bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of a temperature programmed injector with a packed liner for direct water analysis and on‐line reversed phase LC–GC
Authors: Mol Hans G. J. , Janssen Hans‐Gerd M. , Cramers Carel A. , Brinkman Udo A. Th.
Published: May 2005

A system is described that allows the introduction of large volumes of water samples in capillary GC. Water elimination is carried out in the solvent split mode in a PTV injector with a packed liner. Two ways of separating water and analytes, i.e. evaporative and non‐evaporative (solid‐phase extraction), are compared. Sampling in the solid‐phase extraction mode is favorable both in terms of recovery as well as with regard to sampling time. Quantitative recovery is obtained for priority pollutants ranging in volatility from dimethyl‐phenol to phenanthrene. Losses occur for more volatile compounds, but even for these compounds the repeatability of the recoveries remains acceptable. With the system described here, water samples up to at least 1 ml of water can be directly analyzed. The detection limits are in the sub‐ppb range.
Capillary GLC fatty acid fingerprints of seed lipids—a tool in plant chemotaxonomy?
Authors: Aitzetmüller Kurt
Published: May 2005

The fatty acid composition of the seed lipids of plants, in contrast to leaf lipids, may contain highly specific unusual fatty acids, which are often correlated to plant family. For example, petroselinic acid is typical for the Apiacea family, cyclopropene fatty acids are typical for the Malvaceae family, and cyclopentene‐ring containing fatty acids for the Flacourtiaceae family. Other fatty acids may be characteristic for certain sub‐families or only for certain species of plants within a family or genus. γ‐Linolenic acid, Δ5–18:3 and Δ5–20:3 fatty acids and others may occur in several plant families, but are still linked to certain related species only. They can be analyzed by high‐resolution capillary GLC. Particularly interesting is the situation in the family Ranunculaceae. GLC fingerprints of fatty acids are shown that may indicate a closer or less close relationship between species within this family.
SFE of PAHs from soils with a high carbon content and analyte collection via combined liquid/solid trapping
Authors: Meyer Anja , Kleiböhmer Wolfgang , Cammann Karl
Published: May 2005

Polynuclear aromatic hydrocarbons (PAHs) are recovered from a soil with a high carbon content (ca. 50%) with supercritical fluid extraction (SFE) as well as with conventional Soxhlet extraction. The influence of temperature and modifier volume on SFE efficiency and the effect of a combined liquid/solid trap for analyte collection are investigated in this study. Such traps, which make analyte collection and clean‐up possible in one step, are compared with conventional analyte collection in pure organic solvents. A comparison between reproducibility and efficiency of SFE and Soxhlet extraction is presented.
Investigation of high sensitivity GC‐FTIR as an analytical tool for structural identification
Authors: Jackson Peter , Dent Geoffrey , Carter David , Schofield Deborah J. , Chalmers John M. , Visser Tom , Vredenbregt Marjo
Published: May 2005

As part of a detailed investigation into the application of GC‐FTIR in industrial and environmental analysis, representative sets of samples have been analyzed in parallel using commercial high‐sensitivity instruments. Two of the instruments utilize low temperature storage of the GC eluate to extend the time available for FTIR analysis, yielding greater sensitivity than that possible by conventional ‘light‐pipe’ GC‐FTIR. In certain circumstances, instruments using both types of sample storage give rise to spectra exhibiting features characteristic of the interface used. Chromatographic resolution was found not to be significantly degraded by use of either sample storage interface. Particular advantages were found in having parallel flame ionization detection and mass spectrometry; this enabled the location of smaller components and gave greater certainty of identification.
Analysis of tocopherols in margarine by on‐line HPLC–HRGC coupling
Authors: Micali Giuseppe , Lanuzza Francesco , Currò Paolina
Published: May 2005

Tocopherol 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

The 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

To 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

A 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

A 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

The 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

The 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

Expanded 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

The 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

The 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

Degradation 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

Four 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

Three 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

A 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

The 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

A 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

Two‐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

A 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

High 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

A 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

Information 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

Size 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

High 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

A 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

The 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.
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

A 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

The 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

The 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

A 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

A 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

This 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

Fatty 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

In 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

As 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

Identification 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

A 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

A 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

The 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

Levels 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

Racemic 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

A 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

A 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

In 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.