bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study of peak profiles in nonlinear gas chromatography: Application to the peak distortions observed with overloaded capillary columns
Authors: Cardot P. , Ignatiadis I. , Jaulmes A. , Vidal‐Madjar C. , Guiochon G. 
Published: May 2005

AbstractThe elution profiles observed with overloaded capillary columns are well described by a four‐parameter theoretical model derived from the basic mass balance equations which relies on an expansion of the partition isotherm to the second term and takes the sorption effect into account. The reliability of the model is demonstrated by the fact that the peak leaning coefficient obtained from a least squares fit of the model to the experimental peak is in good agreement with that obtained from the variation of peak height with retention time at peak maximum. The coefficeint of apparent axial dispersion is independent of sample size and can be used to characterize the plate height at zero concentration of an overloaded capillary column.
Distribution of weight, density, and molecular weight in crude oil derived from computerized capillary GC analysis
Authors: Osjord E. H. , Rønningsen H. P. , Tau L. 
Published: May 2005

AbstractChromatographic separation of crude oil components has been performed on a 50 m Chrompack Sil 5 fused silica capillary column, temperature programmed from 10 to 300°C. Approximately 70 peaks eluting before n‐nonane (n‐C9) and all normal paraffins to n‐C19 were identified by a retention time table. Peak areas were converted to weight % using 1‐heptene as internal standard and relative response factors. Components were divided into boiling range groups from n‐C6 to n‐C19. Paraffinic, naphthenic, and aromatic distributions were obtained for the boiling point fractions up to n‐C9.Group average densities and molecular weights were calculated from pure component properties up to n‐C9. Knowing the density and molecular weight as functions of boiling range group to n‐C9, these functions can be extrapolated to n‐C19, based on data and correlations from more than 20 distillations of paraffinic North Sea oils adn condensates. The densities and molecular weights of the C10+ and the C20+ residues were calculated to satisfy a balance of weight, volume, and number of moles for the whole sample.Measurements on the residues were used to cross‐evaluate the GC method against distillation. The difference in weight was estimated to be less than ± 0.5% in absolute terms for the C10+ residue. The corresponding figure for C20+ was ± 2%. Relatively, calculated densities are within ± 1%, molecular weights within ± 2% compared to direct measurements. Calculations were performed by a BASIC program in a GC interfaced computer.
Automatic simulated distillation of heavy petroleum fractions up to 800°C TBP by capillary gas chromatography. Part I: Possibilities and limits of the method
Authors: Trestianu S. , Zilioli G. , Sironi A. , Saravalle C. , Munari F. , Galli M. , Gaspar G. , Colin J. M. , Jovelin J. L. 
Published: May 2005

AbstractThe characterization of heavy petroleum fractions is essential for the design and improvement of cracking plants converting heavy feedstock into valuable “white” products. Conventional simulated distillation methods using packed columns are unsuitable for this purposes, being limited to boiling points up to about 600°C. The method presented is able to cover a boiling points interval ranging from about 150°C up to around 800°C. It employs a short, nonpolar, highly thermostable capillary column routinely operated at temperatures around 430°C. The analytical system is based on a high temperature versions of a fully automatic, capillary dedicated gas chromatograph. The experimental data demonstrate that cold on‐column injection is the sole sampling system suitable for such heavy compounds. The conversion of the retention times into boiling points, based on the use of low molecular weight polyethylenes, is extremely reliable, as demonstrated by the excellent retention time reproducibilities. The lower part (up to 550–600°C TBP) of the boiling point distribution curves of heavy petroleum fractions obtained on capillary columns fits well with the corresponding distribution curves based on packed column data. For the petroleum fractions fully eluted from the column the quantitative results obtained either using internal standards or by direct processing of the elution curves are in excellent agreement (less than 0.3 weight% differences). The method has been applied to the determination of the true boiling points corresponding to short path vacuum distillation (DISTACT) cut points over 300°C.
The autoderivatization of 4‐ketocyclophosphamide during capillary gas chromatography
Authors: de Bruijn E. A. , Leclercq P. A. , Tjaden U. R. 
Published: May 2005

