bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stereochemical analysis of constituents of essential oils and flavor compounds by enantioselective capillary gas chromatography
Authors: König Wilfried A. , Krebber Ralph , Evers Petra , Bruhn Gabriele 
Published: May 2005

AbstractModified cyclodextrins interact enantioselectively with a great variety of volatile chiral constituents of essential oils by forming diastereomeric inclusion complexes. Capillary gas chromatography is used for resolving the enantiomers of terpenoid hydrocarbons (camphene, α‐pinene, limonene, α‐phellandrene), carbonyl compounds (carvone, fenchone, menthone, isomenthone, piperitone, camphor, myrtenal), and alcohols (trifluoroacetylated β‐citronellol, myrtenol, trans‐pinocarveol, 1‐octen‐3‐ol, and underivatized linalool). The enantiomeric composition of some of these compounds in a variety of essential oils is investigated.
Simultaneous determination of particle size and density in polydisperse colloidal samples by sedimentation field‐flow fractionation
Authors: Koliadima A. , Dalas E. , Karaiskakis G. 
Published: May 2005

AbstractSedimentation Field‐Flow Fractionation (SFFF), which is a one‐phase chromatographic system, is shown to be a rapid and convenient method for the simultaneous determination of particle size and density in polydisperse colloidal samples. This can be done by a methodology based on the variation of the carrier solution density using various aqueous glycerol solutions having different concentrations. A polydisperse polyvinyl chloride (PVC) latex sample was used as a model colloid. The average diameters and densities found by the proposed methodology are in good agreement with those obtained from the normal. SFFF procedure using a carrier of constant density or given by the manufacturer. Number average, dN, and weight average, dw, particle diameters were determined for the PVC sample at various carrier solutions containing glycerol up to 40 % (w/w) in order to show whether sample aggregation has occurred or not in the presence of glycerol. In all cases, the ratio dw/dN was found to be constant, showing that PVC aggregation has not occurred. Therefore our results, obtained by the proposed methodology in SFFF, are accurate, showing that this approach has considerable promise for characterizing complex colloidal materials.
Significance of minor components of milk fat
Authors: Mariani C. , Contarini G. , Zucchetti S. , Toppino P. M. 
Published: May 2005

AbstractIn order to establish criteria for the evaluation of the genuineness of milk fat and its derivatives, research has been carried out on some minor components (mono‐ and diglycerides and cholestrol esters). Most determinations of milk fat diglycerides showed significant qualitative and quantitative differences compared with other fat sources, and especially with tallow. In particular, the milk fat diglycerides C30–C32–C34–C36 showed characteristic fingerprints. Moreover, the sterol fractions (free and esterified) have also been evaluated. The cholesterol ester profile in milk lipids includs fatty acides from 10 to 18 carbon atoms, while tallow basically showed only C14–C16–C18. In comparison, phytosteral esters with C16 and C18 fatty acids have been found in vegetable fats. These results lead to the hypothesis of possible use of these methods in addition to those most commonly applied (TG‐FAME). Furthermore, the natural variability of milk fat components makes a final evaluation of these methodologies difficult unless experimental work is extended to more samples and performed by several research groups.
Study on retention behavior of cyclic siloxanes by high resolution pyrolysis‐gas chromatography with a fused silica capillary column
Authors: Fujimoto Shinji , Ohtani Hajime , Yamagiwa Katsuya , Tsuge Shin 
Published: May 2005

AbstractThe general gas chromatographic retention behavior of cyclic methylsiloxanes partially substituted with phenyl or 2‐cyanoethyl groups has been systematically studied, with pyrolysis‐gas chromatography being utilized to form the cyclic siloxanes from the corresponding polysiloxanes at a temperature of 600°C. Kovats retention indices (KI) were determined for the cyclic siloxanes by use of the retention data of the pyrolyzates from polyethylene as standards. The effect of phenyl and 2‐cyanoethyl substituents in the cyclic siloxanes on retention behavior has also been considered.
Possibilities and limitations of coiling induced secondary flow in capillary supercritical fluid chromatography
Authors: Janssen Hans‐Gerd M. , Rijks Jacques A. , Cramers Carel A. 
Published: May 2005

