bluuebunny/crossref_metadata_2025 huggingface dataset:
Improving splitless injection with electronic pressure programming
Authors: Wylie Philip L. , Phillips Richard J. , Klein Kenneth J. , Thompson Michael Q. , Hermann Bruce W.
Published: May 2005

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

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

An injector designed for automatic direct liquid injection into narrow bore capillary GC columns has been constructed and evaluated. The tip of the syringe needle is aligned with, and positioned close to, the column entrance in a small, pressurized cavity: when the sample is dispensed it is immediately forced into the column by the action of the surrounding carrier gas. A standard autosampler equipped with a standard stainless steel syringe needle was utilized for at‐column sample transfer into 100 μm i.d. columns.

RSD values for n‐alkanes were between 0.1 and 0.3% for relative area counts and approximately 1% for absolute area counts.
Determination of traces of aromatic compounds in multicomponent mixtures by HRCGC
Authors: Matisová Eva , Kubuš Ľubomír , Jurányiová Eva
Published: May 2005

The possibilities and difficulties of trace analysis of highly complex organic mixtures has been demonstrated by the analysis of traces of numerous aromatic substances in an n‐alkane matrix with a boiling point range of 151–270°C. Single column high resolution capillary gas chromatography (under optimized conditions) was performed after an off‐line LC preseparation step which had been evaluated using a model mixture.

Gas chromatographic quantitation of the 191 aromatic compounds identified was performed with an internal standard; following splitless injection and separation on a polydimethyl‐siloxane column under temperature‐programmed conditions the compounds were detected by flame ionization. The response factors of aromatic hydrocarbons at trace levels were verified and the precision and reproducibility both of the GC determination and the overall analysis, including preseparation, were studied.

Percentage by weight of individual aromatic compounds (mainly alkylbenzenes, indanes, naphthalenes, and acenaphthenes) was in the range 10−3 to 10−6.
A new approach to dynamic deactivation in capillary zone electrophoresis
Authors: Emmer Åsa , Jansson Mårten , Roeraade Johan
Published: May 2005

This paper describes a simple means of obtaining high resolution separations of basic proteins at a pH below their pl. Small amounts of a cationic fluorosurfactant are added to the running buffer. A positively charged wall is thereby obtained which will repel positively charged proteins. The particular chemistry of fluorosurfactants is believed to enhance the efficiency of the deactivation. Examples are presented of the separation of some model proteins, including a human insulin‐like growth factor (IGF‐I), and a misfolded by‐product of the growth factor.
Multichannel autosampler for Curie‐point pyrolysis capillary gas chromatography
Authors: Oguri Naoki , Onishi Akira , Hanai Toshihiko , Jin Xigao
Published: May 2005

A multichannel autosampler which can automatically analyze up to 20 samples in sequence has been developed for on‐line Curie‐point pyrolysis – capillary GC. The results obtained from the system show that the analysis of thermally labile samples could be performed without either thermal degradation or reaction during the waiting time before the final pyrolysis. The reproducibilities of the relative peak areas and retention times of the characteristic pyrolysates of a tricomponent copolymer were significantly better than those obtained by manual sample manipulation.
Analysis of carbohydrates by HPLC with post‐column derivatization
Authors: Krämer Michael , Engelhardt Heinz
Published: May 2005

Post‐column derivatization of oligosaccharides after HPLC separation with a variety of systems has been achieved either by reaction with thymol in concentrated sulfuric acid or after hydrolysis of saccharides with hydrochloric acid and derivatization of the resulting monosaccharides with p‐aminobenzoic acid hydrazide. With both reactions the detection of reducing and non‐reducing sugars is possible even at trace levels. The latter reaction, despite the two reaction steps required, is much more convenient and practical, whereas with the first reaction it is also possible to determine alkylpolyglucosides.
Determination of estrogens in animal tissue by GC‐MS with negative ion chemical ionization
Authors: Busico Fabio , Moretti Gabriella , Cartoni Giampaolo P. , Rosati Felice
Published: May 2005

GC‐MS with negative ion chemical ionization has been used to detect anabolic estrogens (diethylstilbestrol, dienestrol, hexestrol, and 17β‐ and 17α‐estradiol) in bovine muscle tissue. After hydrolysis and extraction, purification by column chromatography, and derivatization, the detection limit for the estrogens is better than 0.1 ppb.
Enantiomeric resolution of dansyl phenylalanine and analogs by microcolumn liquid chromatography with γ‐cyclodextrin as mobile phase additive
Authors: Takeuchi Toyohide , Nagae Norikazu
Published: May 2005

Dansyl derivatives of racemic phenylalanine and its analogs have been resolved by microcolumn liquid chromatography with γ‐cyclodextrin as mobile phase additive. The enantioselectivity of the system was influenced by the concentrations of both γ‐cyclodextrin and acetonitrile in the mobile phase. Enantiomers of phenylalanine, phenylglycine, and tyrosine were resolved by isocratic elution in a single chromatographic run.
Capillary gas chromatographic determination of free amino acids in honey as a means of discrimination between different botanical sources
Authors: Pirini Annalisa , Conte Lanfranco S. , Francioso Ornella , Lercker Giovanni
Published: May 2005

The chemical analysis of honey tends to concentrate on factors related to its state of preservation, e.g. HMF, diastase activity, and water content. Although there is no characteristic of honey officially regarded as suitable for certification of its botanical origin, literature is available in which several of the “minor” components of honey, such as flavors, di‐ and trisaccharides, and free amino acids, have been used to certify the botanical origin of the product.

