bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular characterization of poly(diisopropyl fumarate) by the absolute calibration method in molecular exclusion chromatography (GPC)
Authors: Cortizo M. S. , Andreetta H. A. , Figini R. V. 
Published: May 2005

AbstractThe present work demonstrates that it is possible to obtain the parameters K and a of the Staudinger‐Mark‐Houwink relationship between the intrinsic viscosity [η] and the molecular weight M of a polymer by applying the absolute method of exclusion chromatography to samples of poly (diisopropyl fumarate). The procedure is based on deducing the relationship between molecular weight and elution volume V from chromatographic runs of a stoichiometrically labeled polymer sample with a broad molecular weight distribution. By using double detection it is possible to obtain the relationship f(V)/h(V) = M(V)/Mn = exp (A‐BV)/Mn where Mn is the osmotically determined number average of the molecular weight of the eluted polymer while f(V) and h(V) are the normalized elution curves obtained by the use of the polymer mass detector and the label detector respectively. A and B are the parameters of the calibration curve, i.e., the relationship between M and V which together with the intrinsic viscosity and the elution curves of several samples of the polymer allows us to obtain the relationship between [η] and M.The results have been verified with chromatographic data through the use of the universal calibration concept.
Optimization of the isocratic non‐aqueous reverse phase (NARP) HPLC separation of trans/cis‐α‐and β‐carotenes
Authors: Lesellier E. , Marty C. , Berset C. , Tchapla A. 
Published: May 2005

AbstractNon‐aqueous reverse phase chromatography was used to optimize the separation of all‐trans‐α‐ and β‐carotenes and their cis isomers extracted from dried carrots. The technique can easily be applied to routine assays. Optimization was carried out by modifying the concentrations of methylene chloride and acetonitrile, and by studying the influence of temperature on the capacity factors and selectivity. The effect of the type of C 18 stationary phase bonding (mono‐ and polyfunctional) on separation was also examined. The need for polymeric bonding on the stationary phase is stressed for the realization of the trans/cis isomer separation.
Gas chromatographic determination of organolead compounds with an alternating current plasma detector
Authors: Costanzo R. B. , Barry E. F. 
Published: May 2005

AbstractThe performance of the gas chromatography/alternating current plasma detector as a selective detector for organolead compounds is investigated. The helium make‐up flow rate and the spatial position from which the lead emission is viewed, have an effect on the detector response. The detection limit for tetrabutyl lead was established as 130 pg/s and the lead selectivity ratio was found to exceed 13,800. Some applications of organolead determination in complex matrices were also studied in order to demonstrate the selectivity and sensitivity of the alternating current plasma detector.
Supercritical fluid extraction of PCBs in tandem with high resolution gas chromatography in environmental analysis
Authors: Onuska F. I. , Terry K. A. 
Published: May 2005

AbstractA simple method has been developed for the direct coupling of supercritical fluid extractions (SFE) with a high resolution gas chromatograph (HRGC) equipped with an electron capture detector (ECD). SFE conditions have been investigated for polychlorinated biphenyls (PCBs) from sediments in terms of mobile phase, entrainer, pressure, temperature, and mass‐flow through the extractor. Dynamic leaching and static steady‐state extractions were compared. Extraction efficiencies of up to 100% in less than 15 minutes have been obtained. The extracted PCBs are quantitatively transferred into a fused silica open tubular column (OTC). Determination of PCBs was tested on certified sediment from National Water Research Institute and the results agreed well with certified values.
The use of solid sorbents for direct accumulation of organic compounds from water matrices–a review of solid‐phase extraction techniques
Authors: Liška I. , Krupčíik J. , Leclercq P. A. 
Published: May 2005

AbstractThe main principles of solid‐phase extraction techniques are reviewed in this paper. Various solid sorbents can be used as a suitable trap for direct accumulation of organic compounds from aqueous solutions. The trapped analytes can be desorbed by elution with suitably chosen liquid phases. These preconcentration procedures can be considered as low performance liquid chromatography and the efficiency of the procedure can thus be related to the retention characteristics of the preconcentration column. The main sorbents used for trace enrichment purposes are also reviewed. Besides, the concise methodology, sample storage, and automation are discussed. The advantages of solid phase extraction as compared to liquid‐liquid extraction are given as well as some drawbacks of this method.
Partially concurrent eluent evaporation with an early vapor exit; detection of food irradiation through coupled LC‐GC analysis of the fat
Authors: Biedermann Maurus , Grob Konrad , Meier Werner 
Published: May 2005

