bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature programmed retention indices: Calculation from isothermal data. Part 1: Theory
Authors: Curvers J. , Rijks J. , Cramers C. , Knauss K. , Larson P.
Published: May 2005

Direct conversion of isothermal to temperature programmed indices is not possible. In this work it is shown that linear temperature programmed retention indices can only be calculated from isothermal retention data if the temperature dependence of both the distribution coefficients and the column dead time are taken into account.

Procedures are described which allow calculation of retention temperatures and from these, accurate programmed retention indices. Within certain limits the initial oven temperature and programming rate can be chosen freely. The prerequisite for this calculation is the availability of reliable isothermal retention data (retention times, retention factors, relative retention times, or retention indices) at two different temperatures for one column.

The use of compiled isothermal retention indices at two different temperatures for the calculation of retention temperatures and thus temperature programmed indices is demonstrated. For the column for which programmed retention indices have to be determined, the isothermal retention times of the n‐alkanes and the column dead time as a function of temperature have to be known in addition to the compiled data for a given stationary phase.

Once the programmed retention indices have been calculated for a given column the concept allows the calculation of temperature programmed indices for columns with different specifications. The characteristics which can be varied are: column length, column inner diameter, phase‐ratio, initial oven temperature, and programming rate.
Dynamic headspace enrichment system for CGC analysis of volatiles released by plants
Authors: Termonia M. , Alaerts G.
Published: May 2005

The aim of the present study is to develop a method for following the changes in the chemical composition of volatile substances released by plants. Dynamic headspace enrichment, followed by on‐line thermal desorption and cryotrapping was coupled with capillary gas chromatography. The technique was optimized by adjusting the sampling and desorption parameters and by designing a special condensing device to avoid the transfer of excessive amounts of water into the analytical column. Details are given for the characterization of volatiles compounds released by mosses.
Micro‐HPLC 1: Linear “breakthrough‐gradients” using the discontinuous interface between eluents in a packed gradient‐generator column
Authors: Berry V. , Ishii D. , Takeuchi T.
Published: May 2005

A new approach is described for micro‐HPLC for generating nearly linear gradients in the 40 to 550 μl volume range. These “linear” gradients have a straight line middle portion with a gentle curved onset of the gradient andd rapid attainment of the final 100% composition. Such “breakthrough‐gradients” are produced by the interface between weak and strong eluent when a small (3 × 0.46 cm) packed “gradient‐generator” column is switched abruptly from weak to strong eluent. The model system described here, without an analytical column, shows gradients from weak eluent (water) to strong eluent (modele with water plus acetone) using a 12‐port high pressure valve to 1) vent the “flush” eluent, and simultaneously 2) begin the gradient and 3) make the sample injection.

The volume of the gradient can be changed in two ways. If the breakthrough‐generator is packed with very large (300 to 1600 μm nonporous particles, the gradient volume is nearly independent of the flush flow rate. The flush flow is used to quickly move the breakthrough‐interface to the head of the micro‐HPLC column. However, the gradient volume can be increased by using larger solid particles in the gradient‐generator column because of increased eddy diffusion. If the gradient‐generator is packed with porous particles (75–150 μm), the gradient volume can be changed over a broad range by simply changing the flush flow rate. This simple control over the gradient volume is due to the increased mass transfer of weak eluent out of the porous particles into the strong eluent at higher flush flows.

The breakthrough‐interface gradient‐generator column approach provides the following advantages for micro‐HPLC:

– Gradient volumes can be readily varied over the micro‐HPLC range 40–550 μl.

– Gradient are linear with smooth and rapid onset of intial and final concentrations.

– Gradient are produced inexpensively with a single high‐pressure precision pump.

– Gradient can be automated with a timer and single 12‐port valve that provides both column regeneration and sample injection.
A study of some deactivation methods for fused silica capillary columns by CP‐MAS NMR and capillary gas chromatography
Authors: Rutten G. , de Haan J. , van de Ven L. , van de Ven A. , van Cruchten H. , Rijks J.
Published: May 2005

The effect of deactivating a fused silica surface by silylation with 1,1,3,3‐tetraphenyl‐1,3‐dimethylilazane (TPDMDS), triphenylsilylamine (TPSA), and octamethylcyclotetrasiloxane (D4) and by polydimethylsiloxane degradation (PSD) is studied. Rehydrated, dried, and deactivated Cab‐O‐Sil M5 samples are used as model materials for 29Si CP‐MAS NMR analysis.

At about 350 °C, TPDMDS yelds mainly diphenylmethylsiloxysilane, dimethyldisiloxysilane, and triphenylsiloxysilane groups. TPSA yields phenyltrisiloxysilane, diphenyldisiloxysilane, and triphenylsiloxysilane groups. At 400°C, the products formed initially are eventually replaced by methyltrisiloxysilane or phenyltrisiloxysilane groups, while a substantial number of silanol groups still remains. The possible consequences for wettability are discussed.

