. , Reyner Colin , Williams Alan , Cook Bernard W.
Published: May 2005

The combination of capillary supercritical fluid chromatography (SFC) and Fourier transform infrared spectrometry (FTIR) is demonstrated using a low‐volume (0.8 μL) flow cell capable of withstanding high pressures. The design of the interface is presented, and its effect on peak shape and detector sensitivity is discussed. In order to optimize the system for use with 50‐μ i.d. capillary columns, makeup fluid is added to the column effluent before it passes through the flow cell to a flame ionization detector (FID). Loss in chromatographic resolution caused by the cell's dead volume is therefore minimized, which is clearly demonstrated by the analysis of two ultraviolet curing coatings using carbon dioxide as a mobile phase. This application highlights the analytical power of the system for separating and identifying reactive monomers, oligomers, and photoinitiators in low‐ to medium‐molecular‐weight polymer systems.
Effects of pH on electrokinetic velocities in micellar electrokinetic chromatography
Authors: Otsuka Koji , Terabe Shigeru
Published: May 2005

Effects of pH of micellar solutions on electrokinetic velocities in micellar electrokinetic chromatography were investigated using sodium dodecyl sulfate (SDS) solutions. The electroosmotic velocity decreased with a decrease in pH below 5.5, while the electrophoretic velocity of the SDS micelle was almost constant throughout the pH range of 7.0–3.0. Consequently, the migration velocity of the SDS micelle decreased with a decrease in pH, and its direction changed at pH 5.0: the direction was the same as that of the electroosmotic velocity above pH 5.0 and the reverse below pH 5.0. In the latter case, the retention time and resolution will be infinity at a relevant value of the capacity factor, and a wider elution range can be attained.
Resolution of optical isomers by capillary zone electrophoresis: Study of enantiomeric and diastereoisomeric Co(III) complexes with ethylenediamine and amino acid ligands
Authors: Fanali S. , Ossicini L. , Foret F. , Bocek P.
Published: May 2005

Capillary electrophoresis (CZE), with hydrodynamic injection and UV detection, was applied to the separation of enantiomeric and diastereoisomeric Co (III) complexes.
Separation of saccharides on cross linked chitosan beads with microcolumn liquid chromatography
Authors: Jinno Kiyokatsu , Takayarna Katsumi
Published: May 2005

Porous chitosan beads cross‐linked by hexamethylene‐bis‐2,3‐epoxypro‐pyldimethylammonium chloride were methylated to prevent adsorption of solutes on the hydroxy groups and to be used as the stationary phase in liquid chromatography. The beads were derivatized without loss of their gel permeability. Separation of some monosaccharides was achieved with the beads when boric acid solution was used as the mobile phase. Resolution for monosaccharides was remarkably improved by selecting a suitable pH and concentration of boric acid in the mobile phase. In order to detect saccharides by UV, apostcolumn derivatization method with 2‐cyanoacetamide was adopted.
Supercritical fluid chromatography–supersonic jet spectroscopy: II. Capillary column SFC with a sheath‐flow nozzle
Authors: Goates Steven R. , Sin Chung Hang , Simons John K. , Markides Karin E. , Lee Milton L.
Published: May 2005

Supersonic jet spectroscopic detection has been successfully coupled to capillary supercritical fluid chromatography by introduction of the supercritical effluent into a secondary flow of argon, before supersonic expansion of the combined flow through a converging nozzle. At pressures of 6–10 atm, the flowing sheath of argon efficiently carries eluting sample through a 25‐p.m nozzle orifice into the supersonic jet. Dead volumes are negligible in this arrangement, and high‐resolution fluorescence excitation spectra are obtained. Perylene and benzo[a]pyrene were selectively detected in a standard reference coal tar sample at detection limits of 150 pg and 5 ng, respectively.
Chiral separation of optical isomeric drugs using micellar electrokinetic chromatography and bile salts
Authors: Nishi Hiroyuki , Fukuyama Tsukasa , Matsuo Masaaki , Terabe Shigeru
Published: May 2005

Separation of optical isomeric drugs using micellar electrokinetic chromatography and bile salts as surfactants was studied. Optical isomers of diltiazem hydrochloride, trimetoquinol hydrochloride, and other drugs were separated successfully using chiral bile salts under neutral or alkaline conditions. Capacity factors were determined from the migration times of the solute, the micelle, and methanol. The effects of bile salt species or structures and of the pH value of the buffer solution were investigated. A possible chiral separation mechanism is suggested.
Multidimensional gas chromatography: State of the art
Authors: Himberg Kimmo , Sippola Erkki , Riekkola Marja‐Liisa
Published: May 2005

