bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ion mobility detection after supercritical fluid chromatography
Authors: Eatherton R. L. , Morrissey M. A. , Siems W. F. , Hill H. H. 
Published: May 2005

AbstractUsing a unidirectional flow ion mobility detector, non‐selective detection, tunable selective detection, and complete Fourier transformed ion mobility spectra were successfully obtained after supercritical fluid chromatography on compounds with higher molecular weights than have been previously investigated. In the most selective mode, single oligomers from polymeric material could be independently detected. Using the Fourier transform capabilities of this instrument, complete ion mobility spectra for each oligomer could be obtained in a single chromatographic separation. The collection of individual ion mobility spectra of the components of polymeric material has not been possible prior to the technique described in this paper. Only complex ion mobility spectra of polymeric mixtures are available in the literature. The spectra obtained in this study are all simple, uncomplicated spectra consisting of only one or two product ion peaks. Ko values reported in this work range from 0.633 to 1.61, which are some of the lowest values ever reported in ion mobility spectrometry.With the unidirectional flow design of the detector, the supercritical fluid mobile phase, carbon dioxide, was efficiently eliminated from the detector so that the ion mobility spectrometer could be operated in its normal manner. The fact that CO2 did not interfere with normal ion mobility operation indicates that other supercritical fluids may also be compatible with this sensitive and versatile detection method.
Sample collection, quantification, and identification in preparative anticircular planar chromatography
Authors: Studer A. , Traitler H. 
Published: May 2005

AbstractA preparative anticircular chromatography (PACH) device was constructed to elucidate different applications of separation problems as well as to compare different sample collection techniques in this particular PLC mode. An anticircular PC apparatus had to be established which allowed the utilization of 20 X 20 cm thin‐layer plates as well as sampling positioning at any given radius. Typical solvent migration times were 8–12 minutes and ca. 8–10 ml of solvent was needed for an entire 20 cm plate. It was shown that peak broadening effects due to diffusion during long migration could be avoided in the same way as for analytical anticircular PLC on 10 X 10 plates. On the other hand, longer migration distances allow increased resolution, in turn allowing higher sample loads, particularly in the case of trace compound enrichment. A full description of the apparatus is given, including the sampling device.Different sample collection techniques were tried and evaluated, including the through‐flow technique by on‐line center collection for plate washing as well as classical scraping‐off of interesting zones. Further evaluation of the method included quantification and evaluation of consistency by UV/VIS scanning after spot‐visualization. Several application examples are given to illustrate the efficiency of the preparative anticircular PLC‐system.
Quantitative HPTLC determination of selenium
Authors: Funk W. , Dammann V. , Couturier T. , Schiller J. , Völker L. 
Published: May 2005

AbstractThe present determination of selenium in biological matrices by HPTLC with in situ fluorimetric detection is an accurate alternative method, comparable to other established methods such as photometry, polarography, neutron activation, or X‐ray fluorescence analysis, gas chromatography, and atomic absorption spectrometry.The excellent sensitivity of this procedure is proved by the detection limit of 250 fg of selenium per spot (using purified 2,3,1‐naphthoselenodiazole). The oxidation of organic matrices, applying a novel digestion procedure, may be carried out with little instrumental expenditure.Sample preparation steps, such as the oxidation of selenium to Se (VI) and subsequent reduction to Se (IV) do not lead to significant random or systematic errors, nor does the digestion step, if an optimized procedure is used.A recovery rate of 103% and nearly parallel calibration curves for digested selenocysteine standards compared with spiked human serum samples demonstrate the accurate quantitative preparation of a biological matrix. Any interfering metal ions can be masked by addition of chelate‐forming reagents.
The theory of gradient elution under hydrostatic equilibrium in liquid chromatography. Part 3: Using solvents of different densities
Authors: Al‐Ameeri R. S. , Said A. S. 
Published: May 2005