In this paper, six kinds of honey from different botanical sources (acacia, citrus fruit, chestnut‐tree, rhododendron, rosemary, and lime‐tree) were analyzed by capillary gas chromatography, and the data obtained evaluated statistically to determine whether the amino acid profile could be used to verify the botanical source of the material.

The results have shown that the presence of amino acids such as arginine, tryptophan, and cystine is characteristic of a particular kind of honey, and that others, such as proline, asparagine, lysine, and methionine, can be used for discrimination if quantitative data is available about the levels of the compounds present.

Evaluation of optimum split ratio for amino acid determination, and problems concerning the derivatization process, are also discussed.
The investigation and application of the packed glass capillary column with a core
Authors: Yang Haiying , Lu Wanzhen
Published: May 2005

A new type of packed glass capillary column (PGCC) with a core, and its potential usage in practice are described. The permeability of the column is considerably greater than that of conventional PGCC and its N/(Pi‐Po) value is also higher. This novel PGCC column has been successfully applied to the analysis of trace levels of ethyne, cyclopropane, propadiene, propyne, and other C1C4 impurities in pure ethene, propene, 1,3‐butadiene, and catalytic cracking gas samples as well as other petrochemical gases such as liquified petroleum gas.
Improvements in flame photometric detector design and operation. Determination of organophosphorus pesticide residues at low picogram levels
Authors: Verga G. R.
Published: May 2005

The molecular emission of heteroelements such as phosphorus and sulfur is the basis of the selective response of the flame photometric detector. The behavior of the FPD towards phosphorus compounds has been studied and design improvements sought with regard to burner configuration and temperature distribution. The possibility of differentiating between compounds containing phosphorus atoms and those containing both phosphorus and sulfur atoms has also been examined.

Detection limits and response characteristics have been reported for organophosphorus pesticide residues in samples of natural origin
A continuous two‐phase reaction system coupled on‐line with capillary chromatography for the determination of polar solutes in water
Authors: Goosens Elise C. , Broekman Marcel H. , Wolters Margarete H. , Strijker Richard E. , de Jong Dirk , de Jong Gerhardus J. , Brinkman Udo A. Th.
Published: May 2005

Gas chromatographic procedures are described for the determination of carboxylic acids and chlorinated anilines in water samples.

Propionic acid and 2,6‐difluorobenzoic acid in aqueous solution have been simultaneously alkylated and extracted by means of a continuous two‐phase reaction system, and then quantitated by on‐line coupled capillary gas chromatography; tetrahexyl‐ammonium hydrogen sulfate was used as phase transfer catalyst and pentafluorobenzyl bromide as reagent.

A factorial design approach was used to optimize on‐line derivatization of aqueous propionic acid with regard to pH and concentration of phase transfer catalyst. Alkylation and extraction, under optimized conditions, followed by quantitation of the pentafluorobenzyl ester by flame ionization detection furnished a linear calibration for concentrations between 0.1 and 10 μg/ml. The relative standard deviation was 9–15 %.

The continuous two‐phase reaction system was also used to determine (chlorinated) anilines present in water at concentrations of 0.1–1 μg/ml; pentafluorobenzoyl chloride was used as reagent and analysis was performed by capillary gas chromatography with flame ionization or electron capture detection. The on‐line acylation of p‐chloroaniline was optimized with regard to pH, reagent concentration, and reaction time.

The on‐line reaction system worked satisfactorily for both applications, although excess reagent caused some problems with the chromatography.
High temperature gas chromatography on narrow bore capillary columns
Authors: Damasceno Lucia M. P. , Cardoso Jari N. , Coelho Ricardo B.
Published: May 2005

The use of high‐temperature‐stable, medium polarity glass capillary columns coated with immobilized PS‐090 (a 20 % diphenyl‐substituted, CH3O‐terminated polydimethylsiloxane) has made it possible to analyze routinely, and with good separation efficiency, high molecular weight compounds such as triglycerides and free base porphyrins. Cold on‐column injection was used throughout this work to avoid discrimination against involatile compounds, and disposable (fused silica) retention gaps were used to protect the column against contamination with involatile material. On‐column injection into narrow bore glass columns was achieved by using glass‐to‐silica connections to attach wider bore (0.2 mm i.d.) deactivated fused silica tubing to the columns.
Coupled fused silica capillaries for rapid capillary zone electrophoresis of proteins
Authors: Nashabeh Wassim , Rassi Ziad El
Published: May 2005

