bluuebunny/crossref_metadata_2025 huggingface dataset:
Polyvinylidene fluoride (PVDF) as a biomaterial: From polymeric raw material to monofilament vascular suture
Authors: Laroche Gaétan , Marois Yves , Guidoin Robert , King Martin W. , Martin Louisette , How Thien , Douville Yvan
Published: May 2005

This study identified the effects of various manufacturing processes on the crystalline microstructure, mechanical properties, and biocompatibility of a polyvinylidene fluoride (PVDF) suture. To achieve this, changes in the crystalline microstructure and the tensile behavior of PVDF monofilaments were monitored in vitro after different thermal processing, coloration, and sterilization treatments. In addition, the in vivo biocompatibility of the manufactured and sterilized PVDF suture was assessed by using it to anastomose a preclotted polyester vascular prosthesis as a thoracoabdominal bypass in a series of dogs. The tissue response was followed by histologic and scanning electron microscopy over implantation periods ranging from 4 h to 6 months. Differential scanning calorimetry and infrared spectroscopy (FTIR‐ATR) showed that thermal processing and the addition of a coloring agent had a direct effect on modifying the crystalline microstructure and hence changing the mechanical properties. For example, thermal processing converted some of the α phase into the β and γ polymorphs, whereas coloration led only to a major increase in the β‐to‐α ratio. The tensile properties were found to be optimized when the relative proportion of the β and γ phases combined compared to the α form gave rise to an FTIR A509/A532 absorption ratio between 4.0 and 4.5. Sterilization was found to cause some modifications to the crystalline microstructure near the surface of the monofilaments, but it did not change their mechanical properties. Pathologic examination of the anastomotic regions after different periods of implantation revealed a minimal cellular response, with no mineralization, intimal hyperplasia, or excessive fibrous tissue reaction. This good biocompatibility, together with other desirable characteristics such as ease of manipulation and satisfactory mechanical strength, makes PVDF an attractive alternative monofilament suture material for cardiovascular surgery. © 1995 John Wiley & Sons, Inc.
Estimation of ideal mechanical strength and critical porosity of calcium phosphate cement
Authors: Ishikawa K. , Asaoka K.
Published: May 2005

The ideal mechanical strength and critical porosity of calcium phosphate cement (CPC) were estimated to help determine ways to improve its properties. CPC at various porosities was made by packing CPC paste, at various powder‐to‐liquid (P/L) ratios (2.0–6.0), into a mold under various pressures (0–173 MPa). The mechanical strength of CPC, in terms of diametral tensile strength (DTS), increased with decreases in porosity. Intercrystalline fracture was observed in specimens made without the application of pressure, while fracture within the crystals increased with the packing pressure. These observations support the application of the relationship between DTS and porosity in fractographic equations. The ideal wet DTS and critical porosity of CPC were estimated to be 102 MPa and 63%, respectively. The minimum porosity of the currently used CPC was approximately 26–28%, even when it was packed under 173 MPa, and the maximum DTS value was thus approximately 13–14 MPa. Because reducing the porosity of currently used CPC would be difficult, we conclude that in CPC‐related research, we should focus on ways in which to accelerate bone‐replacing behavior, in addition to improving the mechanical strength of CPC. © 1995 John Wiley & Sons, Inc.
Oxidative and hydrolytic stability of a novel acrylic terpolymer for biomedical applications
Authors: Veleva Anka N. , Khan Saad A. , Cooper Stuart L.
Published: May 2005

Oxidative and hydrolytic biostability assessment was carried out on a novel acrylic material made of hexamethyl methacrylate (HMA), methyl methacrylate (MMA), and methacrylic acid (MAA). To simulate the in vivo microenvironment, solutions of H2O2/CoCl2 and buffered solutions of cholesterol esterase (CE) and phospholipase A2 (PLA) were used. As controls, film specimens were incubated in deionized water. Samples were incubated in these solutions at 37°C for 10 weeks before physical and mechanical properties were evaluated by size exclusion chromatography (SEC), 1H‐ nuclear magnetic resonance (1H‐NMR), acid‐base titration, and Instron tensile testing. The results from this study indicate excellent biostability of HMA‐MMA‐MAA terpolymers and thus their potential for use in biomedical devices for long‐term implantation. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2005
ATP‐dependent protein kinases in bacteria
Authors: Cozzone Alain J.
Published: May 2005

Protein phosphorylation has been shown to occur in over fifty different bacterial species and, therefore, seems to be a universal device among prokaryotes. Most of the protein kinases responsible for this modification of proteins share the common property of using adenosine triphosphate as phosphoryl donnor. However, they differ from one another in a number of structural and functional aspects. Namely, they exhibit a varying acceptor amino acid specificity and can be classified, on this basis, in three main groups: protein‐histidine kinases, protein‐serine/threonine kinases and protein‐tyrosine kinases. © 1993 Wiley‐Liss, Inc.
The role of phosphorylation of HPr, a phosphocarrier protein of the phosphotransferase system, in the regulation of carbon metabolism in gram‐positive bacteria
Authors: Reizer Jonathan , Romano Antonio H. , Deutscher Josef
Published: May 2005

