bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature programmed retention indices: Calculation from isothermal data. Part 2: Results with nonpolar columns
Authors: Curvers J. , Rijks J. , Cramers C. , Knauss K. , Larson P.
Published: May 2005

The procedure for calculating linear temperature programmed indices as described in part 1 has been evaluated using five different nonpolar columns, with OV‐1 as the stationary phase. For fourty‐three different solutes covering five different classes of components, including n‐alkanes and alkyl‐aromatic compounds, both isothermal and temperature programmed indices were determined. The isothermal information was used to calculate temperature programmed indices. For several linear programmed conditions accuracies better than 0.51T‐units were usually obtained. The results are compared with published procedures.

It is demonstrated that isothermal retention information obtained on one column can be transferred to another column with the same stationary phase but different column dimensions and/or phase ratio. The temperature programmed indices calculated in this way also have an accuracy better than 0.51T‐u.

The temperature accuracy and precision of the GC‐instrumentation used was of the order of 0.1°C. All calculations can be run with a Basic‐programmed microcomputer.
Preparation of polysiloxane stationary phases for capillary column chromatography: A New methoxyphenyl phase
Authors: Bradshaw J. S. , Adams N. W. , Johnson R. S. , Tarbet B. J. , Schregenberger C. M. , Pulsipher M. A. , Andrus M. B. , Markides K. E. , Lee M. L.
Published: May 2005

Contemporary methods for the synthesis of alkyl‐ and arylsubstituted polysiloxane stationary phases are reviewed. A new, moderately polar phase containing the 3‐(4‐methoxyphenyl)‐propyl group is reported.
Preparation of inert and high‐temperature stable apolar and medium polar glass‐capillary columns using OH‐terminated polysiloxane stationary phases
Authors: Blum W.
Published: May 2005

Coating intensively leached silica surfaces with OH‐terminated phases provides a new way of producing, by simple means, columns with substantially increased inertness and thermostability. In addition, their separation efficiency is found to be typically higher than that of columns with traditional coatings. The underlying basic effect is a condensation process between terminal silanol groups of the phase and residual silanols, of the glass surface, thus producing the mentioned inertness. Moreover, the surface‐bonded molecules are immobilized without addition of a radical generator. If required, crosslinking can also be effected using a volatile azo compound. No vinyl groups are required for this additional immobilization process. The paper discusses all processes involved, and gives detailed working directions for the following medium polar phases. OV‐1701‐OH, OV‐31‐OH (new, 17% cyanopropyl), OV‐61‐OH, and OV‐17‐OH, and the apolar phases PS‐347.5 and PS‐086. There is no doubt so far that the principle of terminal silanol groups is applicable to all silicone phases, and may replace the traditional endcapped stationary phases in the future.
Coupled HPLC‐capillary GC – state of the art and outlook
Authors: Grob K. , Schilling B.
Published: May 2005

HPLC fractions involving eluents of low to intermediate polarity can be introduced into capillary GC using the retention gap technique. Partial or complete solvent evaporation during sample introduction reduces the length of, or almost eliminates, the zone in the column inlet (retention gap) flooded by the introduced liquid, allowing introduction of larger HPLC fractions and/or use of shorter retention gaps. The corresponding techniques are reviewed. The retention gap technique is poorly suited for water‐containing HPLC eluents (reversed phase HPLC) and fails completely if HPLC eluents contain, e.g., buffer salts. Various techniques for extracting such HPLC eluents are considered, preference being given to extraction into GC stationary phases from where solutes are thermally desorbed into the GC separation column. Limiting factors are diffusion of solutes within the liquid phase to be extracted and retention power of the extraction tubes.
Deactivation of fused silica capillary columns with cyanopropylhydrosiloxanes
Authors: Markides K. E. , Tarbet B. J. , Schregenberger C. M. , Bradshaw J. S. , Lee M. L. , Bartle K. D.
Published: May 2005

A method is described for surface deactivation and modification of fused silica capillary columns with a cyanopropyl‐containing reagent. The deactivation procedure involved a dehydrocondensation reaction between a bis(cyanopropyl)methylhydropolysiloxane reagent and surface silanol groups at an optimum temperature of only 250°C. Actual critical surface tension measurements were made using the capillary rise method. Excellent deactivation for acidic and basic compounds at the low ng level, and wettability for nonpolar and polar polysiloxane stationary phases were obtained. A procedure was developed to remove acidic impurities that are present in polar stationary phases.
Determination of glibenclamide in human serum by HPLC
Authors: Nieder M. , Dilger C. , Jaeger H.
Published: May 2005

