bluuebunny/crossref_metadata_2025 huggingface dataset:
Capturing of volatiles emitted by living plants by means of thick film open tubular traps
Authors: Bicchi C. , D'Amato A. , David F. , Sandra P.
Published: May 2005

Fused silica open tubular traps coated with a 15μm film of methyl silicone have been successfully applied to capture volatiles emitted by living plants. The atmosphere surrounding the plants is sucked through the trap where the volatiles are retained. After sampling, the trap is installed as pre‐column in a multidimensional CGC system. The volatiles are thermally desorbed, reconcentrated in a cold trap and analyzed on‐line on the analytical capillary column.
The solvent venting injection technique in capillary supercritical fluid chromatography
Authors: Berg B. E. , Greibrokk T.
Published: May 2005

A solvent venting technique for injection of volumes up to 1 μl on 50 μm i.d. SFC columns has been compared to direct injection methods. The peak broadening and peak splitting observed with direct injection have been examined and found to be related to the starting pressure, the column temperature, and the sample solvent, in addition to the sample volume. The solvent venting technique removed peak splitting and improved the column efficiency. With a proper selection of experimental conditions, the sample recovery was 100%. The major part of the solvent was eluted in 15–20 s. Several applications have been demonstrated.
Structure‐retention correlation in CGC
Authors: Hanai Toshihiko , Hong Cai
Published: May 2005

The retention time of 24 alkanes (Al‐Al), 11 olefins (OI), 17 alkyl alcohols (Al‐OH), 30 fatty acid methyl esters (FA) and 8 polyaromatic hydrocarbons (PAH) was measured on non‐polar CP‐Sil‐5 and DB‐1 and polar CP‐WAX‐52 and DB‐WAX capillary columns at different temperatures.

The correlation coefficients of the capacity ratios of each group of compounds and that of all the compounds together was excellent; however, there was some selectivity of different types of compounds when their capacity ratios were correlated with their Van der Waals volumes. The elution order of these compounds was Al‐Al < OI < FA < Al‐OH < PAH on both non‐polar columns, while the retention of PAH was greater on the DB‐1 column and those of other compounds were greater on the CP‐Sil‐5‐column. Such selectivity was significant on polar columns.

Further, the energy effect, which was used to make a retention index system in liquid chromatography, was obtained from their capacity ratios to make a retention index system for capillary column gas chromatography. The values of the energy effect of each group of compounds were quite constant compared to the values obtained in liquid chromatography. The selectivity of these capillary columns was further discussed from their capacity ratios, their Kováts retention indices, and their energy effect to make a prediction of retention time.
Supercritical fluid extraction of 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin from sediment samples
Authors: Onuska F. I. , Terry K. A.
Published: May 2005

Supercritical fluid extraction (SFE) is a promising technique for the extraction of 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (2,3,7,8‐TCDD) from environmental matrices such as contaminated sediments. The ability of SFE to solubilize many organic contaminants is well documented in industrial processes but its analytical applications were exploited just recently. In this study supercritical carbon dioxide and nitrous oxide and their mixtures with 2% methanol were used to extract 2,3,7,8‐TCDD from aquatic sediments. An attractive feature of this process is that the carbon dioxide, being a virtually inert fluid, leaves no solvent residue on the processed sediment. Almost 100% of the 2,3,7,8‐TCDD can be extracted from a sediment spiked with 200 μg/kg 2,3,7,8‐TCDD in 30 minutes by using supercritical carbon dioxide + 2% methanol. Cleanup procedure is compared with the Soxhlet extraction procedure currently used as a standard method for extracting dioxins from sediment samples.
Group‐type fractionation of petroleum and alternative fuels by column liquid chromatography
Authors: Lanças F. M. , Carrilho E. , Deane G. H. N. , Camilo M. C. F.
Published: May 2005

The present paper introduces an instrumental procedure based on column liquid chromatography for the total analysis of petroleum heavy ends and similar samples. The procedure avoids the precipitation of asphaltenes and asphaltols. One sequence of eluents fractionates the sample into 8 fractions: 5 non‐polar (hydrocarbons), one intermediate (resins), and 2 polar fractions (asphaltenes and asphaltols).

