bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fast esterification of fatty acids with alkyl chloroformates. Optimization and application in gas chromatography
Authors: Hušek Petr , Rijks Jacques A. , Leclercq Piet A. , Cramers Carl A. 
Published: May 2005

AbstractAlkyl chloroformates with methyl, ethyl, and 2‐chloroethyl substituents can instantaneously esterify fatty acids under proper reaction conditions. Apart from the formation of the corresponding alkyl esters, even the alkoxycarbonyl esters can be prepared. These derivatives are useful for the analysis of short‐chain fatty acids. As alkoxycarbonyl ester, even acetic acid can already be separated from the solvent peak. The reaction conditions were examined, and the Influence of solvent polarity and reagent concentration on the conversion was studied. Quantitative conversion of acids to their easters was achieved in non‐aqueous solutions, but even in the presence of water the yields were acceptable.
Determination of planar chlorobiphenyls in animal fat
Authors: Th. Tuinstra L. G. M. , van Rhijn J. A. , Roos A. H. , Traag W. A. , van Mazijk R. J. , Kolkman P. J. W. 
Published: May 2005

AbstractThe occurrence of the highly toxic non‐ortho substituted (planar) chlorobiphenyls (CBs) at low levels in wildlife, (human) fat, and fish generates the need for a routine analytical procedure. The use of a fully automated system for the separation of planar and non‐planar CBs, consisting of a gel permeation chromatography system, a sample preparation system employing extraction columns, and a porous graphitic carbon HPLC column is described, and tested with horse fat. Gas chromatography on capillary columns, with electron‐capture or high resolution mass spectrometric detection, is used for quantitation of the CBs.
Preparation of thermally stable phenylpolysiloxane fused silica capillary columns. Optimization and evaluation of the deactivation by capillary GC and solid state 29Si NMR
Authors: Wu Q. , Hetem M. , Cramers Carel A. , Rijks Jacques A. 
Published: May 2005

AbstractThe deactivation of fused silica capillary columns with a laboratory‐made poly‐diphenylvinylmethylhydrosiloxane copolymer has been investigated. The deactivation obtained at different temperatures and reaction times is characterized with a dual column capillary GC system [1]. In parallel, the effect of the silylation temperatures and reaction times on the nature, the structure, and the chemical properties of the deactivation layer has also been studied by solid‐state 29Si NMR spoctroscopy. A fumed silica, Cab‐O‐Sil M5, was used as a model substrate for these spectroscopic studies.The deactivated fused silica capillaries show an excellent thermal stability (up to 400°C), a high resistance to solvolysis, and a minimal interaction to various critical test components. A good wettability of the fused silica capillary columns deactivated with this reagent was confirmed by successful subsequent coating with polysiloxanes with different phenyl contents.
Improved analysis by liquid chromatography of iso‐alpha acids
Authors: Verzele M. , Steenbeke G. , Verhagen L. C. , Strating J. 
Published: May 2005

AbstractThis paper shows that the liquid chromatography (LC) methods so far described in the literature for iso‐alpha acids analysis are unsatisfactory. The main reasons for this are the failure of the advocated eluent systems to completely suppress trace metal activity of commercial LC columns and the lack of a stable reference iso‐alpha acid.The trace metal problem can be solved by using a column packing material specifically designed for “Hop Acid” analysis and by adding ethylenediaminetetraacetate (EDTA) to the eluent. The reference problem is more difficult, but possibly a formulation of the iso‐alpha acids in their acid form may be the answer.Chromatographic conditions changing the elution pattern of the individual iso‐alpha acids are studied. This leads to better control of their co‐elution in the analytical procedure.
Trace analysis of agrochemicals by supercritical fluid chromatography
Authors: Ashraf Sameena , Bartle Keith D. , Clifford Anthony A. , Moulder Robert 
Published: May 2005

AbstractCapillary supercritical fluid chromatography was performed using solvent‐vented injection in conjunction with a thermionic ionization detector. Mixtures of organo‐nitrogen and phosphorus containing agrochemicals were chromatographed and detection of low picogram quantities was observed.
LC‐GC analysis of the aromatics in a mineral oil fraction: Batching oil for jute bags
Authors: Grob Konrad , Biedermann Maurus , Caramaschi Adrian , Pacciarelli Bruno 
Published: May 2005