AbstractThe selectivity of a capillary gas chromatographic assay for the anti‐neoplastic and immunosuppressive agent cyclophosphamide (CPA) towards one of its naturally occurring metabolites, i.e. 4‐ketocyclophosphamide (4‐keto CPA), has been studied. Mass spectrometry studies showed that a cyclization product of 4‐keto‐CPA can form using the same chromatographic conditions as those under which CPA was determined. However, the amount produced is relatively small (less than 10%) compared with the percentage produced from CPA. Furthermore, both cyclization products, formed by loss of HCI and intraalkylation of the parent compounds, can be separated well under suitable chromatographic conditions.
Concurrent solvent evaporation for on‐line coupled HPLC‐HRGC
Authors: Grob K. , Walder Ch. , Schilling B. 
Published: May 2005

AbstractA technique is proposed which allows introduction of very large volumes of liquid (10 ml were tested) into capillary columns equipped with short (1–2 m long) retention gaps. It is based on concurrent solvent evaporation, i.e. evaporation of the solvent during introduction of the sample. The technique presupposes high carrier gas flow rates (at least during sample introduction) and column temperatures near the solvent boiling point. The major limitation of the method is the occurrence of peak broadening for solutes eluted up to 30°, in some cases up to 100°, above the injection temperature. This is due to the absence of solvent trapping and a reduced efficiency of phase soaking. Therefore, use of volatile solvents is often advantageous. Application of the concurrent solvent evaporation technique allows introduction of liquids which do not wet the retention gap surface. However, the method is still not very attractive for analysis of aqueous or water‐containing solutions (reversed phase HPLC).
Effect of free hydroxy groups in the separation of polyglycerol esters by capillary supercritical fluid chromatography
Authors: Chester T. L. , Innis D. P. 
Published: May 2005

AbstractSeparations of polyglycerol esters containing 3–5 hydroxyl groups and of their silyl derivatives are demonstrated on DB‐1 and DB‐17 columns. Useful chromatograms are produced in every case. However, the chromatograms are improved on derivatization. The extent of improvement realized increases with the number of free hydroxyl groups per molecule.
A new gas chromatographic retention index for pesticides and related compounds
Authors: Hall G. L. , Whitehead W. E. , Mourer C. R. , Shibamoto T. 
Published: May 2005

AbstractA new gas chromatographic (GC) retention index based on a homologous series of tri‐n‐alkylamines is proposed for use in the detection of pesticides and related compounds because the standard n‐paraffin hydrocarbons used for the Kovats index do not show up well on the nitrogen‐phosphorus detectors commonly used in pesticide analysis. Using fused silica bonded phase capillary columns (DB‐1 or DB‐5), the trialkylamine indices of 106 selected pesticides and related compounds were measured and their relationship to the Kovats index determined.
Simultaneous assay of serum vitamin A and vitamin E by high performance liquid chromatography using time‐switched UV and fluorimetric detectors
Authors: Russell M. J. , Thomas B. S. , Wellock E. 
Published: May 2005

AbstractAn HPLC method utilizing a UV and a fluorimetric detector linked in series is described. By use of a simple integrator‐controlled time‐switched relay, analysis of serum vitamin A and E is accomplished on the same chromatogram and at optimum sensitivity for each detector. A single internal standard (retinyl acetate) monitored only by the UV detector permits measurement of both vitamins over a wide linear range. Precision of the assays is satisfactory, both on a within‐day and on a day‐to‐day basis. Recoveries of both vitamins are virtually 100% whilst sensitivity is 2 μg/L (retinol) and 0.05 mg/L (α‐tocopherol).
Kovats and lee retention indices determined by gas chromatography/mass spectrometry for organic compounds of environmental interest
Authors: Rostad C. E. , Pereira W. E. 
Published: May 2005