Quantitative results from gravimetric measurements and UV‐Vis and FTIR spectra of fractions obtained from petroleum heavy ends are presented, as well as those from GC/MS data obtained from one fraction obtained from liquefaction of biomass. The method presented is easy to set up and operate, requires minimum operator attention, is reliable (no precipitation), reproducible, and inexpensive.
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

The 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

Non‐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

The 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

A 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

The 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

This 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

The 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

Glass 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

The 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

Partially 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

The 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

There 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

The 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

Supercritical 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

This 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

A 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

The 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.
Supercritical fluid extraction strategies of aqueous based matrices
Authors: Hedrick Joseph L. , Taylor Larry T.
Published: May 2005

Liquid‐liquid extraction employing supercritical carbon dioxide has been developed for removal of polar materials from water.
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

An 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

Sugar 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

The 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

Capillary 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

Sub‐ 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

Two 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

The 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

The 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

This 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

Capillary 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

A 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

Polyacrylamide 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.
Fast esterification of fatty acids with alkyl chloroformates. Optimization and application in gas chromatography
Authors: Hušek Petr , Rijks Jacques A. , Leclercq Piet A. , Cramers Carl A.
Published: May 2005

Alkyl chloroformates with methyl, ethyl, and 2‐chloroethyl substituents can instantaneously esterify fatty acids under proper reaction conditions. Apart from the formation of the corresponding alkyl esters, even the alkoxycarbonyl esters can be prepared. These derivatives are useful for the analysis of short‐chain fatty acids. As alkoxycarbonyl ester, even acetic acid can already be separated from the solvent peak. The reaction conditions were examined, and the Influence of solvent polarity and reagent concentration on the conversion was studied. Quantitative conversion of acids to their easters was achieved in non‐aqueous solutions, but even in the presence of water the yields were acceptable.
Determination of planar chlorobiphenyls in animal fat
Authors: Th. Tuinstra L. G. M. , van Rhijn J. A. , Roos A. H. , Traag W. A. , van Mazijk R. J. , Kolkman P. J. W.
Published: May 2005

The occurrence of the highly toxic non‐ortho substituted (planar) chlorobiphenyls (CBs) at low levels in wildlife, (human) fat, and fish generates the need for a routine analytical procedure. The use of a fully automated system for the separation of planar and non‐planar CBs, consisting of a gel permeation chromatography system, a sample preparation system employing extraction columns, and a porous graphitic carbon HPLC column is described, and tested with horse fat. Gas chromatography on capillary columns, with electron‐capture or high resolution mass spectrometric detection, is used for quantitation of the CBs.
Preparation of thermally stable phenylpolysiloxane fused silica capillary columns. Optimization and evaluation of the deactivation by capillary GC and solid state 29Si NMR
Authors: Wu Q. , Hetem M. , Cramers Carel A. , Rijks Jacques A.
Published: May 2005

The deactivation of fused silica capillary columns with a laboratory‐made poly‐diphenylvinylmethylhydrosiloxane copolymer has been investigated. The deactivation obtained at different temperatures and reaction times is characterized with a dual column capillary GC system [1]. In parallel, the effect of the silylation temperatures and reaction times on the nature, the structure, and the chemical properties of the deactivation layer has also been studied by solid‐state 29Si NMR spoctroscopy. A fumed silica, Cab‐O‐Sil M5, was used as a model substrate for these spectroscopic studies.

The deactivated fused silica capillaries show an excellent thermal stability (up to 400°C), a high resistance to solvolysis, and a minimal interaction to various critical test components. A good wettability of the fused silica capillary columns deactivated with this reagent was confirmed by successful subsequent coating with polysiloxanes with different phenyl contents.
Improved analysis by liquid chromatography of iso‐alpha acids
Authors: Verzele M. , Steenbeke G. , Verhagen L. C. , Strating J.
Published: May 2005

This paper shows that the liquid chromatography (LC) methods so far described in the literature for iso‐alpha acids analysis are unsatisfactory. The main reasons for this are the failure of the advocated eluent systems to completely suppress trace metal activity of commercial LC columns and the lack of a stable reference iso‐alpha acid.

The trace metal problem can be solved by using a column packing material specifically designed for “Hop Acid” analysis and by adding ethylenediaminetetraacetate (EDTA) to the eluent. The reference problem is more difficult, but possibly a formulation of the iso‐alpha acids in their acid form may be the answer.

Chromatographic conditions changing the elution pattern of the individual iso‐alpha acids are studied. This leads to better control of their co‐elution in the analytical procedure.
Trace analysis of agrochemicals by supercritical fluid chromatography
Authors: Ashraf Sameena , Bartle Keith D. , Clifford Anthony A. , Moulder Robert
Published: May 2005

Capillary supercritical fluid chromatography was performed using solvent‐vented injection in conjunction with a thermionic ionization detector. Mixtures of organo‐nitrogen and phosphorus containing agrochemicals were chromatographed and detection of low picogram quantities was observed.
LC‐GC analysis of the aromatics in a mineral oil fraction: Batching oil for jute bags
Authors: Grob Konrad , Biedermann Maurus , Caramaschi Adrian , Pacciarelli Bruno
Published: May 2005