AbstractAromatics of a C15C30 mineral oil fraction, the “batching oil” used for producing jute fabrics, were analyzed for estimating the toxicity of oil transferred from jute bags to foods. Group‐type pre‐separation according to ring systems occurred on a LC NH2 column with pentane and small additions of methanol as eluent. LC fractions were characterized by LC‐GC‐MS and quantitated by LC‐GC‐FID. The oil contained 23% aromatics and 1% “polars”; some 99.5% of the aromatics were alkylated.
TEM study on the pore structures of wide‐pore silica and polymer gels
Authors: Tanaka Nobuo , Kimata Kazuhiro , Hosoya Ken , Araki Takeo , Tsuchiya Hajime , Hashizume Katsushi 
Published: May 2005

AbstractInternal structures of wide‐pore packing materials for HPLC were studied by transmission electron microscopy (TEM). TEM gave information about the size, shape, and location of the pores as well as the size of primary structures in corpuscular systems. Visualization of the three dimensional internal structures of wide‐pore materials was attempted by scanning the TEM photographs with a densitometer.
Band broadening evaluation by back‐and‐forth capillary electrophoresis
Authors: Terabe Shigeru , Shibata Osamu , Isemura Tsuguhide 
Published: May 2005

AbstractThe purpose of this study is to develop a method for precise evaluation of band broadening in capillary electrophoresis. A capillary electrophoresis system with on‐column twin detectors is constructed. Back‐and‐forth electrophoresis permits zones to make a round trip between the twin detectors placed at distant positions on the capillary. The system is capable of eliminating extra‐column effects and discriminating between reversible and irreversible band‐broadening mechanisms.
Development of a curie‐point headspace sampler for capillary gas chromatography
Authors: Oguri Naoki , Onishi Akira , Hanai Toshihiko 
Published: May 2005

AbstractA Curie‐point headspace sampler (CPHS) equipped with a purge and trap sampler has been developed for use with capillary gas chromatography. The new system can handle a variety of samples, including gases, liquids, and solids, and can also be used as a pyrolyzer.
Approaches to dioxin analysis by HRGC‐HRMS and hybrid HRGC‐MS‐MS
Authors: Iida Junko , Takeda Takehiro , Takasuga Takumi , Moncur John , Ireland Phil , Wright Barry 
Published: May 2005

AbstractA hybrid mass spectrometer with an EBQQ configuration was used to investigate two approaches to trace dioxin analysis: high resolution gas chromatography – high resolution mass spectrometry (HRGC‐HRMS) and high resolution gas chromatography – mass spectrometry – mass spectrometry (HRGC‐MS‐MS). It is shown that selected ion monitoring (SIM) HRGC‐HRMS exhibits better selectivity for dioxins separated on a cyanopropyl column than is otherwise obtained under medium resolution mass spectrometry (3,000 resolution), while optimization of conditions for HRGC‐MS‐MS allowed the observation of 350 femtograms of the highly toxic 2,3,7,8‐TCDF at a S/N ratio of 5:1. Both methods were applied to environmental samples with good results.
A unified approach to the chromatography‐FTIR interface: GC‐FTIR, SFC‐FTIR, and HPLC‐FTIR with subnanogram detection limits
Authors: Norton Kelly L. , Lange Andrew J. , Griffiths Peter R. 
Published: May 2005

AbstractThe results described in this paper demonstrate that Identifiable FTIR spectra of components separated by gas, supercritical fluid, and liquid chromatography can be measured in real time using a common approach. The sensitivity of each Interface is comparable with that obtained by interfacing the corresponding technique with a bench‐top mass spectrometer. The combination of these two spectroscopic techniques should lead to an even more powerful means of Identification of volatile, semi‐volatile, and non‐volatile components of mixtures.
Sample decomposition in an electrically heated cold‐trap inlet system for high speed gas chromatography
Authors: Klemp Mark , Sacks Richard 
Published: May 2005

AbstractThermal decomposition of some hydrocarbon and chlorinated hydrocarbon compounds in metal capillary tubes used in an inlet system for high speed gas chromatography has been investigated. The metal tube is cooled to about −75°C by a flow of cold nitrogen gas in order to focus a vapor sample cryogenically. A capacitive discharge power supply is then used to heat the metal tube resistively in order to revaporize the sample and introduce it to the separation column as a plug 5‐10 ms wide. The effects of tube temperature, tube material, sample vapor residence time, and type of carrier gas on thermal cracking are described. Use of a copper‐nickel alloy tube resulted in less cracking than either pure platinum or pure nickel. Cracking is more significant with hydrogen as carrier gas than with helium. Cracking also increases with increasing sample residence time in the hot tube. Quantitative sample injection with minimum decomposition can be obtained for a variety of aliphatic and aromatic hydrocarbons and chlorinated hydrocarbon compounds.
A comparative study of the gas chromatographic behavior of liquid crystals and polyester stationary phases using paraffinic hydrocarbons as standards
Authors: Habboush Albertine E. , Farroha Sabri M. , Kreishan Abdul‐Latif Y. 
Published: May 2005