D4 reacts with Cab‐O‐Sil even at 200°C, but a large number of silanol groups remains. This number decreases gradually at higher temperatures and becomes negligible above 400°C. The formation of methyltrisiloxysilane groups, which starts at 425°C, is predominant at 490°C.
Loss of water during heat treatment of acid leached glass and fused silica capillary columns
Authors: Venema A. , Sukkel J. T.
Published: May 2005

A study was carried out on the effects of acid leaching of capillary column wall materials. Leaching experiments with glass and fused silica were performed under static and dynamic conditions; moreover, the influence of the temperature was investigated. The amount of water released during different temperature programs was measured with a microwave plasma detector. Different leaching conditions and column wall materials cause considerable variations in water production. These results probably explain the disappointing deactivation efficiency obtained for fused silica and dynamically leached soft glass if HMDS is used. Evidence was found for an increase in surface area due to acid leaching.
A study in high‐temperature silylation of silica
Authors: Welsch T. , Frank H.
Published: May 2005

High‐temperature silylation (HTS) used for the deactivation of capillary columns was studied on the silica commonly used in HPLC to gain a better insight into this process. LiChrosorb Si 100 was silylated with disilazanes at different temperatures and the materials obtained were compared in terms of organic and silanol group surface concentration, IR reflection spectra, HPLC behavior, and pore distribution parameters. Applying diphenyltetramethyldisilazane, the volatile reaction products were monitored during the HTS process. With increasing silylation temperature up to 400°C the silanol surface concentration is reduced to a very small level independent of the organic group concentration which exhibits a broad maximum depending upon substituents and temperature. Up to 350°C triorganosiloxy groups prevail as bonded organic groups. It could be proved that HTS is accompanied by pore alterations of the silica matrix. Arguments proposed by different authors in explaining HTS effects are discussed.
A new bonded stationary phase for the gas chromatographic separation of volatile priority pollutants and chlorinated pesticides
Authors: Mehran M. F. , Cooper W. J. , Lautarno R. , Freeman R. R. , Jennings W.
Published: May 2005

A new phenyl‐cyanopropyl polymethylsiloxane stationary phase, DB‐1301, which can be crosslinked and bonded to the fused silica surface, has been synthesized. The phase composition was optimized for the separation of 18 volatile priority pollutants, selected from the so‐called “purgables” list because of problems associated with their resolution. The composition of the stationary phase was based on theoretical considerations of binary phase mixtures and window diagram prediction. Columns coated with this stationary phase are compatible with atom selective detectors, such as the electron capture detector. A mixture of 18 volatile priority pollutants and a mixture of chlorinated pesticides were used as test probes on a prototype 30 m × 0.32 mm fused silica column, containing a 1.0 μm film of DB‐1301.
Gas chromatographic – mass spectrometric analysis of compounds generated upon thermal degradation of some stationary phases in gas chromatography – Part II
Authors: Schmidt S. , Hoffmann S. , Blomberg L. G.
Published: May 2005

The applicability of capillary columns for gas chromatography is often limited by stationary phase degradation at elevated temperatures. In order to achieve a better understanding of column thermostability, column bleed products have been analyzed qualitatively by gas chromatography‐mass spectrometry (GC‐MS). Three silicone stationary phases were studied: SE‐52, SE‐54, and OV‐1701. Each of these was immobilized in the columns. The proportion of cyclics containing diphenyl in column bleed from SE‐52 reflected to a large extent the composition of the polymer, while for SE‐54 the proportion of such cyclics was unexpectedly high. The polar moiety of OV‐1701, the cyanopropyl(phenyl)siloxy unit, was found to exert a highly destabilizing effect on the polymer, and the thermal degradation products consisted mainly of cyclosiloxanes containing this unit.
Application of chemometrics in homolog‐specific analysis of polychlorinated biphenyls
Authors: Onuska F. I. , Mudroch A. , Davies S.
Published: May 2005

A principal components multivariable statistical method based on SIMCA 3B (Soft Independent Method of Class Analogy) algorithms was evaluated and applied to interpretation of homolog‐specific analysis of polychlorinated biphenyls by high resolution gas chromatography. High resolution gas chromatograms can be evaluated in high resolution separations of individual PCB isomers and grouped into the homologous series. The chromatograms show distinct differences between PCB compositions with different contents of chlorine atoms in technical mixtures (Aroclors). The objective of utilizing SIMCA 3B was its evaluation for a possible identification, classification, and categorization of Aroclors in environmental samples.
Determination of bile acids and lysolecithin in artificial and natural gastric juice by HPLC for characterization of antacida
Authors: Nieder M. , Jaeger H. , Guthauser U. , Althaus B.
Published: May 2005

Work‐up procedures and HPLC separation systems for determination of taurocholic, glycocholic, chenodeoxycholic, and cholic acids and lysolecithin in artificial and natural gastric juice are described. These compounds are used for testing the binding capacity of antacida to the individual analytes. Work‐up is simple, no extraction or filtration being required. The optimized combinations of stationary and mobile phases allow selective and sensitive determination of the respective bile acids in gastric juice. For optimization, the capacity factors of two related bile acids were evaluated for numerous commercial stationary phases. The mechanism of retention is different for free and conjugated bile acids. Special aspects of routine analysis are discussed.
Characterization of Pygeum africanum bark extracts by HRGC with computer assistance
Authors: Martinelli E. M. , Seraglia R. , Pifferi G.
Published: May 2005

