bluuebunny/crossref_metadata_2025_split huggingface dataset:
Complete separation of the geometical isomers of linolenic acid by high performance liquid chromatography with a silver ion column
Authors: Juanéda Pierre , Sebedio Jean Louis , Christie William W. 
Published: May 2005

AbstractA method has been developed for separation of linolenic acid and its seven isomers by HPLC on a silver‐ion‐loaded column. The standard 18:3 isomers, isolated from a heated linseed oil or prepared by isomerization of linolenic acid, were converted into phenacyl esters and detected by UV at 238 nm. The use of low temperature (10 °C) combined with a gradient of dichloromethane and methanol enabled separation of all the cis/trans isomers. The peaks were identified by comparison of ECL values with those of a standard mixture, by chromatographing collected HPLC fractions on a polar GC column. HPLC quantification was compared with GC analysis. There was satisfactory agreement between the tow methods. This method could be used for seperation, collection and quantification of 18:3 fatty acids with trans double bonds in different oils and foods.
The magnitude and reproducibility of the electroosmotic flow in silica capillary tubes
Authors: Coufal Pavel , Štulík Karel , Claessens Henk A. , Cramers Carel A. 
Published: May 2005

AbstractThe influence of a number of factors, such as the nature of the buffer, the presence of additives therein, the manufacturing conditions, and the pretreatment of the capillary, on the magnitude and repeatability of the electroosmotic flow (EOF) in silica capillary tubes has been investigated. It was established that the nature of the buffer plays the most significant role in respect of the stability and magnitude of EOF, whereas the conditions used for manufacture and pretreatment of the tubing are less important. The EOF obtained using buffers consisting of tris(hydroxymethyl)aminomethane and ethylenediamine was more repeatable than that obtained using pure phosphate buffers. Buffer additives such as sodium dodecylsulfate, 1‐butanol, sodium salts of 1‐pentanesulfonic acid and 1‐heptanesulfonic acid, altered the magnitude of the EOF only, not its repeatability.
GC—MS analysis of carboxylic acids in petroleum after esterification with fluoroalcohols
Authors: Green John B. , Yu Shirley K.‐T. , Vrana Robert P. 
Published: May 2005

AbstractThe GC–MS characteristics of carboxylic acid esters prepared from fluorine‐containing alcohols were compared to those of methyl esters. The GC retention of 2,2,2‐trifluoroethyl (TFE) esters was less than, and 2,2,3,3,4,4,4‐heptafluoro‐1‐butyl (HFB) esters was approximately equivalent to that of methyl esters. Mass spectra of TFE and HFB aliphatic esters show significantly more intense molecular and key fragment ions than those of methyl esters. Also, owing to their significantly higher molecular weights, TFE or HFB ester molecular ions and most fragment ions of interest occur at significantly higher m/z values than most potential interfering ions.Data for about 70 individual TFE and HFB esters are reported. Application of the methodology to a petroleum‐derived carboxylic acid concentrate resulted in identification of straight chain, isoprenoid, methyl‐substituted straight chain (2‐, 3‐, 5‐,10‐, 12‐positions along chain), and dimethyl‐substituted straight chain acids containing from 11 to 22 carbons. Benzoic acid and homologs with up to 3‐carbons in alkyl substitutents were minor components in the sample.The procedure provided for forming TFE and HFB esters from free acids requires less time and effort than a previously reported method, while retaining its capability for achieving essentially quantitative conversion. Free hydroxyl groups in alcohols and phenols are converted to trifluoroacetate esters concurrently with formation of TFE/HFB carboxylic acid esters. The reaction products, including compounds with two functional groups (diacids, salicylic acid, etc.), chromatograph well on conventional nonpolar GC stationary phases.
Importance of quality control in a gas chromatographic method to characterize crude oils
Authors: Yancey Joel A. , Kosman Joseph J. , Grills John J. , Cavalier Roland C. , Irion John W. 
Published: May 2005

