bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optimization of an electrolytic conductivity detector for determination of toxic nitrogen‐containing food contaminants separated by open tubular column gas chromatography
Authors: Fehringer Norbert V. , Gilvydis Dalia M. , Walters Stephen M. , Poole Colin F. 
Published: May 2005

AbstractThe combination of open tubular column gas chromatography with electrolytic conductivity detection has been evaluated for the determination of nitrogen‐containing pesticide residues in food extracts. Optimization of the column position at the column‐detector interface was crucial to the successful operation of the detector. The signal‐to‐noise ratio and response stability of the detector are greatly influenced by the composition of the electrolyte solvent. Large volume splitless injections using retention gaps and optimized detector operating conditions enabled pesticide residues in food extracts to be determined at sub parts‐per‐million levels. Although the electrolytic conductivity detector is less sensitive than the thermionic ionization detector, its greater nitrogen selectivity can he crucial to the determination of nitrogen‐containing contaminants in food extracts, particularly in complex mixtures where phosphorus‐containing contaminants or matrix compounds are also present.
Stereoisomeric flavor compounds part. LV: Stereodifferentiation of some chiral volatiles on heptakis(2,3‐di‐O‐acetyl‐6‐O‐tert‐butyldimethylsilyl)‐β‐cyclodextrin
Authors: Dietrich Armin , Maas Birgit , Karl Volker , Kreis Peter , Lehmann Detmar , Weber Bernhard , Mosandl Armin 
Published: May 2005

AbstractHeptakis(2,3‐di‐O‐acetyl‐6‐O‐tert‐butyldimethylsilyl)‐β‐cyclo ‐dextrin proves to be a versatile chiral stationary phase for the direct differentiation of aroma‐relevant enantiomers.
Enantiomeric composition of the chiral constituents in essential oils. Part 1: Monoterpene hydrocarbons
Authors: König Wilfried A. , Krüger Angelika , Icheln Detlef , Runge Torsten 
Published: May 2005

AbstractUsing a dual column gas chromatograph equipped with two capillary columns coated with heptakis(6‐O‐methyl‐2,3‐di‐O‐pentyl)‐β‐cyclodextrin (6‐me‐2,3‐pe‐β‐CD) and octakis(6‐O‐methyl‐2,3‐di‐O‐pentyl)‐γ‐cyclodextrin (6‐me‐2,3‐pe‐γ‐CD), respectively, all important olefinic monoterpene hydrocarbons occurring in essential oils, including α‐thujene, α‐ and β‐pinene, camphene, sabinene, α‐ and β‐phellandrene, Δ‐3‐carene and limonene can be resolved into enantiomers. With the chromatographic system described the characteristic enantiomeric composition of these monoterpene hydrocarbons in essential oils can be determined.
Sample evaporation in conventional GC split/splitless injectors. Part 1: Some quantitative estimates concerning heat consumption during evaporation
Authors: Grob Konrad 
Published: May 2005

AbstractDuring sample evaporation in conventional vaporizing injection, the supply of heat to the evaporating liquid is a problem, first because the amounts of heat consumed are relatively large and, secondly, because the heat must be transferred to the sample within a very short time. Times available for evaporation, required amounts of heat, possible sources of heat, and the time required to transfer the heat to the sample liquid are discussed. It is shown that mixing with carrier gas contributes little heat to the evaporation process, but also that packings with glass wool have too low a heat capacity to deliver the required amount of heat to the evaporating sample. Transfer of heat from the insert wall to the sample easily requires several seconds, even if cooling of the vaporizing zone by 20° is accepted. Thus “flash evaporation” is usually impossible and most liquids must be held in the vaporizing chamber to allow full evaporation.
Development of analytical SFE of a polar drug from an animal food matrix
Authors: Messer Dale C. , Taylor Larry T. 
Published: May 2005

AbstractThe applicability of supercritical CO2 extraction as a quantitative method for recovery of a hypolipidemic drug from an animal food matrix has been evaluated. Off‐line extraction with solid phase trapping and solvent rinsing has been utilized. An optimized method for quantitative extraction of the pure drug was initially developed with high reproducibility. Three drug/rat feed matrices were examined. The as‐received “crystalline matrix” yielded the poorest reproducibility suggestive of a heterogeneous matrix. A laboratory‐prepared crystalline drug/feed matrix and a matrix prepared by spiking the animal feed with a solution of the drug gave ten‐fold better RSDs than the “crystalline matrix”.
Retention behavior of ions in high performance ion chromatography: III effect of the nature of the cation on anion retention
Authors: Daignault Louis G. , Rillema D. Paul 
Published: May 2005

