bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of tocopherols in margarine by on‐line HPLC–HRGC coupling
Authors: Micali Giuseppe , Lanuzza Francesco , Currò Paolina 
Published: May 2005

AbstractTocopherol analysis in margarine is usually carried out by HPLC after saponification of the sample and extraction of the vitamin compounds; these steps consume both time and solvents. In this paper we propose an on‐line HPLC–HRGC coupling method, which allows us to simplify the preparation of the analytical sample. The sample of margarine is solubilized in hexane in an ultrasonic bath in the dark; the filtered solution is then injected into the liquid chromatograph using a normal phase microbore column eluted with hexane–isopropanol 99.8:0.2. The α‐tocopherol, which is eluted with some wax esters, is transferred on‐line to the gas chromatograph, using a loop‐type interface with the concurrent eluent evaporation and solvent vapor exit, thus it is separated from interfering compounds and determined using an Alltech RSL 300 column (22 m × 0.25 μm i.d., 0.2 μm film thickness). The β, γ, and δ–tocopherols are determined in the same LC run, using fluorimetric detection. The analysis was carried out in 50 min.
Determination of the total phenol content of soils by high speed liquid chromatography with electrochemical detection
Authors: Webster Caroline , Smith Martin , Wilson Peter , Cooke Michael 
Published: May 2005

AbstractThe total phenol content of soil samples has been measured using high performance liquid chromatography with electrochemical detection. Soils are extracted with sodium hydroxide solution and the phenols present in the extract are recovered on solid phase C18 cartridges after pH adjustment. The measurement stage employs a short (3 cm) reversed phase column and electrochemical detection. The short column focuses the phenolic species into a single peak which can be integrated. Electrochemical detection provides both sensitivity and selectivity. Hence high speed measurement of a composite peak representing total phenol content is achieved.
Supercritical fluid extraction as a preparative tool for strawberry aroma analysis
Authors: Polesello Stefano , Lovati Fabio , Rizzolo Anna , Rovida Constanza 
Published: May 2005

AbstractTo improve the aroma characterization of various strawberry cultivars, we tested supercritical fluid extraction (SFE) to determine its suitability for the extraction of aroma compounds from fresh fruit, comparing SFE results with traditional solvent extraction with dichloromethane. Using SFE it was possible to recover the majority of the aroma compounds which can be also found in the solvent extract; patterns related to variety and degree of maturation were preserved. Our results showed, however, that SFE is more selective and was able to recover the ‘character impact’ compound of wild strawberry. Our findings from the odor analysis of furaneol standard emphasize the importance of using a more selective extraction procedure, and always combining instrumental detection with sensory analysis.
Synchronized cyclic capillary electrophores—a novel approach to ion separations in solution
Authors: Burggraf Norbert , Manz Andreas , Effenhauser Carlo S. , Verpoorte Elisabeth , de Rooij Nico F. , Widmer H. Michael 
Published: May 2005

AbstractA novel concept for repeated column switching in capillary electrophoresis is presented. Theoretical considerations predict high plate numbers per volt. Using micromachining techniques, a planar glass structure has been fabricated, which contains four capillaries of 20 mm length arranged in a square. Laser fluorescence detection gave a cycle time of 70 s for 2.5 kV applied. After five cycles a theoretical plate number of 40,000 was reached.
Single pump on‐line mixing system for capillary supercritical fluid chromatography
Authors: Hirata Yukio , Kawaguchi Yukinori , Funada Yasuhiro , Katoh Seiki 
Published: May 2005

AbstractA simple inexpensive system comprising a piston pump, switching valves, and capillary tubing has been developed for preparing mixed mobile phases for capillary supercritical fluid chromatography. The system enables the on‐line preparation of mixed mobile phases without contamination of the pump with modifier. Modifier concentrations, which can be changed stepwise, were determined both experimentally and theoretically, the latter on the basis of density–viscosity relationships. Examples of both isobaric and pressure programmed separations are demonstrated.
Temperature optimization for the separation of PAHs on micropacked LC ODS columns
Authors: Chen Jian , Steenackers Dirk , Medvedovici Andrei , Sandra Pat 
Published: May 2005