Gas chromatography (GC) is one of the most important techniques of organic analytical chemistry. It is widely used in the analysis of complex samples in environmental and medical applications. In order to reliably identify and quantitate the analyte that often exists at a residual concentration level, the GC system must in many cases have a separation power that cannot be achieved using one column within a reasonable analysis time. An extremely high resolution can be achieved by two‐stage GC (multidimensional GC, two‐dimensional GC), where the sample flows of two GC columns have been connected on‐line by a valve or valve system in such a way that only a selected fraction from the partly separated sample eluting from the first column can be transferred to the second column for further separation. This review describes the development of the technique and discusses areas of its applicability.
Supercritical fluid chromatography with Fourier transform infrared and mass spectrometric detection of peracetylated nitrogen derivatives of monosaccharides
Authors: Calvey Elizabeth M. , Roach John A. G. , Taylor Larry T. , Palmer James K.
Published: May 2005

Sugar oximes can be derivatized to yield both the peracetylated oxime and nitrile. The peracetylated oximes do not elute under isothermal (i.e., 200°C) gas chro‐ matography (GC) conditions. When a seven‐component derivatized sugar mixture, as determined by GC, was chromatographed under supercritical fluid chromatography (SFC) conditions with a cyanopropyl capillary column, at least 17 peaks were observed. In an effort to identify the additional derivatization products, the eluates were sub‐ jected to SFC‐FTIR and SFC‐MS. The spectral data indicate that cyclic and acyclic oximes as well as nitrile were formed as part of the derivatization method.
Column technology for packed capillary columns
Authors: Hirata Yukio
Published: May 2005

The packed capillary column is one type of microcolumn. It is used increasingly in liquid chromatography, supercritical fluid chromatography, and multidimensional chromatography. In order to attain high efficiency with packed capillary columns, reliable column preparation methods must be used. The development of the technique is summarized.
Microbore packed column supercritical fluid chromatography using a new polymer stationary phase
Authors: Liu Yan , Yang Frank , Pohl Chris
Published: May 2005

Packed capillary and microbore column supercritical fluid chromatography (SFC) using a newly developed, highly cross‐linked ethylvinylbenzene and divinylbenzene (EVB–DVB) polymer as the packing material is presented. The EVB–DVB polymer stationary phase has been developed specifically for microbore packed column SFC applications. Compared to silica‐based packing materials, the EVB–DVB polymer is much more inert and free of active adsorption sites, has very good temperature and pressure stabilities, and is compatible with common organic solvents and aqueous samples (pH 0 to 14). The capillary and microbore columns packed with the EVB–DVB polymer have been used successfully to separate a number of polar and nonpolar compounds such as alkanes, free fatty acids, aromatic amines, and cyclic amines using pure supercritical CO2 as the mobile phase. The experimental results indicate that the retention mechanism of polar and nonpolar compounds on the EVB–DVB polymer stationary phase is governed by the surface adsorption–desorption that is an apolar–apolar interaction; the retention mechanism also is significantly influenced by the π–π surface interaction in π‐electron‐rich solutes because of the high density of π‐electrons associated with the aromatic components of the stationary phase. Some important practical aspects and comparisons between capillary and microbore packed columns in SFC applications are also discussed.
Polycarbonates as stationary phases for aqueous and acidic samples in capillary gas chromatography
Authors: Ghaoui Labib , Bonadies Joseph
Published: May 2005

Polycarbonates were evaluated as stationary phases for capillary gas chromatography. Advantages of these resins are their high thermal stability and inertness to water. Long column lifetimes are exhibited for analysis of difficult samples such as acrylic acid in an acrylamide/water solution. The chromatographic behavior and typical applications are discussed.
Evaluation of sulfur chemiluminescence detection in supercritical fluid chromatography
Authors: Pekay Lars A. , Olesik Susan V.
Published: May 2005