AbstractThe affects of alkali metal cations on the retention behavior of halide ions has been investigated. In general, the retention times of the anions were found to decrease as the size of the metal ion increased, although an inversion was observed for the rubidium and cesium ions. A similar inversion has been reported for calculated anion polarizabilities.
The performance concept: A contribution to the modern theory of capillary GC
Authors: Gaspar Guy 
Published: May 2005

AbstractAn original theoretical approach, the “performance concept” is introduced.This concept enables the linear carrier gas velocity and column length to be optimized in order to obtain the shortest possible analysis time for a required separation. The optimized gas velocity and column length are expressed as functions of the B and C coefficients of the HETP equation, the extra‐column equipment constant, σ2EC, and the necessary plate number, Nne, determined by the analytical problem. A new equation is given for predicting analysis time as a function of the same parameters.The validity of the concept is illustrated with an example of such an optimization. The fundamental relationships have been proved experimentally and excellent agreement found between predicted and measured values.
Analysis of classes of compounds of environmental concern: III. Organochlorine pesticides
Authors: Lopez‐Avila Viorica , Benedicto Janet , Baldin Emi , Beckert Werner F. 
Published: May 2005

AbstractForty five organochlorine pesticides (currently listed in EPA Method 8081A) have been chromatographed on DB‐5/DB‐1701 and SPB‐5/SPB‐1701 column pairs which were in each case connected to an inlet splitter and separate electron capture detectors. Thirteen additional compounds were evaluated for their suitability as internal standards or surrogate compounds for incorporation into Method 8081A. Method reproducibility and linearity are discussed, and results are presented for extracts of six real samples spiked with fifteen organochlorine pesticides and analyzed using the dual‐column, dual‐detector arrangement.
A detection method for unified chromatography: Ion mobility monitoring
Authors: Hill Herbert H. , St Louis Robert H. , Morrissey Mark A. , Shumate Christopher B. , Siems William F. , McMinn Dennis G. 
Published: May 2005

AbstractIon mobility monitoring has been used for detection in gas, supercritical fluid, and liquid chromatography, illustrating its potential as a method of detection for unified chromatography. Applications presented include GC‐IMD of dioxins in fly ash, SFC‐IMD of vitamin E, and HPLC‐IMD of alkylamines.Ion mobility spectra of several mixed supercritical fluid mobile phases are also presented. Use of methanol, acetonitrile, and dichloromethane as modifiers of supercritical carbon dioxide, and use of supercritical dichlorodifluoromethane and chlorodifluoromethane as mobile phases had little effect on the reactant ion pattern at the flow rates and concentrations used in this study. Only when acetone was used as a modifier of carbon dioxide did the positive reactant ions change significantly. No effect of modifiers or mobile phase was observed for the negative reactant ions.
Detection of rare earth elements by post‐column reaction with xylenol orange and cetylpyridinium bromide
Authors: Hrdlička Aleš , Havel Josef , Valiente Manuel 
Published: May 2005

AbstractRare earth elements have been separated by HPLC on octadecyl‐bonded silica gel, dynamically modified with ammonium dodecylsulfate, using aqueous solutions of α‐hydroxyisobutyric acid as mobile phase.The requirements and characteristics of post‐column reaction with xylenol orange and cetylpyridinium bromide were investigated and optimized, and the reaction found to be highly sensitive and sufficiently rapid. The absorbance of the complex at 598 nm was not affected by the presence of α‐hydroxyisobutyric acid at concentrations of the latter up to 150 mmol/l; at higher concentrations of the acid, the absorbance decreased slightly.For most of the rare earth elements the response was linear up to 0.2 mmol/l; the relative standard deviation of peak area was, typically, ∼1 %. The sensitivity of the method was usually better than 1 μg/ml.The results obtained from the determination of lanthanum, cerium, praseodymium, and neodymium in samples of apatite and bastnesite were in a good agreement with those obtained by ICP‐AES.
A versatile approach to the reproducible synthesis of functionalized polysiloxane stationary phases
Authors: Frank Hartmut , Abe Iwao , Fabian Gerd 
Published: May 2005