AbstractRetention indices of standard organic compounds of environmental interest were determined by gas chromatography/mass spectrometry, using a DB‐5 fused‐silica capillary column. Retention indices are useful references for tentative compound identification by gas chromatography, or confirmation by gas chromatography/mass spectrometry. They provide elution order for isomers that might be indistinguishable based on mass spectra. Modified Kovats and Lee retention indices are given for polycyclic aromatic hydrocarbons; sulfur heterocycles; nitrogen heterocycles; aromatic amines; oxygen heterocycles; phenols; alcohols; ketones; alkanes; nitriles; and methylesters of fatty, dicarboxylic, and aromatic acids for comparison and reference. Retention index values for heterocycles by gas chromatography/mass spectrometry are comparable with gas chromatography values previously reported.
Preparation of glass capillary columns coated with immobilized OV‐240‐OH (33% cyanopropyl substituted, OH‐terminated). An approach to improve the inertness and thermal stability of cyanoalkyl polysiloxane coatings
Authors: Blum W. 
Published: May 2005

AbstractCoating intensely leached glass capillaries with OV‐240‐OH, the most polar commercially available OH‐terminated polysiloxane phase at the present time, is described. Beside chemical bonding of the phase via condensation with silanol groups of the support, additional immobilization using dimethyltetramethoxysiloxane as a crosslinker is carried out. After in situ methylation of the immobilized coating, and transformation of acidic impurities of the cyanopropyl substituted phase into the respective methyl esters, increased inertness of the column was observed. Working instructions are given, and processes involved are discussed.
Loop‐type interface for concurrent solvent evaporation in coupled HPLC‐GC. Analysis of raspberry ketone in a raspberry sauce as an example
Authors: Grob K. , Stoll J.‐M. 
Published: May 2005

AbstractPresently, two coupling techniques are used for directly introducing HPLC fractions into capillary GC: The retention gap technique (involving negligible or partially concurrent solvent evaporation) and fully concurrent solvent evaporation. While the former involves use of a conventional on‐column injector, it is now proposed that concurrent solvent evaporation technique be carried out using a switching valve with a built‐in sample loop. The technique is based on the concept that the carrier gas pushes the HPLC eluent into the GC capillary against its own vapor pressure, generated by a column temperature slightly exceeding the solvent boiling point at the carrier gas inlet pressure. Further improvement of the technique is achieved by flow regulation of the carrier gas (accelerated solvent evaporation) and backflushing of the sample valve (improved solvent peak shape).Concurrent solvent evaporation using the loop‐type interface is easy to handle, allows transfer of very large volumes of HPLC eluent (exceeding 1 ml), and renders solvent evaporation very efficient, allowing discharge of the vapors of 1 ml of solvent through the column within 5–10 min.
Quantitative analysis of ethylenediamine in plasma by capillary column gas chromatography
Authors: Heusler H. , Richter E. , Epping J. , Schmidt M. 
Published: May 2005

AbstractA specific and sensitive method for the determination of ethylenediamine in human plasma is described. The aqueous sample is treated with m‐toluoyl chloride, yielding the N,N′‐bis(m‐toluoyl) derivative of the diamine, which is extracted into dichloromethane and quantitated after “on column” methylation by capillary gas liquid chromatography with alkali flame ionization detection. The corresponding derivative of putrescine serves as internal standard. The assay is reproducible and calibration curves are linear over the concentration range 0.05 to 10 μg · ml−1. The lower detection limit is about 10 ng · ml−1. The structures of the compounds of interest eluting from the capillary column are examined by gas liquid chromatography/mass spectrometry. The assay has been applied to the analysis of ethylenediamine in plasma following the administration of aminophylline and ethylenediamine in a cross‐over study to patients with bronchopulmonary diseases. The method also proves suitable for measuring other primary and secondary amines and diamines in aqueous solutions by gas liquid chromatography.
Simultaneous determination of glyceryl trinitrate and its metabolites in plasma using capillary gas chromatography with on‐column injection
Authors: Langseth‐Manrique K. , Bredesen J. E. , Greibrokk T. 
Published: May 2005

AbstractA specific, sensitive, and precise assay for simultaneous quantitation of glyceryl trinitrate (GTN) and its metabolites 1,2‐and 1,3‐glyceryl dinitrate (GDN) has been developed. The method involves one single extraction step with benzene, followed by evaporation at 55°C. One μl of the extract was injected onto a capillary fused silica column with trifluoropropyl as the stationary phase. The column separated all the nitrates within 17 minutes using temperature programming from 90 to 155°C. The lower limits of detection were 0.05, 0.5, and 0.1 nmol/I for GTN, 1,2‐GDN and 1,3‐GDN respectively. The calibration curves were linear in the concentration ranges 0.05–10.0 nmol/I (GTN), 0.5–10.0 nmol/I (1,2‐GDN) and 0.1–10.0 nmol/I (1,3‐GDN). Plasma concentration data from two patients receiving intravenous GTN infusion are presented.
Limits in arson debris analysis by capillary column gas chromatography/mass spectrometry
Authors: Bertsch W. , Sellers C. S. 
Published: May 2005