A novel two‐dimensional electrophoretic system for the control of electroosmosis in capillary zone electrophoresis has been developed and evaluated for rapid separations of proteins. The system comprises uncoated and polyether‐coated fused silica capillaries coupled in series. An equation relating the average electroosmotic flow velocity in the coupled capillaries to the intrinsic electroosmotic velocities of the connected segments and their corresponding lengths has been derived and verified experimentally. This approach has the advantage of enabling the electroosmotic flow to be tuned independently of the applied voltage. As a consequence, rapid protein analysis at relatively low field strength was achieved without sacrificing the high separation efficiencies obtained with surface‐modified capillaries.
Analysis of deethyl‐ and deisopropylatrazine residues in drinking and ground water by chemical derivatization
Authors: Pachinger Anton , Eisner Elisabeth , Tertsch Claudia , Begutter Helmut , Klus Hubert
Published: May 2005

A gas chromatographic method with alkali flame ionization detection is described for the determination of residue levels (0.1 μg/I and below) of deethylatrazine and deisopropylatrazine in drinking and ground water. Confirmation of the identities of the compounds is achieved by trifluoroacetylation, reaction conditions for which are presented.
Quantitation of diethylene glycol monoethyl ether in citrus oils
Authors: Bonetti Graziano , Pibarot Patrick , Chaintreau Alain , Marion Jean Paul
Published: May 2005

The use of diethylene glycol monoethyl ether as a flavor solvent is restricted. Since existing methods of quantitation are tedious or require sophisticated multi‐dimensional GC instrumentation, a simple method has been developed using low cost GC‐MS. Monitoring of ions 31 and 45 enables quantitation of DEGEE in essential oils at levels down to 1 μg/g with accuracy equal to or better than 15%.
Sample evaporation in conventional split/splitless GC injectors: Part 2: Use of perylene for visual observation of three different scenarios in empty injector inserts
Authors: Grob Konrad , De Martin Mirella
Published: May 2005

Perylene is strongly fluorescent as long as it is in solution. This has enabled visual observation of non‐evaporated sample material in a “transparent injector”, i.e. in a heated glass device imitating a conventional vaporizing injector.

Three scenarios of sample evaporation are described. Some samples (solvents) are nebulized and “flash evaporated” in the gas phase between the needle exit and the column entrance (Scenario 1). With most solvents, the liquid leaves the syringe needle as a thin jet which rushes through both the empty vaporizing chamber and the split outlet at high velocity, often without substantial evaporation. It does not touch the surfaces of the insert and passes round the bend at the bottom of the device without any problem (Scenario 2). Some samples are splashed on to the insert wall, wet it, and evaporate rather slowly from this surface (Scenario 3).
Headspace gas analysis: Comparison of the efficiency of thick film, ultra thick film, and activated charcoal open tubular capillary traps for the concentration of volatile, airborne, organic compounds
Authors: Burger Barend V. , le Roux Maritha
Published: May 2005

Determination of the rate at which volatile organic molecules diffuse through the wall of a polysiloxane rubber tube, shows that the full depth of the rubber lining of ultra‐thick film open tubular traps is utilized for the retention of volatile organic compounds in headspace gas analysis. Small apolar molecules migrate rapidly through the rubber, but larger molecules and polar compounds diffuse relatively slowly into the rubber. Neither traps with a thick film of an apolar stationary phase, nor those with an ultra thick polysiloxane rubber lining retain highly volatile compounds very effectively. Traps containing activated charcoal particles fused into their inside glass surface have a much higher capacity than those with activated charcoal particles embedded in a layer of stationary phase.
Multidirmensional gas chromatography – isotope ratio mass spectrometry (MDGC‐IRMS). Part A: System description and technical requirements
Authors: Nitz Siegfried , Weinreich Bernd , Drawert Friedrich
Published: May 2005

A system is presented which combines multidimensional GC with isotope ratio mass spectrometry. The performance of the system is demonstrated with an application from the field of flavor analysis. Potentials and limitations of the technique are also discussed.
New artificial standards for the HPLC analysis of natural glucosinolates
Authors: Elfakir Claire , Lafosse Michel , Viaud Marie Claude , Dreux Michel
Published: May 2005

The separation of new, artificial, non‐sulfated glucosinolates and desulfated natural glucosinolates on different apolar (C8, TMS, phenyl) or weakly polar (CN) bonded stationary phases by gradient elution has shown that apolar or weakly polar bonded silica‐based adsorbents, in addition to the C8 phase chosen for the standard procedure, can be used with benefit for the analysis of glucosinolate mixtures.

The use of new artificial glucosinolates, not present in cruciferae, as internal standards for the standard HPLC method for the determination of the main glucosinolate composition and content of rapeseed is discussed.

The main factors influencing the retention and selectivity toward several natural and artificial non‐sulfated glucosinolates for different chromatographic systems have been studied, and for additional information the retention data have been analyzed statistically by factor analysis.

The first results from this study show that the mechanism of the HPLC retention of glucosinolates is the sum of only two methematically independent physico‐chemical phenomena. The first is associated with the hydrophobicity of compounds.