The antidiabetic drug glibenclamide can be reliably quantitated in human serum with high performance liquid chromatography. The serum is buffered and extracted with toluene. The organic solvent is evaporated, the residue dissolved in the mobile phase and an aliquot sampled automatically and chromatographed. UV‐detection at 229 m allows a lower limit of quantitation of 5 ng/ml. Precise handling of exact volumes facilitates external calibration. Statistical data for imprecision and inaccuracy are given and illustrate reliable quantification. Application of the method to experimental and clinical pharmacokinetic studies with specific problems is illustrated.
Ion mobility detection after supercritical fluid chromatography
Authors: Eatherton R. L. , Morrissey M. A. , Siems W. F. , Hill H. H.
Published: May 2005

Using 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

A 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

The 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

Gradient 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

With 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

Data 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

General 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

A 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

Two 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

A 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

Racemic 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

A 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

Miniaturized 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

The 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

Concurrent 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

The 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

Smoke 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

A 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

Fused 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

Glass 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

A 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

A 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

This 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

The 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

Different 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.
Selective determination of oxygenates in complex samples with the O‐FID analyzer
Authors: Verga G. R. , Sironi A. , Schneider W. , Frohne J. Ch.
Published: May 2005

A gas‐chromatographic analyzer allowing the selective detection of individual oxygenates in complex organic mixtures, such as gasolines, is described. The analyzer is based on the oxygen‐specific response flame ionization detection (O‐FID) method. The system operates with capillary columns and includes a cracking reactor to convert any oxygenate to carbon monoxide and a special FID equipped with a microreactor for the catalytic hydro‐genation of CO and detection as methane. Hydrocarbons give no signal. The selectivity of the method is better than 1:107 and the linear range approaches 105. The analysis of modern fuels containing oxygenated additives, to improve octane ratings, may greatly benefit from the proposed analytical method.
Coupling micro‐LC and capillary GC as a powerful tool for the analysis of complex mixtures
Authors: Duquet D. , Dewaele C. , Verzele M.
Published: May 2005

A multidimensional chromatography system with a packed fused silica Micro‐LC column connected on‐line with capillary gas chromatography is presented. The Micro‐LC column is used for group separation. Whole peaks are injected into the capillary GC column via an on‐column injector. The reproducibility of the proposed transfer system for polyaromatic hydrocarbons is 3% to 7% relative standard deviation. The potential of this on‐line Micro‐LC‐GC system is demonstrated by the analyses of PAH's and of a complex light gasoline fraction.
The effect of column characteristics on the minimum analyte concentration and the minimum detectable amount in capillary gas chromatography. Part II: The stationary phase film thickness
Authors: Noy Th. , Cramers C.
Published: May 2005

For a typical narrow bore (50 μm) and wide bore (320 μm) capillary column the effects of increased stationary phase film thickness (df) on the minimum detectable amount, Qo, as well as on the minimum analyte concentration, Co, are described. In treating the effect of an increased film thickness, two approaches can be followed; either the separation temperature is kept constant, resulting in larger values of the capacity ratio, k, or the column temperature is increased such as to keep k constant. For normalized chromatographic conditions the effects of both approaches on the minimum plate height, optimum carrier gas velocity, and required plate number are described, finally yielding expressions for Qo and Co for both mass flow and concentration sensitive detectors. At constant temperature, Co always increases with the film thickness for mass flow sensitive detectors (e.g. FID). Wide bore thin film columns offer the lowest value of Co attainable. For concentration sensitive detectors (e.g. TCD), Co is affected neither by column diameter nor by film thickness. The Qo–df plot for constant temperature shows a minimum, suggesting an optimum film thickness for mass flow sensitive as well as concentration sensitive detectors. The corresponding capacity ratio has a value between 0.5 and 1.5. At elevated temperatures (k constant) in combination with mass flow sensitive detectors, again an optimum film thickness exists, corresponding to a minimum value of Co. For constant capacity ratio Qo always increases with the film thickness for both types of detectors. As indicated above, in some situations the lowest values of Co and Qo are obtained at an increased film thickness, the effect being marginal. As an initial guideline, for the daily practice of capillary gas chromatography with respect to minimum values of Co and Qo, the use of thin film columns is to be preferred.
Analysis of dexamethasone, triamcinolone, and their metabolites in human urine by microcolumn liquid and capillary gas chromatography mass spectrometry
Authors: Rodchenkov G. M. , Uralets V. P. , Semenov V. A. , Leclercq P. A.
Published: May 2005