AbstractExploitation of the full potential of selector‐modified polysiloxanes as chromatographic stationary phases is limited because conventional methods of silicone synthesis involve strong acids or strong nucleophiles such as water or bases; under these conditions many potentially useful selectors decompose. The general approach to polysiloxane synthesis presented herein gives access to functionalized polysiloxanes under mild conditions. The functional groups incorporated can serve as chromatographic selectors or as electrophilic sites for secondary modification or cross‐linking.
Analysis of nitriles at low parts per million levels by capillary gas chromatography
Authors: Ehrmann Ursula , Carbognani Lante , Ceccarelli Claudio 
Published: May 2005

AbstractTwo methods have been developed for the determination of trace levels of acetonitrile and propionitrile in light naphthas. One involves clean‐up and preconcentration by medium pressure liquid chromatography (MPLC) in which nitriles are concentrated ten‐fold while the complex hydrocarbon matris is removed. The concentrated solution is then analyzed by high resolution GC with flame ionization detection. The second method involves direct injection of samples into a capillary GC equipped with chemiluminescence nitrogen detection.The results and repeatability obtained from both methods are comparable. Preconcentration enables identification by GC‐MS and simultaneous analysis of other polar species, with no need for selective detectors. Direct analysis is, on the other hand, much less time‐consuming and requires less sample.
Combined Cl and El mass spectra in the analysis of essential oils
Authors: Zupanc Mira , Prošek Mirko , Dušan Milivojevič 
Published: May 2005

AbstractAs part of a study directed at introducing GMP recommendations to the production of non‐alcoholic beverages, combined Cl and El mass spectra have been used for the identification of compounds present in extracts of “Cockta” beverage following GC‐MS analysis. The amount of useful information present both in the separate Cl and El spectra, and in two of the possible combinations of the spectra, is described.
Cyclodextrin derivatives in the GC separation of racemic mixtures of volatile compounds, part V: Heptakis 2,6‐dimethyl‐3‐pentyl‐β‐cyclodextrins
Authors: Bicchi Carlo , Artuffo Giuseppe , D'Amato Angela , Manzin Valeria , Galli Anna , Galli Mario 
Published: May 2005

AbstractThis paper describes an evaluation of the chromatographic performance of columns coated with amorphous cyclodextrin (CD) derivatives, in particular 2,3,6‐tripentyl‐β‐CD (2,3,6‐TriPe‐β‐CD), 2,6‐dipentyl‐3‐methyl‐β‐CD (2,6‐DiPe‐3‐Me‐β‐CD), and 2,6‐dimethyl‐3‐pentyl‐β‐CD (2,6‐DiMe‐3‐Pe‐β‐CD), all diluted in polysiloxane (OV‐1701 or OV‐1701‐OH), for the separation of the enantiomers of volatile compounds. 2,6‐DiMe‐3‐Pe‐β‐CD in OV‐1701 offers performance comparable with (or better than) that of the other two CDs, and without their drawbacks (inconsistency of results, as described previously).This article compares the separating ability of 2,6‐DiMe‐3‐Pe‐β‐CD and 2,3,6‐TriMe‐β‐CD, and describes the influence of the CD derivative to polysiloxane ratio, the minimum operating temperatures of the columns, and the reproducibility and consistency of performance of columns coated with the former CD derivative diluted in polysiloxane.
Investigation into the GC separation of enantiomers on a trifluoroacetylated cyclodextrin. I. Effect of analyte structure on stereoselectivity for alcohols
Authors: Smith Lan D. , Simpson Colin F. 
Published: May 2005

AbstractMore than 30 enantiomeric alcohols have been analyzed, without prior derivatization, by gas chromatography using a fused silica capillary column coated with octakis(3‐O‐trifluoro‐acetyl‐2,6‐di‐O‐n‐pentyl)‐γ‐cyclodextrin. Most were analyzed over a range of isothermal temperatures from 35 to 70°C. Enantiomeric separations were observed for most of the analytes, even at temperatures as low as 35°C.The stereoselectivity of the stationary phase was found to depend on the length of the longest carbon chain attached to the stereogenic centre in 2‐ and 3‐hydroxy alkanes, the relative positions of the methyl and hydroxyl substituents in methylsubstituted alcohols, and the effects of multiple bonds in the analyte molecule. Thermodynamic data calculated from the results suggest that the enantiomers of all the analytes are resolved by a similar process. Retention and thermodynamic data are presented and possible mechanisms discussed.
The effect of dietary fish oil supplementation on the concentration of 3‐carboxy‐4‐methyl‐5‐propyl‐2‐furanpropionic acid in human blood and urine
Authors: Wahl Hans Günther , Tetschner Birgid , Liebich Hartmut M. 
Published: May 2005