AbstractA quality control scheme has been developed to achieve reproducible capillary GC characterization of crude oils and petroleum condensates. The method uses an internal standard to quantify the amount of non‐eluted material in the crude oil sample. Correlation between the gas chromatographic results and actual distillation was 2 %. After repeated use, however, weekly analysis of the same standard crude oil did not give the correct composition. This was a result of discrimination, which worsened with time, as a result of leaks in the septum or the graphite ferrules. More reproducible results were obtained by performing frequent analyses of quality control samples to ensure that the gas chromatographic system was operating properly. The use of quality control charts was a convenient way of ensuring correct operation and identifying the need for corrective action on the gas chromatographic system.
Detailed hydrocarbon analysis of gasoline by GC‐MS (SI‐PIONA)
Authors: Teng Siu T. , Williams Anthony D. , Urdal Kjell 
Published: May 2005

AbstractA gas chromatographic – mass spectrometric (GC‐MS) method has been developed for detailed analysis of the hydrocarbon content of gasoline. The method is equipped with special software and includes the analysis of oxygenated compounds in a single run. The technique utilizes three basic components: the separating power of high resolution capillary gas chromatography, a mass spectrometer with a controllable ion source and ion fragmentation ratios, and unique software for data handling and preparation of reports. The C4 to C12 range of hydrocarbons in gasoline is covered by the method. A sample of unleaded gasoline from a gas station was analyzed without sample preparation. The results are discussed.
Analysis of kerogens and kerogen precursors by flash pyrolysis in combination with isotope‐ratio‐monitoring gas chromatography‐mass spectrometry (irm‐GC‐MS)
Authors: Goñi Miguel A. , Eglinton Timothy I. 
Published: May 2005

AbstractThis study describes the application of isotope ratio monitoring gas chromatography‐ mass spectrometry (irm‐GC‐MS) for compound‐specific stable carbon isotopic analysis of aliphatic hydrocarbon and phenolic products from flash pyrolysis (800 °C, 20s) of natural biopolymers and sedimentary kerogens. As part of this work, we provide a detailed description of the analysis of complex samples, including approaches for peak integration, data handling and correction for derivative carbons. Several aliphatic and aromatic biopolymers are analyzed by irm‐GC‐MS in order to establish relationships between the isotopic signatures of pyrolysis products and those of their parent macromolecules. We also analyze a select group of kerogens and kerogen precursors of different ages and biopolymer compositions to evaluate the applicability of combined pyrolysis/irm‐GC‐MS to complex geochemical mixtures. Our findings suggest that, in spite of the wide degree of heterogeneity, the isotopic values of individual aliphatic and phenolic pyrolysis products determined by irm‐GC‐MS can be related to the isotopic composition of the total organic carbon in kerogens and used to trace its biological sources. This study also highlights the need for optimum chromatographic separation in order to fully realize the potential of compound specific isotope analyses.
Separation and identification of unsaturated fatty acid isomers in blood serum and therapeutic oil preparations in the form of their oxazoline derivatives by GC‐MS
Authors: Liebich Hartmut M. , Schmieder Norbert , Wahl Hans Günther , Wöll Josef 
Published: May 2005

AbstractFatty acids from blood serum lipids and fish oil preparations are derivatized with 2‐amino‐2‐methyl‐1‐propanol to form 2‐substituted 4,4‐dimethyloxazolines. The derivatives are separated on a 25 m × 0.25 mm FFAP column and identified by mass spectrometry using electron impact ionization. The positions of the double bonds of mono‐ and polyunsaturated fatty acids can be easily and reliably recognized from a characteristic fragmentation feature of the oxazolines. Several unsaturated C16 to C22 fatty acid isomers are identified whose exact structure has not been derived from the commonly used methyl esters.
The use of precolumns for solvent focusing in capillary column gas chromatography
Authors: Yan Zimeng , Nikelly John G. 
Published: May 2005

AbstractIn trace analysis by capillary GC it is often desirable to use larger than normal injection volumes to obtain sufficient sensitivity. This, however, results in a wider solvent peak and tailing, and may reduce column efficiency. This paper describes the use of a short length of a capillary precolumn coated with a stationary phase of polarity similar to that of the sample solvent and a film thickness greater than that of the analytical column; provided the right combination of polarities of injection solvent and liquid phases are used, the precolumn focuses the solvent band, thereby enabling the maximum injection volume to be increased without measurably reducing efficiency. Typical precolumn dimensions are 1 m length, 0.32 mm i.d., and 0.5 μm stationary phase film thickness. Using a precolumn increases the maximum injection volume up to 8 or 10 μl, or three times that appropriate for a conventional analytical column, with little or no loss in efficiency.
Simultaneous determination of organotin, organolead, and organomercury compounds in environmental samples using capillary gas chromatography with atomic emission detection
Authors: Liu Yan , Lopez‐Avila Viorica , Alcaraz Marcela , Beckert Werner F. 
Published: May 2005