Adult male volunteers were administered orally 10 mg of the espective drug. Urine samples were investigated by micro‐column liquid chromatography and capillary gas chromatography combined with on‐line mass spectrometry. The former technique was found to be usable for the detection of these drugs. The latter method appeared to be superior in terms of sensitivity and for metabolism studies. The major excretion products of dexamethasone were identified as isomeric 6‐hydroxy metabolites. Dexamethasone as such and its 20‐hydroxy metabolite were found in minor quantities. Unlike dexamethasone, triamcinolone is excreted largely unchanged from the human body. Two metabolites were identified as 11‐keto and 4,5‐dihydrotriamcinolone. With the gas chromatography methods developed, abuse of these drugs can be detected up to 24 h after administration of a 5 mg single dose.
New method for the preparation of small diameter columns with polymeric stationary phases for open tubular liquid chromatography
Authors: Dluzneski P. R. , Jorgenson J. W.
Published: May 2005

The purpose of this report is to introduce a new method for use in coating polymeric stationary phase films on the inside wall of small bore diameter fused silica capillary tubing. This technique is being developed for use in fabricating capillary columns for open tubular liquid chromatography.
Cyclodextrins as chiral stationary phases in capillary gas chromatography. Part II: Heptakis(3‐O‐acetyl‐2,6‐di‐O‐pentyl)‐ß‐cyclodextrin
Authors: König W. A. , Lutz S. , Wenz G. , von der Bey E.
Published: May 2005

Heptakis (3‐O‐acetyl‐2,6‐di‐O‐pentyl)‐ß‐cyclodextrin is used as a chiral stationary phase in capillary gas chromatography. High enantioselectivity towards trifluoro‐acetylated α and β‐chiral amines, amino alcohols, α‐ and β‐amino acid esters, and cyclic trans‐diols is observed. In contrast to chiral polysiloxane phases, where hydrogen bonding interaction is essential for enantiomer separation, in cyclodextrins inclusion properties contribute to enantioselectivity. This can be concluded from the separation of N‐alkylated amino compounds. The new chiral stationary phase exhibits a wide operating temperature range and is stable above 200°C.
Deactivation by polysiloxane and phenyl containing disilazane: A 29SI CP‐MAS NMR study after the formation of polysiloxane chains at the surface
Authors: Hetem M. , Rutten G. , van de Ven L. , de Haan J. , Cramers C.
Published: May 2005

A high degree of deactivation of glass and fused‐silica capillary column walls is attainable by means of high temperature silylation (HTS) with or without a preceding leaching process. HTS with a phenyl containing disilazane, diphenyltetramethyldisilazane (DPTMDS), and polydimethylsiloxane (PDMS) are studied on Cab‐O‐Sil, a fumed silica, as a model substrate. Using 29Si CP‐MAS NMR, it was shown that no dimethylsiloxane chains were formed upon silylation with DPTMDS under different conditions of humidity and stoichiometry at 377°C. With DPTMDS deactivation it is possible that amino trisiloxy silane groups are formed, these groups add extra activity to the surface. Silylation with a PDMS, OV 101, at various temperatures between 300°–420°C did show that dimethylsiloxane chains were bonded at the surface. Using the 29Si CP‐MAS NMR technique with variable contact times to reveal siloxy group mobility, the degradation of dimethylsiloxane chains at the surface was studied. PDMS degradation at an optimal temperature gives a more effective diminuation of the silane activity caused by chemical reaction with the silanol groups and the effective screening of the remaining silanol groups with anchored polydimethylsiloxane chains and small cyclodimethylsiloxane ring structures at the surface.
Co‐solvent effects for preventing broadening or loss of early eluted peaks when using concurrent solvent evaporation in capillary GC. Part 2: n‐Heptane in n‐pentane as an example
Authors: Grob Konrad , Müller Eugen
Published: May 2005

Co‐solvent effects are applied to allow use of concurrent solvent evaporation for applications requiring analysis of compounds eluted less than some 50° above the column temperature during sample introduction, i.e. at oven temperatures below some 100–120°C. Required conditions such as GC even temperature, concentration of the co‐solvent and length of the uncoated pre‐column (retention gap) are studied theoretically as well as experimentally for the case of n‐heptane as co‐solvent in n‐pentane.
PTV splitless injection of sample volumes up to 20 μl
Authors: Grob Konrad , Li Zhangwan
Published: May 2005