Abstract3‐Carboxy‐4‐methyl‐5‐propyl‐2‐furanpropionic acid (furanpropionic acid), a metabolite commonly found in human blood and urine, is one of the major acidic components which accumulates in the blood of patients with renal failure. Polyunsaturated fatty acids such as eicosapentaenoic acid (C20:5 ω−3) and long chain furan fatty acids, both present in commonly available fish oil capsules, are regarded as possible precursors of furanpropionic acid. Because of its strong binding to albumin and its various interactions with other endogenous and exogenous components, it is of great importance to determine the concentration of furanpropionic acid in blood and urine regularly.Solid phase extraction has been used to concentrate furanpropionic acid from both blood and urine samples. After esterification with ethereal diazomethane, gas chromatographic separation was performed on a HP‐1 column (dimethylpolysiloxane). Quantitation with an internal standard was performed by mass selective detection in SIM‐mode, qualifier ions being used for identification and accuracy.Fish oil supplementation of the diet of 24 patients for four weeks led to 3‐fold and 5 to 6‐fold increases in the levels of furanpropionic acid in serum and urine, respectively.
High performance liquid chromatographic–mass spectrometric detection of giant fullerenes
Authors: Anacleto Joseph F. , Boyd Robert K. , Quilliam Michael A. 
Published: May 2005

AbstractFullerene‐rich soot generated by resistive heating of graphite has been gently extracted with toluene, in order to remove some C60 and C70 compounds, followed by extraction with boiling 1,2,4‐trichlorobenzene at 214°C. After filtration and removal of the solvent, the residue was re‐dissolved in dichloromethane and characterized by non‐aqueous reversed phase liquid chromatography coupled on‐line with atmospheric pressure chemical ionization mass spectrometry. Several novel fullerenes were detected, including C72, C80, C86, and C88 as well as other fullerenes up to C108 and higher. The results indicate that chromatographic separation of large fullerene molecules can be achieved with low boiling point solvents and conventional liquid chromatographic techniques.
Carbon layer open tubular capillary columns
Authors: Sidisky Leonard M. , Robillard Mark V. 
Published: May 2005

AbstractCapillary columns coated with Carbopack materials, which provide separation by a mixed partition/adsorption mechanism or by adsorption alone, have recently been developed. The reproducibility of the columns is demonstrated and applications shown in which they provide separations which are either unique or are faster than can be achieved with the wall coated open tubular capillary columns currently available.
On‐line single column capillary gas chromatographic analysis of all reactants and products in the synthesis of fuel methanol from hydrogen and oxides of carbon
Authors: Marsman Jan Henk , Breman Berthold B. , Beenackers Antonie A. C. M. 
Published: May 2005

AbstractThe main problems with complete analysis of the components of fuel methanol, or in Fischer‐Tropsch studies, are the several classes of compound present in the sample (permanent gases, water, alcohols, hydrocarbons), its wide range of components, its boiling point range, and the wide range of component concentrations.A flexible on‐line GC method has been developed for kinetic study of catalyzed chemical reactions of hydrogen and oxides of carbon. The single capillary column, temperature programmed method was designed for complete analysis of reactants and products (hydrogen, carbon monoxide, carbon dioxide, water, C1‐C10 hydrocarbons, and C1‐C6 alcohols): a sample selection valve is used to switch between either the heated line used for input of the synthesis gases or the heated line used to transport reaction products from the reactor.Sample is introduced to the capillary column by means of a 10‐port heated gas sampling valve with two external injection loops (0.07 and 1.95 cm3); this results in the determination of components over a wide range of concentrations in the sample (ppm to percentage levels). Helium from a pressure‐controlled supply is used as carrier gas and detection of the components is performed by serial connection of thermal conductivity and flame ionization detectors. Peak identification is performed by mass spectrometry and by comparison of component retention times.The automated analytical equipment is integrated with a process control computer and delivers repeatable analytical results for the individual components (RSDs varying between 0.3 and 10% depending strongly on the concentration of the component and the accuracy of the determination of its peak area).
On‐line SFE‐GC for determination of PCBs in human milk and blood serum
Authors: Johansen Hege Rebecka , Thorstensen Christian , Greibrokk Tyge , Becher Georg 
Published: May 2005