AbstractGradient elution under hydrostatic equilibrium is extended to the treatment of the case where the two liquids have different densities. Analytic expressions are derived only for the cases where both mixing chamber and reservoir have constant cross‐sectional areas.As in the case where the densities of the liquids are equal, pressigned concentration gradients can be duplicated quite satisfactorily by combining a mixing chamber having a constant cross‐sectional area and a reservoir having an area which changes linearly with reservoir height. A numerical example is given to illustrate the use of the derived equations.
High temperature gas chromatography: The development of new aluminum clad flexible fused silica glass capillary columns coated with thermostable nonpolar phases: Part 1
Authors: Lipsky S. R. , Duffy M. L. 
Published: May 2005

AbstractWith the simultaneous development of blank aluminum clad flexible fused silica glass capillary tubing capable of withstanding temperatures up to 500°C, coincident with a series of special high temperature methyl polysiloxane polymers, it was possible to produce for the first time, long lived fused silica capillary columns containing thin films of thermostable stationary phases which could be maintained isothermally at 400425°C and temperature programmed to 425–440°C. The “bleed rate” here for a well conditioned column was 5 picoamperes or less. Under these circumstances, alkanes with carbon numbers in the C‐90 to C‐100 area were rapidly and efficiently eluted from these columns. By extrapolation here, one can easily detect certain compounds with boiling points in the 750°C range. Since this type of capillary column was found to possess certain favorable properties, it was thought that it will soon replace the packed column and will probably be more popular than the borosilicate capillary column for many high temperature applications. Moreover, evidence has now accumulated which leads us to further believe that the majority of analyses of “high molecular weight” compounds performed by Supercritical Fluid Chromatography (SFC), utilizing very narrow bore fused silica capillary columns at several hundred atmospheres, can be much more simply, much more rapidly, much more economically, and much more efficiently accomplished by gas chromatography utilizing this new generation of high temperature capillary columns.
Putative water effects on the cryogenic FSOT capillary chromatography of sulfur‐containing gases
Authors: Barinaga C. J. , Farwell S. O. 
Published: May 2005

AbstractData are presented to illustrate putative water effects on the retention times and peak shapes for seven sulfur‐containing compounds when determined by sub‐ambient FSOT capillary GC/FPD. The observations are consistent with explanations based upon reported “phase soaking” and “reverse solvent effect” phenomena.
New description of heterogeneity effects in adsorption from multicomponent solutions and liquid adsorption chromatography
Authors: Jaroniec M. 
Published: May 2005

AbstractGeneral equations describing adsorption from solutions on solids and liquid adsorption chromatography with mixed mobile phases are formulated in terms of the bulk and surface activity coefficeints. Definition of the surface activity coefficients is extended; they describe nonideality of surface solution due to difference in molecular interactions of the components as well as nonideality of this solution generated by the adsorbent heterogeneity. It is shown that the above general equations predict simpler expressions known already in the literature.
The mobile‐phase effects on stationary‐phase properties in capillary supercritical fluid chromatography
Authors: Novotny M. , David P. 
Published: May 2005

AbstractA significant uptake of supercritical mobile phases into immobilized stationary phases has been observed. The phase swelling effect has been evaluated hydrodynamically for SE‐30, SE‐54, and cyanopropyl silicone phases with respect to the mobile‐phase density of supercritical butane, column temperature, and the presence of a polar retention moderator. Some kinetic and retention consequences of the swelling phenomena are discussed.
Prediction of molecular structures of aza‐arenes by retention indices and fluorescence spectra
Authors: Morishita F. , Morimoto S. , Kojima T. 
Published: May 2005

AbstractTwo methods are described for predicting the molecular structures of aza‐arenes eluted from a capillary column. The first is based on a combination of retention indexes (RI) and a post‐column reaction. The RI of an aza‐arene is calculated by using the incremental contributions of some atomic groups to RI. Once the molecular weight is determined by the mass spectrum, the possible compounds are picked up, based on comparison of the observed RI with the calculated RI values and information about the intramolecular environment around the nitrogen atom obtained from the degree of peak shift resulting from interaction with Ni(II). The second is due to combination of information from fluorescence spectrometry and TLC fractionation. The fluorescence spectrum allows the identification of the fused ring system.
Microwave‐induced plasma emission spectrophotometer combined with a photodiode array monitor for capillary column gas chromatography
Authors: Takigawa Y. , Hanai T. , Hubert J. 
Published: May 2005