The components of Pygeum africanum bark extracts, used for the treatment of benign prostatic hypertrophy, were characterized by high resolution gas chromatography (HRGC) and mass spectrometry (MS). Among various compounds n‐docosyl trans‐ferulate was identified and quantitated by HRGC as a derivative of n‐docosanol, which is considered to be one of the active components of the extract. The origin of different Pygeum a. extracts can be studied by eigenvector projection of HRGC profiles with computer assistance.
Study of protein association and micelle formation in surfactants by microcolumn exclusion chromatography
Authors: Zimina T. M. , Maltsev V. G. , Belenskii B. G.
Published: May 2005

The application of microcolumn exclusion chromatography to the determination of equilibrium and kinetic association constants for proteins is described. Taking phospholipase A2 as an example, the relationship between association and enzymatic activity was investigated. A procedure for determination of the critical concentration of micelle formation (CCM) in surfactants was developed.
New detection strategies through supercritical fluid chromatography
Authors: Novotny M.
Published: May 2005

This article reviews the current status and developmental trends in detection for supercritical fluid chromatography. The “GC‐like” and “LC‐like” detection techniques are treated separately, while the needs of structural identification techniques for SFC separations are emphasized.
Evaluation of a thermionic detector for capillary supercritical fluid chromatography of nitrated polycyclic aromatic compounds
Authors: West W. R. , Lee M. L.
Published: May 2005

A thermionic detector was evaluated for capillary supercritical fluid chromatography of polar nitro‐containing polycyclic aromatic compounds (nitro‐PAC). Three modes of detector operation were studied. The best performance was obtained using a nitro‐selective mode of detection. Although linearity was confined to a narrow range for a given source current, the sensitivity was excellent; 20 pg injected for p‐nitrophenol gave a signal‐to‐noise ratio of 3. Conventional thermionic detection also produced good sensitivity; however, serious baseline drift was observed at high operating temperatures using density programming. A third mode, flame thermionic detection, was not acceptable because of low sensitivity. A number of nitro‐PAC were successfully chromatographed using density programming at 101°C. Hydroxynitropyrenes, nitropyrene quinones, and 9‐hydroxy‐2‐nitrofluorene, which could not be eluted in capillary gas chromatography, were successfully chromatographed here. Retention of these compounds increased sequentially on 50% n‐octyl‐, 5% phenyl‐, and 25% biphenyl polysiloxane stationary phases, respectively. Stationary phase interactions appeared to be more a function of the polar functional groups on the aromatic rings than of the hydrocarbon character of the compounds. Solute solubility in the mobile phase and volatility were additional factors contributing to the elution of these molecules. Finally, these results were used to identify a number of nitro‐PAC in a polar subfraction of a diesel particulate extract.
Capillary supercritical fluid chromatography of archaebacterial glycerol tetraether lipids
Authors: DeLuca S. J. , Voorhees K. J. , Langworthy T. A. , Holzer G.
Published: May 2005

The analysis of bacterial glycerol tetraethers by capillary supercritical fluid chromatography is described. Complete separation of ethers, differing only by the number of cyclopentane rings present in the isopranyl side chains could be achieved. On a 50% methylphenylpolysiloxane coated capillary, the ethers eluted in the order of increasing cyclopentane content. The analysis revealed the presence of two previously unreported structural isomers of glycerol tetraethers. The method can be used qualitatively and quantitatively as a fast and sensitive screening test for such compounds in living organisms and sedimentary organic matter.
A linear relationship between partition ratio and composition of a binary mobile phase in reversed‐phase liquid chromatography using chemically bonded stationary phases
Authors: Jaroniec M. , Jaroniec J. A.
Published: May 2005

A simple linear relationship which enables the effect of the composition of a binary mobile phase on the retention of a solute to be assessed in reverse phase liquid chromatography using a bonded stationary phase has been derived. The equations have been tested using published experimental data.
Stationary‐phase focusing in capillary gas‐liquid chromatography: Enhancement of the maximum permissible sample size
Authors: Pretorius V. , Lawson K.
Published: May 2005

Equations have been derived to predict the extent to which the sample size may be increased, without decreasing the column performance, by stationary‐phase focusing at sub‐ambient temperatures. Under favorable circumstances the sample size may be enhanced several hundredfold.
Stationary‐phase swelling and its consequences in capillary gas‐liquid chromatography
Authors: Pretorius V. , Lawson K.
Published: May 2005

Sample introduction using the solvent effect can lead to significant swelling of the stationary phase. The phenomenon has been studied theoretically and experimentally. The longitudinal profile of the swollen phase has been established. Swelling can affect the retention time of solutes, the shape of solute bands emerging from the inlet, and the maximum permissible sample size.
A study of thermal peak splitting in capillary GC
Authors: Reed G. D. , Hunt R. J.
Published: May 2005

Fluctuating thermal gradients are recognized as a distinct source of peak splitting in capillary column gas chromatography. In this study, the influence of analyte signal level, temperature oscillation amplitude, and oscillation frequency on splitting are quantitatively examined. Stable gradients are also considered. A simple, effective method is proposed for virtually eliminating thermal peak splitting in isothermal capillary GC analysis.
Relation between the programmed and isothermal retention indices in chromatography
Authors: Said A. S. , Jarallah A. M. , Al‐Ameeri R. S.
Published: May 2005