HPr of the Gram‐positive bacterial phosphotransferase system (PTS) can be phosphorylated by an ATP‐dependent protein kinase on a serine residue or by PEP‐dependent Enzyme I on a histidyl residue. Both phosphorylation events appear to influence the metabolism of non‐PTS carbon sources. Catabolite repression of the gluconate (gnt) operon of B. subtilis appears to be regulated by the former phosphorylation event, while glycerol kinase appears to be regulated by the latter phosphorylation reaction. The extent of our understanding of these processes will be described. © 1993 Wiley‐Liss, Inc.
Response regulation in bacterial chemotaxis
Authors: Lukat Gudrun S. , Stock Jeffry B.
Published: May 2005

The signal transduction system that mediates bacterial chemotaxis allows cells to moduate their swimming behavior in response to fluctuations in chemical stimuli. Receptors at the cell surface receive information from the surroundings. Signals are then passed from the receptors to cytoplasmic chemotaxis components: CheA, CheW, CheZ, CheR, and CheB. These proteins function to regulate the level of phosphorylation of a response regulator designated CheY that interacts with the flagellar motor switch complex to control swimming behavior. The structure of CheY has been determined. Magnesium ion is essential for activity. The active site contains highly conserved Asp residues that are required for divalent metal ion binding and CheY phosphorylation. Another residue‐at the active site, Lys109, is important in the phosphorylation‐induced conformational change that facilitates communication with the switch complex and another chemotaxis component, CheZ. CheZ facilitates the dephosphorylation of phospho‐CheY. Defects in CheY and CheZ can be suppressed by mutations in the flagellar switch complex. CheZ is thought to modulate the switch bias by varying the level of phospho‐CheY. © 1993 Wiley‐Liss, Inc.
Development and implementation of a multisite evaluation for the Women, Co‐Occurring Disorders and Violence Study
Authors: Giard Julienne , Hennigan Karen , Huntington Nicholas , Vogel Wendy , Rinehart Debbie , Mazelis Ruta , Nadlicki Terri , Veysey Bonita M.
Published: May 2005

In this article we describe the development and implementation of the Substance Abuse and Mental Health Services Administration's (SAMHSA's) multisite Women, Co‐Occurring Disorders and Violence Study (WCDVS), highlighting some of the challenges encountered, decisions made, and lessons learned. Four themes are discussed. First, the unique contributions of the consumer/survivor/recovering (C/S/R) women to the research process are described through instances where their knowledge and advocacy were clearly influential. Second, the solutions chosen to address research design challenges are recounted, as are the ways in which these choices played out. Third, the procedures for standardizing recruitment, data collection, and data management across sites are described. Finally, the strategies employed by the nine sites to retain contact with this challenging population are reviewed and successful techniques are highlighted. © 2005 Wiley Periodicals, Inc. J Comm Psychol 33: 411–427, 2005.
Racial/ethnic differences in social vulnerability among women with co‐occurring mental health and substance abuse disorders: Implications for treatment services
Authors: Amaro Hortensia , Larson Mary Jo , Gampel Joanne , Richardson Erin , Savage Andrea , Wagler Debra
Published: May 2005

Little attention has been given to racial/ethnic differences in studies of co‐occurring disorders among women. In this article, we present findings from analyses conducted on the influence of racial/ethnic differences on the demographic and clinical profiles of 2,534 women in the Substance Abuse and Mental Health Services Administration‐sponsored Women, Co‐Occurring Disorders and Violence Study. Black and Hispanic women demonstrated more disadvantaged economic and social life conditions than White women. After controlling for socioeconomic differences, Hispanic women experienced more criminal justice involvement than others did, and both Black and Hispanic women were more likely to be exposed to community violence although they did not demonstrate more severe clinical symptoms than White women. In the design and delivery of services racial/ethnic differences should be considered, and research questions regarding underlying explanatory factors raised. © 2005 Wiley Periodicals, Inc. J Comm Psychol 33: 495–511, 2005.
Recent advances in rational gene transfer vector design based on poly(ethylene imine) and its derivatives
Authors: Neu Michael , Fischer Dagmar , Kissel Thomas
Published: May 2005

The continually increasing wealth of knowledge about the role of genes involved in acquired or hereditary diseases renders the delivery of regulatory genes or nucleic acids into affected cells a potentially promising strategy. Apart from viral vectors, non‐viral gene delivery systems have recently received increasing interest, due to safety concerns associated with insertional mutagenesis of retro‐viral vectors. Especially cationic polymers may be particularly attractive for the delivery of nucleic acids, since they allow a vast synthetic modification of their structure enabling the investigation of structure‐function relationships. Successful clinical application of synthetic polycations for gene delivery will depend primarily on three factors, namely (1) an enhancement of the transfection efficiency, (2) a reduction in toxicity and (3) an ability of the vectors to overcome numerous biological barriers after systemic or local administration. Among the polycations presently used for gene delivery, poly(ethylene imine), PEI, takes a prominent position, due to its potential for endosomal escape. PEI as well as derivatives of PEI currently under investigation for DNA and RNA delivery will be discussed.

This review focuses on structure‐function relationships and the physicochemical aspects of polyplexes which influence basic characteristics, such as complex formation, stability or in vitro cytotoxicity, to provide a basis for their application under in vivo conditions. Rational design of optimized polycations is an objective for further research and may provide the basis for a successful cationic polymer‐based gene delivery system in the future. Copyright © 2005 John Wiley & Sons, Ltd.
Preparative gas chromatography with glass capillary columns
Authors: Roeraade J. , Enzell C. R.
Published: May 2005

The present paper describes an automated system for preparative gas chromatography with glass capillary columns, controlled by a microprocessor. The effluent from the capillary column is divided by a pneumatically controlled splitter and any desired split ratio between traps and detector can be obtained. Moreover, a second pneumatic control allows instantaneous change‐over to a different split ratio, thus minimizing loss of material during collection.