A better understanding of the chromatographic behavior of glucosinolates has made it possible to investigate the synthesis of new, artificial standard glucosinolates with the intention of providing an ideal standard for every kind of analysis. It also supplies a tool to enable laboratories to choose the best chromatographic system for a particular selectivity problem.
Separation of mixtures of solvents with wide bore capillary columns connected in series
Authors: Gerbino Tomaso C. , Castello Gianrico
Published: May 2005

The gas chromatographic separation of the components of a complex mixture of industrial solvents, not possible on a single stationary phase owing to coelution of some of the compounds, has been achieved on two serially connected wide bore capillary columns of different polarity.

The analysis of a mixture of twenty five compounds was optimized using the serial gas chromatography theory of Purnell and Williams. The capacity factors of sample components measured with the two columns coupled in series were found to agree with those predicted by theory, regardless of the order in which they were connected.
On‐line liquid chromatography – gas chromatography for automated clean‐up and analysis of polycyclic aromatic hydrocarbons
Authors: Östman Conny , Bemgård Agneta , Colmsjö Anders
Published: May 2005

A fully automated system, comprising a liquid chromatograph (LC) coupled on‐line to a gas chromatograph (GC) by means of a loop interface, has been constructed for clean‐up and analysis of polycyclic aromatic hydrocarbons (PAH). An autosampler was utilized for sample injection into the LC. By the use of a back‐flush technique in conjunction with an ordinary analytical aminopropylsilica column, PAH could be isolated by LC: a concurrent solvent evaporation injection technique was then used for on‐line transfer of the PAH fraction to the GC, where the PAH analysis was completed.

Compared with ordinary off‐line LC clean‐up followed by GC analysis, the sensitivity has been increased by a factor of 50–100, yielding a detection limit for individual PAH of a few nanograms per sample when using flame ionization detection. Further, irreproducible losses of low molecular weight PAH as a result of solvent evaporation steps in off‐line clean‐up procedures have been eliminated. Reproducibility of retention times and relative peak areas is high, facilitating automatic peak identification and calculation of concentrations, and the system can thus be used for automatic sample evaluation. The total time required for clean‐up and analysis is only 1.5 hours, and the demand on personnel time for the analysis of PAH has been drastically reduced.

The technique has been demonstrated with samples of urban air and of used automobile engine lubricating oil.
CZE separations of basic proteins at low pH in fused silica capillaries with surfaces modified by silane derivatization and/or adsorption of polar polymers
Authors: Gilges Martin , Husmann Heribert , Kleemiß Maria‐Helen , Motsch Stephan R. , Schomburg Gerhard
Published: May 2005

Mixtures of several basic proteins have been used to test CZE capillaries with surfaces modified by new pretreatment procedures; the performance obtained has been compared with that achieved using capillaries treated by procedures described in the literature.

It has been shown that addition of non‐ionic polyvinylalcohols (PVA) to CZE buffer solutions deactivates even bare, i.e. untreated, fused silica surfaces and renders them suitable for separations of basic proteins. The performance obtained from such surfaces was comparable with that of capillaries modified by the more elaborate procedures of etching, silanol derivatization, and/or adsorptive coating (again with polymers).

A home‐made device is described which enables derivatization and coating reactions to be performed on fused silica capillaries under an inert atmosphere, i.e. one free from oxygen and water.
Unified gas and supercritical fluid chromatography on 50 μm i.d. Columns
Authors: Tong Daixin , Bartle Keith D. , Clifford Anthony A. , Robinson Robert E.
Published: May 2005

A unified approach to sequential gas and supercritical fluid Chromatography using 50 μm i.d. open tubular columns is described. Sample introduction is performed by means of a rotary injection valve. In order that linear velocities can be optimized independently, a second rotary valve in the chromatographic oven is used to direct the flow of column eluate to the flame ionization detector through either fused silica tubing in GC, or a frit restrictor in SFC.

Applications of sequential GC‐SFC on a 50 μm i.d. open tubular column are demonstrated, and comparisons made between sequential GC‐SFC on 50 and 100 μm i.d. columns.
Reproducibility of sample separation using liquid or forced air convection thermostatted high performance capillary electrophoresis systems
Authors: Landers James P. , Oda Robert P. , Madden Benjamin , Sismelich Tamara P. , Spelsberg Thomas C.
Published: May 2005

Run‐to‐run sample separation reproducibility has been compared on two commercial high performance capillary electrophoresis units which differ in the mode by which the capillary temperature is thermostatted. Three standard analytes, differing dramatically in molecular character and size, were used for the analysis: benzoic acid, a 14 amino acid peptide from human chorionic gonadotropin, and ribonuclease A represent, respectively, small stable organic molecules, small peptides with little or no secondary structure, and proteins with secondary structure. These standards were evaluated with regard to reproducibility of migration time, peak area, and peak height. The analyses, performed in buffers of optimum pH for the separations, demonstrated that the liquid and forced air convection thermostatted systems both performed extremely well. The reproducibility, as judged by the percent coefficient of variance (% CV) of replicate analyses, was generally found to be less than 1 % (migration time); the reproducibility decreased in the order migration time > peak height > peak area. Whereas the absolute % CV values for MTrel (migration relative to a standard) observed with the liquid thermostatted system were 2‐ to 4‐fold lower than those observed with the forced air convection thermostatted system, there was little statistically significant difference between the two. As expected, the data indicated a reduction in reproducibility as the complexity of the analyte increased, perhaps as the result of an increased potential for wall interactions. Comparing separations in which low (≈︁1 watt/meter [W/m] of capillary) and high (>5 W/m) Joule heat was generated by altering the sodium chloride content of the buffer revealed few statistically significant differences in the reproducibility obtained from the two systems. With these particular standard analytes and their respective buffer systems, there appears to be little difference between forced air convection and liquid thermostatting of the capillary.
Application of coupled LC‐GC to the analysis of the polar fraction of diesel particulate matter
Authors: Kelly Grant W. , Bartle Keith D. , Clifford Anthony A. , Robinson Robert E.
Published: May 2005