A systematic approach was utilized to deduce the relation between the programmed and isothermal retention indices in chromatography. The relation was given in the form of a chart from which the equivalent isothermal temperature Te is plotted vs ΔT′ with IP as the parameter. ΔT′ is a function of both the inlet and outlet temperatures during the temperature programmed run and Te is the temperature at which the isothermal index is equal to the programmed index IP.
Dual capillary gas chromatographic analysis of alcohols and methyl tert‐butyl ether in gasolines
Authors: Levy J. M. , Yancey J. A.
Published: May 2005

A gas chromatographic method has been developed for the identification and direct determination of alcohols and methyl tert‐butyl ether (MTBE) in gasolines. The technique involves simultaneous injection of the gasoline without any sample preparation onto two fused silica capillary columns of differing polarities. The method permits simultaneous determinations of methanol, ethanol, 2‐propanol, tert‐butanol, 1‐propanol, sec‐butanol, 1‐butanol, and MTBE. By using an automatic sampler in combination with electronic pressure programming and BASIC programming, the determinations were performed automatically and reproducibly with a relatively short analysis time.
Automated determination of nifedipine in human plasma by capillary gas chromatography with electron capture detection
Authors: Lutz D. , Ilias E. , Jaeger H.
Published: May 2005

A rapid, sensitive, and reliable method for the determination of nifedipine in human plasma is described. Using a single‐step solvent extraction and capillary gas chromatography combined with electron capture detection, an assay sensitivity of 2 ng/ml is achieved routinely using 0.5 ml of plasma. Intact nifedipine is quantitated and separated from its nitroso‐ and nitropyridine‐derivatives. The suitability of the assay for pharmacokinetic studies is illustrated.
Multidimensional GC with macrobore WCOT and PLOT Columns
Authors: Naizhong Z. , Green L. E.
Published: May 2005

Multidimensional GC (MDGC) with macrobore WCOT and PLOT columns has shown several benefits: (1) Higher flow rates, which are used, makes possible the use of common valves as the switching device; (2) very simple system configurations are possible; (3) because the columns have relatively large capacity, the TCD can be used to measure both organic and inorganic components; (4) micropacked or open tubular columns are precolumns which provide a wide range of selectivity; (5) both precolumn and analytical columns can be operated at the same flow rate without splitting of the sample. Four rapid sample analyses: (1) Oxygenates in gasohol; (2) natural gas; (3) refinery gas; (4) hydrocarbon types in naphtha, have been developed and performed on a less complex and economical gas chromatograph.
Separation and detection of doxylamine and its rhesus monkey urinary metabolites by high resolution gas chromatography utilizing nitrogen/phosphorus detection
Authors: Rushing L. G. , Gosnell A. B. , Holder C. L. , Korfmacher W. A. , Slikker W.
Published: May 2005

A high resolution gas chromatographic method is described for the separation of rhesus monkey urinary metabolites of doxylamine with the use of on‐column injection, a fused silica column (DB‐1701), and nitrogen/phosphorus detection. An ancillary separation of doxylamine and six other antihistamines is also presented.
High resolution chromatographic techniques for the evaluation of atmospheric pollutants
Authors: Liberti A. , Ciccioli P.
Published: May 2005

The use of high resolution chromatographic techniques for the determination of species of great importance in atmospheric pollution is critically reviewed. Attention has been focused on those pollutants recently recognized to be responsible for biological activity of particulate matter, acid deposition, and photochemical smog generation. The unique contribution made by capillary GC to the solution of environmental problems is demonstrated by the results obtained in the identification of several nitrofluoranthene/pyrene isomers in urban dust, industrial emissions, and automobile exhaust and by the selective determination of 2,3,7,8‐tetrachlorodibenzo‐ρ‐dioxin in fly‐ash emitted from urban incinerators. Also organic components dissolved in rain‐water can be analyzed by capillary chromatography after sample enrichment on traps filled with solid sorbents. The recent availability of sampling precedures suitable for the collection of gaseous species which play an important role in acid deposition makes possible their determination by chromatographic techniques. Inorganic acids, sampled through high efficiency annular denuders to obtain discrimination between gaseous species and aerosols, can be determined by ion chromatography. Peroxyacyl nitrates, relevant to photochemical pollution, can be determined by GC combined with electron capture detection. New fields of application for high resolution chromatography are discussed.
Gas chromatography of amino acids: Use of a fused‐silica capillary column in the determination of plasma amino acids
Authors: Labadarios D. , Moodie I. M. , Burger J. , Shephard G. S.
Published: May 2005

A capillary chromatographic procedure using a fused silica column is described which can be used to quantitatively determine amino acids in plasma following the pre‐chromatographic “clean‐up” described in a recent paper [1]. In substituting this procedure for that involving a packed column, advantage has been taken of the greater resolving power to separate amino acids from background component peaks. In order to extend this advantage and provide a sound basis for quantitative analysis, the technique of cold on‐column injection was employed. As a result, good precision of standard analysis was obtained with relative standard deviation (RSD) values for all amino acids of less than 4%. Application of the entire procedure to plasma samples yields RSD values of better than 10% for all amino acids with recoveries ranging from 72% to 104%. Simultaneous determination of plasma amino acid levels by gas chromatography (GC) using capillary columns and by classical ion exchange (CIE) showed reasonable agreement. Statistical evaluation showed no significant difference between twelve amino acids. Values for the remaining two, namely, phenylalanine and histidine are significantly different (p < 0.005). Comparison of the values obtained from GC capillary and packed columns reveals no significant difference between fourteen amino acids. Significant differences exist between results for phenylalanine and tyrosine (p < 0.001). It is concluded that there is good agreement between data obtained by GC capillary and CIE techniques and that differences between results for phenylalanine and histidine are method related.
Selective quantification of ambroxol in human plasma by HPLC
Authors: Nieder M. , Jaeger H.
Published: May 2005