AbstractSample enrichment technology and instrumental sensitivity are no longer limiting factors in arson debris analysis. When pyrolyzed, petroleum based composite materials may produce artifacts. Urban air is another major source of interference since some of the components typically found in air, in particular alkylated aromatic hydrocarbons, are customarily used as indicators for the presence of gasoline. It is suggested to replace qualitative analysis with a quantitative approach, taking the sample matrix into consideration.
The effect of column characteristics on the minimum analyte concentration and the minimum detectable amount in capillary gas chromatography
Authors: Noy Th. , Curvers J. , Cramers C. A. 
Published: May 2005

AbstractThe need for faster and more efficient separations of complex mixtures of organic compounds by gas chromatography has led to the development of small inner diameter open tubular columns. Owing to their decreased plate height, extremely narrow peaks are obtained. When differently sized columns with equal plate numbers are compared, injection of a fixed amount of a solute will give the highest detector signals for the smallest bore columns. When P is defined as the ratio of the column inlet and outlet pressures, it can be seen from theory that under normalized chromatographic conditions the minimum detectable amount (Qº) for a mass flow sensitive detector increases proportionally to the square of the column diameter for P = 1. In the situation of greater interest in the practice of open tubular gas chromatography where P is large, a linear relationship is derived between Qº and the column diameter.It is a widespread misunderstanding, however, that narrow bore capillary columns should be used for this reason in trace analysis. If a fixed relative contribution of the injection band width to the overall peak variance is allowed, a decreased plate height drastically restricts the maximum sample volume to be injected. It is shown that the minimum analyte concentration in the injected sample (Cº) is inversely proportional to the column inner diameter when a mass flow sensitive detector is used. For actual concentrations less than Cº, sample preconcentration is required. The effect of peak resolution and selectivity of the stationary phase in relation to Cº and Qº will be discussed as well. The validity of the given theory is experimentally investigated. Minimum analyte concentrations and minimum detectable amounts are compared using columns with different inner diameter.
Liquid chromatographic trace enrichment with on‐line capillary gas chromatography for the determination of organic pollutants in aqueous samples
Authors: Noroozian E. , Maris F. A. , Nielen M. W. F. , Frei R. W. , de Jong G. J. , Th. Brinkman U. A. 
Published: May 2005

AbstractTrace enrichment for the GC analysis of a series of chlorinated pesticides and polychlorinated biphenyls (PCBs) in aqueous samples has been achieved through a simple on‐line technique involving sorption on an LC micro‐precolumn followed by direct elution into a gas chromatograph with hexane. A 5‐m retention gap coupled to the capillary GC column served as the recipient of a relatively large sample volume (ca. 100 μl) introduced into the GC. Partially concurrent solvent evaporation during sample introduction allowed a large sample capacity. Recoveries of more than 95% were observed for the majority of the compounds studied. Using 1.0 ml aqueous samples, detection limits of less than 1 ppt were found. The applicability of the developed method was demonstrated for a river water sample.
Micro high performance liquid chromatography of aliphatic amines by means of resonance raman detection
Authors: Koizumi H. , Suzuki Y. 
Published: May 2005

AbstractA micro high performance liquid chromatography coupled with a resonance Raman detection system is described. For highly sensitive Raman detection, aliphatic amines were derivatized with dabsyl chloride (4‐dimethylaminoazobenzene‐4′‐sulfonyl chloride). The derivatives were separated on an ODS micro column (0.5 mm i.d. × 145 mm PTFE tube). Chromatograms were obtained by measuring the intensity of Raman scattering at 1136 cm−1 with the 488.0 nm line of an Arion laser. The lower detection limit was 1.5 ng and the RSD of relative peak height (n = 9) was 5.9% at 11 ng of methylamine derivative. Moreover, by stopping the flow of the micro HPLC system at the retention time of the individual derivatives, it was possible to measure their resonance Raman spectra.
Evaluation of dead time calculation in liquid chromatography using a linearization procedure for homologous series
Authors: van Tulder P. J. M. , Franke J. P. , de Zeeuw R. A. 
Published: May 2005