AbstractA microwave‐induced plasma emission spectrophotometric detector (MIPD) was used as an element‐specific detector for capillary column gas chromatography. The atmospheric pressure microwave helium plasma generated with an original device called a SURFATRON was used as an atomization and excitation source. Combining a photodiode array spectrophotometer with the above system made the emission spectrophotometric detector very powerful. A wide range of spectra could be instantly monitored without any mechanical device.However, the spectrum of atmospheric helium emission plasma was complicated by the presence of air around the plasma discharge. An on‐line background correction scheme was developed to handle such complicated spectra.
Resolution of gossypol: Analytical and large‐scale preparative HPLC on non‐chiral phases
Authors: Matlin S. A. , Belenguer A. , Tyson R. G. , Brookes A. N. 
Published: May 2005

AbstractRacemic gossypol is resolved by HPLC of its amino acid ester Schiff's base derivatives on non‐chiral columns. This provides a rapid and accurate method for determination of optical purity on a small scale and, combined with hydrolysis and fractional crystallization, for the preparation of pure gossypol enantiomers on a multi‐gram scale.
Separation and determination of purpurea glycosides in Digitalis purpurea leaves by micro‐HPLC
Authors: Fujii Y. , Ikeda Y. , Yamazaki M. 
Published: May 2005

AbstractA micro high‐performance liquid chromatographic (micro‐HPLC) method was developed for the determination of purpurea glycoside A, purpurea glycoside B, and glucogitaloxin in Digitalis purpurea leaves. The extract of dry leaf powder was applied to a Sep‐Pak silica cartridge followed by preparative thin‐layer chromatography prior to micro‐HPLC analysis. The analysis was performed on an ODS micro column, using acetonitrile‐methanol‐water (21:20:45) and ultraviolet detection (220 nm). The amounts of purpurea glycoside A, purpurea glycoside B, and glucogitaloxin per 100 mg of dry leaf powder were estimated to be 52.6, 50.7, and 108.6 μg, respectively.
Liquid chromatography in packed fused silica capillaries or Micro‐LC: A repeat of the capillary gas chromatography story?
Authors: Verzele M. , Dewaele C. 
Published: May 2005

AbstractMiniaturized and capillary techniques will gradually become more important in Liquid Chromatography (LC). Micro‐LC, or the chromatography in fused silica packed capillary columns, has so many important advantages and characteristics that this is probably the form of miniaturized LC that has the greatest chance to make it. These advantages, as discussed in the present paper should lead to LC in less than 30 minutes with a plate number for the column of 20,000 to 50,000. Unlike Capillary GC which took about 25 years to assert itself Micro‐IC will probably not take so long.
Multipurpose cold injector for high resolution gas chromatography
Authors: Saravalle C. A. , Munari F. , Trestianu S. 
Published: May 2005

AbstractThe multipurpose cold injector described in this paper represents a solution for an universal sampling system for high resolution gas chromatography. The system is modular and is built around the Carlo Erba cold on‐column injector provided with secondary cooling. An auxiliary module, easily fixable on the bottom of the on‐column injector, creates a temperature programmable vaporizing chamber making the system also suitable for cold split‐splitless injections or solvent venting prior to the sample transfer into the capillary. The system can be operated manually or in a fully automatic mode using the auto‐sampler for cold on‐column injections. The experimental data illustrate its benefits and limitations.
Column temperature during eluent transfer with concurrent eluent evaporation in coupled HPLC‐HRGC
Authors: Grob K. 
Published: May 2005

AbstractConcurrent solvent evaporation is suited for coupled HPLC‐HRGC if solutes elute at intermediate to high column temperatures—otherwise retention gap techniques are more appropriate. Concurrent eluent evaporation using a loop‐type interface requires that the GC oven temperature during eluent introduction be above the eluent boiling point at the carrier gas inlet pressure applied. An experimental background is given for facilitating selection of the appropriate column temperature.
Siloxane/silarylene copolymers as stationary phases for capillary gas chromatography part I: Evaluation of silanol terminated dimethyl substituted polymers
Authors: Bemgård A. , Blomberg L. , Lymann M. , Claude S. , Tabacchi R. 
Published: May 2005