The bronchosecretolytic drug ambroxol can be reliably quantified in human plasma by high performance liquid chromatography. Plasma is buffered alkaline, extracted with ether, and the organic solvent back‐extracted with diluted acid. An automatically sampled aliquot is separated by reversed phase HPLC; the analyte is well separated from two metabolites that interfered strongly in earlier methods. UV detection at 230 nm enables a lower limit of quantitation of 5 ng/ml. Internal standardization with propranolol allows accurate and precise quantification. Evaluation of the optimized combination of mobile and stationary phase is described, and application of the method to experimental and clinical pharmacokinetic studies is illustrated.
Isocratic networks in supercritical fluid chromatography
Authors: Leyendecker D. , Leyendecker D. , Schmitz F. P. , Klesper E.
Published: May 2005

For chromatography with supercritical fluids (SFC), the dependence of the capacity ratios k′ and of the mean resolution Rm on temperature and pressure is presented as a three‐dimensional diagram. A sufficient number of test chromatograms were run for the diagram to lead to an isocratic network in form of a curved surface. The isocratic network possesses a characteristic shape and contains all information about the temperature and pressure dependence of k′ and Rm for a given volume flow rate and chromatographic system. The specific system studied comprised pentane as the mobile phase, unmodified silica as the stationary phase, and a set of four polycyclic hydrocarbons as the test mixture. The isocratic net of this system allows interpolation of k′ and Rm for any temperature and pressure. Together with similar experimental data from other systems, this allows qualitative forecasts about the isocratic nets of other systems.
Determination of UV‐transparent compounds by liquid chromatography using the UV detector
Authors: Gupta P. K. , Nikelly J. G.
Published: May 2005

An indirect UV photometric detection technique is described in which a low concentration of a UV‐absorbing compound (UVAC) is added to the mobile phase in reversed phase liquid chromatography, thereby making it possible for non UV‐absorbing compounds such as the lower alcohols to be detected by the UV detector. This happens because the injected analyte may extract a portion of the UV absorbing compound from the mobile and/or stationary phase and the complex is co‐eluted as a positive peak at the retention time of the analyte. Alternatively, the injected analyte may appear as a negative peak if the UV‐absorbing compound is transferred to the mobile and stationary phases. In any case, the injected compound appears either as a positive or negative peak depending on the relative polarities and concentrations of all the compounds in the system. In addition, the resulting excess or deficiency of detection agent in the stationary phase is eluted separately as a positive or negative peak, indicating that the system has returned to equilibrium. In the work described herein, the chromatographic conditions and variables of the indirect photometric technique were studied to develop a quantitative HPLC method for UV‐transparent compounds. It was found that under optimal conditions it is possible to determine some analytes quantitatively at concentrations as low as 0.05%.
A high resolution GC‐analysis method for determination of C2‐C10 hydrocarbons in air samples
Authors: Matuška P. , Koval (deceased) M. , Seiler W.
Published: May 2005

An analytical method for the determination of non‐methane hydrocarbons (NMHC) in air was developed using simultaneously pressure and temperature programmed gas chromatography (GC) on a capillary column. The separation of C2‐C10 hydrocarbons was performed in a single GC‐run using a fused silica capillary column (FSCC) with a chemically bonded non‐polar stationary phase (CP‐Sil‐5‐CB). A combination of on‐column cryofocusing and GC reinjection provided baseline separation of C2 hydrocarbons at subambient initial temperature (−40°C). The cryofocusing was performed on the column head immersed in liquid nitrogen. Quantitative retention of all C2‐C10 hydrocarbons was achieved only when a temperature gradient is created along the cooled column section. The focused components are eluted from the column head without supplementary heating by removing the coolant. To eliminate matrix effects, the enrichment procedure was designed to remove CO2 and H2O. The detection limit was found to be 2.0 × 10−12 g propane.
Violation of the linearity principle of additivity of sorption energy in chromatography. A universal equation describing retention behavior
Authors: Golovnya R. V. , Grigoryeva D. N.
Published: May 2005

Deviations from the additivity of energy contributions to substance sorption energies, determined on the basis of thermodynamic studies of GC behavior of homologous series of organic compounds fall into two categories: one for n‐alkanes, the other for homologous series containing a functional group. A previously derived equation is proposed for homologous series, describing the deviation from the linear dependence of retention parameters with a propagating homolog n‐alkyl chain. The equation permits calculation of retention parameters of homologs starting from the first member in gas‐liquid, gas‐solid, and liquid‐liquid systems. The results prove its universal applicability.
Fused silica capillary tube isotachophoresis using a multichannel photodiode array detector
Authors: Goto M. , Ueda Y. , Ishii D.
Published: May 2005