Emissions from diesel engines contain mutagenic compounds, many of which are derivatives of polycyclic aromatic hydrocarbons. The complexity of extracts of particulate matter requires multi‐stage chromatographic analysis performed off‐line.

In this study, coupled LC‐GC is presented as an alternative method for the analysis of the polar fraction of extracts of diesel particulate matter. Preseparation of the sample was achieved by normal phase HPLC and fractions were transferred to the GC through an on‐column interface. Through selective transfer, extensive characterization of the extract is possible and chromatograms can be greatly simplified, thus aiding identification.
Optimum performance of capillary GC columns as a function of column diameter and film thickness under various operating conditions: Part II: Computer program extensions for n‐alkane solutes and polydimethylsiloxane phases
Authors: Leclercq Piet A.
Published: May 2005

A BASIC computer program for calculation of maximum plate number and minimum analysis time conditions for columns operated at various outlet pressures was presented in 1985 [1]. This sequel reports extensions to the program for n‐alkanes separated on polydimethylsiloxane stationary phases, specifically for n‐C2 through n‐C20 on phases equivalent to SE‐30 or OV‐1. For these solute–phase systems the amount of thermodynamic data available is sufficient to enable calculation of several parameters.

Firstly, the separation temperature is now automatically calculated for a requested capacity ratio, or vice versa. Secondly, the computation of solute diffusivities in the stationary phase has been improved to approach experimental data more realistically, particularly for higher n‐alkanes at higher temperatures.

The largest extension to the program is the inclusion of a facility enabling calculation of column sample capacity, minimum detectable amounts for FID and TCD detectors, and column working ranges. These parameters are again calculated for n‐alkanes, but are, of course, independent of the nature of the stationary phase. The updated program has been and is being used on a routine basis in our laboratory; it has been found to be reliable and has on numerous instances been proven in the field.
A novel algorithm for chromatogram matching in qualitative analysis
Authors: Mason John P. , Kirk Ian , Windsor Colin G. , Tipler Andy , Spragg Richard A. , Rendle Mark
Published: May 2005

The matching of the pattern of peaks produced during gas chromatography is of importance to many applications. At present, this task is generally performed manually, but this generates the usual problems associated with human inspection, such as a lack of objectivity and reproducibility, proneness to errors, and practical restriction of the volume of data which can reasonably be processed.

This paper explores the use of a novel algorithm for automation of this task. The performance of the method on well controlled simulated data sets and real chromatograms is used to show not only how problems of manual inspection can be circumvented, but also how the existence of such a powerful method should open up the possibility of many new analyses for quality control, discrimination of varieties of sample, and the identification of specific components within a sample.
Splitless injection of up to hundreds of microliters of liquid samples in capillary GC: Part 1, concept
Authors: Grob Konrad , Brem Sandra , Fröhlich Dieter
Published: May 2005

If a sample evaporates by flash vaporization in an empty injector insert, the solute material is well mixed with the expanding solvent vapors and the maximum injection volume is determined by the requirement that no vapors must leave the vaporizing chamber. If evaporation occurs from a surface (e.g., of Tenax packing), however, the solvent evaporates first. The site of evaporation is cooled to the solvent's boiling point, and the cool island formed in the hot injector retains solutes of at least intermediate boiling point (visually observed for perylene). Solvent vapors, free from such solutes, may now expand backwards from the injector insert and leave through the septum purge exit. When solvent evaporation is complete, the site of evaporation warms up, causing the high boiling solutes to evaporate and to be carried into the column by the carrier gas. The technique somewhat resembles PTV injection, but is performed using a classical vaporizing injector.
Operational theory and instrumental implementation of the thermal gradient programmed gas chromatography (TGPGC) mode of analysis
Authors: Rubey Wayne A.
Published: May 2005