Aromatics of a C15C30 mineral oil fraction, the “batching oil” used for producing jute fabrics, were analyzed for estimating the toxicity of oil transferred from jute bags to foods. Group‐type pre‐separation according to ring systems occurred on a LC NH2 column with pentane and small additions of methanol as eluent. LC fractions were characterized by LC‐GC‐MS and quantitated by LC‐GC‐FID. The oil contained 23% aromatics and 1% “polars”; some 99.5% of the aromatics were alkylated.
TEM study on the pore structures of wide‐pore silica and polymer gels
Authors: Tanaka Nobuo , Kimata Kazuhiro , Hosoya Ken , Araki Takeo , Tsuchiya Hajime , Hashizume Katsushi
Published: May 2005

Internal structures of wide‐pore packing materials for HPLC were studied by transmission electron microscopy (TEM). TEM gave information about the size, shape, and location of the pores as well as the size of primary structures in corpuscular systems. Visualization of the three dimensional internal structures of wide‐pore materials was attempted by scanning the TEM photographs with a densitometer.
Band broadening evaluation by back‐and‐forth capillary electrophoresis
Authors: Terabe Shigeru , Shibata Osamu , Isemura Tsuguhide
Published: May 2005

The purpose of this study is to develop a method for precise evaluation of band broadening in capillary electrophoresis. A capillary electrophoresis system with on‐column twin detectors is constructed. Back‐and‐forth electrophoresis permits zones to make a round trip between the twin detectors placed at distant positions on the capillary. The system is capable of eliminating extra‐column effects and discriminating between reversible and irreversible band‐broadening mechanisms.
Development of a curie‐point headspace sampler for capillary gas chromatography
Authors: Oguri Naoki , Onishi Akira , Hanai Toshihiko
Published: May 2005

A Curie‐point headspace sampler (CPHS) equipped with a purge and trap sampler has been developed for use with capillary gas chromatography. The new system can handle a variety of samples, including gases, liquids, and solids, and can also be used as a pyrolyzer.
Approaches to dioxin analysis by HRGC‐HRMS and hybrid HRGC‐MS‐MS
Authors: Iida Junko , Takeda Takehiro , Takasuga Takumi , Moncur John , Ireland Phil , Wright Barry
Published: May 2005

A hybrid mass spectrometer with an EBQQ configuration was used to investigate two approaches to trace dioxin analysis: high resolution gas chromatography – high resolution mass spectrometry (HRGC‐HRMS) and high resolution gas chromatography – mass spectrometry – mass spectrometry (HRGC‐MS‐MS). It is shown that selected ion monitoring (SIM) HRGC‐HRMS exhibits better selectivity for dioxins separated on a cyanopropyl column than is otherwise obtained under medium resolution mass spectrometry (3,000 resolution), while optimization of conditions for HRGC‐MS‐MS allowed the observation of 350 femtograms of the highly toxic 2,3,7,8‐TCDF at a S/N ratio of 5:1. Both methods were applied to environmental samples with good results.
A unified approach to the chromatography‐FTIR interface: GC‐FTIR, SFC‐FTIR, and HPLC‐FTIR with subnanogram detection limits
Authors: Norton Kelly L. , Lange Andrew J. , Griffiths Peter R.
Published: May 2005

The results described in this paper demonstrate that Identifiable FTIR spectra of components separated by gas, supercritical fluid, and liquid chromatography can be measured in real time using a common approach. The sensitivity of each Interface is comparable with that obtained by interfacing the corresponding technique with a bench‐top mass spectrometer. The combination of these two spectroscopic techniques should lead to an even more powerful means of Identification of volatile, semi‐volatile, and non‐volatile components of mixtures.
Sample decomposition in an electrically heated cold‐trap inlet system for high speed gas chromatography
Authors: Klemp Mark , Sacks Richard
Published: May 2005

Thermal decomposition of some hydrocarbon and chlorinated hydrocarbon compounds in metal capillary tubes used in an inlet system for high speed gas chromatography has been investigated. The metal tube is cooled to about −75°C by a flow of cold nitrogen gas in order to focus a vapor sample cryogenically. A capacitive discharge power supply is then used to heat the metal tube resistively in order to revaporize the sample and introduce it to the separation column as a plug 5‐10 ms wide. The effects of tube temperature, tube material, sample vapor residence time, and type of carrier gas on thermal cracking are described. Use of a copper‐nickel alloy tube resulted in less cracking than either pure platinum or pure nickel. Cracking is more significant with hydrogen as carrier gas than with helium. Cracking also increases with increasing sample residence time in the hot tube. Quantitative sample injection with minimum decomposition can be obtained for a variety of aliphatic and aromatic hydrocarbons and chlorinated hydrocarbon compounds.
A comparative study of the gas chromatographic behavior of liquid crystals and polyester stationary phases using paraffinic hydrocarbons as standards
Authors: Habboush Albertine E. , Farroha Sabri M. , Kreishan Abdul‐Latif Y.
Published: May 2005