AbstractTwo new categories of stationary phase have been studied: liquid crystals and polyesters. The liquid crystals were p,p′‐azoxyphenetol, p(n‐hexyloxy)phenyl‐p′‐methoxy benzoate, and p‐pentyloxy‐p′‐ethoxyazoxybenzene; and the polyester phases 1,4‐butanediol succinate (LAC‐860), ethylene glycol succinate (LAC‐886), diethylene glycol succinate (LAC‐738), diethylene glycol adipate (LAC‐296), and neopentyl glycol adipate (LAC‐769).Abnormal chromatographic behavior, has been observed: an increase in specific retention volumes and an improvement in the separation of normal, branched, and cycloparaffins, depending on their structures, at high temperatures within a specified range. This phenomenon is the opposite of the behavior of traditional stationary phases. From the chromatograms obtained, plots of log v against 1/T, and differential thermal analysis it is concluded that this abnormal behavior may be attributed to the penetration of solutes through the ordered structure of the mesophase and the rod‐like molecules of the polyesters. Furthermore, the chromatographic behavior of some of the polyester (LAC‐series) stationary phases in respect of temperature changes is similar to that of the nematic mesophases.
Permethylated cyclodextrins in the GC separation of racemic mixtures of volatiles: Part 1
Authors: Bicchi Carlo , Artuffo Giuseppe , D'Amato Angela , Nano Gian Mario , Galli Anna , Galli Mario 
Published: May 2005

AbstractThe chromatographic separation of racemic mixtures of volatile compounds by 2,3,6‐trimethyl‐α‐, β‐ and γ‐cyclodextrins is discussed. Columns were prepared by mixing the derivatized cyclodextrin with OV‐1701 or hydroxy‐terminated OV‐1701 (OV‐1701‐OH) following Schurig's method [1]. About 130 racemates with widely differing structures were used to test the performances of 2,3,6‐permethylated‐α, β‐ and, γ‐cyclodextrins mixed with the polysiloxane polymers in different ratios. The influence of the different types of cyclodextrin on racemate separation is shown, and some phenomena which might be helpful in the elucidation of the chromatographic behavior involved are also described. The influence both of the percentage of cyclodextrin in the polysiloxane, and of the operating conditions (carrier gas, flow rate, and temperature) in the separation of flavor and fragrance racemates is also evaluated.
Density of methanol‐carbon dioxide mixtures at three temperatures: Comparison with vapor‐liquid equilibria measurements and results obtained from chromatography
Authors: Berger Terry A. 
Published: May 2005

AbstractThe density of methanol‐carbon dioxide mixtures has been measured at 40, 50, and 60°C and the data presented as constant density curves in plots of pressure against composition. Mixtures containing from 1 to 23.5% methanol were covered. The density information was compared with liquid‐vapor equilibria data from the literature and with results from chromatographic separations using both sub‐ and supercritical conditions. The results indicate that phase transitions do not usually occur when the concentration of the modifier is increased while holding temperature and pressure constant. Similarly, no phase transition occurs when the temperature is increased from 28 to 80°C, at a constant (high) pressure and modifier concentration.Binary fluids with many desirable compositions cannot be prepared at low densities: densities below 0.4–0.5 g/cm3 cannot be obtained from methanol‐carbon dioxide mixtures because the fluids separate into two phases. This means that density programming with many binary fluid combinations will be of secondary importance compared with composition programming.
Supercritical fluid chromatographic separation of polychlorinated biphenyls (PCBs) using a negative temperature gradient for density programming
Authors: Cammann Karl , Kleiböhmer Wolfgang 
Published: May 2005

AbstractThe technical PCB mixtures Aroclol and Clophen have been analyzed by packed column supercritical fluid chromatography using negative temperature programming. The chromatographic method was successfully applied to the analysis of PCBs, polycyclic aromatic hydrocarbons, and polychlorinated dibenzo‐p‐dioxins in extracts from environmental matrices.
Pyrolysis – capillary gas chromatography combined with on‐line alkylation for the compositional analysis of liquid crystalline aromatic polyesters
Authors: Ohtani Hajime , Fujii Ryuichi , Tsuge Shin 
Published: May 2005