Thermal gradient programmed gas chromatography (TGPGC) separations involve the application of three‐dimensional thermal field programming. The operational aspects associated with TGPGC are such that rapid GC analyses can be achieved for complex and broad‐volatility‐range samples using open tubular columns with high thermal compliance, physical compactness, and geometric conformity. Elapsed times for TGPGC analyses of complex samples have ranged from 50 to 300 s. The application of rapidly changing thermal fields (or temperature surfaces) in TGPGC is accomplished through the use of a column sheath assembly. Recent research has centered upon different column sheath assembly designs and instrumental implementation of the TGPGC mode of operation. The instrumental implementation of the TGPGC mode for conducting GC and GC‐MS analyses places special demands upon the design and performance of numerous operational aspects of the system, e.g., the response‐time characteristics associated with analyte detection and the analytical output signal handling capabilities.
Recent advances in sample introduction for supercritical fluid chromatography
Authors: Kirschner Cynthia H. , Taylor Larry T.
Published: May 2005

New strategies for sample introduction in supercritical fluid chromatography are reviewed. Both open tubular and packed column systems are examined as the injection demands of each column type are addressed. In addition to advances made in solvent injection methods, supercritical fluid extraction (SFE) is discussed as a solventless injection technique for supercritical fluid chromatography.
Temperature program optimization by computer simulation for the capillary GC analysis of fatty acid methyl esters on biscyanopropyl siloxane phases
Authors: Sippola Erkki , David Frank , Sandra Pat
Published: May 2005

The selectivity of capillary columns coated with biscyanopropyl siloxane stationary phases for the separation of fatty acid methyl esters has been optimized by means of computer‐assisted column temperature optimization software. Temperature programming rates yielding the highest resolution in the shortest analysis time were selected for split, splitless, and on‐column injection operated in the constant pressure and pressure programmed modes.
Stereoisomeric flavor compounds, part LXI: Enantioselective analysis of aroma‐relevant dihydrofuranones
Authors: Bruche Günther , Dietrich Armin , Mosandl Armin
Published: May 2005

The odor impression of the pure enantiomers of various chiral dihydrofuranones which are important flavor compounds has been evaluated by sniffing the well separated optical antipodes in the GC eluate from heptakis(2,3‐di‐O‐methyl‐6‐TBDMS)‐β‐cyclodextrin as the chiral phase for capillary gas chromato‐graphic separation. Liquid chromatographic separation has been achieved by the use of bonded β‐cyclodextrin as the chiral stationary phase and methanol–water as eluent. Enantiomer separation in the latter was improved by addition of triethylammonium acetate to the eluent.
Determination of organotin compounds in environmental samples by supercritical fluid extraction and gas chromatography with atomic emission detection
Authors: Liu Yan , Lopez‐Avila Viorica , Alcaraz Marcela , Beckert Werner F.
Published: May 2005

The extraction of six tetraalkyltin and seven ionic organotin compounds from spiked topsoil samples with supercritical carbon dioxide and carbon dioxide modified with 5 percent methanol was investigated. Analysis of the soil extracts was performed by gas chromatography with atomic emission detection. Retention times, minimum detectable concentrations, and detector linear ranges are included for nine organotin compounds (seven of the nine compounds were derivatized with n‐pentylmagnesium bromide prior to gas chromatographic analysis). A 23 factorial experimental design was used to study the effect of three variables (pressure, temperature, and extraction time) on compound recovery. The results indicate that the tetraalkyltin compounds are extracted from topsoil samples with recoveries ranging from 90 to 110 percent. Recoveries for the ionic organotin compounds ranged from 50 to 75 percent for trimethyltin chloride, triethyltin bromide, and tributyltin iodide; they were below 20 percent for dimethyltin dichloride, dibutyltin dichloride, diphenyltin dichloride, and butyltin trichloride. When sodium diethyldithiocarbamate was added to the soil samples prior to extraction, followed by extraction with carbon dioxide modified with 5 percent methanol, recoveries ranged from 70 to 90 percent for trimethyltin chloride, triethyltin bromide, dimethyltin dichloride, tributyltin iodide, and dibutyltin dichloride; recoveries were approximately 40 percent for butyltin trichloride and diphenyltin dichloride.
GC‐MS identification of styrene and oligomers in polystyrene plastic for milk packaging. Headspace and solution injection technique
Authors: Abrantes Shirley
Published: May 2005

Twenty compounds have been determined by GC‐MS in polystyrene used for milk packaging. The major components identified in milk were styrene and its dimer at concentrations of 13 and 43 mg/kg, respectively. The detection limit for styrene by the equilibrium headspace method was 0.29 mg/kg. Another method used to determine the concentration of styrene and its dimer in milk was the use of acetone to precipitate the proteins and extract both the fat and the residues from the plastic packaging. The solution obtained was then directly injected into the GC. The detection limits were found to be 0.16 mg/kg for styrene and 0.28 mg/kg for the dimer. The solution injection method thus proved to be much more sensitive.
Experimental design optimization of the separation of the aromatic compounds in petroleum cuts by supercritical fluid chromatography
Authors: Fraile Rebeca , Sánchez Vicente
Published: May 2005

A experimental design optimization method is demonstrated for evaluation of the resolution of the performance mixture used in the proposed ASTM test to determine the aromatic content of aviation fuels. The method uses a Doehlert experimental matrix test to optimize the resolution and analysis time by varying the pressure and temperature of the supercritical carbon dioxide mobile phase. The separation between saturated and aromatic compounds was optimized using only seven experiments. With this procedure, the analysis time required for determination of the total aromatic content of more complex samples can be reduced to less than 10 min.
Gas chromatographic enantiomer separation with modified cyclodextrins: Carboxylic acid esters and epoxides
Authors: König Wilfried A. , Gehrcke Bärbel
Published: May 2005