The effluent containing the compounds of interest is passed through a multiple manifold and collected in coiled glass capillary traps. To ensure maximum trapping efficiency even for very small amounts of material, the inner walls of the capillary traps are wetted with a suitable solvent, which gives a quantitative recovery of micro‐ and nanogram amounts of material.

After repetitive sampling, sufficient amounts of material can be obtained for NMR spectroscopy and possibilities exist to enrich trace components with the aid of a double column system. Two examples of such applications are given, employing mixtures of both synthetic and natural origin.
Selective determination of substituted PAH in aerosols using liquid CO2‐extraction, HPLC prefractionation on chemically activated silica, and HRGC combined with negative ion mass spectrometry
Authors: Stray H. , Manø S. , Mikalsen A. , Oehme M.
Published: May 2005

A method is described which allows the determination of different substituted polycyclic aromatic hydrocarbons (PAH) such as NO2‐PAH, carbazoles, keto‐PAH, and aza‐arenes in aerosol samples. Liquid CO2‐extraction is used to minimize the loss of reactive compounds. High performance liquid chromatography on chemically activated silica is employed to prefractionate the samples into subfractions with a minimum of overlap between different PAH compound classes. Both electron capture detection and negative ion chemical ionization combined with capillary gas chromatography are used for identification and quantification. The latter method also allows distinction between isomers with different toxic properties when N2O/CH4 reaction gas mixtures are used. Selectivity for tetrachlorodibenzo‐p‐dioxins as against pesticides and polychlorinated biphenyls can be improved by this technique. The applicability of the method is critically discussed and different examples are given.
Practical aspects of mixed mobile phases in capillary supercritical fluid chromatography
Authors: Fields S. M. , Markides K. E. , Lee M. L.
Published: May 2005

Studies of mixed mobile phases in supercritical fluid chromatography must include consideration of a number of factors. Phase equilibria and critical parameters of a mixed fluid are very important in both the solvent delivery system and in the chromatographic column. The effects of pressure and temperature on retention with mixed mobile phases were studied and compared to estimated density values. System equilibration times with regard to pressure, temperature, and composition were studied. A mixed mobile phase was applied to the analysis of a high‐molecular‐weight metalloporphyrin.
On‐line extraction and separation by supercritical fluid chromatography with packed columns
Authors: Engelhardt H. , Gross A.
Published: May 2005

The application of fluid extraction in combination with fluid chromatography with packed column and flame ionization detection is described. Fluid chromatographic equipment is shown. Applications of this system to drug characterization are demonstrated.
Classification of polymer batch variations by dynamic headspace/capillary gas chromatography/multivariate data analysis
Authors: Hagman A. , Karlsson K. , Jacobsson S.
Published: May 2005

Gas chromatographic profiles have been generated from different batches of a polypropylene/polyethylene copolymer. The profiles generated from polymer pellets have been obtained by dynamic headspace/capillary gas chromatography analysis. Initially 10 to 40 peaks were chosen at random from the quantitative reports and transferred to a data table. After appropriate scaling the table has been analyzed by a multivariate statistic program, SIMCA (Soft Independent Modeling of Class Analogy) a pattern recognition technique. The method has been used to differentiate batches according to sensory qualities of the final packaging product and changes in polymer peilet production.
Quantitative determination of airbone C1‐ and C2‐halocarbons by GC/ECD
Authors: Frank H. , Frank W.
Published: May 2005

The atmospheric levels of C1‐ and C2‐halocarbons are determined by trapping on an adsorbent, thermodesorption, cryofocussing, gas chromatographic separation on a thick‐film capillary, and electron‐capture detection. The various aspects relevant to reliability and accuracy are discussed, such as type of adsorbent, range of detector response, and levels of contaminants present in blanks. These in turn have implications for optimum sample size and amount of adsorbent. The adopted method is suitable for routine analysis of airborne halocarbons at variable locations. The air concentrations of C1‐ and C2‐halocarbons on the ground of mountain forests are similar to those in cities, a fact which supports the hypothesis that chlorocarbons are involved in the initiation of a phytotoxicological phenomenon commonly referred to as “forest decline”.
CGC analysis of the essential oils of citrus fruits on 100 μm i.d. columns
Authors: Lancas F. , David F. , Sandra P.
Published: May 2005

Narrow bore columns (100 μm) have successfully been applied in the analysis of commercial lemon oils. On these columns, high resolution is obtained in a short analysis time. Different Brazillian lemon oils are characterized qualitatively and quantitatively.
Enantiomer separation of 2‐halocarboxylic acid esters by chiral complexation gas chromatography
Authors: Schurig V. , Ossig A. , Link R.
Published: May 2005

The enantiomer separation of 2‐halocarboxylic acid esters on two chiral nickel(II) bis‐((perfluoroacyl)terpeneketonates) by complexation gas chromatography is described. The quantitative entiomer separation of branched 2‐halocarboxylic acid esters is achieved with nickel (II) bis (3‐(heptafluorobutanoyl)(1R, 2S)‐pinan‐4‐onate) 1 while unbranched 2‐halocarboxylic acid esters are preferably separated on nickel(II) bis(3‐(heptafluorobutanoyl)‐(1S)‐10‐methylenecamphorate) 2. The metal chelates 1 and 2 are accessible in both enantiomeric forms allowing the determination of the enantiomeric excess (ee) effective and reliable.
Determination of Broxaterol in Plasma by Coupled HPLC‐GC
Authors: Gianesello V. , Bolzani L. , Brenn E. , Gazzaniga A.
Published: May 2005

