bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rapid and ultra‐sensitive GC/MS analyses with a microchannel plate array detector Part I: Possibilities of simultaneous ion detection in narrow‐bore GC/MS
Authors: Leclercq P. A. , Snijders H. M. J. , Cramers C. A. , Maurer K. H. , Rapp U. 
Published: May 2005

AbstractIdentification and detection limits for scanning and non‐scanning mass spectrometers are discussed. It is theoretically deduced and experimentally confirmed that these limits are on the low pico‐and femtogram levels, respectively, when using conventional secondary electron multiplier‐amplifier systems. The sensitivity can be increased at least tenfold by pulse‐counting techniques, instead of current amplification, provided the chemical noise is sufficiently low. The potential advantages of a detection system for simultaneous ion detection in a significant mass range, for obtaining complete mass spectra in fast GC/MS analyses, are demonstrated. A double focusing mass spectrometer was constructed, using the well‐proven Mattauch‐Herzog principles. By application of an “electronic photoplate”, substance identification in the low femtogram range on a millisecond time scale, so far only accessible for single ion monitoring techniques, is feasible.
Sampling device for a simple, fast calibration technique in gas chromatographic trace analysis of gas phases and vapor phases
Authors: Hachenberg H. 
Published: May 2005

AbstractIn order to accommodate continually changing tasks in the [μl/l]–[nl/m3] ranges of gas chromatographic trace analysis of gas phases and vapor phases, a simple and time‐saving calibration technique is presented which renders unnecessary conventional test mixtures of the abovementioned concentration ranges.This new method is based on the simulation of such mixtures at the inlet of the GC unit with the aid of commercially available multiway sampling valves of various volumes by means of partial pressure sampling.
A new configuration for coupling purge‐and‐trap/cryogenic focusing/capillary column gas chromatography with splitless injection mode
Authors: Liu Shili , Kang Jiangshi , Strother Dennis L. , Carley Robert J. , Stuart James D. 
Published: May 2005

AbstractA new configuration for coupling a purge‐and‐trap unit to a capillary column gas chromatograph via a cryogenic focusing interface has been developed. In this configuration, the precolumn of the cryogenic focusing interface was inserted through the septum of a split/splitless injection port where it served as both sample transfer and carrier gas supply lines. The injection port of the gas chromatograph was modified by plugging the carrier gas and the septum purge lines. This configuration allowed for the desorption of analytes at high flow rates while maintaining low, analytical‐column flow rates which are necessary for optimum capillary column operation. The capillary column flow rate is still controlled by the column backpressure regulator. Chromatograms of purgeable aromatics exhibited improved resolution, especially for early eluting components compared to those obtained by direct liquid injection using the normal splitless injection mode. Quantitative sample transfer to the analytical column afforded excellent linearity and reproducibility of compounds studied.
Automated sample clean‐up and fractionation of organochlorine pesticides and polychlorinated biphenyls in human milk using NP‐HPLC with column‐switching
Authors: Hogendoorn E. A. , van der Hoff G. R. , van Zoonen P. 
Published: May 2005

AbstractA method has been developed for the automated sample pretreatment of organochlorine pesticides (OCP's) and polychlorinated biphenyls (PCB's) in extracts of human milk. This work was part of a regular monitoring program presently carried out at our institute. In this program several hundreds of human milk samples have to be analyzed for the occurrence of PCB's and OCP's.With a normal bore straight phase HPLC system, utilizing column switching we are able to separate the fat from the compounds of interest and, moreover, complete separation of the PCB fraction from the OCP's can be achieved. Under the conditions used to separate the PCB fraction from intefering OCP's column‐switching is essential since the retention times for the OCP's vary from 4 minutes for hexachlorobenzene (HCB) to more than 2 hours for dieldrin.1 ml of an extract containing 45 mg of fat is injected on the first (pre)column, the fat is retained on this column and the early eluting HCB, the PCB fraction, and the DDT complex are transferred to the second (analytical) column. Compounds eluting later than p,p′‐DDT are collected directly from the precolumn. Meanwhile, the PCB fraction is separated from the rest of the OCP's on the analytical column.Contrary to conventional gravity‐controlled chromatography or solid phase extraction the clean‐up process can be monitored on‐line by UV‐detection, thus rendering a fast and reliable optimization of the system. The OCP‐fractions collected from the LC are pooled before they are transferred to a high resolution gas chromatograph equipped with a large volume option. The PCB‐fraction is injected directly in a HRGC equipped with a concurrent solvent evaporation injection device.The limits of detection for the OCP's (HCB, α‐,β‐ and γ‐HCH, β‐Hepo (heptachlorepoxide), dieldrin, p,p′‐DDE, o,p′‐DDT p,p′‐DDT and TDE) and the PCB's investigated are at sub‐ppb level (fat basis); the recoveries vary from 80 to 100%.
Cyclodextrins as chiral stationary phases in capillary gas chromatography. Part VI: Octakis (2,3,6‐tri‐O‐pentyl)‐γ‐cyclodextrin
Authors: König W. A. , Kebber R. , Wenz G. 
Published: May 2005