AbstractA mathematical method for the calculation of the dead time (tm) in HPLC was evaluated using a computer simulation approach, in which artificial perturbations were introduced to Simulated homolog retention times. The calculation was based on a modified and extended Grobler and Bálisz (GB) method. Investigated wav how the precision of the calculated tM is affected by: statistical fluctuations in retention times and which, and how many homolog retention times are used. Based on these simulations a two‐step procedure for the tM calculation is proposed: In the first step the linearity of log tR, n vs carbon number n is checked using as many homolog retention times as possible. The slope value bo of the first linear regression in the GB method is used for the selection of homolog retention times in the final tM calculation. In the second step the optimal selection of homologs is made and the final tM calculation is carried out. Guidelines for homolog selection are given.
Use of computerized pattern recognition in the analysis of stress induced changes in coffee aroma
Authors: Roberts D. , Bertsch W. 
Published: May 2005

AbstractThe aim of the study was to evaluate changes in the aroma of coffee that has been exposed to heat for some time. Coffee grinds were extracted with water. The coffee was kept hot and sampled periodically using a continuous gas phase extraction method. Gas chromatography/mass spectrometry was used to follow changes in chromatographic profiles. Data were subjected to pattern recognition. About 20 substances were found that significantly changed when exposed to heat.
Sample introduction in high speed capillary gas chromatography; input band width and detection limits
Authors: van Es A. , Janssen J. , Bally R. , Cramers C. , Rijks J. 
Published: May 2005

AbstractThe speed of analysis in capillary gas chromatography can be substantially increased by reduction of the column inner diameter. However, special demands are then posed upon instrumental design. In particular, the sampling system is highly critical because it has to be capable of delivering extremely small injection band widths which must be compatible with the column inside diameter. This study focuses on the evaluation of two potentially suitable sample introduction systems with respect to input band width and detection limits and their compatibility with small bore (≦ 100 μm) columns in capillary gas chromatography. One of them allows liquid on‐column injection, based on liquid splitting, of only a few nl onto small bore (≦ 100 ◂m) fused silica columns. For gases, input band widths as low as 1 ms are obtained with this system. The other one is part of a miniaturized gas chromatograph with extremely low dead volume interfaces and detector volumes. It allows input band widths for gases of a few ms. Without any preconcentration ppm concentrations are measured in gaseous samples with a 80 ◂m thick film capillary column. It will be shown that a further reduction of the minimum detectable amount and analysis time is possible with this equipment.
Concepts and comparisons in multidimensional separation
Authors: Giddings J. C. 
Published: May 2005

AbstractMultidimensional separation methodology provides a mechanism for a very substantial increase in the resolving power of chromatographic and related systems. After defining the conditions required for multidimensional separation and reviewing the origin of its high resolving power, a comparison is drawn between the two principal kinds of multidimensional systems, represented by continuous two‐dimensional operation and coupled column assemblies. It is shown that their roles are complementary. The two‐dimensional system gives a broad powerful overview of a sample while the coupled column system can be used flexibly to magnify and resolve selected regions of the sample space.
Modifications of a commercial thermodesorption unit to obtain more efficient cryotrapping and compatibility with a mass selective detector (HP 5970)
Authors: Schmidbauer N. , Oehme M. 
Published: May 2005

AbstractIncreased O2 content of the carrier gas due to connections which were not diffusion tight and long cooling time of the cryotrap due to insufficient insulation were the main drawbacks of a commercial thermodesorption unit intended for coupling to a GC/ mass selective detector. These shortcomings were overcome by redesigning the cryotrap part and testing different seals for the desorption tube. Furthermore, the modified unit can now be easily mounted on various gas chromatographys without any risk of cold spots in the transfer line. A detailed working description of the modifications is given.