For the analysis of broxaterol 1‐(3‐bromoisoxazol‐5‐yl)‐2‐(tert‐butylamino)ethanol in human plasma and urine an on‐line HPLC‐GC apparatus was used applying the “concurrent solvent evaporation” technique described in previous studies. Broxaterol is quantitatively determined by capillary GC with ECD detection, after extraction from plasma and derivatization. The detection limit of 0.03 ng/ml permits pharmacokinetic studies in man after oral and intravenous administration of the drug.
Determination of the calcium entry blocker verapamil in plasma by capillary gas chromatography with on‐column injection
Authors: Rosseel M. T. , Belpaire F. M.
Published: May 2005

A specific, sensitive, and accurate assay for quantitation of verapamil has been developed. The method involves a single extraction step with n‐heptane, followed by evaporation at room temperature under nitrogen. 0.1 μl of the extract was injected into a capillary column coated with crosslinked 5% phenylmethylsilicone. The column separated verapamil, norverapamil, and its internal standard within 15 minutes using temperature programming from 90 to 290°C. The lower limit of detection was 1 ng/ml for verapamil. The calibration curve was linear in the concentration range (5–300 ng/ml). Plasma concentration data from dogs receiving intravenous verapamil infusion are presented.
High performance microcolumn exclusion chromatography of proteins and peptides
Authors: Gankina E. S. , Kever J. J. , Kostiuk I. O. , Saminsky A. E. , Belenkii B. G.
Published: May 2005

A new method for the determination of the molecular weight of proteins and peptides has been developed. It is based on microcolumn exclusion chromatography in trifluoroacetic acid on silica gel sorbents of different porosities with a linear molecular‐weight calibration dependence in the range of 5 × 102 ‐ 7 × 104 Da. It was shown that in this eluent proteins and peptides adopt the random‐coil conformation and do not undergo hydrolysis for 2–3 days at room temperature.
Dynamic headspace capillary gas chromatography: A versatile analytical technique
Authors: Venema A.
Published: May 2005

The applicability of dynamic headspace analyses for viscous liquids and solid samples is demonstrated. Some comments on the usefulness of this technique for quantifying volatiles in polymeric matrices are made.
GC column effluent splitter for problematic solvents introduced in large volumes: Determination of di‐(2‐ethylhexyl) phthalate in triglyceride matrices as an application
Authors: Pacciarelli B. , Müller E. , Schneider R. , Grob K. , Steiner W. , Fröhlich D.
Published: May 2005

Introduction of solutions of up to several milliliters by on‐column injection of large volumes or by coupled HPLC‐GC may cause problems with GC detectors (FID, AFID, MS). For instance, dichloromethane forms large amounts of hydrochloric acid and carbon black in FIDs.

A column effluent splitter was developed for keeping the major portion of the solvent vapors away from the detector; approximately 99% of the vapor is vented while the remaining 1% of vapor is used for detecting the widths of the solvent peaks. During analysis, the split ratio is reversed by a strong increase of the resistance to the gas flow through the split exit line.

The system was used for the determination of di‐(2‐ethylhexyl)‐phthalate (DEHP) in triglyceride matrices of various foods. Direct determination by HPLC is not sufficiently sensitive, whereas direct analysis by GC is hindered by the triglycerides. Solutions of fats or oils were pre‐separated on a silica column using dichloro‐methanelcyclohexane 1:l with addition of 0.05 % acetonitrile as eluent. The HPLC fraction containing the DEHP was transferred to GC through a loop‐type interface using concurrent solvent evaporation. Detection limits were around 0.1 ppm.
Capillary electrokinetic separations: Influence of mobile phase composition on performance
Authors: Sepaniak Michael J. , Swaile David F. , Powell A. Craig , Cole Roderic O.
Published: May 2005

The composition of the mobile phase employed in capillary zone electrophoresis and the related technique, micellar electrokinetic capillary chromatography, is an important factor in determining separation performance. The influences of ionic salt, surfactant, and organic solvent mobile phase additives on separation efficiency, retention, and elution range are discussed and demonstrated.
Band broadening effects in capillary column recycle gas chromatography with valves
Authors: Zhang Q. W. , Hathcock L. , Bertsch W.
Published: May 2005

Sources leading to band broadening and peak distortion have been studied in a capillary column recycle system, based on a commercial microvalve. The ferrule system was a major contributor to band broadening. It was found that the quality of connections is very critical but the internal volume of the valve is not important. The pressure pulses resulting from each switching operation produced some band broadening with substances that had just been transferred through the valve but no adverse effects were noticed when they had travelled some distance into the column. Flow into valve cavities and through tees also produced a drop in efficiency. It is not clear whether this is solely due to problems in column connection or if changes in flow pattern also contribute.