AbstractThis paper reports two subjects. It describes LC‐GC transfer by partially concurrent eluent evaporation at a greatly accelerated rate, as required for optimal compatibility with 2–3 mm i.d. LC columns and LC flow rates up to some 500 μl/min. Evaporation rates around 200 μl/min were obtained using a 0.53 mm. i.d. uncoated pre‐column and an early vapor exit. A stationary‐phasecoated “retaining” pre‐column was used for preventing escape of volatile solutes through the vapor exit.The technique was used for the detection of food irradiation by analyzing selected radiolysis products of triglycerides, namely alkanes/alkanes and aldehydes. Extracted fat of chicken, hazel‐nuts, and soup mixes was injected in LO and the relevant fractions were transferred on‐line to GC. For chicken and nuts, detection of irradiation was possible down to doses below 0.5 kGy. Detection limits were higher for soup mixes due to interfering peaks.
The role of adsorption phenomena in capillary gas‐liquid‐solid chromatography
Authors: Berezkin V. G. , Korolev A. A. 
Published: May 2005

AbstractThe method of invariant relative retention value determination using commerciallly produced fused silica open‐tubular columns with different contents of stationary liquid phase has been tested. Invariant retention values are determined only by interaction of analyzed compound with stationary liquid phase and are independent of the adsorptive interactions in the studied system.
Chromatographic properties of various polysiloxane stationary phases for separation of 2,3,7,8–chloro‐substituted dibenzo‐p‐dioxin and dibenzofuran isomers–a systematic comparison
Authors: Schmid P. 
Published: May 2005

AbstractGlass capillaries coated with four crosslinked and surface‐bonded OH‐terminated polysiloxanes [PS 347.5, OV‐17‐OH, OV‐225‐OH, and OV‐240‐OH] were compared with commonly used methyl‐terminated SP‐2330‐coated columns with respect to their selectivity for the separation of 2,3,7,8‐chloro‐substituted dibenzo‐p‐dioxins and dibenzofurans. The methyl‐ and phenyl‐substituted phases [PS 347.5 and OV‐17‐OH] exhibit only moderate isomer selectivity which limits their applicability in this field. The examined 3‐cyanopropyl‐substituted phases [OV‐225‐OH, OV‐240‐OH, and SP‐2330] allow complete separation of all 2,3,7,8‐chlorosubstituted PCDDs and PCDFs. With SP‐2330 longer columns are required (50 m) for baseline separation of critical groups of isomers. OV‐225‐OH was found to be the most suitable phase as to isomer selectivity. In comparison to SP‐2330, the analysis times can be reduced by a factor of two.
Some applications of multidimensional gas chromatography to the enrichment of minor components in essential oil analysis
Authors: Bicchi C. , D'Amato A. , Frattini C. , Nano G. M. , Pisciotta A. 
Published: May 2005

AbstractThe use of multidimensional gas chromatography (MDGC) for the analysis of essential oils is gaining in importance. A rarely used application consists in the enrichment of minor components through a MDGC system provided with a cold trap between trap column and analytical column. Under suitable conditions, in fact, the cold‐trap can store a trapped compound (or a fraction) for a long time. Consequently, the same fraction can be heart‐cut from several successive chromatographic runs on the first column and stored together in order to accumulate trace compounds; afterwards the accumulated fraction can be injected in the analytical column. The possibilities of this technique will illustrated through some examples of analysis of complex essential oils.
Coupled LC‐GC: Evaporation rates for partially concurrent eluent evaporation using an early solvent vapor exit
Authors: Schmarr Hans‐Georg , Mosandl Armin , Grob Konrad 
Published: May 2005

AbstractPartially concurrent eluent evaporation presupposes an eluent evaporation rate in the GC pre‐column that approaches the LC flow rate. Discharging the vapors through the whole GC column, evaporation rates reach 10–30 μl/min, i.e. are suitable just for LC flow rates typical for packed capillary LC columns. With an early vapor exit, evaporation rates are increased to 100–200 μl/min (under extreme conditions to some 800 μl/min), thus fitting the LC flow rates of 2 mm i.d. columns.Evaporation rates were measured for a standard set of pre‐columns and conditions. The dependence of the evaporation rate on temperature, inlet pressure, carrier gas, and internal diameter of the retaining pre‐column are discussed in order to allow the design of a GC system producing a desired evaporation rate.
Solventless injecction for packed column supercritical fluid chromatography
Authors: Dean T. A. , Poole C. F. 
Published: May 2005