AbstractThe effect of column temperature on the separation of the sixteen polycyclic aromatic hydrocarbons (PAHs) of mixture SRM 1647a of the US Environmental Protection Agency has been studied on different micropacked ODS columns. Isothermal temperature optimization was successfully used for complete separation of the PAHs on a polymeric ODS stationary phase, whereas temperature programmed conditions were selected for separation on a monomeric ODS stationary phase.
Use of micropacked columns for quantitative SFC
Authors: Ibáñez Elena , Herraiz Marta , Reglero Guillermo 
Published: May 2005

AbstractThe performance of a type of micropacked column for the quantitative SFC analysis of samples containing solutes at very different concentrations has been studied. The chromatographic characteristics of the column were compatible with high sample volume loadability, and at the same time adequate efficiency and low pressure drop. In order to increase both the separating power and sample capacity of the column, the percentage liquid phase loading was optimized. The accuracy, precision, and detection limit obtainable with the micropacked column are compared with the performance of a wall coated open tubular capillary column having the same phase ratio.
Analysis of volatiles associated with industrial scale processing of expanded polystyrene Part II: Identification and quantitation
Authors: Hathcock Stanley L. , Bertsch Wolfgang 
Published: May 2005

AbstractExpanded polystyrene was pyrolyzed on a laboratory scale hot wire cutter. The resulting volatiles were characterized using GC/MS as the primary analytical tool. Use was also made of retention data from a complex petrochemical standard. In situ bromination of the pyrolysate further helped in structure elucidation. Air samples were collected in the field and compared to the model experiments from a laboratory scale hot wire cutter. The results indicate that alkylbenzene type compounds were the primary compounds in this environment. A few oxygenated substances were also formed. Traces of brominated compounds were detected in the model experiments but not in the samples collected in the field, with one exception. Quantitative data are presented from a typical industrial operation.
Application of supercritical fluid extraction and supercritical fluid chromatography to the production of taxanes as anti‐cancer drugs
Authors: Heaton Darren M. , Bartle Keith D. , Rayner Christopher M. , Clifford Anthony A. 
Published: May 2005

AbstractThe supercritical fluid extraction (SFE) of taxicin from the dried needles of the English yew tree, Taxus baccata is described. Analysis by supercritical fluid chromatography (SFC) and proton NMR spectroscopy was used to confirm identity and purity. The extraction efficiency of SFE is comparable with that obtained using liquid solvents. Such taxanes may be used semi‐synthetically to prepare potential anti‐cancer drugs.
6‐tert‐Butyldimethylsilyl‐2,3‐dimethyl‐α‐, β‐, and γ‐cyclodextrins, dissolved in polysiloxanes, as chiral selectors for gas chromatography. Influence of selector concentration and polysiloxane matrix polarity on enantioselectivity
Authors: Kobor Frank , Schomburg Gerhard 
Published: May 2005

AbstractThe enantioselectivity of three chiral selectors, 6‐t‐butyldimethyl‐silyl‐2,3‐dimethyl‐α‐, β‐ and γ‐cyclodextrin (TB‐α‐CD, TB‐β‐CD, TB‐γ‐CD), are compared and discussed for a range of chiral test compounds. TB‐β‐CD in particular offers high enantioselectivity for a variety of chiral compounds and has the special property of excellent solubility in different alkylpolysiloxanes, including the weakly polar variety, because of its weak self‐association. To investigate the influence of the polarity of polysiloxane matrices this selector can be used at a wide range of concentrations in the most suitable polysiloxane matrices and at low separation temperatures without impairment of resolution by peak broadening and symmetry distortion.
Elucidation of the structure of drug degradation products by on‐line coupled reversed phase HPLC‐GC‐MS and on‐line derivatization
Authors: Wessels Peter , Ogorka Jörg , Schwinger Gerhard , Ulmer Martin 
Published: May 2005