The wide range of application of 2,6‐di‐O‐methyl‐3‐O‐pentyl‐β‐and y‐cyclodextrins is demonstrated by the resolution of the enantiomers of the methyl esters of chiral carboxylic acids: α and β hydroxy acids with up to 18 carbon atoms, hydroxy di‐ and tricarboxylic acids, and alkyl/aryl‐substituted carboxylic acid methyl esters, including the plant hormone abscisic acid, insect juvenile hormones, and some non‐steroidal anti‐inflammatory drugs can be resolved with generally large separation factors. The new cyclodextrin derivatives also exhibit high selectivity for epoxides.
Stainless steel capillary columns for high temperature gas chromatography
Authors: Zou Naizhong , Yusheng Tsui , Jiahe Sun , Wanzhen Lu
Published: May 2005

A layer of elemental silicon has been deposited on the surface of stainless steel tubing by means of chemical vapor deposition (CVD). Two kinds of capillary column were prepared from the deactivated tubing: cross‐linked, silanol‐terminated polydime‐thylsiloxane wall coated open tubular (WCOT) columns and molecular sieve 13X porous layer open tubular (PLOT) columns. Unlike fused silica capillary columns, stainless steel WCOT and PLOT columns can be operated at temperatures in excess of 400°C. High temperature simulated distillation has been performed successfully with a macro bore WCOT column and rapid PNA (paraffin, naphthene, and aromatic) analysis with a multidimensional gas solid chromatographic (GSC) system using PLOT columns.
The use of nitrous oxide for supercritical fluid extraction of pharmaceutical compounds from animal feed
Authors: Sauvage E. , Rocca J.‐L. , Toussaint G.
Published: May 2005

Supercritical fluid extraction (SFE) coupled “off‐line” with HPLC analysis has been applied to pharmaceutical analysis: two different matrixes (rodent and dog feed) were spiked with compounds under investigation in pharmacological studies in order to study the supercritical extraction of such matrixes prior to further analysis and quantification of the compounds of interest.

The fluid flow‐rate in the SFE system was governed by the geometric characteristics (internal diameter and length) of the linear fused silica capillaries. The changes in fluid flow‐rate, between experiments, for each new restrictor, required the introduction of the term Total Gaseous Fluid Volume (TGFV), which enabled a series of extraction results to be compared.

The comparative behavior of nitrous oxide and carbon dioxide as supercritical extraction fluids was investigated. Results obtained using pure supercritical fluids with high solvating power (density 0.79 g ml−1) and fluids modified with a polar liquid solvent (methanol and acetonitrile) are discussed.
Stereoisomeric flavor compounds. Part LXV: Preparative resolution of the enantiomers of chiral dihydrofuranones by recycling chromatography
Authors: Bruche Günther , Mosandl Armin , Kinkel Joachim N.
Published: May 2005

Preparative resolution of the enantiomers of several chiral dihydrofuranones, known to be important flavor compounds, has been achieved by combining the use of bonded β‐cyclo‐dextrin as chiral stationary phase with closed‐loop recycling chromatography. The purity of the separated enantiomers has been determined by chirospecific capillary GC analysis, using heptakis(2,3‐di‐O‐methyl‐6‐TBDMS)‐β‐cyclodextrin as the chiral stationary phase.
Unified nomenclature for chromatography
Authors: Ettre Leslie S.
Published: May 2005

The background of the new Unified Nomenclature for Chromatography just accepted by the International Union of Pure and Applied Chemistry (IUPAC) is explained and selected highlights of the new rules are elaborated.
Memory effects in gas chromatographic detection with a microwave‐induced plasma
Authors: Valente Antonio Luiz Pires , Uden Peter C.
Published: May 2005

Capillary gas chromatography coupled to microwave‐inducedplasma detection furnishes sensitivity adequate for trace analysis when the signal is monitored at a carbon emission line. Work performed with one of these systems at high electronic gain for the carbon signal has revealed solvent band widths in excess of four minutes; these impeded quantification of peaks eluting after the solvent. This report discusses two phenomena which could be related to the unexpected intensity of this solvent response: photomultiplier tube saturation and carbon deposits in the quartz plasma discharge tube.
An instance of temperature‐dependent elution order of enantiomers from a chiral brush‐type HPLC column
Authors: Pirkle William H. , Murray Patrick G.
Published: May 2005

Typically, reduction of column temperature increases the enantioselectivity of a chiral stationary phase. An instance in which progressive reduction of temperature initially reduces enantioselectivity, then inverts the elution order of the enantiomers, and finally causes enantioselectivity to increase has been observed. This behavior is related to the nature and concentration of the polar modifier in the mobile phase, and requires particular chiral phase‐analyte‐mobile phase combinations. A rationalization is presented as to the possible origin of this behavior. This rationale may aid in finding other examples of this temperature‐dependent elution order of enantiomers and ultimately increase our understanding of chiral recognition processes.
Chirasil‐Dex‐TFA: A new polysiloxane‐bonded and immobilizable cyclodextrin stationary phase for enantiomer separation by GC
Authors: Jung Martin , Schurig Volker
Published: May 2005