Isotachophoresis carried out in a 0.25 mm i.d. fused‐silica capillary tube yielded high resolution, compared with that in a fluorinated ethylene‐propylene polymer tube. The use of an ultraviolet‐visible multichannel spectrophotometer with photodiode array as detector together with a cross flow cell (volume 0.01 μl) was investigated. The system was successfully applied to the analysis of cationic dyes such as neutral red, bismarck brown, and basic fuchsine.
High speed capillary GC on 10 m × 100 μm i.d. FSOT Columns
Authors: Proot M. , Sandra P.
Published: May 2005

The chromatographic performance of 10 m × 100 μm i.d. capillary columns, coated with different stationary phases, was studied. TZ‐ū plots were measured at different temperature program rates. The polarity and selectivity are strongly influenced by the temperature program rate. The analysis time depends on the capacity ratio and the selectivity factor; stationary phase selection thus is an important aspect in high speed capillary GC. A number of applications is presented and the applicability of split injection is discussed.
Refractive index detection in slurry‐packed capillary column LC
Authors: Fujimoto C. , Morita T. , Jinno K.
Published: May 2005

An existing commercial refractive index detector was modified for use with slurry‐packed capillary column LC systems. The cell gasket of the original detector cell was replaced by a micro cell gasket giving a volume of 0.8 μL. The relationship between detector response and the amount of sample injected was examined. The limit of detection was 2‐3 ng for di‐n‐pentyl phthalate.
Tapered versus constant diameter post‐column restrictors in capillary SFC
Authors: Bally R. W. , Cramers C. A.
Published: May 2005

A one‐dimensional compressible flow model is used in the description of actual flow through ducts. This model serves well in the explanation and prediction of the characteristics towards signal distortion, noise, mass flow rate and influence on dead‐time behavior of end‐restrictors as used in supercritical fluid chromatography (SFC) with post‐column detection. It was experimentally verified that tapered restrictors have a better performance than constant diameter restrictors at relatively low detection temperatures (200°C).

The mass flow rate of a tapered restrictor is found to be linearly proportional to applied inlet pressure, implying the same linear dependence of the product of linear velocity and on‐column density. A more than proportional rise of density will, therefore, lead to a decrease in linear velocity and vice versa. Since thermostat temperature fluctuations are directly translated into linear velocity variations, a very temperature stable thermostat has to be used.

As will be discussed, this complicated dead‐time dependence on applied pressure has a large effect on the chromatographic results.
Supercritical fluid chromatography with a slurry‐packed capillary column
Authors: Hirata Y. , Nakata F. , Kawasaki M.
Published: May 2005

A versatile system with a slurry‐packed capillary column was developed for supercritical fluid chromatography, which is capable of programming both inlet and outlet pressure independently, as well as using a restrictor to apply back pressure. This system revealed the relationships between pressure drop, flow rate, and linear velocity in pressure‐programmed supercritical fluid chromatography. In the restrictor system, both the pressure drop and the flow rate increased almost linearly with inlet pressure, while under conditions of constant pressure drop characteristic behavior was observed which depended on the density‐viscosity relationships of supercritical fluid. Resolution in the separation of polysiloxane oligomers was found to be increased by increasing the ratio of pressure drop to pressure‐programming rate, although the sensitivity decreased due to the increase in peak volume. The system controlling both inlet and outlet pressure has distinct advantages over the restrictor system controlling both inlet and outlet pressure has distinct advantages over the restrictor system in practical in practical operations.
Possibilities of dynamic headspace analysis coupled with capillary GC for the investigation of solid samples
Authors: Venema A.
Published: May 2005

The advantages of the dynamic headspace method for the analysis of solid samples, as compared with the static head space method, are discussed. Examples of dynamic headspace analyses are given to illustrate its possibilities.
High resolution chemically bonded fused‐silica capillary gas chromatography of organochlorine insecticides and related compounds in arable soil samples
Authors: Suzuki M. , Morimoto M.
Published: May 2005

Electron capture gas chromatography with three chemically bonded fused‐silica capillary columns (CB‐FSCs), OV‐17, OV‐1701, and SE‐52, was performed to evaluate peak separability of 28 organochlorine insecticides and related compounds. Relative retention times and relative peak heights to aldrin were measured and calculated. OV‐17 CB‐FSC showed the best separability among the three CB‐FSCs employed and was applied to analysis of extracts from several soil samples with minimum clean‐up procedure. The chromatograms obtained demonstrated steady baseline tracings free of interference. Residue data from soil samples were also tabulated.
Application of capillary gas chromatography to environmental analysis
Authors: Matsushita H. , Iida Y.
Published: May 2005

Routine analytical methods for benzo[a]pyrene and nitroarenes in airborne particulates are presented. Benzo[a]pyrene in airborne particulates was easily analyzed by a capillary GC/NCIMS. Analysis time was about 10 min and analytical values obtained by this method agreed well with those by HPLC/spectrofluorometry. Nineteen nitroarenes were analyzed by capillary GC/FTD following a simple clean‐up procedure. Fifteen out of 19 nitroarenes analyzed were mutagenic for Salmonella typhimurium TA100 and TA98, and 4 nitroarenes were carcinogenic to experimental animals.
High temperature gas chromatography: The development of new aluminum clad flexible fused silica glass capillary columns coated with thermostable nonpolar phases: Part 2
Authors: Lipsky (deceased) S. R. , Duffy M. L.
Published: May 2005