The sulfur chemiluminescence detector was optimized for the analysis of organosulfur compounds by supercritical fluid chromatography. The flame gases used in this study were hydrogen and air. The highest sensitivity was found when a fuel‐rich flame was used. The noise characteristics of the detector were determined. Flicker noise is the primary source of noise in this detector when analyte is present. The linear dynamic range of the detector under supercritical fluid chromatography conditions was typically three orders of magnitude. For the optimum flame gas conditions, the detection limits for two‐and three‐ring organosulfur compounds were 10–1400 pg injected. The detection of sulfur in high molecular‐weight polymers was also demonstrated.
Stopped‐flow FTIR detection in capillary supercritical fluid chromatography
Authors: Raynor Mark W. , Bartle Keith D. , Clifford Anthony A. , Cook Bernard W.
Published: May 2005

A stopped‐flow procedure for capillary supercritical fluid Chromatography with Fourier transform infrared detection is described. The flow of mobile phase is stopped so that the analyte peak is held under liquid conditions in the flow cell while FTIR scans are recorded. An increase in the IR spectrum signal‐to‐noise ratio is demonstrated during the analysis of a polymer additive.
Technique for injecting very large volumes in capillary supercritical fluid chromatography
Authors: Hirata Yukio , Kadota Yasuhiko , Kondo Tadashi
Published: May 2005

A new technique for injecting very large volumes was developed for capillary supercritical fluid chromatography, which is based on dilution and venting techniques. Dilution of sample solution with carbon dioxide mobile phase made the selective venting of sample solvent very effective. Pressure at the end of the precolumn was also an important parameter for venting. With this method, injection of 100‐μL volumes was performed within 15 min. On‐line coupling of liquid chromatography to capillary supercritical fluid chromatography was demonstrated.
Determination of aldrin in natural matrices by gas chromatography following supercritical fluid extraction
Authors: Murphy Brett J. , Richter Bruce E.
Published: May 2005

The effectiveness of extracting aldrin from several natural food matrices using supercritical fluid extraction (SFE) was examined. Extraction efficiency was optimized by varying the extraction time and pressure using carbon dioxide as the extraction fluid. The extraction system was coupled directly on‐line with capillary column gas chromatography (GC) using flame ionization detection (FID). Results were linear over three orders of magnitude. Recoveries averaged 100% at 100 ppm. Reproducibility for all samples was less than 3.8% relative standard deviation. The minimum detectable limit for the system with FID was 1.20 ppm (S/N = 3). The use of off‐line SFE with GC and electron capture detection (ECD) was found to reduce the minimum detection level (MDL) to the sub‐ppb range (0.23 ppb), while recovery at 10 ppb was 96% with 3.1% RSD.
Quantitative determination of adsorption‐active silanol groups on the surface of reversed‐phase sorbents by microcolumn LC
Authors: Trushin Sergei A. , Kever Jeno J. , Vinogradova Lyudmila V. , Belenkii Boris G.
Published: May 2005

A method for quantitative determination of residual silanol groups on the surface of reversed‐phase sorbents with the aid of microcolumn chromatography has bee developed. This method is based on the linear dependence of retention coefficients of phenol and benzyl alcohol on the surface concentration of silanol groups for reversed‐phase sorbents. Some commercial reverse‐phase sorbents were characterized.
Microcolumn liquid chromatography with sample induced internal pH gradient
Authors: Šlais Karel
Published: May 2005

An internal pH gradient of a wide renge of pH can be developed using the pumped mobile phase containing only a few [3–6] simple buffering salts which differ in pka values by about 1 pka unit or less. The use of several types of surface ionizable groups allows the internal pH gradient to be effective not only for separation of ampholytes but also for separation of anions of both strong and weak acids. The internal pH gradient can be induced simultaneously with solute introduction into the separation column. For this new method, the term “sample induced internal gradient” (SIIG) of pH was suggested. The method is demonstrated by separation of model mixtures of UV detectable anions and ampholytes on a dynamically modified microcolumn.
Effect of methanol/water mobile phase on the properties of immobilized Carbowax 20M stationary phase
Authors: Horká Marie , Janák Karel , Krejčí Miloš
Published: May 2005

Capillary columns with immobilized Carbowax 20M based on polyurethane (25.6‐μm i.d., 0.06‐μm df, 2.5–4‐m length, and water/methanol mobile phase) were used in capillary liquid chromatography. Stationary phase film swelling occurs due to the effects of the water/methanol mobile phase. The degree of swelling ranges from 0 to 50%. Owing to the resistance to mass transfer decreases, which improves the operation in capillary columns of this type even at temperatures below that of glass transition. The diffusion coefficients in the stationary phase measured by open tubular column liquid chromatography are comparable with those measured by gas chromatography. They range from 10−4 to 10−6 mm2 s−1.
Evaluation of etched borosilicate glass capillary columns in reversed phase open tubular liquid chromatography
Authors: Dohmeier Daniel M. , Jorgenson James W.
Published: May 2005