AbstractThe adverse effects of injection solvent strength on microbore packed column SFC band broadening are demonstrated and a solventless injection system that eliminates these effects is introduced. The injection system removes solvent in a GC‐like manner using a retention gap and an on‐column capillary GC syringe. The analyte is delivered to the analytical column in a solvent‐free plug of supercritical fluid mobile phase.
Some design considerations in miniaturized electrokinetic separation systems
Authors: Jansson M. , Emmer Å. , Roeraade J. 
Published: May 2005

AbstractThere is a great potential for miniaturized analytical separation systems, e.g. in process control, environmental monitoring, or clinical chemistry. Particularly, miniaturized electro‐driven systems open many new possibilities. Most efforts in this area have been focused on cylindrical capillary columns. In the present paper, thin rectangular conduits are considered and comparisons with cylindrical tubes are made on the basis of theoretical models. A critical and limiting factor in electro‐driven separations is the generation of heat. For a given cross‐section, heat dissipation is more efficient in rectangular columns. Silicon is proposed as column material. Apart from the better thermal conductivity, monocrystalline silicon can be machined with an extraordinary precision when selective chemical etching procedures are employed. This precision is of central importance in the development of miniaturized high performance systems.
The effect of the Knox‐Parcher ratio in microcolumn LC
Authors: Wilson W. H. , McNair H. M. , Maa Y. F. , Hyver K. J. 
Published: May 2005

AbstractThe effect of the column diameter to particle diameter ratio (the Knox‐Parcher ratio, designated ϱ) on reduced plate height (h) is examined. The mean diameters of spherical and irregular particles are varied while the column diameter is fixed at 530 μm. For spherical particles a transition in the h versus ϱ plot is observed as in the previous studies.
Analysis of coal tar polycyclic aromatic hydrocarbon LC‐fractions by capillary SFC on a liquid crystalline stationary phase
Authors: Kithinji J. P. , Raynor M. W. , Egia B. , Davies I. L. , Bartle K. D. , Clifford A. A. 
Published: May 2005

AbstractSupercritical fluid chromatography (SFC) on a capillary column coated with a smectic mesomorphic crystalline phase is shown to exhibit a typical turnover effect (retention versus column temperature) for polycyclic aromatic hydrocarbons (PAHs) at lower temperatures than are found on a methylpolysiloxane phase. Liquid chromatography is used to separate various fractions from a coal tar, which are analyzed by high resolution capillary SFC. Different density and temperature programs were investigated to optimize the separations. Simultaneous density and temperature programs gave the best results, and this is thought to be due to increased solute diffusion coefficients which yield highly efficient separations for the high molecular weight polycyclic aromatic hydrocarbons. The separation mechanism is based on the shape of the liquid crystalline phase, solubility, volatility, and molecular geometry of the PAHs.
Coupling of high temperature glass capillary columns to a mass spectrometer. GC/MS analysis of metalloporphyrins from Julia Creek oil shale samples
Authors: Blum Wolfgang , Ramstein Philippe , Eglinton Geoffrey 
Published: May 2005

AbstractThis paper reports on the instrumental and experimental prerequisites of the combination of high temperature gas chromatography (HTGC) with electron impact‐ (El) and chemical ionization (Cl) mass spectrometry (HTGC/EI/CIMS). It describes a newly developed high temperature GC/MS interface in detail and discusses the particular problems arising in HTGC/MS. The capabilities of the system are demonstrated by direct analyses of nickel‐ and vanadyl porphyrins, extracted from Julia Creek oil shale. The use of CI/NH3 in the GC/MS analysis of metalloporphyrins is demonstrated for the first time.
Determination of residual solvents and reagents in X‐ray contrast media by automatic static headspace capillary gas chromatography
Authors: Evje Dag M. , Figenschou Erik , Langseth‐Manrique Karina 
Published: May 2005