AbstractPerpentylated γ‐cyclodextrin is a very hydrophobic liquid which exhibits enantioselectivity toward a number of non‐polar chiral substrates including the saturated hydrocarbons cis‐ and trans‐pinane, β‐chiral olefins, iron(O) tricarbonyl complexes of prochiral olefins and 3,3,8,8‐tetramethyl‐trans‐cyclooctene, a compound with planar chirality.
Intra‐ and intermolecular interactions in the first members of homologous series of carbonyl containing compounds in gas chromatography
Authors: Golovnya R. V. , Grigoryeva D. N. , Vasilyev A. V. 
Published: May 2005

AbstractVariation of the values of free energy of sorption of the methylene unit has been studied in the homologous series of n‐alkyl methyl ketones, n‐alkyl butyl ketones, n‐alkyl acetates, and methyl esters of carboxylic acids, depending on the homologue number and the temperature of analysis. The experiment was carried out on a capillary column with a thick film of immobilized Silicone SE‐54 and on packed columns with OV‐210 and Silar‐10C. An intramolecular donor‐acceptor interaction between neighboring CH3 and CO groups is assumed to be the reason for anomalously high values of free energy of sorption of the first CH2 unit in the series: RmC(O)OCH3, RmC(O)CH3, and RmC(O)C4H9. The anomaly disappeared in stationary phases containing strongly electronegative CF3 and CN groups because of specific inter molecular interactions.
Automated on‐line HPLC‐HRGC with gradient elution and multiple GC transfer applied to the characterization of citrus essential oils
Authors: Munari F. , Dugo G. , Cotroneo A. 
Published: May 2005

AbstractCitrus essential oil analysis is characterized by the complexity of the separation of all the components which may belong to different classes of compounds and be present in a wide range of concentrations.Capillary GC is the best technique for characterizing the volatile fraction of citrus essential oil. In many cases, however, this technique does not achieve complete separation of all the components.A combination of LC and HRGC in off‐line methods is necessary to achieve complete resolution of the minor components present in the oil and in general to facilitate the identification of the components belonging to different classes. Very recently we have demonstrated the possibility of using on‐line HPLC‐HRGC coupling for fractionation and identification of alcohols in lemon oils.In the present work, a fully automatic HPLC‐HRGC instrument was used for the pre‐separation of the essential oils into the various classes of compounds, using gradient elution and multiple fraction transfer into the capillary column.This method allowed a pre‐separation of the components into four major classes of compounds: hydrocarbons, aldehydes, esters, and alcohols before their transfer into the GC. A good correlation with the existing off‐line methods was found.The ability of the Instrument to perform, In a fully automatic way, HPLC pre‐separation with gradient elution and GC transfer of more than one fraction from a single HPLC injection, was found to be very useful for routine characterization of various essential oils.
Ethyl acetate for the desorption of a liquid chromatographic precolumn on‐line into a gas chromatograph
Authors: Vreuls Jolan J. , Cuppen Wilhelmus J. G. M. , De Jong Gerhardus J. , Th. Brinkman Udo A. 
Published: May 2005