AbstractAs part of a continuing evaluation of new analytical and sample preparation techniques conducted by the US Environmental Protection Agency (EPA), the use of capillary gas chromatography with atomic emission detection (GC‐AED) for the simultaneous determination of organotin, organolead, and organomercury compounds in environmental samples was investigated. Pentylmagnesium bromide was used to pentylate ionic organotin, organolead, and organomercury compounds; the pentyl derivatives were then separated by GC and determined by AED. Several important GC‐AED parameters, including the type of injector inlet, carrier gas flow rate, and helium make‐up gas flow rate, were optimized for the simultaneous determination of these organometallic compounds. Their minimum detectable concentrations were approximately 1.0 to 2.5 ng/mL using a 0.5‐μL on‐column injection. The calibration curves exhibited good linearity between 2.5 and 2500 ng/mL for organotin and organolead compounds, and between 2.5 and 10000 ng/mL for organomercury compounds.
Identification of cis/trans isomers of methyl ester and oxazoline derivatives of unsaturated fatty acids using GC–FTIR–MS
Authors: Wahl Hans Günther , Habel Silke‐Yvonne , Schmieder Norbert , Liebich Hartmut M. 
Published: May 2005

AbstractIdentification of cis/trans isomers of unsaturated fatty acids cannot usually be achieved by GC‐MS (gas chromatography‐mass spectrometry) without reference substances. In this study a GC‐FTIR‐MS system (gas chromatography‐Fourier transform‐mass spectrometry) was used to identify fatty acid methyl esters (FAMEs) and differentiate between the cis/trans isomers. Besides methyl esters, 2‐alkenyl‐4,4‐dimethyloxazoline derivatives (DMOX), which have been used to locate double bond positions of unsaturated fatty acids, were examined with respect to their suitability for cis/trans differentiation.A combined GC‐FTIR‐MS system with a wide band (4000–550 cm−1) mercury cadmium telluride (MCT) detector was used in series and parallel to identify 31 reference unsaturated fatty acids, including 7 pairs of cis/trans isomers. Serum samples of healthy persons and commercially available fish oil were analyzed as examples of complex mixtures. Using splitless injection the detection limit for the less sensitive IR detector was 25 ng/μl in case of the weak cis and trans bands.In the FTIR spectra cis/trans isomers were identified by analysis of bands arising from CH out‐of‐plane (oop) bending: for both the FAME and DMOX derivatives cis‐1,2‐disubstituted double bonds give a strong band near 720 cm−1 and the corresponding trans isomers near 967 cm−1. cis Isomers could be identified further by a band at 3012 cm−1. With the combined data of the GC‐FTIR‐MS system it is now possible to identify polyunsaturated fatty acids with regard to the discrimination of cis/trans isomers.
Liquid–liquid extraction of silylated polyalcohols from vinegar, and their determination by capillary GC
Authors: Antonelli Andrea , Carnacini Alberta , Versari Andrea 
Published: May 2005

AbstractA capillary gas chromatographic method has been developed for the determination of glycerol, erythritol, arabitol, sorbitol, and inositol in vinegar. After addition of phenyl‐β‐glucopyranoside as internal standard, the sample was then dried and silylated. The analysis was performed both on the crude silylated sample and after liquid – liquid extraction. The repeatability of the two methods was evaluated on twenty three different types of vinegar and the extraction did not seriously affect the analysis. Extraction of the TMS‐ethers enables elimination of a large number of interfering substances such as acids and polyphenols and so acts as a purification of the sample.
Optimization of capillary SFC‐MS for the determination of additives in polymers
Authors: van Leuken Ron , Mertens Manuel , Janssen Hans‐Gerd , Sandra Pat , Kwakkenbos Gerard , Deelder Rob 
Published: May 2005