Two new categories of stationary phase have been studied: liquid crystals and polyesters. The liquid crystals were p,p′‐azoxyphenetol, p(n‐hexyloxy)phenyl‐p′‐methoxy benzoate, and p‐pentyloxy‐p′‐ethoxyazoxybenzene; and the polyester phases 1,4‐butanediol succinate (LAC‐860), ethylene glycol succinate (LAC‐886), diethylene glycol succinate (LAC‐738), diethylene glycol adipate (LAC‐296), and neopentyl glycol adipate (LAC‐769).

Abnormal chromatographic behavior, has been observed: an increase in specific retention volumes and an improvement in the separation of normal, branched, and cycloparaffins, depending on their structures, at high temperatures within a specified range. This phenomenon is the opposite of the behavior of traditional stationary phases. From the chromatograms obtained, plots of log v against 1/T, and differential thermal analysis it is concluded that this abnormal behavior may be attributed to the penetration of solutes through the ordered structure of the mesophase and the rod‐like molecules of the polyesters. Furthermore, the chromatographic behavior of some of the polyester (LAC‐series) stationary phases in respect of temperature changes is similar to that of the nematic mesophases.
Permethylated cyclodextrins in the GC separation of racemic mixtures of volatiles: Part 1
Authors: Bicchi Carlo , Artuffo Giuseppe , D'Amato Angela , Nano Gian Mario , Galli Anna , Galli Mario
Published: May 2005

The chromatographic separation of racemic mixtures of volatile compounds by 2,3,6‐trimethyl‐α‐, β‐ and γ‐cyclodextrins is discussed. Columns were prepared by mixing the derivatized cyclodextrin with OV‐1701 or hydroxy‐terminated OV‐1701 (OV‐1701‐OH) following Schurig's method [1]. About 130 racemates with widely differing structures were used to test the performances of 2,3,6‐permethylated‐α, β‐ and, γ‐cyclodextrins mixed with the polysiloxane polymers in different ratios. The influence of the different types of cyclodextrin on racemate separation is shown, and some phenomena which might be helpful in the elucidation of the chromatographic behavior involved are also described. The influence both of the percentage of cyclodextrin in the polysiloxane, and of the operating conditions (carrier gas, flow rate, and temperature) in the separation of flavor and fragrance racemates is also evaluated.
Density of methanol‐carbon dioxide mixtures at three temperatures: Comparison with vapor‐liquid equilibria measurements and results obtained from chromatography
Authors: Berger Terry A.
Published: May 2005

The density of methanol‐carbon dioxide mixtures has been measured at 40, 50, and 60°C and the data presented as constant density curves in plots of pressure against composition. Mixtures containing from 1 to 23.5% methanol were covered. The density information was compared with liquid‐vapor equilibria data from the literature and with results from chromatographic separations using both sub‐ and supercritical conditions. The results indicate that phase transitions do not usually occur when the concentration of the modifier is increased while holding temperature and pressure constant. Similarly, no phase transition occurs when the temperature is increased from 28 to 80°C, at a constant (high) pressure and modifier concentration.

Binary fluids with many desirable compositions cannot be prepared at low densities: densities below 0.4–0.5 g/cm3 cannot be obtained from methanol‐carbon dioxide mixtures because the fluids separate into two phases. This means that density programming with many binary fluid combinations will be of secondary importance compared with composition programming.
Supercritical fluid chromatographic separation of polychlorinated biphenyls (PCBs) using a negative temperature gradient for density programming
Authors: Cammann Karl , Kleiböhmer Wolfgang
Published: May 2005

The technical PCB mixtures Aroclol and Clophen have been analyzed by packed column supercritical fluid chromatography using negative temperature programming. The chromatographic method was successfully applied to the analysis of PCBs, polycyclic aromatic hydrocarbons, and polychlorinated dibenzo‐p‐dioxins in extracts from environmental matrices.
Pyrolysis – capillary gas chromatography combined with on‐line alkylation for the compositional analysis of liquid crystalline aromatic polyesters
Authors: Ohtani Hajime , Fujii Ryuichi , Tsuge Shin
Published: May 2005