Heptakis(2,6‐di‐O‐methyl‐3‐O‐trifluoroacetyl)‐†‐cyclodextrin has been chemically bonded to a polydimethylsiloxane via an octamethylene spacer and subsequently immobilized on to the surface of fused silica capillaries, the first time a cyclodextrin derivative with mixed substituents has been immobilized in this way. The enantioselectivity of the new chiral stationary phase has been investigated as a function of the cyclodextrin content. It was found to be higher than that reported for heptakis (2,6‐di‐O‐methyl‐3‐O‐trifluoroacetyl)‐†‐cyclodextrin or hepta‐kis(2,6‐di‐O‐methyl‐3‐O‐acetyl)‐†‐cyclodextrin dissolved in polysiloxane (e.g. OV‐1701). The degree of immobilization was over 90 %. The temperature stability is, however, inferior to that of Chirasil‐Dex (a permethylated cyclodextrin): the maximum operating temperature is approximately 200 °C.
Molecular modelling experiments on chiral recognition in GC with specially derivatized cyclodextrins as selectors
Authors: Kobor Frank , Angermund Klaus , Schomburg Gerhard
Published: May 2005

The results of gas chromatographic enantiomeric separations of selected non‐polar and polar test solutes (limonene and 1‐phenylethanol) using two different derivatives of β‐cyclodextrin, permethyl‐β‐CD and 2,3‐dimethyl‐tert‐butyldimethylsilyl‐β‐CD (PMCD and TBCD) are interpreted in combination with the conclusions from molecular modelling calculations based on docking experiments. A comparison of the two selectors which were used as solution in a polysiloxane matrix (OV 1701) indicated that the less flexible TBCD which is blocked on one side by the bulky tert‐butyldimethylsilyl groups seems to possess advantages for certain chiral separations, especially of the non‐polar type. The special properties of TBCD as selector are also demonstrated by chiral separations of other compounds.
An autosampler with a short transfer line for Curie point pyrolysis capillary gas chromatography
Authors: Onishi Akira , Endo Makoto , Uchino Shigeki , Harashima Naoto , Oguri Naoki
Published: May 2005

A new multichannel autosampler which can automatically analyze up to twenty samples in sequence has been developed for Curie point pyrolysis – capillary GC. Compared with a previous system [1] the transfer line between the pyroysis unit and chromatograph is shorter, and thus has less dead volume, and can be operated at a higher temperature (300 °C). The relative yields of higher boiling point, highly polar, and thermally labile pyrolysates generated from polymers, and the reproducibility, were better than those obtained from the previous autosampler. To facilitate rapid operation an additional flow controller is installed on the new device to shorten the time taken to purge air from the sampler.
Separation of geometric isomers of metal β‐diketonates by supercritical fluid chromatography
Authors: Laintz Kenneth E. , Meguro Joshihiro , Iso Shuichi , Tachikawa Enzo
Published: May 2005

The separation of the geometric isomers of chromium and rhodium chelates of trifluoroacetylacetone and thenoyltrifluor‐oacetone was investigated using packed column supercritical fluid chromatography. Mobile phases consisting of neat and alcohol‐modified carbon dioxide were used, and the most favorable isomeric resolution was obtained with a phenyl stationary phase. The chromatographic performance was better for chelates with trifluoroacetylacetone than for the corresponding chelates with thenoyltrifluoroacetone. Chromatographic peak area analysis of the metal chelates investigated showed appropriate isomeric concentrations in the final diastereomeric products resulting from the synthetic procedures.
Residual solvent content in heatset offset print
Authors: Aurela Birgit , Räisänen Tapio
Published: May 2005

A method was developed for measuring the residual solvent content in a dried offset print. The method is based on hexane extraction. The presence of additives and resins in the printing inks necessitated purification of the extract on an aluminum oxide column. In the study concerning the effect of the heatset web offset drying process on print quality, a distinct correlation was found between the residual solvent content of the print and the drying parameters.
Miniaturization of separation techniques using planar chip technology
Authors: Manz Andreas , Verpoorte Elisabeth , Effenhauser Carlo S. , Burggraf Norbert , Raymond Daniel E. , Harrison D. Jed , Widmer H. Michael
Published: May 2005

Miniaturization of separation columns implies equally reduced vol‐ umes of injectors, detectors, and the connecting channels. Planar chip technology provides a powerful means for the fabrication of micron‐sized structures such as channels. This is demonstrated by two examples. An optical absorbance detector chip exhibits the expected behavior of a 1 mm optical path length cell despite its volume of 1 nL. A capillary electrophoresis device allows integrated injections of 100 pL samples, efficiencies of 70,000 to 160,000 theoretical plates in 10 to 20 seconds, and external laser‐induced fluorescence detection at any capillary length of choice between 5 and 50 mm.