AbstractDegradation products obtained under severe alkaline stress of the drug substance ENA 713, a compound developed for the treatment of DAT (dementia of the Alzheimer type), have been identified by on‐line coupled reversed phase HPLC‐GC‐MS as 3‐hydroxyaceto‐phenone and 3‐hydroxystyrene. Their structures were proven by mass spectroscopic investigation of the products obtained by on‐column derivatization during LC‐GC transfer. On‐column trimethyl‐silylation and bromination of the degradation products during the transfer were achieved by the introduction of the reagent via the loop‐type interface. The usefulness of the technique was further demonstrated by the on‐column methylation of carboxylic acids with diazomethane solution (using naproxen as model compound). First results are also given of the use of the liquid‐liquid extraction unit of the LC‐GC interface for extractive derivatization during reversed phase HPLC‐GC‐MS transfer.
The effect of the trifluoropropyl group in polysiloxane stationary phases used for capillary gas chromatography
Authors: Dai Qiong , Lebrón‐Aguilar Rosa , Fernández‐Sánchez Elena , García‐Domínguez José Antonio , Quintanilla‐López Jesus Eduado 
Published: May 2005

AbstractFour poly(methyl 3,3,3‐trifluoropropyl siloxanes) with trifluoro‐propyl group content (group substitution) between 8 and 35 percent have been synthesized and characterized as stationary phases for gas chromatography in borosilicate glass capillary columns. Results are compared with those from two commercial stationary phases–a polydimethylsiloxane and a poly(methyl 3,3,3‐trifluoropropyl siloxane) with a fifty percent trifluoropropyl group content (group substitution).Retention index values, McReynolds constants, polarity (as defined by McReynolds) and retention polarity (as defined by Takács) increase regularly with the trifluoropropyl group content of the stationary phase. The temperature coefficient of the retention indices of the McReynolds probes, and that of the polarities, have been determined at temperatures between 60 and 180 °C. Specific retention volumes do not follow the linear dependence on trifluoropropyl group content observed for retention indices or polarities. Substances with electron‐donor groups show maximum retention for a trifluoropropyl group content of ca 30%, whereas the retention of hydrocarbons, halogenated compounds, and alcohols decreases as the degree of trifluoropropyl group substitution increases from 0 to 50%. It is felt that a polysiloxane with a trifluoropropyl group content of ca 30 to 35% would be the best choice for the separation of ketones, nitro compounds or amines.
Comparison of combustion sources for sulfur chemiluminescence detection
Authors: Burdge J. R. , Farwell Sherry O. 
Published: May 2005

AbstractThree different types of SCD combustion source have been evaluated for use in the chromatographic analysis of atmospheric sulfur compounds. The conventional FID source and the newer inverted burner source were found to be less sensitive and less stable than the flameless design. Overall, the flameless source was superior for use with HRGC‐SCD.
The direct combination of HPLC solute focusing with supercritical fluid chromatography and mass spectrometry to enhance sensitivity and improve identification of trace components in polar solvent extracts
Authors: Games David E. , Rontree John A. , Fowlis Ian A. 
Published: May 2005

AbstractA system for combining normal and reversed phase high‐performance liquid chromatography solute focusing with packed column supercritical fluid chromatography and supercritical fluid chromatography–mass spectrometry has been developed. The technique has been used to identify paracetamol and stanozolol in spiked plasma extracts and its utility for the analysis of a sample from a process waste stream is illustrated.
A study of the adsorption activities of silanol surface structures on a fused silica model substrate by combining 29Si CP MAS NMR and inverse gas chromatographic data
Authors: Scholten Alex B. , Janssen Hans‐Gerd , de Haan Jan W. , Cramers Carel A. 
Published: May 2005

AbstractThe possibilities of inverse gas‐solid chromatography (IGC) in obtaining chromatographic data on fumed silica were examined. Aerosil A‐200, a fused silica model substrate in 29Si nuclear magnetic resonance analysis, was trimethylsilylated to different degrees. IGC was used to very reproducibly determine the free specific energies of adsorption of several functionalized probe solutes. Hydrogen bonding solutes have a free specific energy of adsorption that is at least about 50% higher than that of non‐hydrogen bonding probe solutes. NMR was used in combination with elemental analysis to calculate surface concentrations of the different chemical surface structures. IGC data and surface concentrations were combined in order to determine the contribution of each type of surface structure to the total free specific adsorption energy. It could be concluded that residual silanols from the reaction of dihydroxydi‐siloxysiloxane (Q2 groups) with trimethylchlorosilane possess a higher adsorption activity than the silanols initially present.
Use of experimental design to optimize the analysis of volatile compounds by dynamic headspace extraction followed by cold trapping and capillary GC
Authors: Contarini G. , Leardi R. 
Published: May 2005