AbstractA standard direct introduction capillary interface is used for the SFC‐MS analysis of polymer additives. The system is optimized with respect to the position of the restrictor, probe tip temperature, and ion source temperature. El‐like charge‐exchange spectra are obtained. Cl using ammonia as the reagent gas is used for the quantitative analysis of a real world sample.The experimental capillary SFC‐MS spectra obtained show a good similarity with those recorded using the direct insertion probe. The influence of the experimental conditions on the mass spectra obtained is evaluated statistically.
A brief study of the supercritical fluid chromatographic behavior of lanthanide β‐diketonates
Authors: Laintz Kenneth E. , Iso Shuichi , Meguro Yoshiro , Yoshida Zenko 
Published: May 2005

AbstractThe chromatographic behaviors of lanthanide chelates of acetylacetone (ACAC), trifluoroacetylacetone (TFA), thenoyltrifluoroacetone (TTA), dipivaloylmethane (THD), 6,6,7,7,8,8,8‐heptafluoro‐2,2‐dimethyl‐3,5‐octanedione (FOD), and the thenoyltrifluoroacetonepyridine (TTA·Py) adduct were investigated using packed column supercritical fluid chromatography. Mobile phases consisting of neat and alcohol modified CO2 were used with a phenyl packed stationary phase. Lanthanide complexes of ACAC, THD, and FOD were shown to have better chromatographic performance compared to the corresponding chelates with TFA, TTA, and TTA·Py. In particular, TTA complexes such as Eu(TTA)3 showed characteristic thermal decomposition in the mobile phase at elevated temperature. In addition, retention behavior was found to be a temperature dependent function of volatility and solubility for all chelates studied.
Extraction and determination of linear alkylbenzenesulfonate detergents from the aquatic environment using a membrane disk and gas chromatography
Authors: Yamini Yaddah , Ashraf‐Khorassani Mehdi 
Published: May 2005

AbstractLevels of linear alkylbenzenesulfonate (LAS) detergents have been measured in Anzali lagoon water sampled at fourteen stations. All samples were extracted with octadecyl‐bonded silica membrane disks. Extraction efficiency, maximum capacity, and the effect of the solvent used to extract the LAS from the membrane disks were evaluated. Extraction efficiencies > 95% were obtained by elution of the disks with minimal amounts of solvent. It was demonstrated that membrane disk extraction introduced less error into analytical results than liquid – liquid extraction. Quantitative determination of total LAS levels and measurement of the distribution of LAS homologs with C10C13 alkyl chains were performed by high resolution gas chromatography with flame ionization detection after derivatization of the detergents with sulfonyl chloride. The total level of LAS ranged from 0.01 to 0.89 ppm.
Enantiomeric separation of amino alcohols by gas chromatography on a chiral stationary phase; influence of the perfluoroacylating reagent on the separation
Authors: Küsters Ernst , Portmann Andrea 
Published: May 2005

AbstractRacemic amino alcohols have been separated as perfluoroacylated derivatives by gas chromatography using either improved Chirasil‐Val or heptakis(2,6‐di‐O‐methyl‐3‐O‐pentyl)‐β‐cyclodextrin as stationary phase. Using Chirasil‐Val all the amino alcohols investigated were separated to baseline (α values between 1.03 and 1.08) whereas only a few amino alcohols were resolved on the modified cyclodextrin column. The enantioselectivity obtained on the latter phase was, however, significantly higher.The separations were performed as trifluoroacetyl, pentafluoropropionyl, and heptafluorobutyryl derivatives and the chiral discrimination observed for the different derivatives was significantly different for both stationary phases.In oder to obtain a better understanding of the separation mechanism, the Gibbs‐Helmholtz parameters Δ(R,S)ΔH° and Δ(R,S)ΔS° were determined. The most extraordinary result was obtained for the trifluoroacetyl derivative of allo‐threoninol. In addition to the order of elution of the enantiomers being the opposite of that for the other compounds, the separation seems to be entropy controlled (the sign Δ(R,S)ΔH° is positive), i.e. the separation improved at higher temperatures.
Home‐made temperature‐control unit for the Waters Quanta 4000 capillary electrophoresis system
Authors: Lukkari Pekka , Jussila Matti , Riekkola Marja‐Liisa 
Published: May 2005

AbstractA home‐made temperature control unit has been developed for a commercial capillary electrophoresis apparatus, the Waters Quanta 4000. The effect of the unit on the absolute migration times and peak areas of nine β‐blockers is described. It was found that this homemade temperature control unit considerably (≥ 100 %) improved the repeatability of the separation.
Use of tryptophan peptides for an HPLC racemization test with fluorescence detection
Authors: Griehl Carola , Weigt Jana , Jeschkeit Hans 
Published: May 2005