The activity of the valve toward polar substances was also assessed. No attempt was made to deactivate valve surfaces. The components of the Grob test mixture were almost unaffected but highly polar and acidic compounds such as nitrophenol showed severe losses. No evidence for catalysis was found.
Influence of extra‐column effects in capillary gas chromatography
Authors: Bemgård Agneta K. , Colmsjö Anders L.
Published: May 2005

The contribution of extra‐column effects to the height equivalent to a theoretical plate (HETP) in capillary gas chromatography is calculated. Four extra terms are added to the Golay‐Giddings equation and evaluated in order to verify their significance. The paradox of negative A terms is resolved by curve fitting of experimental values to the theoretical function of HETP, including the extra‐column effects. The importance of the A term and the diffusion process for an injection in split mode were determined to be negligible compared to the other terms in the HETP equation. On the other hand, extra‐column contributions, proportional to the square of the gas velocity, are of significant importance. This contribution is inversely proportional to the column length.
Pesticide residue analysis in food with CGC — study of long‐term stability by the use of different injection techniques
Authors: Müller Hans‐Martin , Stan Hans‐Jürgen
Published: May 2005

An experiment was designed to study the long‐term stability of analyses of pesticide residues in a complex food matrix using three different injection techniques. A spinach sample was spiked with five sulfur‐containing pesticides of varying volatility and thermolability: azinphos‐ethyl, dimethoate, methiocarb, ethiofencarb, and tri‐allate. Tri‐allate was selected as internal standard because of its thermal stability and its good chromatographic properties. Flame photometric detection resulted in chromatograms not subject to interference by peaks of compounds of the matrix. Starting with a clean and freshly, silanized injector an additional deactivation was found to occur on the first injection of a food sample resulting in an increased peak area for all pesticides in relation to tri‐allate. Highest long‐term stability was found with PTV injection. Best results for thermolabile carbamates were obtained using on‐column injection. However, they were prone to faster deterioration.
Cyclodextrins as chiral stationary phases in capillary gas chromatography. Part VII: Cyclodextrins with an inverse substitution pattern – synthesis and enantioselectivity
Authors: König Wilfried A. , Icheln Detlef , Runge Torsten , Pforr Ingo , Krebs Adolf
Published: May 2005

Transferring the site of specific substitution of dipentylated cyclodextrins with methyl or acyl residues from the secondary 3‐hydroxyl group to the primary 6‐hydroxyl group was expected to provide new information on the mechanism of chiral recognition. The 3‐position points towards and the 6‐position points away from the cyclodextrin cavity which via inclusion complex formation is supposed to play a major role in chiral separation. The “inverse” 6‐O‐acyl‐2,3‐di‐O‐pentyl‐cyclodextrins displayed almost no enantioselectivity but the corresponding 6‐O‐methyl derivatives are a versatile supplement to the chiral capillary GC phases nowadays available. Among the compounds that could be enantiomerically resolved are alcohols, amino acids, alkyl halides, bicyclic ethers, acetals, olefins, other hydrocarbons and chiral pharmaceuticals.
Analysis of sucrose fatty acid esters by high temperature gas chromatography
Authors: Karrer Randolf , Herberg Hanna
Published: May 2005

A commercially available high temperature GC system has been investigated to determine its suitability for the automated analysis of sucrose fatty acid esters. In comparison with conventional GC, the high temperature variety broadens the scope of the technique to encompass high molecular weight carbohydrate derivatives while maintaining high separation efficiency. Despite the broad range of polarities, simultaneous quantification of educts and sucrose fatty acid ester fractions is possible in one run, after derivatization. Chromatographic requirements, sample preparation, structure verification by direct chemical ionization mass spectrometry, and advantages and limitations of the high temperature GC‐analysis are discussed.
Use of mercuric resins for selective abstraction of mercaptans in capillary gas chromatography
Authors: Sun Jeffrey J. , Fritz James S.
Published: May 2005

A small amount of mercuric non‐porous resin placed in the liner of the injection splitter of a gas chromatograph retains mercaptans but allows other organic sulfur and non‐sulfur compounds to be chromatographed normally: mercaptans in the gaseous state are retained by the mercuric resin. The method works well at 200°C but an increasing number of impurity peaks are observed as the temperature is increased to 250°C.
Quality control of vegetable oil methyl esters used as diesel fuel substitutes: Quantitative determination of mono‐, di‐, and triglycerides by capillary GC
Authors: Plank Christina , Lorbeer Eberhard
Published: May 2005

Vegetable oil methyl esters are increasingly being used as substitutes for petroleum‐based diesel fuels. Because the presence of triglycerides and partial glycerides in the fuel as a result of incomplete transesterification of vegetable oils can lead to serious engine problems, continuous quality control of the product is essential. A rapid gas chromatographic method has been developed for the quantitative determination of mono‐, di‐, and triglycerides in vegetable oil methyl esters.

Prior to analysis, mono‐, and diglycerides were silylated with N,O‐bis(trimethylsilyl)trifluoroacetamide; tridecanoin was used as internal standard. Calibration was performed by analysis of standard solutions containing mono‐, di‐, and triolein: the calibration plots for mono‐ and diglycerides showed good linearity, whereas for triglycerides no linearity was observed for triolein concentrations below 0.05 mg/ml. When a non‐linear multi level calibration was employed for the quantitation of triglycerides, the method gave excellent quantitative results for mono‐, di‐, and triglycerides in vegetable oil methyl esters.
Calculation of retention factors in capillary electrochromatography from chromatographic and electrophoretic data
Authors: Vissers Johannes P. C. , Claessens Henk A. , Coufal Pavel
Published: May 2005

Retention factors in capillary electrochromatography (CEC) were calculated by means of theoretically derived equations and experimentally determined parameters in microcolumn liquid chromatography and capillary zone electrophoresis. It was found that the retention factor of uncharged components in CEC was about 20% higher than was calculated. The derived equations do not take into account alteration of the nature of the stationary phase or distribution constant by the applied electric field. However, the influence of the electric field on the retention in CEC can be estimated. Individual field contributions could not be determined.
Low flow rate modifier addition in packed capillary column supercritical fluid chromatography
Authors: Ibañez Elena , Li Wenbao , Malik Abdul , Lee Milton L.
Published: May 2005