AbstractThe feasibility of using ethyl acetate for the desorption of trace pollutants from a liquid chromatographic precolumn on‐line into a diphenyltetramethyldisilazane‐deactivated retention gap and, subsequently analysis by means of capillary gas chromatography has been demonstrated. First 5% of methanol are added to the water sample to prevent sorption of analytes onto parts of the preconcentration system. About 1 ml of this aqueous sample is injected onto a precolumn containing a polymeric stationary phase, using water–methanol (95:5, v/v) for transport and clean‐up. The precolumn is desorbed with ethyl acetate and a fraction of 75 μl is injected on‐line into the retention gap; separation is then achieved on a capillary CP Sil 19 column. No breakthrough of the test compounds was observed in the preconcentration step. The recovery was quantitative and the response obtained with flame ionization detection was linear in the range 0.1–100 ng/ml. The effect of varying the sorption flow rate on the recovery was studied. The system was applied to the analysis of river water.
Computer‐assisted optimization of selectivity (mobile phase, pH, and ion concentration) in high‐perfomance liquid chromatography
Authors: Qin‐Sin Wang , Ru‐Yu Gao , Heng‐Yan Wang 
Published: May 2005

AbstractA computer‐assisted method is presented for optimization of mobile phase composition in reverse‐phase and normal‐phase HPLC. The method is based on window diagrams, but only three preliminary tests are required. The method is successfully applied to two examples and there is good agreement between predicted and experimental results. Optimal values for ion concentration and pH in ion chromatography from a published optimization method are compared to values calculated using the computer‐assisted method presented in this paper. The same results are obtained, but the method presented here is simpler and faster than previously published one.
Quantitative determination of paraffin oil in blood by capillary gas chromatography
Authors: Tsikas Dimitrios , Brunner Georig 
Published: May 2005

AbstractA capillary gas chromatographic method is described for the quantitative determination of liquid paraffin in blood. Paraffin is extracted from blood into n‐heptane. After solvent evaporation and dissolution of the residue in 100–200 μl n‐heptane one μl is injected into a gas chromatograph fitted with a fused silica capillary column (Permabond® OV‐1‐CB‐0.1, 10 m × 0.32 mm i.d.) and flame ionization detector. Analysis is performed by using an oven program [50°C (3 min)−285°C (5 min), rise 10%min]. The sensitivity (1.5 ng hexadecane) and the reproducibility prove the applicability of the method for the determination of liquid paraffin in blood and for the study of the stability of the liquid paraffin hollow fiber membranes used in an extracorporeal liver support system.
Microbore columns vs. open tubular columns for supercritical fluid chromatography in environmental analysis: Separation of polychlorinated biphenyls and terphenyls
Authors: Onuska Francis I. , Terry Ken A. , Rokushika Souji , Hatano Hiroyuki 
Published: May 2005

AbstractThe supercritical fluid chromatographic behavior of polychlorinated biphenyls (PCBs) and polychlorinated terphenyls (PCTs) is described. The method uses a microbore C‐18 column and an open tubular capillary column coated with SE‐52 and carbon dioxide as the supercritical fluid. Factors affecting the separation and retention of these compounds are discussed.
Variable splitter for regulation of the solvent evaporation rate in the coupling of liquid chromatography with gas chromatography
Authors: Dolecka Ewa , Vreuls Jolan J. , de Jong Gerhardus J. , Th. Brinkman Udo A. , Maris Frans A. 
Published: May 2005

AbstractA system is described which accelerates the solvent evaporation rate in the retention gap. The evaporation is due to a saturation effect of the carrier gas stream, and a considerable increase in evaporation rate is obtained by inserting a split outlet between the retention gap and the capillary separation column in the gas chromatograph. By varying the backpressure of the spliter device, the flow rate through the retention gap can be adjusted and so too the evaporation rate. The evaporation process was monitored by inserting a dectecter in the split outlet line. The technique was applied to the on‐line LC trace enrichment/GC analysis of water containing a mixture of polycyclic aromatic hydrocarbons.
Qualitative supercritical fluid extraction coupled to capillary gas chromatography
Authors: Levy Joseph M. , Rosselli Athos C. , Boyer David S. , Cross Kathryn 
Published: May 2005

AbstractThe usefulness and ease of utilizing supercritical fluid extraction (SFE) directly coupled to capillary gas chromatography (GC) as quantitative or qualitative analytical problem‐solving tools will be demonstrated. As an alternative to conventional liquid solvent extractions, SFE presents itself as a means to achieve high extraction efficiencies of different compounds in complex solid matrices in very rapid tims frames. Moreover, SFE has an additional advantage of being able to achieve distinct extraction selectivities as a function of the solubilizing power of the supercritical fluid extracting phase. For on‐line SFE/GC, the extraction effluent is directly transferred to the analytical chromatograph. On‐line SFE/GC involves the decompression of pressurized extraction effluent directly into a heated, unmodified capillary split injection port of the GC. In this respect, SFE introduction into GC can be used as an alternative means of GC injection, comparable to such modes of injection as pyrolysis and thermal desorption. This paper will show applications of SFE/GC where mass spectrometric detection together with flame ionization detection was used for component identification from environmental, tobacco, and petroleum matrices.
An investigation of gas chromatography with atomic emission detection for the determination of empirical formulas
Authors: Wylie Philip L. , Sullivan James J. , Quimby Bruce D. 
Published: May 2005