Samples, representative of certain classes of “high molecular weight” and/or less volatile substances, were analyzed by gas chromatography utilizing a new generation of aluminum clad flexible fused silica glass capillary columns containing thin films of a methyl polysioxane stationary phase capable of being operated isothermally to 400–425°C and temperature programmed to 425–440°C. The results obtained here were compared with those described in the literature discussing the latest advances in Supercritical Fluid Chromatography (SFC) in the analysis of precisely the same types of samples. In all instances, the gas chromatographic method provided superior speed of analysis, superior column efficiency, and superior resolution of the component bands. This was due to fundamental factors, favoring the diffusivity of the solutes in both the gas and liquid phases in this process at these high temperatures. Under these circumstances, it is thought that the strength of SFC mainly lies in the analysis of thermally labile samples until the advocates of this technique make more definitive strides in the handling of still higher molecular weight substances well beyond the newly expanded range of gas chromatography.
Deactivation with silazanes in chromatography, mechanism of the reaction and practical consequences in capillary GC and RP‐HPLC: A29Si CP‐MAS NMR study
Authors: van de Ven L. J. M. , Rutten G. , Rijks J. A. , De Haan J. W.
Published: May 2005

The reaction of Cab‐O‐Sil, a highly dispersed vitreous quartz, with hexamethyldisilazane (HMDS) was studied in the temperature range 380–500°C, using 29Si solid state NMR and other techniques. Such studies are of importance in view of deactivation procedures of fused silica at high temperatures in capillary GC.

The commonly accepted reaction equation:

predominates only below ca. 400°C. Above ca. 400°C the intermediate cleavage product Me3SiNH2 reacts with surface silanol groups to form SioSiMe2NH2 + CH4. At higher temperatures these groups may ultimately form (SiO)3SiNH2 groups (analogously to the formation of bi‐and tridentate linkages starting from SiOSiMe3 groups), but (SiO)3SiNH2 groups are also directly formed at lower temperatures, simultaneously with the SiOSiMe3 groups, probably by reaction with siloxane bridges:

.

The reactions of the trimethylsilylamine part of HMDS with Cab‐O‐Sil were confirmed by an independent series of silylations using N,N‐dimethyltrimethylsilylamine instead of HDMS. The presence of amino groups as SiNH2 was confirmed by FT‐IR. This may be one of the reasons why very high temperature silylation with disilazanes does not provide a satisfactory deactivation of fused silica GC columns: the active SiOH groups are “replaced” by active SiNH2 groups. However, such a material may be of interest in LC. Silylation with silazanes at ca. 350°C in humid atmosphere and/or after extensive hydroxylation (leaching) of the surface should yield sufficiently deactivated surfaces with a rather well defined surface structure.
Preparation of inert glass capillary columns coated with UCON 50 HB‐5100. An attempt to rediscover industrially produced α, ω‐polyethylene/polypropyleneglycol ethers as stationary phases in capillary gas chromatography
Authors: Blum W.
Published: May 2005

Using UCON 50 HB‐5100, one of the most successful stationary phases in capillary gas chromatography during the past decade, as an example, we wish to redirect attention to the excellent properties of the polyethylene/polypropyleneglycol ether copolymer coatings. Based on experience gained in work with OH‐terminated polysiloxanes, a method is described for preparing inert and relatively temperature stable chemically bonded and crosslinked coatings in a single working step. Methyltrimethoxysilane was used as coupling agent, and trifluoroacetic acid was introduced as an acidic catalyst. The reaction mechanisms involved as well as the influence of additional crosslinking on the column behavior are discussed, particularly with respect of the inertness of the coatings.
(S)‐O‐acetyllactyl chloride – a versatile chiral auxiliary in stereodifferentiation of enantiomeric flavor components
Authors: Mosandl A. , Gessner M. , Günther C. , Deger W. , Singer G.
Published: May 2005

The stereodifferentiation of chiral secondary alcohols, 4(5)‐alkyl‐substituted γ (δ)‐lactones via corresponding 1, 4(1, 5)‐diols, chiral 1, 3‐diols, and 1‐thioalkan‐3‐ols was carried out by diastereomeric derivatization with (S)‐O‐acetyllactyl chloride as a chiral auxiliary. This procedure is a convenient and reliable method for screening the enantiomeric composition of these naturally occurring flavor volatiles.
Isolation and purification oil glucuronides with preparative anion exchange chromatography in methanol
Authors: Delaborde S. , Loosli H.‐R. , Ponelle M. , Griesser R. , Maurer G.
Published: May 2005

890 ml of urine of rats treated with [14C] 205–734 was desalted over an Amberlite XAD‐2 adsorption column. The methanol extract dissolved in 10 ml methanol was injected onto an anion exchange column (Nucleosil 10 SB 250 × 16 mm i.d.) equilibrated in methanol. A gradient of decreasing methanol proportionversusa 0.2Mammonium hydrogen carbonate buffer eluted a pure glucuronide of 205–734. Its structure was established by NMR, MS, UV, and IR analyses. This procedure is simple, rapid, and very selective for the compound of interest.
A study of chromatographic properties of liquid crystalline polyacrylates using WCOT columns in gas chromatography
Authors: Jadhav A. L. , Naikwadi K. P. , Rokushika S. , Hatano H. , Ohshima M.
Published: May 2005