A new method to accurately deliver small amounts (0.5 to 20 mol%) of modifier into CO2 was used to study the effects of three different modifiers (methanol, water, and formic acid) in packed capillary column SFC. The method allows the use of different modifiers, with minimal instrument modification. The effects of the different modifiers at different concentrations on retention and peak shape are shown by analyzing a polarity test mixture and a sample of free fatty acids.
Separation of polycyclic aromatic hydrocarbons with a C60 bonded silica phase in microcolumn liquid chromatography
Authors: Saito Yoshihiro , Ohta Hatsuichi , Terasaki Hiroshi , Katoh Yoshiyuki , Nagashima Hideo , Jinno Kiyokatsu , Itoh Kenji
Published: May 2005

A chemically bonded C60 silica phase was synthesized as a stationary phase for liquid chromatography (LC) and its retention behavior evaluated for various polycyclic aromatic hydrocarbons (PAHs) using microcolumn LC. The results indicate that the C60 bonded phase offers selectivity different from that of octadecylsilica (ODS) bonded phases in the separation of isomeric PAHs. With the C60 phase, PAH molecules having a partial structure similar to that of the C60 molecule, e.g. triphenylene and perylene, were retained longer than with ordinary ODS stationary phases. The results also show that good correlation exists between the retention data with this C60 bonded phase and with C60 itself as the stationary phase.
The pure‐rotational Raman spectrum of disilane
Authors: Shotton K. C. , Lee A. G. , Jones W. J.
Published: May 2005

From a study of the rotational Raman spectra of disilane and hexadeutero‐disilane the following rotational constants were determined: for Si2H6, B0 = 0.16998 ± 0.00003 cm−1; for Si2D6, B0 = 0.13796 ± 0.00004 cm−1. The rotational constants were used to provide values for the internuclear distances in these modecules.
Infrared and Raman spectra of trithiadiborolanes, SB(X)SB(X)S, with X  Cl, Br, I or Ch3
Authors: Sacher Robert E. , Siebert Walter , Nakovich John , Miller Foil A.
Published: May 2005

Infrared and Raman spectra of the above four compounds have been obtained in the liquid and solid states down to 35 cm−1 (infrared) or to about 70 cm−1 (Raman). The results provide good evidence (but not rigorous proof) that the molecules are planar and have C2ν symmetry. The presence of boron isotopes causes splitting of some of the higher frequency bands. Assignments have been made for 57 of the 60 skeletal fundamentals of the 11B–11B isotopic molecules About ⅔ of these are reliable; the remainder are not well established. The S–S stretching frequency is at 449, 436, 425 and 479 cm−1 in the Cl, Br, I and CH3 compounds respectively.

The planarity of the rings can be explained on the basis of bond angles alone, or on the postulate of an aromatic ring system. There is at present no other evidence to support the latter. The vibrational spectra provide no evidence about π bonding in these molecules.
Resonance Raman effect of anthracene in the pre‐resonance region
Authors: Schmid E. D. , Derner H. , Berthold G.
Published: May 2005

The Raman intensities (RI) of ten vibrations of Anthracene have been measured as a function of the excitation frequency using nine lines from an argon ion and a krypton ion laser. The intensities taken relative to those for a particular excitation frequency, S/S (v0), do not show uniform resonance behaviour. However uniformity arises, when the relative intensities are expressed on the same scale, and such ΔS/ΔS0 values may reflect the influence of frequency factors and varying percentage π‐dependence.
Analyse Vibrationnelle et Structurale en Série Aliphatique Saturée. I—Spectres de Vibration de l'Acide Malonique et de Ses Sels Alcalins en Solution Aqueuse
Authors: Maury Luc , Bardet Lucette
Published: May 2005

Vibrational spectra (Raman and infrared) of malonic acid, potassium hydrogen malonate and dipotassium malonate in aqueous solutions (H2O and D2O) were recorded from 250 to 4000 cm−1. The analysis of the polarisation ratio of the Raman lines had lead us to establish that the malonic acid belongs to the C1, the acid salt to Cs group. The potassium hydrogen malonate spectra, invalidate the existence of an intramolecular hydrogen bond suggested by thermodynamic data and show the characteristic vibrations of the simple COOH and COO− group. An assignment of the observed lines as fundamentals is proposed.
Raman scattering and vibrational dynamics of MnCl2·2H2O
Authors: Srivastava Bipin K. , Khandelwal D. P. , Bist H. D.
Published: May 2005

The laser excited Raman spectrum of MnCl2·2H2O has been reported in the 4000–150 cm−1 region and discussed in conjunction with the known IR spectra. The bands have been assigned to internal and librational modes of water and other lattice modes. It has been found that the correlation splitting parameter Δν/νmean is distinctly larger for the librational modes than for the internal modes of water. The increase in intensity of the ν1 over the ν3 band of water in passing from the free to crystal water state and the low intensity of the librational bands have been explained.
Investigation of broad molecular absorption bands with the help of line shape analysis in coherent Raman scattering experiments
Authors: Pfeffer M. , Lau A. , Werncke W.
Published: May 2005