AbstractThe atomic emission detector (AED) is a valuable tool for the identification of unknowns in complex mixtures. To the extent that elemental response factors are independent of compound structure, gas chromatographic results allow calculation of atomic ratios for unknown compounds. In favorable cases, empirical formulas can be found. An algorithm for automated calculation of empirical formulas for all the peaks in a chromatogram has been developed. When finite accuracy prevents an exact determination of empirical formulas, the algorithm gives a list of all formulas for each compound which are compatible with the user‐defined limits.Examples are given of calculations for fatty acid methyl esters, substituted phenols, and pesticides. Analyses of volatile pollutants and polychlorinated biphenyls reveal a nonlinearity for hydrogen response, and an interference of chlorine on hydrogen. A lubricating oil analysis is used to illustrate the identification of unknowns.
Direct injection of large sample volumes into capillary columns with packed column injector
Authors: Watanabe Chuichi , Hashimoto Keiji 
Published: May 2005

AbstractA direct injection method for large volume samples which avoids severe tailing of the solvent peak has been developed using a packed column injector (up to 100 μl) leading into an ordinary capillary column (0.3 mm i.d.). Modifications are made to the cooler zones of the inlet port and on the carrier gas flow control system. This injection technique is based on the effective use of phase soaking and cold trapping using a retention gap. The large volume of solvent vapor is rapidly purged out of the injector with a higher flow of carrier gas while the solutes trapped at the head of the column are subsequently analyzed with another optimum flow rate. The proposed carrier gas flow regulation system is also compared with conventional split/splitless injection methods.
Electron capture ion mobility spectrometry for the selective detection of chlorinated and brominated species after capillary gas chromatography
Authors: St. Louis Robert H. , Hill Herbert H. 
Published: May 2005

AbstractThis paper reports the first investigation of electron capture ion mobility spectrometry as a detection method for capillary gas chromatography. In previous work with negative ion mobility detection after gas chromatography, the principal reactant ion species were O2− or hydrated O2− due to the presence of oxygen in the drift gas. These molecular reactant ions have a mobility similar to chloride and bromide ions, which are the principal product ions formed by most halogenated organics via dissociative ion‐molecule reactions. Oxygenated reactant ions thus interfere with the selective detection of chloride and bromide product ions. A recently described ion mobility detector design efficiently eliminated ambient impurities, including oxygen, from infiltrating the ionization region of the detector; consequently, in the negative mode of operation, the ionization species with N2 drift gas were thermalized electrons. Thermalized electrons have a high mobility and their drift time occupies a region of the ion mobility spectrum not occupied by chloride, bromide, or other product ions. The result was improved selectivity for halogenated organics which ionize by dissociative electron capture. This was demonstrated by the selective detection of 4,4′‐dibromobiphenyl from the components of a polychlorinated biphenyl mixture (Aroclor 1248).
Structure‐type separation of diesel fuels by solid phase extraction and identification of the two‐ and three‐ring aromatics by capillary GC‐mass spectrometry
Authors: Bundt Joachim , Herbel Walter , Steinhart Hans , Franke Stefan , Francke Wittko 
Published: May 2005

AbstractA simple and effective solid phase extraction (SPE) method using silica gel micro glass columns has been developed for the separation of diesel fuel into groups of aliphatic, and mono‐, di‐ and polyaromatic hydrocarbons. It is based on a stepwise gradient of dichloromethane in n‐pentane. The resulting fractions were analyzed by capillary gas chromatography with a flame ionization detector and coupled gas chromatography‐mass spectrometry.Commercially available standards, and retention indices and mass spectra were used for identification of individual aromatic compounds. The principal polycyclic aromatic hydrocarbons (PAHs) in diesel fuel are naphthalene, biphenyl, fluorene, phen‐anthrene and their alkylated derivatives. Sulfur‐containing PAHs are mainly represented by methyl‐substituted dibenzo‐thiophenes.
A polymeric liquid crystal capillary column for GC‐MS analysis of PCDD and PCDF
Authors: Albrecht Iris D. , Naikwadi Krishnat P. , Karasek Francis W. 
Published: May 2005