AbstractThe possibility of enhancing radial mass transfer in capillary SFC by tightly coiling the column is discussed. The influence of coiling‐induced secondary flow on the plate height and the speed of analysis in capillary SFC is investigated. It is shown that the experimental plate height in tightly coiled metal or fused silica columns departs from the Golay theory for laminar flow. The effect of the pressure drop associated with the use of higher mobile phase linear velocities is studied. The capacity factors of retained components are used as sensitive probes for pressure drop over the column. Experimental plate heights in coiled columns are compared with values calculated from Tijssen's theory for coiling induced secondary flow. At low velocities a good quantitative agreement was observed between the theory and the experimental results. At intermediate velocities only a qualitative agreement is found. The speed of analysis in coiled columns was found to be up to 5 times higher than in straight capillaries. The largest gain in analysis speed was obtained for solutes with low capacity factors. It is shown that coiling the column can have a positive influence on the detectability. For tightly coiled 210 μm i.d. columns the advantages of coiling‐induced secondary flow could be fully exploited without adverse effects of the column pressure drop. For 50 μm columns the possibility to increase the speed of analysis by coiling was limited due to the high pressure drop.
Differences in absorbance levels as found in capillary zone electrophoresis under stacking conditions
Authors: Vinther Anders , Everaerts Frans M. , Søeberg Henrik 
Published: May 2005

AbstractDuring some capillary zone electrophoresis (CZE) experiments, the baseline UV absorbance signal at 200 nm “jumped” from one stable level prior to the water plug (marking the flow of neutrals) to another stable level after the water plug. The phenomenon was further examined with distilled water as the sample and with different buffers, applied potentials, and salt concentrations in the buffer. It seems that there is an “isotachophoretic effect” on top of the CZE separations when running under stacking conditions. The effect results in a higher pH value of the buffer after the water plug compared to the pH prior to the plug. The nature of the buffer, the salt concentration in the buffer, and the applied potential all affect this phenomenon.
Partition and adsorption in the separation of long chain lipids by normal phase high performance liquid chromatography
Authors: Netting A. G. , Rhodes S. H. 
Published: May 2005

AbstractMartin's adaption of Raoult's Law has been shown to describe partition phenomena in normal phase HPLC. Thus, in the separation of fatty acid pentaflorobenzyl esters and of triacylglycerols in dichloromethane or acetonitrile in half‐water‐saturated hexane, the natural logarithm of the corrected retention volume is proportional to the number of double bonds that these solutes contain. By extending Martin's adaption of Raoult's Law with activity coefficients, evidence was obtained that deviations observed for the homologous series of saturated fatty acid pentafluorobenzyl esters from C2 to C5 could be accounted for by a diminution of adsorption by the inductive effect. For chain lengths longer than C5, it appeared that there were additional field and inductive effects from the methyl end of the hydrocarbon chains.Thus, with these half‐water‐saturated solvent systems, the silica surface is probably covered with a bilayer of water which, in the dynamic situation in an HPLC column, attracts several layers of the polar organic component of the mobile phase by dispersive interactions. This stationary phase surface may, then, be considered to be immiscible with the predominantly hexane mobile phase due to these dispersive interactions and thus partition can occur between these two phases. Solutes that enter the stationary phase are then free to interact with the underlying aqueous phase by adsorption.
Optimization of resolution in micellar electrokinetic chromatography
Authors: Rasmussen Henrik T. , Goebel Lisa K. , McNair Harold M. 
Published: May 2005

AbstractA comparison of separations conducted in sodium dodecyl sulfate (SDS) and SDS modified with Brij 35 indicates that selectivity, in Micellar Electrokinetic Chromatography (MEKC), is governed by the composition of the micellar phase. Beyond selectivity optimization, resolution may be improved by increasing efficiency or decreasing electroosmotic flow. Of these approaches, increasing capillary length (to improve efficiency) should be a more time effective means of improving separation.
Selective detection of volatile nickel, vanadium, and iron porphyrins in crude oils by gas chromatography‐atomic emission spectroscopy
Authors: Quimby Bruce D. , Dryden Paul C. , Sullivan James J. 
Published: May 2005