The line shape observed in coherent Raman scattering (CRS) with excitation under conditions of electronic resonance is discussed, For the case of A‐type scattering, the complex Raman amplitude is related directly to the molecular one‐photon absorbance of the resonance transition concerned. The basis for this relation is transform theory, a method known from spontaneous resonance Raman scattering to relate the Raman excitation profile to the observed molecular absorbance. Features of the Raman amplitude, determining the observed line shapes for coherent anti‐Stokes Raman scattering (CARS) and for coherent Stokes Raman scattering (CSRS), are discussed qualitatively. The discussion considers two typical forms in which broad molecular absorption spectra of polyatomic molecules in the condensed phases appear, Inhomogeneous broadening leads to characteristic changes of the Raman amplitude in relation to molecular absorbance in the case of CSRS (formolecules in the electronic ground state), whereas for CARS the relation derived in the homogeneous broadened case remains valid. The special advantages of the CRS technique for determining the complex non‐Raman resonant (background) susceptibility from concentration dependence are demonstrated.
Herman‐wallis factors for Raman transitions of 1∑‐state diatomic molecules
Authors: Tipping R. H. , Ogilvie J. F.
Published: May 2005

Accurate theoretical expressions for Herman‐Wallis factors for the pure rotational, fundamental and first two overtone vibration‐rotational bands have been derived. These are expressed for arbitrary rotational quantum numbers in terms of the Dunham potential parameters and the coefficients of a general operator represented by a power series expansion. The inclusion of higher order corrections in a consistent way reduces the discrepancy reported by previous workers for H2 between results obatined numerically and analytically. The present expressions are of sufficient accuracy to enable one to obtain precise experimental values for the anisotropy of the polarizability and its derivatives from an analysis of Raman line intensities.
Raman study of the high‐temperature phase transition of malonic acid
Authors: de Villepin J. , Limage M.‐H. , Novak A. , Toupry N. , Le Postollec M. , Poulet H. , Ganguly S. , Rao C. N. R.
Published: May 2005

The Raman spectra of the high‐temperature (α) phase of crystalline malonic acid, CH2(COOH)2, and its deuteriated derivative, CD2(COOD)2, have been investigated at 370 K in the wavenumber shift range 0–4000 cm−1. An assignment of the internal and external vibrations is given. Comparison of the infrared and Raman spectra of the α and β phases shows that the high‐temperature phase (α) consists of quivalent centrosymmetric dimer rings and that the corresponding space group is CC2/c with molecules occupyging C2 sites. The temperature dependence of various Raman lines, in particular those due to lattice modes, indicates that the phase transition is of first order and that during the transition, reorientation of the molecules about the c axis is strongly coupled with the low‐frequency torsional (γOH…O) and librational modes.
Raman and infrared spectra of crystalline cyanogen
Authors: Andrews Bruce , Anderson Anthony , Torrie Bruce
Published: May 2005

Raman and infrared spectra of polycrystalline cyanogen, C2N2, at 20 K are reported. Multiplet structure of the intramolecular fundamentals is observed and interpreted in terms of a group theoretical analysis based on the known orthorhombic crystal structure. Seven of the eight predicted librational and five of the predicted six translational modes are observed in the low‐frequency regions of the Raman and infrared spectra, respectively.
Raman spectra of the lanthanide oxalates
Authors: Morris D. E. , Hobart D. E.
Published: May 2005

Raman and infrared spectral data are presented for the trivalent lanthanide sesquioxalates, M2(C2O4)3 · nH2O, except the promethium complex, in the region from 100 to 4000 cm−1. These complexes were isolated by precipitation from aqueous solution using Na2C2O4. In addition, several commercially available oxalate complexes were examined. On the basis of nearly identical Raman spectral patterns, two distinct structural groups have been identified. The first group consists of the isostructural (monoclinic) decahydrates of La3+ through Er3+. For this group, a linear correlation is found for the frequencies of several skeletal stretching modes versus the lanthanide ionic radius. The second group consists of the isostructural (triclinic) hexahydrates of Er3+ through Lu3+. In agreement with existing x‐ray diffraction data, these vibrational data indicate structural differences between the hexa‐ and deca‐hydrates. In addition, unique vibrational spectral patterns have been obtained for what appear to be other hydrated forms of the oxalates of Ho3+, Er3+ and Lu3+, possessing structures different from those of the above hexa‐ and deca‐hydrates. For all of these complexes, the Raman data suggest that the oxalate ligand is tetradentate coordinated to two lanthanide ions. Thus, the structural differences undoubtedly result from the lanthanide contraction and changes in the disposition of coordinated and interstitial water molecules.
Calculation of anharmonic force constants for the CD3 group from the Raman spectra of (CD3)(CH3)3NI
Authors: Vidal Luis Sastre , Bertrán José FernáNdez
Published: May 2005

The anharmonic force constants for the CD3 group, W12(k122), W13(k133) and W23(k2233), were calculated by a method in which the only approximation is the neglect of the intrinsic intensities of the unperturbed transitions 2δs° and 2δa°. Using Raman data for (CD3)(CH3)3NI solutions, the calculated values of the anharmonic forces constants are W12 = 42.5 cm−1, W13 = 21.5 cm−1 and W23 = 9.4 cm−1.
Charge‐transfer and orientation effects of SERS from pyridine adsorbed on a silver electrode
Authors: Lin H. J. , Chou Y. C.
Published: May 2005