AbstractA specific, sensitive, and simple method for the quantitation of residual methanol, 2‐propanol, 2‐butanol, 2‐methoxy‐1‐ethanol, 1‐chloro‐3‐methoxy‐2‐propanol, 3‐chloro‐2‐methoxy‐1‐propanol, and 1,3‐dimethoxy‐2‐propanol in two non‐ionic X‐ray contrast media, has been developed. The headspace of a 25 % w/V aqueous solution of contrast media, obtained at 90–110°C in 15 min, was injected onto a capillary column coated with cyanopropyl, phenyl, dimethylpolysiloxane polymer. The internal standards used were 2‐pentanol and 3‐methoxy‐1‐butanol. The limits of detection were below 5 μg/g. The repeatability of the method at 50 μg/g of each solvent was below 5 %; and at 100 μg/g of the methoxypropanol compounds and 2‐methoxy‐1‐ethanol, below 10 % (RSD, N = 5).
Effect of enthalpy on structure‐relation correlation in capillary gas chromatography
Authors: Hanai Toshihiko 
Published: May 2005

AbstractThe retention times of 24 alkanes, 11 olefins, 17 alkyl alcohols, 30 fatty acid methyl esters, and 8 polyaromatic hydrocarbons were measured on two non‐polar and two polar capillary columns at different temperatures. The enthalpy of these compounds was calculated from the Van't Hoff plot.The log k′s and enthalpies of each group of compounds showed individual linear relations. The relation of the enthalpy and Van der Waals volume was similar to that of log k′ and Van der Waals volume, and differed from that of their log k′ and boiling point. Enthalpy thus indicates selectivity of columns.
Optimization of selectivity by tuning column temperatures for series‐coupled columns in a dual‐oven GC system
Authors: Repka Dušan , Krupčík Jan , Benická Eva , Maurer Thorsten , Engewald Werner 
Published: May 2005

AbstractAn improved optimization criterion has been introduced for computer assisted optimization of selectivity of two different capillary columns coupled in series and placed in two independently heated ovens. The suitability of this criterion, which incorporates the change of resolution power with the change of working conditions, has been verified by simultaneously tuning the temperatures of two columns differing in retention mechanism for separation of isomeric branched C8 hydrocarbons.
Automatic sugar analysis in the beet industry. Part II: Apparatus and results
Authors: Morin‐Allory Luc , Herbreteau Bernard , Lafosse Michel , Dreux Michel 
Published: May 2005

AbstractSugar analysis in the beet industry presents some difficulties due to the highly complex composition of the raw products. This is particularly important in molasses, which contains a considerable ionic component. However, precise determination of raffinose concentration is necessary to optimize the crystallization process. Purification of raw products on mixed‐bed ion exchangers followed by passage through a ODS precolumn is performed before the actual chromatographic step. These steps must be automated in order to improve precision and productivity. A completely automatic system, designed for maximum stability of chromatographic columns and good analytical precision of results is presented.
Fused silica substrate effects on capillary column performance
Authors: Broske Alan D. 
Published: May 2005

AbstractThe effect of a pretreatment step on the polarity of fused silica capillary tubing prior to coating was evaluated. Columns were tested prior to and after coating with a 50% phenl stationary phase, and the chromatographic findings were compared. The results confirmed that the polarity of the fused silica substrate affects the inertness and reproducibility of the final coated columns.
CGC using a programmable electronic pressure controller
Authors: Hermann Bruce W. , Freed Lesley M. , Thompson Michael Q. , Phillips R. John , Klein Ken J. , Snyder W. Dale 
Published: May 2005

AbstractCapillary gas chromatographic separations were performed with an electronic pressure control system developed to provide precise closed‐loop control of inlet pressure through the use of a solid state micro‐machined pressure sensor and electronically controlled proportional valve. The closed‐loop control of the electronic system provided better precision than the open‐loop control achieved by manual pressure regulation. Closed‐loop control can perform pressure programming, which can be combined with temperature programming to optimize separations. The pressure sensor monitors the integrity of the flow system and singals the controller to reduce flow in the presence of a sudden loss of system pressure.
Gradient separation of pharmaceuticals employing supercritical CO2 and modifiers
Authors: Mulcahey Leah J. , Taylor Larry T. 
Published: May 2005

AbstractSub‐ and Supercritical Fluid Chromatography (SFC) were used to separate seven purine and pyrimidine‐based drugs. A two‐pump system was used, where one pump delivered the carbon dioxide, and the other pump delivered modifier. The modifiers used in this work were methanol, and methanol containing 0.001 M tetrabutylammonium hydroxide. Two of the compounds studied were hydrochloride salts. These compounds were analyzed by a Supercritical Fluid Extraction (SFE)/SFC method.
Influence of the siliceous support structure on the coverage density of the chemically bonded phase
Authors: Buszewski Bogusław 
Published: May 2005