PTV splitless injection cannot compete with on‐column injection as far as simplicity, reliability, and accuracy of quantitative analysis is concerned. However, PTV splitless injection is attractive for trace analysis of samples containing high concentrations of involatile sample by‐products. Maximum injection volumes are limited by the amount of liquid that can be retained within the PTV injector chamber and are around 20–30 μl injected at once. Solvent evaporation must be carried out in such a way that injector overflow is avoided.
Gas chromatographic and mass spectrometric characterization of isomeric alkylthiophenes (C20) and their occurrence in deep sea sediments
Authors: Rullkötter J. , Landgraf M. , Disko U.
Published: May 2005

Six isomeric C20 alkylthiophenes were synthesized in order to prove the occurrence of such compounds in various deep sea sediments. As expected from the analogy with the corresponding saturated hydrocarbons, 2‐ and 3‐heptadecylthiophene have considerably longer relative retention times than the isomeric isoprenoid compounds, i.e. 2‐ and 3‐(4,8,12‐trimethyltridecyl)thiophene and 3‐ and 4‐methyl‐2‐(3,7,11‐trimethyldodecyl)thiophene. Covats retention indices for all compounds were determined by isothermal analysis at 190°C on two different silicone‐coated capillary columns. The mass spectra of the monoalkylated thiophenes show a base peak at m/z 98 corresponding to a Mcafferty rearrangement product in the case of the 3‐substituted isomers, whereas a simple benzylic cleavage dominates in the mass spectra of 2‐alkylthiophenes. 4‐Methyl‐2‐(3,7,11‐trimethylodecy)thiophene is an exception from this simple rule because also shows the McLafferty rearrangement as dominant fragmentation. Two of the isoprenoid thiophenes are prominent compounds in various deep sea sediments.
Analysis of turkish lignite tar by coupled LC/GC, GC/MS, and capillary SFC
Authors: Davies I. L. , Raynor M. W. , Urwin D. J. , Bartle K. D. , Tolay M. , Ekinci E. , Schwartz H. E.
Published: May 2005

This work describes the analysis of a pyrolysis product of a lignite sample obtained from the Turkish Goynuk reserve. The aliphatic, aromatic and polar compounds present in the tar are separated and identified by various chromatographic techniques: Capillary gas chromatography/mass spectrometry (GC/MS), on‐line high performance microbore liquid chromatography/capillary gas chromatography (LC/GC) and capillary supercritical fluid chromatography (SFC). The suitability of each technique for this particular application is discussed, and semi‐quantitative results are presented for the major components detected.
Automation in the chemical analysis of suspect arson samples by GC/MS. A systematic approach
Authors: Bertsch W. , Sellers C. S. , Babin K. , Holzer G.
Published: May 2005

A method ist described that permits direct comparison of ion chromatograms between an isolate from a suspect fire debris sample and corresponding accelerant profiles. The system is highly automated and produces a diagnostic one page summary report for each sample. Side by side comparison of ion profiles is carried out between 4 common fuel types, e. g. gasoline, naphthenic type charcoal lighter fluid, mineral spirits, and kerosene, and the sample. Both qualitative and semiquantitative information is available. An on‐line search can also be carried out in which mass spectra are compared between components in a suspect sample and standards that are contained in an accelerant library. The system is flexible and requires only minimal interaction with the analyst.
Quantitative determination of volatiles in polyolefins by dynamic headspace/capillary gas chromatography/mass spectrometry
Authors: Hagman A. , Jacobsson S.
Published: May 2005

The possibilities of quantitative dynamic headspace by use of a multiple extraction method and an internal gas standard system for various classes of organic compounds in polyethylene and polypropylene are demonstrated. Numerous compounds can be analyzed over wide ranges of concentration and vapor pressure. However, the present study shows that the precision of the desorption parameters is of critical importance for assuring good quantitative results. The possibilities of using a theoretical model are also described. The recovery may be determined and the use of repeated desorption cycles can be reduced.
Gas chromatographic method for simulated distillation up to a boiling point of 750°C using temperature‐programmed injection and high temperature fused silica wide‐bore columns
Authors: Curvers J. , van den Engel P.
Published: May 2005

It is demonstrated that linear injection characteristics are obtained for a wide boiling point range sample using a temperature‐programmed injector in combination with wide‐bore fused silica columns. The applicability of the described combination for high temperature simulated distillation is described. The method, using external standardization, gives accurate and repeatable results for different types of samples in the boiling range between 50 and 750°C. The lifetime of the fused silica wide‐bore columns was found to be acceptable, viz. over 80 temperature‐programmed cycles between ambient and 430°C. Some comments are made on the accuracy of boiling points for normal alkanes.
Cyclodextrins as chiral stationary phases in capillary gas chromatography. Part IV: Heptakis(2,3,6‐tri‐O‐pentyl)‐β‐cyclodextrin
Authors: König W. A. , Lutz S. , Hagen M. , Krebber R. , Wenz G. , Baldenius K. , Ehlers J. , Dieck H. Tom
Published: May 2005