Excitation profiles of the Raman modes of pyridine adsorbed on a silver electrode in sodium chloride electrolyte of different concentrations do not agree with expectation from the charge‐transfer model based on the dependence of the maximum voltage on the incident photon energies. The orientation of the adsorbed molecules might correlate with the position of the charge‐transfer band.
Raman spectra of some complexes containing methyldihalo‐ and dimethylhalo‐sulphonium cations: Isomerism in the dimethyl sulphide–bromine complex
Authors: Askew Herbert F. , Gates Peter N. , Muir Alan S.
Published: May 2005

Vibrational assignments for the skeletal modes of some complexes containing CH3SX2+ and (CH3)2SX+ (X = Cl, Br) have been made on the basis of their solid‐state Raman spectra and compared with any previous data. The stabilities of the parent CH3SX3 and (CH3)2SX2 compounds are discussed; two isomers of (CH3)2SBr2 were obtained under varying reaction conditions and assigned as ionic [(CH3)2SBr+Br−] and charge‐transfer [(CH3)2S → Br2] forms. The transition of the ionic (metastable) form to the more stable charge‐transfer form was monitored by differential scanning calorimetry. High‐frequency shifts occur in some fundamental modes of (CH3)2SBr+Br− when Br− is replaced with a polyatomic anion, analogous to those seen in halophosphonium complexes; this is rationalized in terms of anion‐cation interaction.
Vibrational spectra of trifluoromethylsulphenyl cyanide, CF3SCN
Authors: Altabef A. Ben , Cutin E. H. , Védova C. O. Della
Published: May 2005

The infrared spectra of trifluoromethylsulphenyl cyanide, CF3SCN, in the vapour phase and the Raman spectrum of the liquid were obtained and interpreted in terms of Cs symmetry. Assignment of 14 of the 15 fundamental vibrations is carried out. The valence force constants were calculated by a stepwise coupling method for the A′ species. These values compare favourably with results from previous calculations on related compounds.
Surface‐enhanced Raman scattering of 4‐picolylamine and its [Fe(CN)5]n− complexes
Authors: Temperini M. L. A. , Rubim J. C. , Sala O. , Jubert A. H. , Villalba M. E. Chacon , Aymonino P. J.
Published: May 2005

The SER spectra of the complexes [Fe(CN)5(4‐picolylamine)]3− and [Fe2(CN)10(4‐picolylamine)]6− adsorbed on a silver electrode were investigated. The analysis of the frequency shift of the CN stretching mode indicated that both molecules adsorb via one or more CN ligand groups. For potentials more positive than 0.0 V the CN stretching frequency for both complexes moves towards higher wavenumbers charcterizing the presence of Fe(III) over the surface. The SER spectra of 4‐picolylamine adsorbed on a silver electrode in solutions of pH 2.8, 6.5 and 10.3 were also investigated. From the data obtained it was concluded that 4‐picolylamine in solution at pH 6.5 and 10.3 adsorbs on the electrode through the nitrogen of the pyridine ring.
Surface‐enhanced Raman spectra of thiourea in acidic solutions
Authors: Kim Hyeongon , Kim Jong‐Jean
Published: May 2005

Surface‐enhanced Raman scattering (SERS) of thiourea [SC(NH2)2] was studied in acidic solutions of 0.1 M H2SO4 and 0.1 M HCl. Very strong SERS bands of thiourea were observed in the acidic solutions, in contrast to very weak SERS spectra of thiourea in standard SERS solutions employing K2SO4 or KCl. Thiourea seems to have a strong and stable surface adsorption at a silver electrode in the acidic solutions where protonation and anionic co‐adsorption may enhance this surface stability of thiourea.
Surface‐enhanced Raman spectroscopic study of isomeric anisidines adsorbed on colloidal silver particles
Authors: Sarkar Uttam K. , Chakrabarti Subhasis , Misra T. N.
Published: May 2005

Surface‐enhanced Raman scattering (SERS) spectra of o‐, m‐ and p‐anisidine molecules were compared with the solution Raman spectra. The experimental results suggest that the o‐ and m‐anisidine molecules are adsorbed on the metal surface principally through the nitrogen atom, whereas the p‐anisidine molecules are adsorbed through the π‐system of the phenyl ring. This observation is explained in terms of the electron densities on the N and O atoms and in the phenyl ring as reflected by the Hammett σ values of the isomers. Charge‐transfer interactions have been shown to contribute significantly to SERS.
Surface‐enhanced Raman scattering of triphenylmethane dyes on colloidal silver
Authors: Persaud Indira , Grossman William E. L.
Published: May 2005

Surface Raman spectral studies of triphenylmethane dyes on colloidal silver were carried out. An assessment of the surface and solution spectra led to the conclusion that the dye molecules are most likely lying parallel to the surface of the sol and adopting C3 symmetry. The major vibrational changes suggest that the most important center of interaction is the central carbonium ion, since the greatest changes are observed for the vibrations of the central bonds and only small changes are observed for the N–phenyl stretching modes. For a fixed concentration of sol the lowest level of detection was 5 × 10−8 M.
Excitation profiles versus potential profiles in the determination of the charge‐transfer contribution to SERS of pyridine on a silver electrode
Authors: Kudelski A. , Bukowska J.
Published: May 2005

The relative SERS enhancement factors for pyridine adsorbed on a silver electrode were determined as a function of the laser wavelength and applied potential. The charge‐transfer (CT) contribution to the SERS intensity (I), Gct, was estimated from the excitation profiles (I vs. hv) and compared with the Gct values previously obtained from the I vs. electrode potential curves. A critical discussion of the determination of Gct with the aid of both methods is given.