Liquid crystalline polyacrylates (LCPAs) are evaluated as stationary phases for capillary gas chromatography (CGC). Aromatic hydrocarbons as well as polar isomeric compounds are used as test solutes to compare the polarity of the LCPAs with a conventional polysiloxane column and a Carbowax 20M column. The relative polarity of the columns with respect to change in the lateral and terminal substituents is also discussed. Lateral substitution, polarity of the terminal group, together with the solute size, affect the LCPA selectivity.
A simple miniature gradient system for micro‐HPLC
Authors: Šlais K. , Preussler V.
Published: May 2005

A miniaturized continuous gradient elution system with variable gradient profile was designed. A retention time reproducibility below 1% was achieved. The system was applied to the separation of phenolic compounds with a wide range of polarities.
Rayleigh instability of stationary phase films in capillary column chromatography
Authors: Bartle K. D. , Woolley C. L. , Markides K. E. , Lee M. L. , Hansen R. S.
Published: May 2005

The film of stationary phase on the wall of a capillary column and that of the phase solution during both static and dynamic coating is subject to Rayleigh instability, which is quite independent of so‐called wettability. A theory is developed which shows that the logarithmic growth rate of Rayleigh instabilities is proportional to the surface tension and to the third power of the film thickness, and inversely to the viscosity and to the fourth power of the capillary diameter. Determination of the variation of the viscosities of stationary phase solutions with concentration in coating solvents, and the variation of the viscosities of neat stationary phases with temperature, both revealed that heating and/or diluting changed the viscosities of phases with π‐electron‐containing, groups much more than for polydimethylsiloxanes. Rayleigh instability is therefore more important during coating of phenyl‐containing phases such as OV‐17, and later during column operation. The efficiencies of capillary columns of different diameters coated with a number of phases under different conditions of temperature and coating rate, and then operated at different temperatures were in good agreement with the predictions of the theory.
Capillary chromatography in the condensed mobile phases: From the concepts to analytically useful separations and measurements
Authors: Novotny M.
Published: May 2005

Recent advances in microcolumn (capillary) Liquid chromatography and open tubular supercritical fluid chromatography are reviewed. New detection and ancillary techniques are emphasized. Further trends of capillary separations are briefly discussed.
Confirmation of heptachlor epoxide and octachlor epoxide in milk via fused silica gas chromatography/negative ion chemical ionization mass spectrometry
Authors: Korfmacher W. A. , Rushing L. G. , Siitonen P. H. , Branscomb C. J. , Holder C. L.
Published: May 2005

A method for the mass spectral confirmation of heptachlor epoxide and octachlor epoxide in milk is described. The method includes the use of a 30 m × 0.25 mm DB‐1701 fused silica gas chromatography column combined with negative ion chemical ionization mass spectrometry. By using this technique, confirmation of these compounds in milk can be performed at a level of 0.1 parts‐per‐million in milk fat.
The “disturbing zone” in overpressure layer chromatography (OPLC)
Authors: Nyiredy Sz. , Mészáros S. Y. , Dallenbach‐Toelke K. , Nyiredy‐Mikita K. , Sticher O.
Published: May 2005

This paper describes the fundamental factors causing the “disturbing zone” in OPLC. This phenomenon of distorted substance zones appears when the OPLC separation is started with a dry layer and is due to interaction between the gas that is physically bound to the surface of the sorbent (ma) and the gas molecules dissolved in the eluent (ms). Possibilities for elimination of the adverse effects of disturbing zones ultimately depend on the establishment of operating conditions that inhibit their initial formation. Since modification of the location of the disturbing zone is only possible within a very narrow range, the sole solution to this problem is to conduct a pre‐run, which may be carried out with hexane in the case of separation of apolar compounds. For separation of polar substances, the pre‐run may also be performed with hexane or with a solvent of the mobile phase in which the components are unable to migrate. The selection of this solvent may be considered during the optimization of the eluent system.
Elution order inversions observed on using different carrier gas velocities in temperature programmed gas chromatography
Authors: Pell R. J. , Gearhart H. L.
Published: May 2005

Observations of chromatographic elution order inversions are reported which have occurred as a result of using different initial carrier gas velocities with oven temperature programming in GC and GC/MS systems.
Comparison of methods to enhance flame ionization detector (FID) signals in gas chromatography
Authors: Gonnord M. F. , Ignatiadis I. , Jaulmes A. , Vidal‐Madjar C.
Published: May 2005

The performances of some numerical methods to improve the signal to noise ratio are compared and applied to enhance noisy signals obtained in gas chromatography with capillary columns and a flame Ionization detector. Several methods have been considered: cutoffs In the Fourier transform of the recorded signal; real time numerical filtering; theoretical model curve fitting; and the correlation of a chromatogram recorded from a pseudorandomly injected sample with the pseudorandom injection function. Numerical real time filtering is shown to be the most convenient method when the main periodic component of the noise has been determined by Fourier analysis.
Antihormonal agents. Part 1: HPLC of RU 38486 and its metabolites
Authors: Matlin S. A. , Abderabbani N.
Published: May 2005

Procedures are described for the TLC and reverse phase HPLC analysis of the antihormonal steroid RU 38486 and its metabolites. Conditions are developed for the HPLC of the pure drug substance and a tablet formulation, and also for following its pharmacokinetics and metabolism.