bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractThe 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.
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

AbstractA 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

AbstractThis 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.
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

AbstractThe 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

AbstractProcedures 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.
Minimum column temperature required for concurrent solvent evaporation in coupled HPLC‐GC
Authors: Grob K. , Läubli Th. 
Published: May 2005

AbstractConcurrent solvent evaporation using the loop‐type HPLC‐GC interface requires that the GC oven temperature be above the eluent boiling point at the given carrier gas inlet pressure in order to prevent eluent flowing into the GC capillary column. Corresponding oven temperatures representing minimum oven temperatures for eluent transfer were experimentally determined for solvents and solvent mixtures of interest for use as HPLC eluents. Evaluation of eluents for concurrent evaporation is discussed. Recommended lengths of uncoated column inlets (pre‐columns) are derived from the mechanisms involved in solvent evaporation. Temperatures listed as minimum column temperatures for concurrently evaporating HPLC eluents are also useful for estimating maximum applicable column temperatures when working with the conventional retention gap or partially concurrent solvent evaporation techniques in coupled HPLC‐GC.
Porous ceramic bed supports for fused silica packed capillary columns used in liquid chromatography
Authors: Cortes H. J. , Pfeiffer C. D. , Richter B. E. , Stevens T. S. 
Published: May 2005

AbstractPorous ceramic bed supports for fused silica packed capillary columns utilized in liquid chromatography were prepared by polymerizing solutions containing potassium silicate in‐situ within a column to create a mechanically stable, rugged, and easily constructed termination. The effect of the bed support length on efficiency, and comparisons to glass wool bed supports, were considered in terms of column efficiencies and hydrodynamic variables. Results obtained indicate better performance for the ceramic bed support.
Solvent removal/thermal desorption (SRTD) for extract concentration and capillary column injection
Authors: Hart K. M. , Pankow J. F. 
Published: May 2005

AbstractMany solvent extracts must be concentrated prior to analysis. Both Kuderna‐Danish (K‐D) concentration and inert gas blowdown are commonly used. Significant losses often occur with the latter. Solvent removal/thermal desorption (SRTD) on a precolumn was investigated here as an alternative or supplement to these methods. The compounds studied included polychlorinated biphenyls (PCBs) and polybrominated biphenyls (PBBs). SRTD was carried out by injecting 100 μL of extract into a cartridge‐type precolumn, selectively volatilizing the solvent with a stream of carrier gas, then thermally desorbing the analytes to a fused silica capillary gas chromatography (GC) column. The mean total recoveries and mean standard errors obtained were 109 and ±12%, respectively. SRTD was found to give sharper peaks than were obtainable with on‐column injection. Method detection limits accessible for PCBs by capillary GC with electron impact mass spectrometry with the assistance of SRTD were estimated. Overall, SRTD was found to be an effective, rapid, high recovery concentration method for solvent extracts.
Supercritical fluid chromatographic solvatochromic modifier polarity studies
Authors: Levy J. M. , Ritchey W. M. 
Published: May 2005

AbstractTo understand the chromatographic process as a whole, whether it be for gas chromatography (GC), liquid chromatography (LC), or supercritical fluid chromatography (SFC), one needs to know the chemical and physical nature of the mobile and stationary phases and also the interactions that take place between analytes (solutes) and the two phases. An approach towards Investigating the ways that stationary and mobile phases contribute to chromatographic retention Involves exploring the effects of solvent polarity on the strength of the mobile phase. In SFC this could involve determining the polarity of several different modifier/carbon dioxide mobile phases. In this paper, the use of a solvatochromic indicator to learn more about the effects of SFC modifier/mobile phase polarity will be investigated and discussed using several different modifiers and a diolmodified silica column.
High resolution recycle gas chromatography with off‐line flame ionization detection
Authors: Miller R. J. 
Published: May 2005

AbstractPreliminary results of a recycle system employing fused silica capillary columns are discussed. The unit, which can be operated with a pre‐column for multidimensional GC, utilizes continuous stream splitting for off‐line flame ionization detection. Commercially available rotary valves were used for recirculation of the chromatographic zone between column loops. Adsorptive activity, which is shown to be additive, is a serious limitation in the analysis of polar compounds. The successful application of recycle chromatography to increase resolution on non‐polar mixtures is demonstrated.
Rapid determination of organochlorine pesticide residues in feeds by capillary gas chromatography
Authors: Torreti L. , Simonella A. , Falgiani A. , Filipponi C. , Gramenzi F. 
Published: May 2005