The performance of etched borosilicate capillary columns with a bonded octadecyl stationary phase has been examined. Plate heights for three test compounds in columns with inner diameters between 6.5 and 14.6 μm were measured as a function of mobile phase velocity. The reduced plate height vs. reduced velocity curves were then fit to the Golay equation using nonlinear regression analysis. It was found that in addition to longitudinal diffusion in the mobile phase, longitudinal diffusion in the stationary phase was a significant contributor to broadening at low mobile phase flow rates. At higher flow rates, resistance to mass transfer in the stagnant mobile phase in the porous glass produced by the etching procedure became measurable.
Nitrogen‐selective detection in capillary supercritical fluid chromatography of derivatized oligosaccharides
Authors: Shirota Osamu , Liu Jinping , Novotny Milos
Published: May 2005

Methoximation of reducing oligosaccharides, combined with the additional derivatization of hydroxy groups, yields derivatives suitable for capillary supercritical fluid chromatography with thermionic detection. Detection limits on the order of picogram‐per‐second can easily be achieved. The utility of this analytical procedure has been verified by the analysis of the carbohydrate content of chicken trypsin inhibitor.
Unified open tubular column chromatography: Sequential gas chromatography, at normal pressures, and supercritical fluid chromatography on the same column
Authors: Robinson Robert E. , Tong Daixin , Moulder Robert , Bartle Keith D. , Clifford Anthony A.
Published: May 2005

A unified chromatograph was constructed in which open tubular column gas chromatography, at normal helium carrier gas pressures, followed by supercritical fluid chromatography with carbon dioxide mobile phase was carried out in a single run using a 100‐μm i. d. column. Sample introduction was accomplished by means of a pneumatically‐actuated rotary injection valve. A second rotary valve was used post‐column to direct the flow of column effluent to the flame ionization detector through an uncoated fused silica restrictor during the GC separation mode or to the FID through a frit restrictor during the SFC separation mode. This novel valve switching arrangement allowed system operating parameters of temperature and pressure programs and linear velocities to be optimized independently of each separation mode. The unified GC/SFC system was demonstrated for practical applications in various fields of process and product quality control.
Examination of the properties of different 20% phenyl‐substituted polymethylsiloxane stationary phases for capillary chromatography
Authors: Hägglund Ingela , Blomberg Lars , Janàk Karel , Claude Saturnin , Tabacchi Raffaele
Published: May 2005

Three polysiloxanes, each having 20% phenyl substitution, have been evaluated for use as stationary phases in fused silica open tubular columns for gas and supercritical fluid chromatography. The columns were coated with PS–090 which had been treated in an aluminum pan in order to improve immobilization properties, OV‐7, and a newly synthesized phase, Polymer S.

Excellent columns were prepared with PS‐090; however, treatment in the aluminum pan was an uncontrolled process, and the reproducibility of polarity may be questioned. For comparison, OV‐7 could not be immobilized, but columns coated with this phase showed good thermal stability. The silanol terminated Polymer S was immobilized via a mechanism involving scission of phenyl groups; thus polarity was decreased after immobilization. However, columns for which Polymer S was immobilized in the presence of a cross‐linking reagent maintained their polarity. Such columns showed very good chromatographic performance. These columns were applied to the separation of polynuclear aromatic compounds by GC and to the analysis of extracts from a thermomechanical pulping white water and lichen by SFC.
Solute focusing in supercritical fluid chromatography
Authors: Koski Iina J. , Lee Milton L.
Published: May 2005

Solute focusing is an important topic in chromatography, but it has not been discussed extensively in the recent supercritical fluid chromatography literature. The purpose of this paper is to review the different methods that have been used to focus solutes in supercritical fluid chromatography. The theoretical basis for phase ratio and partition coefficient focusing is described. Different solute focusing devices that are used in on‐line supercritical fluid extraction and chromatography are shown. The methods and principles of removing the solvent from the solutes prior to the analytical column, and hence reducing band broadening in the column due to the solvent, are discussed in context with the use of a retention gap or a mixing chamber, and in solvent vent injection.
Capillary electrophoresis with surface coated capillaries
Authors: Kohr Joerg , Engelhardt Heinz
Published: May 2005