AbstractThe thermal stability of silicones can be improved on replacement of certain of the oxygen atoms in the polymer backbone by phenyl groups. Such a polymer has been synthesized and evaluated for use as stationary phase in fused silica capillary gas chromatography; the polymer was dimethyl substituted and silanol terminated. A selectivity was provided by the phenyl groups in the backbone. For comparative purposes, a silanol‐terminated dimethylpolysiloxane has also been evaluated.Both stationary phases gave columns of highest separation efficiency and the supporting fused silica surface was deactivated by the stationary phases on thermal treatment. Further, low column bleeding was observed at the maximum temperature tested, 370°C. The phenyl‐containing phase could be immobilized to 60% by heat treatment, but the pure dimethylpolysiloxane was 10% immobilized. The influence on immobilization of factors such as nature of the supporting surface, stationary phase silanol content, reaction temperature and atmosphere in the column during reaction has been studied.
An off‐line two‐dimensional analytical procedure for determination of polycyclic aromatic hydrocarbons in smoke aerosol
Authors: Claessens H. A. , Lammerts van Bueren L. G. D. 
Published: May 2005

AbstractSmoke aerosol from stoves consists of a wide variety of chemical substances of which a number have toxic properties. To study the impact of aerosol emissions on health and environment reliable analytical procedures must be available for these samples. An off‐line two‐dimensional HPLC method is described for the determination of a number of polycyclic aromatic hydrocarbons (PAH). The method consists of a HPLC clean‐up step yielding distinct fractions on activated silica and followed by analysis of each of the fractions by isocratic reversed phase HPLC. Detection is by UV and fluorescence monitors in series. Combination of the chromatographic data obtained from both the clean‐up and analytical step provides additional qualitative information.
Correction method for quantitative area determination of overlapping chromatographic peaks based on the exponentially modified Gaussian (EMG) model
Authors: Binsheng Lin , Peichang Lu 
Published: May 2005

AbstractA simple method is presented for peak area correction of overlapping peaks. This correction is necessary for the normal approach of dealing with overlapping peaks by a vertical line at the valley point. The relative area errors caused by this vertical line are calculated as the correction factors in three dimensions of peak separation, peak ratio, and peak tailing skew. The calculation is based on the exponentially modified Gaussian asymmetric peak model.
Noncryogenic FSOT column separation of sulfur‐containing gases
Authors: Barinaga C. J. , Farwell S. O. 
Published: May 2005

AbstractFused silica open tubular (FSOT) capillary column GC separations of low molecular weight, reactive sulfur‐containing gases (S‐gases) are significant improvements over packed column separations in terms of resolution, detection limits, and conditioning effects. Nevertheless, some of the problems with current FSOT capillary systems include matrix Injection incompatibilities; detector dead volumes; the necessity for cryogenic initial oven temperatures to separate CO2, H2S, COS, and SO2; and relatively long analysis times to separate later, closely eluting compounds. A noncryogenic FSOT GC‐FPD system that either reduces or eliminates these problems is reported. Baseline separation of seven common S‐gases (H2S‐DMDS) is achieved in less than 5 min with ambient initial oven temperatures via this system, which is a combination of (1) a cryogenic sample concentration/injection design that is flow compatible with a wide‐bore FSOT column; (2) a combined DB‐1/DB‐WAX thick phase, wide‐bore FSOT column for greater capacity, retention, and tuned selectivity; and (3) a reduced dead volume FPD to minimize peak width and tailing.
Preparation and evaluation of OV‐240‐OH coated glass capillary columns for isomer specific determination of PCDDs and PCDFs
Authors: Schmid P. , Müller M. D. 
Published: May 2005