AbstractA newly developed side chain liquid crystal polysiloxane has been investigated as a stationary phase for the isomer‐specific analysis of polychlorinated dibenzo‐p‐dioxins and polychlorinated dibenzofurans substituted at positions 2, 3, 7, and 8. The retention times from the chromatograms of a standard solution containing all PCDD and PCDF isomers were compared with those from solutions containing only those tetra‐ to octa‐chlorinated compounds substituted at positions 2, 3, 7, and 8. In general, PCDDs substituted at positions 2, 3, 7, and 8 eluted later than most other isomers of the same congener group. The separations obtained on this stationary phase were compared with those obtained elsewhere using a commercially available product.
On‐line coupled HPLC‐HRGC: A powerful tool for vapor phase FTIR analysis (LC‐GC‐FTIR)
Authors: Full Gerhard , Krammer Gerhard , Schreier Peter 
Published: May 2005

AbstractThe design of an on‐line LC‐GC‐FTIR system using an on‐column interface and partially concurrent solvent evaporation with early vapor exit is described. The integration of LC‐GC coupling into vapor phase FTIR analysis enables problems of sensitivity encountered with HRGC‐FTIR detection to be over‐come. The applicability of the method is demonstrated by the identification and determination of citropten and bergapten in bergamot oil.
GC‐MS investigation of α‐polyfluoroalkylbenzyl phosphorus esters
Authors: Shcherbina T. M. , Laretina A. P. , Goryunov E. I. , Kabachnik M. I. 
Published: May 2005

AbstractThe stereochemistry of some α‐polyfluoroalkylbenzyl phosphorus esters has been studied by capillary gas chromatography (CGC). The compounds are mixtures of two or three diastereomers, depending on the number of asymmetric centers and the molecular symmetry. The primary fragmentation processes in the mass spectra of the phosphorus esters and their deuterated analogous have also been studied.
Determination, by GC‐MS using deuterated internal standards, of formaldehyde and methanol evolved during curing of coatings
Authors: McGuire Jeffrey M. , Nahm Steven H. 
Published: May 2005

AbstractA quick and accurate capillary GC‐MS method based on dynamic headspace analysis has been developed for elucidating the curing chemistry and evaluating the degree of curing of new high performance coatings. This method quantitatively analyzes volatile reaction products, particularly formaldehyde and methanol, evolved from these coatings during curing. The reaction volatiles are cryogenically trapped, and then chromatographed with deuterated formaldehyde and methanol as internal standards. The relative standard deviations of the method are 3–6% and 1‐2% for determinations of formaldehyde and methanol, respectively.
Microcolumn liquid chromatography of the enantiomers of organophosphorus pesticides with thermionic and ultraviolet detection
Authors: Kientz Charles E. , Langenberg Jan P. , de Jong Gerhardus J. , Th. Brinkman Udo A. 
Published: May 2005

AbstractMicrocolumn liquid chromatography (micro‐LC) of some chiral organophosphorus pesticides has been studied using Chiralcel OD columns and simultaneous ultraviolet (UV) and phosphorus selective detection, the latter by means of a micro‐UV cell coupled on‐line to a thermionic detector (TID). Micro‐LC showed a ca. 5‐fold improved separation impedance, a ca. 1.8‐fold increased column permeability, and greater inertness compared with conventional LC.By using the TID, organophosphorus pesticides could be satisfactorily determined at trace levels, the detection limit being 4 pg/s of phosphorus. The response of the micro‐LC‐TID system is linear in the range of 0.05–20 ng (r = 0.9994).
Determination of the migration times of flow measurement markers in CEC
Authors: Hanai Toshihiko , Hatano Hiroyuki , Nimura Noriyuki , Kinoshita Toshio 
Published: May 2005

AbstractThe electroosmotic migration times of fructose, water, and phenol have been measured in several solutions. The electroosmotic flow rate was fundamentally dependent on buffer concentration and on the concentration of additives such as sodium chloride; additives such as methanol and sodium dodecylsulfate did not influence the flow rate, yet tetrabutylammonium bromide had a significant effect.