O‐Perpentylated β‐cyclodextrin has been evaluated as chiral stationary phase in capillary gas chromatography. Enantioselectivity is observed towards many chiral hydroxy compounds, including cyanohydrins and carbohydrates. Most importantly, the enantiomers of many olefins and alkyl halides can be resolved on this chiral phase. The thermal stability of the cyclodextrin derivative exceeds 200°C.
Gas chromatographic analysis of traces of light hydrocarbons. A review of different systems in practice
Authors: Schaeffer Hans‐Jörg
Published: May 2005

In recent years air quality and atmospheric investigations have become very important topics. This results from a new legal basis for environmental protection which generates the need for the accurate measurement of ambient conditions. Despite the importance of these investigations, detailed reviews characterizing the existing analytical GC systems are scarce. The author has attempted to remedy this unsatisfactory situation by presenting a comprative review of the principal commercially available systems as well as some homemade set‐ups. No single method will be optimal for all purposes. The system of choice will depend on the particular application and on the quality and composition of the sample. This review does not attempt to cover all existing systems, but some exotic or lesser known systems have also been included.
Resolution–definition and nomenclature
Authors: Sandra P.
Published: May 2005

Chromatographic resolution is a well defined concept, which is expressed in terms of column efficiency N, separation factor α, and retention factor k. The influence of the three factors on resolution is discussed and illustrated by examples taken from capillary gas chromatography.
Determination of amino acids in human cerebrospinal fluid by gas chromatography
Authors: Labadarios D. , Moodie I. M. , Hough B. J. , Burger J. A.
Published: May 2005

In the present study, the use of gas chromatography (GC) for the determination of amino acids in human cerebrospinal fluid (CSF) is described. Although some amino acids may be determined using a packed column following the removal of glucose, the major interfering component, the inadequate resolution of other amino acids from remaining unidentified components results in poor quantitation. The use of wide bore columns improves reproducibility considerably, but still it does not provide sufficient resolution to enable quantitative determination of all amino acids in human CSF. Good reproducibility data, with CV values for all amino acids of 7% or less and recoveries generally between 80% and 100%, can only be obtained using the fused silica open tubular (FSOT) column. Normal amino acid levels are presented for 10 samples of human CSF, which compare well with data previously reported in the literature.
Preparation of high temperature stable glass capillary columns coated with PS‐090 (20% diphenyl substituted CH3O‐terminated polysiloxane) a selective stationary phase for the direct analysis of metal‐porphyrin complexes
Authors: Blum W. , Eglinton G.
Published: May 2005

In this report we describe the coating of delonized glass surfaces with commercially available CH3O‐terminated diphenyl‐dimethylpolysiloxane (PS‐090). This new type of reactive, high temperature stable stationary phases withstands temperatures up to 430°C. As already reported for OH‐terminated polymers, the underlying stabilization process is a condensation of methoxy groups of the phase with surface silanol groups arising from high temperature silylation. The good selectivity of this medium polar coating for substrates bearing π‐electron systems is demonstrated by the separation of various metalloporphyrins.
Detection limits of thermal conductivity and photoionization detectors in high speed narrow bore CGC
Authors: van Es A. , Cramers C. , Rijks J.
Published: May 2005

Not only the required input band width and the availability of compatible instrumentation limit the reduction of column diameter but so do the column sample capacity and detector characteristics, such as volume and sensitivity. In this paper the scope and limitations of thermal conductivity and photoionization detection at atmospheric and reduced pressures for capillary gas chromatography are discussed at length.

It is shown that the sensitivity of a thermal conductivity detector is inversely proportional to the pressure. Reduction of cell volume and decrease of pressure appear equivalent with respect to minimum detectable amount and peak broadening. This results in femtogram detection limits for column diameters as low as 10 μm.

For photoionization detectors the sensitivity did not improve at reduced pressures, so that the effect of reduced pressure and addition of make‐up gas on the detection limits is the same. Nevertheless, the applicability of a low volume photoionization detector (40 μl) for capillary columns with a diameter as low as 50 μm will be demonstrated by series coupled PID and FID detectors and illustrated with various applications.