With uncoated fused silica capillaries, the electroosmotic flow and its contribution to solute migration are in part responsible for problems with the reproducibility of migration time due to hysteresis effects. In transferring coating procedures from silica to capillary surfaces, it has been possible to prepare stable polymeric coatings where hysteresis effects are negligible. Acrylamide coatings reduce the electroosmotic flow. A pH independent flow could be achieved with bonded cation exchange groups. With bonded anion exchangers, reversal of electroosmotic flow is possible.
Narrow (5‐50‐μm i.d.) open tubular columns in liquid chromatography using immobilized polymethyloctadecylsiloxane as stationary phase
Authors: Göhlin Karin , Larsson Marita
Published: May 2005

This paper presents in detail the preparation of highly efficient, stable open tubular (OT) columns for reversed‐phase liquid chromatography. Chromatographic properties of 5‐50‐μm i.d. fused silica columns (1.5‐5 m in length) are described, and details of the coating procedure are discussed. On‐column fluorescence detection was used for the model substituted‐anthracene test solutes. Gas chromatography was used as a complementary technique for column characterization.

The stationary phase studied, immobilized polymethyloctadecylsiloxane, PMSC18, was chosen because of its more lipophilic character compared to other siloxanes. As expected, a higher retention power was found compared to polydimethylsiloxane coatings.

The polymeric stationary phase showed good properties. More than 900,000 plates were achieved in 25 min (k = 0.1) in a 5‐μm i.d. fused silica OT column. The stationary phase contribution to band broadening was less than 10% in an 11‐μm i.d. column at a flow rate thirty times uopt (k = 1.3).
Fabrication and characterization of a silicon microvalve
Authors: Emmer Åsa , Jansson Mårten , Roeraade Johan , Lindberg Ulf , Hök Bertil
Published: May 2005

The fabrication of a unidirectional micro‐valve in silicon is reported. Pressure/flow characteristics between 0–1 bar for water were measured. Practically no leakage was observed (less than 1 nL min−1) when the valve was pressurized in the backward direction. A nonlinear pressure‐flow relation, believed to be due to the particular design of the closing cantilever beam, was observed in the forward direction. Some of the merits of the construction are discussed.
Enantiomer separation by capillary SFC and GC on immobilized permethyl‐β‐cyclodextrin: A systematic comparison
Authors: Schmalzing Dieter , Nicholson Graeme J. , Jung Martin , Schurig Volker
Published: May 2005

Immobilized permethyl‐β‐cyclodextrin was used for enantiomer separation by capillary supercritical fluid chromatography and gas chromatography. The influences of pressure and temperature on chiral separation factors, α, and capacity factors, k, have been studied for four representative racemic solutes. The enantioselectivities in supercritical fluid chromatography and gas chromatography are compared. Solvation effects by supercritical carbon dioxide are discussed.
Quantitative polymer additive analysis by multidimensional chromatography using on‐line coupled microcolumn size exclusion chromatography as a preliminary separation
Authors: Cortes Hernan J. , Bormett Gary E. , Graham Jeffrey D.
Published: May 2005

The quantitative determination of polymer additives using a multidimensional system consisting of microcolumn size exclusion chromatography (micro SEC) coupled on‐line to a capillary gas chromatograph and to a conventional size LC system is described. The results obtained were compared to conventional sample preparation procedures consisting of dissolution of the polymer followed by precipitation and analysis of the supernatant. Results obtained for two polymer systems studied indicated losses for some additives using the precipitation approach.

An on‐line coupled micro‐SEC‐LC system was investigated for the separation of compounds in which the volatility may not allow determination via capillary GC. The lower volumetric dispersion given by the microcolumns allowed introduction of the complete additive fraction without detrimental effects on the peak shape or resolution.
Effects of different mobile phases on immobilized carbowax 20M stationary phase in capillary liquid chromatography
Authors: Horká Marie , Krejčí Miloš , Kahle Vladislav
Published: May 2005