AbstractPyrolysis–capillary gas chromatography combined with on‐line alkylation has been employed for compositional analysis of liquid crystalline aromatic polyesters (LCPs) based on p‐ hydroxybenzoic acid. The fundamental conditions were examined using an LCP prepared from p‐hydroxybenzoic acid, terephthalic acid, and 4,4′‐biphenol and every constituent of a sample weighing ca. 50 μg was almost quantitatively recovered as its dimethyl derivative in the pyrogram obtained following pyrolysis at 400°C in the presence of 1 μl of 25% tetramethyl‐ammonium hydroxide in methanol. The compositions of a variety of terpolyesters and LCPs containing isophthalic acid or 2‐hydroxy‐6‐naphthoic acid units have been precisely deter‐mined by pyrolysis‐methylation GC.
Towards on‐line SEC‐GC of pesticide residues? The problem of tailing triglyceride peaks
Authors: Grob Konrad , Kälin Iren 
Published: May 2005

AbstractSEC is used for clean‐up of food extracts obtained for analysis of pesticide residues primarily to remove high molecular weight material, among which fat may be present at the largest concentrations. The triglyceride peak, which is usually very large, is eluted before the components of interest. The problem described in this paper deals with the tail of the triglyceride peak: this may intrude into the fraction containing the pesticides and contaminate the GC.
Clean‐up of some organochlorine and pyrethroid insecticides by automated solid‐phase extraction cartridges coupled to capillary GC‐ECD
Authors: van der Hoff G. René , Gort Steven M. , Baumann Robert A. , Van Zoonen Piet , Brinkman Udo A. Th. 
Published: May 2005

AbstractThe ASPEC (Automatic Sample Preparation with Extraction Columns) system has been coupled on‐line to capillary GC‐ECD by means of a loop‐type interface equipped with a solvent vapour exit. Both ASPEC and GC conditions have been optimized leading to an effective clean‐up of the extracts analyzed.By means of solid‐phase extraction cartridges filled with silica, it has been possible to analyze concentrated surface water extracts for a group of 18 electron‐capturing compounds present in the water at ppt levels. ASPEC‐GC has also been applied to the determination of synthetic pyrethroids at ppt levels in surface water.The complete analytical procedure is greatly facilitated by automation and miniaturization. Miniaturization results in a considerable decrease in the sample volume required. The potential of the method for the analysis of other pesticides is estimated.
The automated determination of volatile organic contaminants in ambient air and/or soil gas by gas chromatography with selective detectors
Authors: Kirshen Norman , Almasi Elizabeth 
Published: May 2005

AbstractTwo systems have been developed which are suitable for the determination of sub parts per billion levels of organic contaminants in ambient air and soil gas. Gas samples are passed through an adsorbent where the contaminants are trapped. Following thermal desorption the contaminants are quantitated by capillary GC employing photoionizations electrolytic conductivity, and electron capture detection.The performance of the systems is described in detail.
The application of capillary SFC, packed column SFC, and capillary SFC‐MS in the analysis of controlled drugs
Authors: MacKay Graham A. , Reed Graham D. 
Published: May 2005

AbstractMulti–component mixtures of controlled drugs, drug impurities, and adulterants have been analyzed by capillary SFC‐FID, packed column SFC‐UV, and capillary SFC‐MS. Isocratic packed column SFC has been performed with binary and ternary mobile phases using a single syringe pump. The combination of capillary SFC and double focusing MS is described with reference to MS source pressures and the spectra obtained. The use of negative temperature programming in SFC is described.
Composition and major odorous compounds of the essential oil of Bifora radians, an aldehyde‐producing weed
Authors: Latrasse Alain , Sémon Etienne , Le Quéré Jean‐Luc 
Published: May 2005

AbstractThe composition of the essential oil of Bifora radians, an aldehyde‐producing weed, has been investigated by capillary gas chromatography, coupled gas chromatography – mass spectrometry, on‐line catalytic hydrogenation and coupled gas chromatography – infrared spectrometry. The nineteen compounds identified included eighteen aldehydes: seven alkanals (C6, C9, C10, C11, C12, C13, and C14), ten alkenals, including five (E)‐2‐alkenals (C12, C13, C14, C15, and C16), and one (E,E)‐2,4‐alkadienal (C13). Typical Bifora odors were attributed to three major (E)‐2‐alkenals, C12, C13, and C14.
Analysis of beer iso‐α‐acids by micellar electrokinetic chromatography and multi‐wavelength UV detection
Authors: Vindevogel Johan , Szücs Roman , Sandra Pat , Verhagen Leen C. 
Published: May 2005