AbstractTwo different types of silica support, viz. silica gel and porous glass, have been modified by mono‐ and difunctional octade‐cylsilane. The resulting materials were characterized by physicochemical and chromatographic methods. Special attention was paid to the influence of the siliceous support structure and coverage density of chemically bonded phases on the retention data.
Column selection and optimization for sulfur compound analyses by gas chromatography
Authors: Hutte Richard S. , Johansen Neil G. , Legier Marianne F. 
Published: May 2005

AbstractThe analysis of sulfur‐containing compounds using fused silica capillary columns and the Sulfur Chemiluminescence Detector has been investigated. This combination of an inert chromatographic system and a high sensitivity, selective detector provides significant advantages for the analysis of low levels of sulfur compounds in complex matrices over existing techniques. Capillary columns coated with thick films (1–4 μm) of methyl silicone stationary phase permit separation of most sulfur containing compounds and, when used with sub‐ambient column temperatures, these columns can be used for the separation of sulfur gases. The effects of stationary film thickness, column length, and internal diameter for the measurement of sulfur compounds in hydrocarbon matrices has been determined.
At‐column injector for capillary GC — design and evaluation
Authors: Hagman Gunnar , Roeraade Johan 
Published: May 2005

AbstractThe present paper describes constructional details and evaluations of an at‐column injector for capillary GC. Injections were made via a sample loop on a 0.32 mm i.d. capillary column. Two rotary valves were employed to allow a wash of the sample loop and a backflush of the transfer line. Repeatability, calculated from absolute area counts for n‐alkanes was between 0.3–1% RSD, for injected sample volumes between 5 and 100 μl. Promising results were also obtained with syringe‐based injections on narrow bore (100 μ i.d.) columns. Repeatability on the basis of normalized area counts was in the order of 0.1–0.2% RSD, while solvent tailing was practically absent.
Coupled LC‐GC: A new method for the on‐line analysis of organochlorine pesticide residues in fat
Authors: Barcarolo Roberto 
Published: May 2005

AbstractThis paper describes the use of coupled LC‐GC for the determination of organochlorine pesticide residues in fat samples. Organochlorine pesticide residues are preseparated from fat by LC on a short C‐18 column using an organic solvent as the mobile phase. Evaporation of the LC eluent is achieved by a modified on‐column interface, introducing an on‐line vaporizer module using the fully concurrent evaporation technique.
Gas chromatography of hydrocarbons using packed liquid chromatographic capillary columns
Authors: Takeuchi Toyohide , Watanabe Mototada , Hamanaka Tadashi , Haraguchi Hiroki , Ishii Daido 
Published: May 2005

AbstractCapillary columns of 0.3‐0.5 mm i.d. packed with 3‐ to 30‐μm silica‐based stationary phases for liquid chromatography were used for gas chromatographic separation of hydrocarbons. Column efficiencies were evaluated for various commercially available packing material. The best column efficiency was achieved with 5‐μm octadecyl group bonded silica gel, the surface of which was coated with a poly (dimethylsiloxane) film. The 30‐cm column produced 11,000 theoretical plates.
Introduction of large sample volumes in capillary supercritical fluid chromatography
Authors: Hirata Yukio , Koshiba Hisato , Maeda Tsuneaki 
Published: May 2005

AbstractA splitless injection method using make‐up flow was developed for SFC. Dilution of sample solvent with carbon dioxide mobile phase was very effective for focusing the solutes onto the column. Injection of a 4.5‐μl sample volume on a 100‐μm i.d. capillary column became possible.
Production of polyacrylamide gel filled capillaries for capillary gel electrophoresis (CGE): Influence of capillary surface pretreatment on performance and stability
Authors: Yin Hong‐Feng , Lux Jürgen A. , Schomburg Gerhard 
Published: May 2005

AbstractPolyacrylamide gel filled capillaries for electrophoresis can be improved in performance and stability by a specially optimized and reproducible production procedure. After surface pretreatment as described in this contribution, gels polymerized in capillaries are stable for long series of routine separations. Bubbles formation during gel polymerization can be avoided. The procedure is compared with those described by other authors. Separations of different oligonucleotide samples illustrate the quality of the gel capillaries obtained. The peak symmetry achieved proved to be better than that obtained without surface pretreatment.