AbstractA central composite design has been used to improve the extraction performance of a dynamic headspace method; extraction yield was evaluated on a homogeneous sample of cheese powder. The volatile compounds were stripped from the sample with nitrogen and adsorbed on a Tenax trap, analysis being performed with a thermal cold trapping injector connected directly to a capillary GC. Three variables (sample temperature, extraction time, and nitrogen flow rate) were investigated, and a quadratic model with interactions was postulated. Twenty experiments was performed, each producing five responses. It was shown that the best conditions for the extraction procedure were those characterized by the highest values of the three variables investigated.
Comparison of two‐stage retention index monitoring capillary gas chromatography and selected ion monitoring capillary gas chromatography – mass spectrometry as analytical tools
Authors: Enqvist Jouni , Enqvist Maarit 
Published: May 2005

AbstractTwo‐stage capillary GC with two‐stage retention index monitoring is an efficient analytical technique which can be used for detection and determination of small amounts of volatile compounds in complex mixtures of hundreds or thousands of other compounds. The system employs two capillary columns, coated with different stationary phases, connected on‐line with the aid of a micro valve; the first column acts as a pre‐separating unit from which unresolved fractions of interest are cut (transferred) into another column for final, interference‐free separation of the compounds to be determined. This technique has been compared with selected ion monitoring capillary GC‐MS using a hydrocarbon mixture as a test sample for comparing resolution, repeatability, and the practical usefulness of the techniques. Results indicate that two‐stage capillary GC is very useful for mixtures containing compounds which produce mostly non‐specific ions in the MS ion source whereas compounds producing specific ions can be easily analyzed by capillary GC – single ion monitoring MS even if they are not perfectly separated by a single capillary column.
High resolution capillary gas chromatography and gas chromatography–mass spectrometry of protein and non‐protein amino acids, amino alcohols, and hydroxycarboxylic acids as their tert‐butyldimethylsilyl derivatives
Authors: Šimek Petr , Heydová Anna , Jegorov Alexandr 
Published: May 2005

AbstractA simple, single‐step derivatization technique is presented for capillary GC‐FID and GC‐MS separation and identification of common protein and non‐protein constituents of natural peptides as their tert‐butyldimethylsilyl (TBDMS) derivatives. The tert‐butyldimethyl‐silylation of more than sixty compounds was accomplished with high yields and a single peak observed for each component. The TBDMS derivatives of both the protein and non‐protein substances, moreover, exhibit excellent separation on apolar capillary columns and can be resolved completely using a polydimethylsiloxane or 5 % phenyl polydimethylsiloxane column and, complementarily, a 50 % phenyl polydimethylsiloxane column. Retention data and molar responses of the TBDMS derivatives on the polydimethylsiloxane column are compiled. Direct coupling of the 5 % phenyl polydimethylsiloxane column to an ion trap mass spectrometer enabled fast separation and identification of the investigated components, at nanomole to picomole levels, on the basis of retention and mass spectral data. The general usefulness of the method is demonstrated by research into new biologically active peptides isolated from entomopathogenic fungi.
High resolution capillary GC–MS analysis of low molecular weight organic compounds in municipal wastewater
Authors: Nguyen Dang‐Khoa , Bruchet Auguste , Arpino Patrick 
Published: May 2005

AbstractHigh resolution capillary gas chromatography–mass spectrometry has been used in combination with various sample preparation methods to analyze a wide range of low molecular weight organic contaminants in municipal wastewaters. Volatile organic compounds were extracted using a purge and trap concentrator connected directly to a wide bore DB‐624 capillary column. Because of the high organic load in wastewater samples, this method was preferred to the more sensitive closed loop stripping technique which suffered from competition effects and insufficient adsorbent capacity. Volatile and semi‐volatile base/neutral compounds and acids were extracted with dichloromethane at pH 11 and pH 2, respectively, or were recovered using a simultaneous distillation‐extraction procedure. Acidic compounds were subsequently derivatized using diazomethane methylation. Both fractions were separated with a 30m DB‐5ms capillary column. Specific ionic substances (LAS, NTA, EDTA) were isolated by solid‐phase extraction then derivatized with diazomethane (LAS) or acetyl chloride in n‐butanol (NTA, EDTA) before GC–MS analysis.This array of techniques enabled the identification of more than 150 organic contaminants in the influent of a municipal wastewater treatment plant in northern suburban Paris. The individual concentrations of these contaminants ranged from < 0.1 μg/l to 5.7 mg/l.
GC‐MS quantitation of isocitric acid in the presence of a large excess of citric acid
Authors: Tisza Sándor , Molnár‐Perl Ibolya 
Published: May 2005