AbstractGlass capillaries were leached, dehydrated, persilylated with 1, 3‐bis (3‐cyanopropyl) tetramethyldisiloxane, and coated with OV‐240‐OH. After crosslinking and binding the phase to the glass surface the columns showed high separation efficiency, high temperature stability, and inertness comparable to persilylated apolar columns. Column performance is shown to be superior to liquid phase cyanopropyl columns such as SP 2330. The excellent separation capabilities together with the selectivity of the phase makes OV‐240‐OH coated columns a valuable tool for the determination of toxic isomers in complex mixtures of polychlorinated dibenzo‐p‐dioxins (PCDDs) and dibenzofurans (PCDFs). The order of elution of individual TCDD isomers was found to be similar to that described for SP 2330 or Silar 10c. The detection of PCDDs and PCDFs in a fly ash extract further illustrates the utility of OV‐240‐OH coated columns. The high temperature limit of these columns opens the way for the analysis of high boiling compounds such as mixed brominated/chlorinated dibenzo‐p‐dioxins and dibenzofurans.
CGC‐MS determination of mixtures of long chain aliphatic esters
Authors: Audisio G. , Rossini A. , Bianchi G. , Avato P. 
Published: May 2005

AbstractA method is described for the determination of the acid and alcohol moieties in long chain wax esters. The co‐eluting esters are differentiated by means of CGC‐MS operating in the ion monitoring mode. The technique allows to detect ester components present in very low amounts in plant surface waxes.
Automated on‐line HPLC‐HRGC: Instrumental aspects and application for the determination of heroin metabolites in urine
Authors: Munari F. , Grob K. 
Published: May 2005

AbstractA fully automated on‐line HPLC‐HRGC instrument is described. Samples are loaded into an HPLC autosampler. Pre‐separation is carried out, automatically transferring the previously determined HPLC fraction to GC. Total HPLC fractions are introduced into GC, using the on‐column or the loop‐type interface, depending on the solvent evaporation technique applied. The HPLC column is automatically backflushed with a suitable solvent during GC analysis. The instrument was used for analyzing heroin metabolites, particularly morphine, in urine samples. Raw urine extracts were injected into HPLC and analyzed by GC using FID.
On‐line combination of liquid chromatography and capillary gas chromatography. Preconcentration and analysis of organic compounds in aqueous samples
Authors: Noy Th. , Weiss E. , Herps T. , van Cruchten H. , Rijks J. 
Published: May 2005

AbstractThis paper describes the design of a new, versatile, and low‐cost on‐line LC‐GC interface that allows the fast and reliable introduction of large sample volumes onto a capillary GC column. The sample introduction procedure consists successively of: evaporation of the entire sample (LC fraction), selective removal of the solvent and simultaneously cold‐trapping of the solutes, splitless transfer of the solutes to the GC column, on‐column focusing, GC separation and detection. Quantitative and qualitative aspects of various experimental parameters are evaluated and optimum conditions are reported. The applicability of the method is demonstrated on a synthetic aqueous sample of chlorinated pesticides.
The use of multidimensional capillary chromatography in conjunction with a triple quadropule mass‐spectrometer in the analysis of complex mixtures (GC‐GC‐MS‐MS)
Authors: Claude S. G. , Tabacchi R. 
Published: May 2005

AbstractThe analysis of complex mixtures, such as essential oils requires high resolution chromatographic separation and even the use of very efficient columns cannot prevent the overlapping of certain peaks. This means that it is very difficult to obtain high quality mass spectra when the sample contains numerous constituants. The pre‐separation by column or preparative GC leads to a considerable loss of material and, often, to the formation of artefacts. In order to overcome some of these difficulties, we have built a simple multi‐column system that is connected to an MS‐MS instrument. Two independent chromatographs equipped with capillary columns were connected. The interface, which consists of a modified PTV injector, gives the possibilities of direct transfer, back‐flushing, heart‐cutting, intermediate cold trapping, trace enrichment and selective sample introduction. These operations are controlled by a switching valve system (DANI‐MFC 393 unit). The chromatographic system was first connected to a MS‐MS instrument which may result in high MS and collision activated MS spectra.
Instrumentation for SFC systems: Different sampling and restriction designs
Authors: Köhler J. , Rose A. , Schomburg G. 
Published: May 2005

AbstractDifferent designs of injection and restriction devices for capillary supercritical fluid chromatography (SFC) have been investigated with respect to their practical applicability and usefulness for reproducible and accurate qualitative and quantitative analyses. In combination with a self‐made instrument a fast switching valve is preferable as an injection device compared to a split‐injector, and an integral restrictor made from the end of the fused silica (FS) separation column was superior to a linear restrictor made by coupling a small diameter FS‐column to the separation column.