AbstractThe identification of beer bitter acids in a pre‐isomerized hop extract by means of their UV‐spectra is described. Preliminary data for the analysis of these compounds in beer samples are presented.
Improving splitless injection with electronic pressure programming
Authors: Wylie Philip L. , Phillips Richard J. , Klein Kenneth J. , Thompson Michael Q. , Hermann Bruce W. 
Published: May 2005

AbstractAn experimental injection port has been designed for split or splitless sample introduction in capillary gas chromatography; the inlet uses electronic pressure control, in order that the column head pressure may be set from the GC keyboard, and the inlet may be used in the constant flow or constant pressure modes. Alternatively, the column head pressure may be programmed up or down during a GC run in a manner analogous to even temperature programming. Using electronic pressure control, a method was developed which used high column head pressures (high column flow rates) at the time of injection, followed by rapid reduction of the pressure to that required for optimum GC separation. In this way, high flow rates could be used at the time of splitless injection to reduce sample discrimination, while lower flow rates could be used for the separation. Using this method, up to 5 μl of a test sample could be injected in the splitless mode with no discrimination; in another experiment, 2.3 times as much sample was introduced into the column by using electronic pressure programming. Some GC peak broadening was observed in the first experiment.
Abstraction of basic compounds by sulfonated polymeric resins in capillary gas chromatography
Authors: Sun Jeffrey J. , Fritz James S. 
Published: May 2005

AbstractA small amount of a lightly sulfonated non‐porous resin placed in the liner of the injection splitter of a gas chromatograph retains basic organic compounds but allows neutral compounds to be chromatographed normally. The organic bases in the gaseous state react with sulfonic acid groups on the resin surface to form protonated ions. Abstraction of bases is complete at a base: neutral molar ratio as high as 200:1 and a large number of samples can be injected before the sulfonated resins need to be replaced.
Automated at‐column injection into narrow bore capillary GC columns
Authors: Hagman Gunnar , Roeraade Johan 
Published: May 2005

AbstractAn injector designed for automatic direct liquid injection into narrow bore capillary GC columns has been constructed and evaluated. The tip of the syringe needle is aligned with, and positioned close to, the column entrance in a small, pressurized cavity: when the sample is dispensed it is immediately forced into the column by the action of the surrounding carrier gas. A standard autosampler equipped with a standard stainless steel syringe needle was utilized for at‐column sample transfer into 100 μm i.d. columns.RSD values for n‐alkanes were between 0.1 and 0.3% for relative area counts and approximately 1% for absolute area counts.
Determination of traces of aromatic compounds in multicomponent mixtures by HRCGC
Authors: Matisová Eva , Kubuš Ľubomír , Jurányiová Eva 
Published: May 2005

AbstractThe possibilities and difficulties of trace analysis of highly complex organic mixtures has been demonstrated by the analysis of traces of numerous aromatic substances in an n‐alkane matrix with a boiling point range of 151–270°C. Single column high resolution capillary gas chromatography (under optimized conditions) was performed after an off‐line LC preseparation step which had been evaluated using a model mixture.Gas chromatographic quantitation of the 191 aromatic compounds identified was performed with an internal standard; following splitless injection and separation on a polydimethyl‐siloxane column under temperature‐programmed conditions the compounds were detected by flame ionization. The response factors of aromatic hydrocarbons at trace levels were verified and the precision and reproducibility both of the GC determination and the overall analysis, including preseparation, were studied.Percentage by weight of individual aromatic compounds (mainly alkylbenzenes, indanes, naphthalenes, and acenaphthenes) was in the range 10−3 to 10−6.
A new approach to dynamic deactivation in capillary zone electrophoresis
Authors: Emmer Åsa , Jansson Mårten , Roeraade Johan 
Published: May 2005

AbstractThis paper describes a simple means of obtaining high resolution separations of basic proteins at a pH below their pl. Small amounts of a cationic fluorosurfactant are added to the running buffer. A positively charged wall is thereby obtained which will repel positively charged proteins. The particular chemistry of fluorosurfactants is believed to enhance the efficiency of the deactivation. Examples are presented of the separation of some model proteins, including a human insulin‐like growth factor (IGF‐I), and a misfolded by‐product of the growth factor.