AbstractOn‐line coupled supercritical fluid extraction and gas chromatography (SFE‐GC) has been utilized for the determination of PCBs and other organochlorine compounds in human milk and blood serum. The procedure involved preconcentration of the sample on C18‐silica sorbent in an extraction cell: after precipitation of the proteins up to 20 ml of human milk was concentrated on 0.5 g of sorbent. Serum (up to 5 ml) was applied to the C18 material without pretreatment. Basic alumina was utilized as a selective adsorbent for lipids in the on‐line SFE‐GC system. The method was used to analyze milk and serum spiked with 0.5 and 10 ng of Aroclor 1260 and the results compared with those obtained by liquid–liquid extraction of serum.
Fast identification of mycobacterium species by GC analysis with trimethylsulfonium hydroxide (TMSH) for transesterification
Authors: Müller Karl‐Dieter , Nalik H. Peter , Schmid Ernst N. , Husmann Heribert , Schomburg Gerhard 
Published: May 2005

AbstractTrimethylsulfonium hydroxide (TMSH) reproducibly converts fatty acids bound in, e.g., biomolecules such as phospholipids and/or glycerides, into the corresponding fatty acid methyl esters (FAMEs). The transesterification can be performed at room temperature in a fast single step reaction. Surprisingly, secondary alcohols and mycolic acid cleavage products (MACPs) are also released from mycobacteria under these conditions.The complex reaction mixtures containing FAMEs, MACPs, and secondary alcohols can easily be separated by high resolution temperature‐programmed capillary GC. Different species of mycobacteria give rise to characteristic chromatographic patterns and the amount of lipids from a single colony of mycobacteria is sufficient for reliable identification of the bacteria. The profiles of the chromatograms match well those obtained from other sample preparation techniques.The TMSH method of identification of mycobacteria from the patterns of the gas chromatograms is faster and more sensitive than conventional methods, which also involve transesterification. The identification of mycobacterial species by microbiological culture techniques is difficult to perform and requires several weeks.
Selectivity and efficiency enhancement of supercritical fluid extraction by application of reactive additives. I. The analysis of calcium montanate using citric acid as a complexing agent
Authors: Venema Arnold , Jelink Theo J. 
Published: May 2005

AbstractIt has been demonstrated that calcium montanate (a mixture of aliphatic hydrocarbons, fatty acid esters of C28–C32 acids, the calcium salts of these fatty acids, and the acids themselves) can be selectively extracted with supercritical fluids. By use of carbon dioxide, carbon dioxide containing 10% methanol, and carbon dioxide containing 10% methanol and citric acid (as a further additive), the various compound classes could be isolated with high selectivity. The addition of citric acid results in the complexation of Ca2+ and the simultaneous formation of the free fatty acids, which are soluble in the extractant.
Potential and limitations of differently designed programmed‐temperature injector liners for large volume sample introduction in capillary GC
Authors: Staniewski Jacek , Rijks Jacques A. 
Published: May 2005

AbstractProgrammed temperature sample introduction is an attractive technique both for the introduction of large volumes of dilute samples in capillary gas chromatography and for LC‐GC interfacing.In this study a new type of liner containing a porous bed of sintered glass is introduced and evaluated. Solute recoveries achieved with this liner are compared with those obtained from liners packed with Tenax TA and Thermotrap TA. An open liner containing baffles and a small plug of silanized glass wool in its upper section was used as a reference.The maximum speed of sample introduction allowable using the new liner is ca one order of magnitude higher than for the standard liner. For similar liner operating conditions the trapping efficiency is substantially improved: at a liner temperature of −30°C components with a volatility lower than or equal to that of n‐tridecane are trapped quantitatively.Liners packed with trapping materials such as Tenax TA or Thermotrap TA also provide significantly improved trapping efficiencies, even when used at relatively high temperatures.