Polyurethane immobilized Carbowax 20M stationary phase was used in capillary liquid chromatography. Mobile phases tested in this study (distilled water and aqueous solutions of the following solvents: 5.5% methanol, 5% acetone, 5, 10, 20% acetonitrile, 0.815% chloroform, 0.178% benzene and up to 0.00095% hexane) cause considerable swelling of the stationary phase polymeric film. The stationary phase swelling index reached a maximal value of S = 131. Diffusion coefficients in the stationary phase vary between 2.6 × 10−5 and 6.5 × 10−4 mm2 s−1.
Determination of naproxen in serum by capillary electrophoresis with ultraviolet absorbance and laser‐induced fluorescence detection
Authors: Soini Helena , Novotny Milos V. , Riekkola Marja‐Liisa
Published: May 2005

Methodology for quantitative determination of an anti‐inflammatory drug, naproxen, in human serum by capillary electrophoresis (CE) is described. Ultraviolet absorbance (UV) and laser‐induced fluorescence (LIF) detection without derivatization procedures have been applied in two concentration ranges: the UV absorbance detection method is applicable in the concentration range of 0.5 ‐ 25 μg mL−1 (2 μM – 100 μM), permitting pharmacokinetic studies after a single oral dose of naproxen; for the lower concentration range of 0.01 – 0.5 μg mL−1 (40 nM ‐ 2 μM), LIF detection has been utilized. Sample preparation includes a simple liquid‐liquid extraction of 1.0 mL (UV) or 0.25 mL (LIF) serum aliquots. After solvent evaporation, redissolved samples were analyzed using Tris‐Tricine buffer. UV absorbance measurement was set at 254 nm. LIF using the helium‐cadmium (He‐Cd) laser as a source (excitation at 325 nm) was measured at 375 nm due to the native fluorescence of naproxen. Both methods provided interference‐free, linear and highly precise results. At the quantitation limit, 0.1‐pmol (UV) and 3‐fmol (LIF) naproxen levels were detected. Using ketoprofen (UV) and warfarin (LIF) as internal standards, analytical precision improved substantially.
Cu‐phthalocyanine stationary phase in microcolumn liquid chromatography
Authors: Jinno Kiyokatsu , Uemura Takashi , Haginaka Jun , Saito Yutaka
Published: May 2005

In this investigation, liquid chromatography using Cu‐phthalocyanine stationary phases were examined for polycyclic aromatic hydrocarbon (PAH) analyses. The results have indicated that Cu‐phthalocyanine phases can be useful for PAH separations by their planarity recognition capabilities.
Programmed‐temperature injector for large‐volume sample introduction in capillary gas chromatography and for liquid chromatography‐gas chromatography interfacing
Authors: Staniewski Jacek , Janssen Hans‐Gerd , Cramers Carel A. , Rijks Jacques A.
Published: May 2005

The introduction of large sample volumes in capillary gas chromatography is becoming increasingly important in various application areas. Especially in the analysis of very dilute sample (e.g., environmental samples) and in coupled LC‐GC, large volume sampling is extremely important. Programmed‐temperature sample introduction is shown to be an attractive technique for these purposes.

In this paper we present some applications of large volume sampling in environmental analysis. Water samples were analyzed using both off‐line and on‐line extraction with gas chromatography (GC) analysis. In the off‐line method, pollutants were extracted into hexane or methylene chloride. Using the programmed‐temperature injector, up to 250 μL of the extract could be introduced into the GC system. In this way, reproducible quantitative analysis of PAHs and herbicides were achieved at sub‐ppb concentrations using flame ionization detection. In the on‐line mode, pollutants were preconcentrated on a short liquid chromatography (LC) column packed with a PLRP‐S solid phase extraction material. After the trapping step, the components were desorbed by ethyl acetate and transferred directly into the programmed‐temperature vaporizer (PTV‐GC) system. Using this method, detection limits below about 1 ppb of herbicides in water were obtained.
Preparation of polyacrylamide gel‐filled capillaries by photopolymerization for capillary electrophoresis
Authors: Bruin Gerard J. M. , Wang Tianlin , Xu Xiaoma , Kraak Johan C. , Poppe Hans
Published: May 2005

A new preparation method for polyacrylamide gels in fused silica capillaries is described. In this method use is made of riboflavin as a light sensitive initiator for the polymerization reaction. Also, results from measurements on the diffusion coefficients of four oligonucleotides in a polyacrylamide gel are reported. Furthermore, a new preparative method to purify and collect oligonucleotides is presented. Separation performance of the gels was tested with various samples of oligonucleotides.