AbstractThis report describes the selective detection of volatile nickel, vanadium, and iron metalloporphyrins in crude oil samples. An atomic emission detector (AED) was used for simultaneous detection of these metals using the Ni 301.2 nm, V 292.4 nm, and Fe 302.1 nm emission lines. Detection limits for these metals range from 0.05 to 5 pg/sec. The presence of volatile forms of these metals in several crude oil samples has been confirmed.
GC with LC‐like packed capillary columns
Authors: Takeuchi Toyohide , Watanabe Mototada , Haraguchi Hiroki , Ishii Daido 
Published: May 2005

AbstractCapillary columns of 0.3–0.35 mm internal diameter and 0.3–7.7 m length, packed with 3 to 30 μm octadecylsilica stationary phases as used for liquid chromatography, were applied to gas chromatographic separation of low boiling hydrocarbons. Van Deemter plots for these columns showed the optimum column efficiency to occur at linear velocities of 4–5 cm/s. A short column was applied to the rapid separation of components of a natural gas and impurities in standard gases, while a long column was applied to the separation of complex mixtures.
Fast separations with open tubular ion exchange capillary columns
Authors: Müller Stephan , Scheidegger David , Haber Carsten , Simon Wilhelm 
Published: May 2005

AbstractFused silica columns of 4.6 μm i.d. were coated with 3‐sulfopropylsilane as a cation exchanger and 3‐(2‐aminoethyl‐amino)‐propylsilane as an anion exchanger. Fast separations of cations (< 25 seconds) and of anions (< 35 seconds) were obtained, using a potentiometric microelectrode as a detector. In proceeding towards smaller i.d.s, a mixture of alkali metal cations could be separated successfully in an uncoated fused silica capillary of 2.3 μm i.d. as a result of retention by the surface silanol groups at pH 9.4.
Simultaneous determination of creatinine and uric acid in human plasma and urine by micellar electrokinetic chromatography
Authors: Miyake Mamoru , Shibukawa Akimasa , Nakagawa Terumichi 
Published: May 2005

AbstractHigh performance capillary electrophoresis using a buffer solution containing micelles of ionic surfactant (e.g. sodium dodecyl sulfate), called micellar electrokinetic chromatography, has been applied to the separation and simultaneous determination of creatinine and uric acid in human plasma and urine. The sample was introduced into the capillary by siphoning an appropriate volume of untreated plasma or urine spiked with an internal standard (antipyrine). Creatinine, uric acid, and antipyrine were separated mutually, and from other endogeneous components within 18 min. The calibration plots showed good linearity (correlation coefficient > 0.999) over the concentration range needed for clinical analysis. Standard addition tests indicated that the recoveries of creatinine and uric acid from urine samples ranged, respectively, from 97 % to 106 % and 97.4 % to 108 % with a coefficient of variation (C.V.) of 3.3 % (n = 5), and that those from plasma samples ranged, respectively, from 100 % to 112 % and 101 % to 107 % with a C.V. of 4.7 % (n = 5). The results were in agreement with those obtained by conventional methods.
Temperature dependence of equivalent chain length values on capillary columns of different polarity
Authors: Sidisky Leonard M. , Ridley Heloise J. 
Published: May 2005

AbstractThe influence of temperature and capillary column stationary phase polarity on the equivalent chain length (ECL) values of unsaturated fatty acid methyl esters (FAMEs) is discussed. Comparisons are made of a bonded, nonpolar methyl silicone, bonded and nonbonded polyethylene glycols, and a highly polar, stabilized cyanosilicone stationary phase. The change in the ECL values over a 20° temperature range is used to demonstrate selectivity shifts and the influence of temperature on the separation of FAMEs on these phases. The effect of the degree of unsaturation of the FAME components, on the various stationary phases is also investigated.
Mobilities of metal β‐diketonato complexes in micellar electrokinetic chromatography
Authors: Saitoh Koichi , Kiyohara Chikara , Suzuki Nobuo 
Published: May 2005

AbstractElectrically neutral acetylacetonato complexes of chromium(III), cobalt(III), rhodium(III), and platinum(II) (or palladium(II)) have been separated successfully by capillary zone electrophoresis in a micellar solution of sodium dodecyl sulfate (SDS). The distribution coefficient of each metal complex between the SDS micelle and the aqueous solution surrounding the micelle was calculated from the capacity factor. A linear log‐log relationship was found between the distribution coefficient and the partition coefficient of the complex between dodecane and water. The linear relationship was effectively used for prediction of both the distribution coefficients and the migration times of other metal complexes, such as palladium(II) acetylacetonate and chromium(III) 3‐methyl acetylacetonate.
Effects of the sample matrix on the separation of peptides by high performance capillary electrophoresis
Authors: Satow Takashi , Machida Akiko , Funakushi Kayo , Palrnieri Richard 
Published: May 2005