AbstractA GC‐MS method has been developed for the analysis of the sugar and carboxylic acid content of citrus fruits, including the quantitation of isocitric acid in the presence of a large excess of citric acid. Optimum conditions have been determined for the analysis (from one solution, by one injection, on a 30 m DB‐5 column) of the TMS oxime and/or TMS derivatives of sugars and acids obtained from various lemon, grapefruit, and orange samples. Quantitation was based on the monitoring of the total ion current and of selective fragments. The utility of the method has been demonstrated by the determination of isocitric acid in the presence of 10‐ to 200‐fold excess of citric acid.
Simulated distillation of petroleum and its products by gas and supercritical fluid chromatography: A review
Authors: Peaden Paul A. 
Published: May 2005

AbstractInformation about the boiling point distribution of petroleum and its products is obtained either by actual distillation, or by analyses designed to simulate the distillation process. These analytical techniques are called simulated distillations. Simulated distillations are most often performed by gas or supercritical fluid chromatography. This paper reviews the use of gas and supercritical fluid chromatography for simulated distillation, and the development of element‐specific detection coupled with these analyses.
Size exclusion chromatography sample pretreatment for GC‐AED analysis of metalloporphyrins in crude oils
Authors: Zeng Yadi , Uden Peter C. 
Published: May 2005

AbstractSize exclusion chromatography (SEC) has been demonstrated to be an effective and reproducible sample pretreatment procedure for removal of heavy oil matrices prior to GC‐AED analysis of metalloporphyrins, and for the resolution of volatile metal species into clean and defined fractions. This paper also discusses the results obtained by SEC for determination of the distribution of metallopor‐phyrins in crude oils and the correlation between total metal, metal‐loporphyrin, and total distillable metal content.
High temperature gas chromatography – atomic emission detection of metalloporphyrins in crude oils
Authors: Zeng Yadi , Uden Peter C. 
Published: May 2005

AbstractHigh temperature gas chromatography‐atomic emission spectroscopy is used for the detection of vanadyl, nickel, and iron porphyrins in crude oils. The operational variables are investigated with regard to the effects on performance in high temperature GC‐AED. Under optimal conditions, the method provides charactersitic metal distributions for oils from different sources. The method is also advantageous in the study of decomposition of petroleum metal species. Several crude oils were analyzed for the content of the distillable metals in comparison with total metals as determined by a direct spectroscopic method.
Determination of the sulfur components of gasoline streams by capillary column gas chromatography with sulfur chemiluminescence detection
Authors: Di Sanzo Frank P. , Bray William , Chawla Birbal 
Published: May 2005

AbstractA method using a sulfur chemiluminescence detector (SCD) has been developed for the qualitative and quantitative determination of sulfur components in stabilized gasoline‐range process streams, including blended gasolines containing between 1 and > 4000 ppm total sulfur. The detection limit per sulfur component was approximately 50 ppb. On‐column injection was employed for optimum precision and accuracy. A new probe material was found which did not soften under FID operating conditions. A new method, using a hydrogen sulfide permeation tube, was developed for rapid alignment of the probe in the FID.
Automated HPLC‐HRGC: A powerful method for essential oil analysis. Part III. Aliphatic and terpene aldehydes of orange oil
Authors: Mondello Luigi , Bartle Keith D. , Dugo Giovanni , Dugo Paola 
Published: May 2005

AbstractThe application of a new method, computer‐controlled on‐line HPLC‐HRGC, to the analysis of the components of sweet orange oil has enabled the determination of aldehydes without interferences. HPLC was used to separate the oil aldehydes into three fractions, aliphatic aldehydes, sesquiterpene aldehydes, and monoterpene aldehydes. These fractions were transferred automatically to the GC, where the individual aldehydes were separated into well resolved chromatographic peaks.