Pyrolysis–capillary gas chromatography combined with on‐line alkylation has been employed for compositional analysis of liquid crystalline aromatic polyesters (LCPs) based on p‐ hydroxybenzoic acid. The fundamental conditions were examined using an LCP prepared from p‐hydroxybenzoic acid, terephthalic acid, and 4,4′‐biphenol and every constituent of a sample weighing ca. 50 μg was almost quantitatively recovered as its dimethyl derivative in the pyrogram obtained following pyrolysis at 400°C in the presence of 1 μl of 25% tetramethyl‐ammonium hydroxide in methanol. The compositions of a variety of terpolyesters and LCPs containing isophthalic acid or 2‐hydroxy‐6‐naphthoic acid units have been precisely deter‐mined by pyrolysis‐methylation GC.
Towards on‐line SEC‐GC of pesticide residues? The problem of tailing triglyceride peaks
Authors: Grob Konrad , Kälin Iren
Published: May 2005

SEC is used for clean‐up of food extracts obtained for analysis of pesticide residues primarily to remove high molecular weight material, among which fat may be present at the largest concentrations. The triglyceride peak, which is usually very large, is eluted before the components of interest. The problem described in this paper deals with the tail of the triglyceride peak: this may intrude into the fraction containing the pesticides and contaminate the GC.
Clean‐up of some organochlorine and pyrethroid insecticides by automated solid‐phase extraction cartridges coupled to capillary GC‐ECD
Authors: van der Hoff G. René , Gort Steven M. , Baumann Robert A. , Van Zoonen Piet , Brinkman Udo A. Th.
Published: May 2005

The ASPEC (Automatic Sample Preparation with Extraction Columns) system has been coupled on‐line to capillary GC‐ECD by means of a loop‐type interface equipped with a solvent vapour exit. Both ASPEC and GC conditions have been optimized leading to an effective clean‐up of the extracts analyzed.

By means of solid‐phase extraction cartridges filled with silica, it has been possible to analyze concentrated surface water extracts for a group of 18 electron‐capturing compounds present in the water at ppt levels. ASPEC‐GC has also been applied to the determination of synthetic pyrethroids at ppt levels in surface water.

The complete analytical procedure is greatly facilitated by automation and miniaturization. Miniaturization results in a considerable decrease in the sample volume required. The potential of the method for the analysis of other pesticides is estimated.
The automated determination of volatile organic contaminants in ambient air and/or soil gas by gas chromatography with selective detectors
Authors: Kirshen Norman , Almasi Elizabeth
Published: May 2005

Two systems have been developed which are suitable for the determination of sub parts per billion levels of organic contaminants in ambient air and soil gas. Gas samples are passed through an adsorbent where the contaminants are trapped. Following thermal desorption the contaminants are quantitated by capillary GC employing photoionizations electrolytic conductivity, and electron capture detection.

The performance of the systems is described in detail.
The application of capillary SFC, packed column SFC, and capillary SFC‐MS in the analysis of controlled drugs
Authors: MacKay Graham A. , Reed Graham D.
Published: May 2005

Multi–component mixtures of controlled drugs, drug impurities, and adulterants have been analyzed by capillary SFC‐FID, packed column SFC‐UV, and capillary SFC‐MS. Isocratic packed column SFC has been performed with binary and ternary mobile phases using a single syringe pump. The combination of capillary SFC and double focusing MS is described with reference to MS source pressures and the spectra obtained. The use of negative temperature programming in SFC is described.
Composition and major odorous compounds of the essential oil of Bifora radians, an aldehyde‐producing weed
Authors: Latrasse Alain , Sémon Etienne , Le Quéré Jean‐Luc
Published: May 2005

The composition of the essential oil of Bifora radians, an aldehyde‐producing weed, has been investigated by capillary gas chromatography, coupled gas chromatography – mass spectrometry, on‐line catalytic hydrogenation and coupled gas chromatography – infrared spectrometry. The nineteen compounds identified included eighteen aldehydes: seven alkanals (C6, C9, C10, C11, C12, C13, and C14), ten alkenals, including five (E)‐2‐alkenals (C12, C13, C14, C15, and C16), and one (E,E)‐2,4‐alkadienal (C13). Typical Bifora odors were attributed to three major (E)‐2‐alkenals, C12, C13, and C14.
Analysis of beer iso‐α‐acids by micellar electrokinetic chromatography and multi‐wavelength UV detection
Authors: Vindevogel Johan , Szücs Roman , Sandra Pat , Verhagen Leen C.
Published: May 2005

The identification of beer bitter acids in a pre‐isomerized hop extract by means of their UV‐spectra is described. Preliminary data for the analysis of these compounds in beer samples are presented.