AbstractThe effects of the sample matrix on the separation of peptides by HPCE has been investigated. Under both acidic and alkaline conditions, use of 25–30 mM salts in the sample zone resulted in much better resolution than did 100 mM salts. Prefocusing effects and acceleration of elution were also observed. These results agree well with the theory developed by Everaerts. In this paper a practical guide for high sensitivity, high resolution separation of salt‐containing peptide mixtures is proposed.
Determination of mono‐, di‐ and tri‐substituted butyltin, phenyltin and methyltin compounds as free halides using gas chromatography with flame photometric detection
Authors: Hashimoto Shinya , Otsuki Akiro 
Published: May 2005

AbstractA simple chromatographic procedure has been developed for the sensitive determination of mono‐, di‐ and tri‐substituted butyltin, phenyltin, and methyltin compounds as halides. The organotin compounds were separated on a DB‐1 capillary column and detected by flame photometric detection (FPD) equipped with a 611.5 nm filter.Pretreatment of the capillary column with an ethyl acetate solution of hydrobromic acid, or doping of standard solutions with hydrobromic acid, was found to be necessary if reproducibly sharp peaks of organotin halides were to be obtained. Column treatment and acid doping did not cause any background problems or undesirable degradation of the organotin compounds.Three different standard solutions in ethyl acetate had to be Jrepared, because undesirable degradation of the organotin halides was observed when all the compounds were dissolved in the same solution. The first, standard solution I, contained tri‐n‐butyltin chloride (TBTCI) and trimethyltin chloride (TMTCI), the second, standard solution II, contained triphenyltin chloride (TPTCI), and the third, standard solution III, contained hydrogen bromide and the other organotin compounds: di‐n‐butyltin chloride (DBTCI), mono‐n‐butyltin chloride (MBTCI), dimethyltin chloride (DMTCI), monomethyltin chloride (MMTCI), diphenyltin chloride (DPTCI), and monophenyltin chloride (MPTCI). An ethyl acetate solution containing hydrobromic acid (20 × 10−3 mol/I) was used for column treatment.
Simplex optimization of a programmed temperature capillary gas chromatographic separation
Authors: Lanças Fernando M. , Francelin Roseli A. , de Souza Ailton J. 
Published: May 2005

AbstractThe modified simplex algorithm proposed by Nelder and Mead has been used to optimize the separation by temperature programmed capillary GC, of volatile compounds present in alcoholic beverages. An adequate objective function, CRF, based on the separation factor of Kaiser has been used for the optimization process.A factorial design was initially performed to verify the relationship between the several parameters of interest. Following this, the optimization was executed and a surface adjusted within the set of experimental data.
Polymer analysis using pyrolysis‐GC‐FTIR‐MS and GC‐AED
Authors: Oguchi Rimiko , Shimizu Ayako , Yamashita Satoru , Yamaguchi Kenji , Wylie Philip 
Published: May 2005

AbstractVolatile pyrolysates of a methyl methacrylate‐butadiene‐styrene copolymer (MBS) have been analyzed using a capillary gas chromatograph equipped with a Fourier transform infrared detector in tandem with a mass selective detector, and a gas chromatograph‐atomic emission detector system.Among the volatile compounds observed were monomers used for synthesis of the polymer. Numerous oligomers of higher boiling point were also found; identification of these could be used to give structural information about the parent polymer.Combining information from these techniques was found to be extremely useful for the analysis of polymer pyrolysis products. In characterizing each compound it was found particularly helpful to juxtapose feature‐specific chromatograms (e.g., single ion monitoring from the mass‐selective detector and the selected wavelength chromatography from the infrared detector).
Determination of pyrethroids and their degradation productds in indoor air and on surfaces by HRGC‐ECD and HRGC‐MS(NCI)
Authors: Class Thomas J. 
Published: May 2005