AbstractA new HPLC test has been developed for monitoring the racemiza‐tion which occurs during the coupling of Z‐Ala‐Trp‐OH with Val‐OMe by various methods. It is based on reversed phase HPLC separation of tripeptide diastereomers (LLL – LDL) and fluorescence rather than UV detection. The extent of racemization has been estimated for different carbodiimides, mixed anhydrides, and additive‐releasing reagents.
Use of zwitterionic buffer additives to improve the separation of proteins in capillary zone electrophoresis
Authors: Fang Xiao‐hong , Zhu Tao , Sun Vi‐hang 
Published: May 2005

AbstractIn CZE, the adsorption of the proteins on the capillary wall is a common problem. This paper describes the simple method of utilizing zwitterionic buffer additives to improve the separation of proteins in untreated fused silica capillaries at neutral pH. Three kinds of zwitterion are evaluated in the separation of acidic, neutral, and basic proteins, including their effect on protein efficiency, mobility, separation, and resolution; the difference between the effects of the different additives are also highlighted. The method has proved to be a possible means of reducing protein adsorption, especially for basic proteins.
Preparation of amino‐zirconia bonded phases and their evaluation in hydrophilic interaction chromatography of carbohydrates with pulsed amperometric detection
Authors: Yu Jim , Rassi Ziad El 
Published: May 2005

AbstractA series of non‐porous, microspherical zirconia‐based stationary phases with surface bound amine functionality have been introduced and evaluated in hydrophilic interaction chromatography (HILIC) of underivatized, neutral carbohydrates and anion exchange chromatography of nucleotides using pulsed amperometric detection and ultraviolet detection, respectively. Three aminopropyl alkoxysilane compounds were used in the surface modification of the non‐porous zirconia support, namely 3‐aminopropyltrimethoxysilane (monoamine), N‐(2‐aminoethyl)‐3‐aminopropyltrimethoxysilane (diamine), and trimethoxysilylpropyldiethylenetriamine (triamine). Due to the relatively low specific surface area of the non‐porous zirconia support used in this study (ca. 7.3 m2/g), zirconia with surface coating of the triamine type yielded the best results as far as the separations of chitooligosaccharides and maltooligosaccharides are concerned. Since a non‐porous zirconia could be readily modified with amine functionality via ZrOSi bonds, it is expected that all the three aminopropyl alkoxysilane compounds would yield satisfactory results with porous zirconia microparticles because of their much higher specific surface areas. Although the non‐porous zirconia exhibited some limitations, the present study has demonstrated that microspherical zirconia particles are suitable supports for the production of polar sorbents for HILIC of carbohydrates. Another surface modification, which involved the activation of the zirconia surface with aldehyde groups followed by reductive amination with tetraethylenepentamine, was also evaluated. Although this chemistry would in principle yield sorbents with higher concentration in amine groups, the conversion of the majority of the primary amine groups of the tetraethyle‐nepetamine molecules to secondary amine functions in the course of the reductive amination reaction have provided a stationary phase that did not afford satisfactory resolution for carbohydrates. However, this same stationary phase behaved as a weak anion exchanger and allowed the high resolution separation of nucleoside‐5′‐mono‐, ‐di‐, and triphosphates. Overall, the results obtained with zirconia‐based hydrophilic sorbents paralleled those obtained on amino‐silica bonded phases.
Optimizing the gas chromatographic separation and detection of polychlorinated biphenyls by use of electronic pressure programming and experimental design
Authors: Chen Chiu‐Yun , Ling Yong‐Chien 
Published: May 2005

AbstractThe applicability of electronic pressure control and Taguchi L27 experimental design to the optimization of the gas chromatographic separation and detection of polychlorinated biphenyls has been evaluated. The influence of several experimental variables, column temperature program, carrier gas pressure program, on‐column injector temperature program, and make‐up gas pressure program, was studied using analysis of variance. Simultaneous optimization of sample introduction, column efficiency, and detector performance could be achieved without compromising system performance. The relationships between system performance and experimental variables were established using regression analysis. Agreement between the simulated and experimental results obtained using suggested optimum conditions demonstrated the applicability of the technique developed in this study. The improvement achieved in the chromatographic separation of PCBs is presented.