AbstractAir and surface samples taken following indoor applications of natural pyrethrins and pyrethroids have been analyzed by HRGC‐ECD and HRGC‐MS using negative chemical ionization (NCI). It has been found that pyrethroids persist on surfaces as long as sixty hours after application.Primary pyrethroid degradation products have been characterized by mass spectrometry; their identities and route of formation by ozonolysis have been verified by degradation studies and NMR.
On‐line solid phase extraction ‐ thermal desorption for introduction of large volumes of aqueous samples into a gas chromatograph
Authors: Vreuls Jolan J. , Th. Brinkman Udo A. , de Jong Gerhardus J. , Grob Konrad , Artho Anna 
Published: May 2005

AbstractA new approach to the introduction of large aqueous samples into a gas chromatograph, solid phase extraction ‐ thermal desorption, is presented. Carrier gas pushes the sample through a packed liner mounted in a programmed temperature vaporizer; analytes retained by the packing material are thermally desorbed after drying of the adsorbent. The sorption properties and thermal stability of some packing materials have been studied off‐line. Tenax GC®, and octyl‐modified silica silylated with diphenyltetramethyldisilazane to improve its thermal stability, appeared to be suitable materials.The drying period and the desorption temperature are critical for satisfactory performance of the method. When Tenax GC® is used as packing material, thermal desorption at 250°C for 15 min gives quantitative recovery for methyl esters up to hexacosanoic acid methyl ester. With the silylated octyl‐modified silica, the application range is limited to the methyl esters of decanoic to octadecanoic acids.
A trapping column for the coupling of reversed‐phase liquid chromatography and capillary gas chromatography
Authors: Vreuls Jolan J. , Goudriaan Vincent P. , Th Udo A. , de Jong Gerhardus J. 
Published: May 2005

AbstractA new technique for coupling reversed‐phase liquid chromatography (RPLC) with gas chromatography is described. A fraction eluting from an RPLC column is trapped on a short column packed with polymeric adsorbent. After the mobile phase has been displaced with water, the analytes are desorbed with ethyl acetate. Following a delay time to enable the water to be flushed to waste, the ethyl acetate containing the analytes is introduced into the gas chromatograph under conditions suitable for partially concurrent solvent evaporation, i.e. below the solvent boiling point and at a rate just exceeding the evaporation rate. Post‐column addition of water to the RPLC eluent helps to prevent breakthrough of compounds which are only modestly retained on the trapping column. The relationship between the capacity factors of the analytes on the trapping column and the required dilution factor is discussed. Polycyclic aromatic hydrocarbons are used as test compounds to study the system.
Enantiomer separation by gas chromatography on cyclodextrin chiral stationary phases
Authors: Keim Wilhelm , Köhnes Angela , Meltzow Wilhelm , Römer Helmut 
Published: May 2005

AbstractFused silica capillary columns coated with several alkyl or acyl cyclodextrin derivatives, especially those of α‐ and β‐cyclodextrins, are suitable for the enantiomer separation of a wide variety of volatile compounds of different molecular size and functionality. Positional isomers and more than 250 pairs of optical isomers have been resolved, including chiral hydrocarbons, acetals, ethers, epoxides, carbonates, lactones, esters, acids, ketones, aldehydes, alcohols, halocarbons, and also nitrogen‐and sulfur‐containing compounds.The physical properties of the cyclodextrin derivatives, even those obtained as viscous fluids, could be improved by dissolving them in polysiloxane liquid phases commonly used for GLC.
Determination of amino acids in the hepatic and brain tissue of the rat by gas chromatography
Authors: Moodie T. M. , van der Westhuizen L. , Labadarios D. 
Published: May 2005

AbstractA procedure is described for the quantitative determination of amino acids in hepatic and brain tissue samples from the rat. Because the presence of certain matrix components in the tissue material led to interference with chromatographic analysis they were removed by a prechromatographic “clean‐up” step.Quantitative analysis of amino acids, as their N‐heptafluorobutyryl iso‐butyl ester derivatives, was achieved by high resolution gas chromatography on an apolar fused silica open tubular column. Reproducibility data from the complete procedure are presented; coefficients of variation for arginine and histidine in hepatic tissue varied between 7.1 and 10.1% whereas those for most other amino acids were better than 5%, with a mean recovery of 90%.