AbstractA simple micro‐method is described for determination of 15 organochlorine pesticide residues in mixed feeds. Clean‐up of the petroleum ether extract is by basic alumina minicolumn chromatography and quantitative identification is by capillary gas chromatography with electron capture detection. Cyanopropyl‐polysiloxane chemically bonded fused silica capillary columns have been used to perform high resolution analyses in short time as well as to overcome possible interferences by PCBs. Recovery, repeatability, and detection limits of the proposed procedure are checked and results are also reported for non random samples of 180 feeds collected in Italy.
Antihormonal agents. Part 2: HPLC of ZK 98734 and its metabolites and ZK 98299
Authors: Matlin S. A. , Wu Z. Y. 
Published: May 2005

AbstractProcedures are described for the reverse phase HPLC analysis of the antihormonal steroid ZK 98734 and two of its metabolites. Conditions are developed for the HPLC of the pure drug substance and for following its pharmacokinetics and metabolism. Analysis conditions are also reported for the antiprogestin ZK 98299.
HPTLC fingerprint identification of commercial ginseng drugs ‐ reinvestigation of HPTLC of ginsenosides
Authors: Peishan Xie , Yuzhen Yan 
Published: May 2005

AbstractThe optimized HPTLC of ginsenosides reported in this paper shows that the recommended solvent system has a higher resolution, greater spot capacity, and better reproducibility by comparison with the established ones in the previous literature. Detection and scanning in the fluorescence mode after visualization with 5% sulfuric acid/EtOH by the dipping technique improved and enhanced the sensitivity by a factor of nine compared to the commonly used absorbance made.Sample pretreatment by an adsorption clean‐up step on a small alumina column followed by 1‐butanol extraction instead of only a butanol‐extraction step made the chromatogram clearer, caused less background contamination, and reduced the tailing of some ginsenosides spots.The ‘peak grouping’ method was effectively used in HPTLC fingerprint identification of various commercial ginseng medicines and the chromatograms of roots of ginseng (white and red; Panax ginseng), American ginseng (P. quinquifolium), and sanchi (P. notoginseng) obtained under recommended condition are perfectly recognizable.
An optimized gas chromatographic determination of priority pollutant phenols
Authors: Masi O. H. , Gulick W. M. 
Published: May 2005

AbstractPriority pollutant phenols are determined by gas chromatography on an SE‐30 WCOT column using hydrogen carrier and flame ionization detection with dual internal standards. Linear responses over ranges ca. 12–125 ng per component are achieved and detection limits at or below 1 ng are obtained. Carrier flow and temperature program are optimized to maintain baseline resolution while affording an analysis time of less than 15 minutes.
Comparison of eluents in supercritical fluid chromatography as based on density and free volume
Authors: Schmitz F. P. 
Published: May 2005

AbstractA comparative study of chromatographic properties of different supercritical eluents has been performed by considering the retention at equal density or at equal free volume for different mobile phases. At equal density, the temperature dependence of the capacity ratios of aromatic hydrocarbons is the same for different alkane mobile phases, whereas significant deviations are observed when carbon dioxide is employed as the mobile phase. At equal free volume, a comparison of the capacity ratios measured in carbon dioxide and in alkane eluents showed a pronounced similarity for the different mobile phases when the free volume was low, i.e., at high densities. With increasing free volume, the chemical differences of the alkanes on the one hand and carbon dioxide on the other become more apparent in their elution behavior. Furthermore, it is demonstrated that the free volume can also be used as a reference basis for the data of solvatochromic shift experiments.
Analysis of calcium blocker drugs in plasma, HRGC and HPLC analytical conditions for pharmacokinetic studies
Authors: Giachetti C. , Poletti P. , Zanolo G. 
Published: May 2005

AbstractCalcium blocker drugs are of increasing therapeutic relevance. Verapamil, nifedipine, diltiazem, and flunarizine are the most widely applied drugs of this type. New dihydropyridines (felodipine, nitrendipine) and related agents are presently undergoing intense investigation. HRGC and HPLC were used to determine eight of these drugs in spiked plasma samples. Both methods allow separation of most of the compounds in a single run and are specific, sensitive, and reproducible both for therapeutic monitoring and for pharmacokinetic studies in man and animals.
Glass capillary gas chromatography‐mass spectrometry at high temperatures. direct analysis of free base porphyrins and metal porphyrin complexes extracted from the serpiano oil shale
Authors: Blaum W. , Richter W. J. , Eglinton G. 
Published: May 2005

AbstractThis contribution describes GC/MS analysis of natural petroporphyrin extracts containing alkylporphyrins either as vanadyl complexes or as demetalated free bases. The combination of high temperature glass capillary gas chromatography with mass spectrometry allows, for the first time, direct determination of electron impact mass spectra of separated alkylporphyrins, making additional purification and derivatization unnecessary. The separation is carried out on glass capillary columns coated with the high temperature‐stable medium polar, OH‐terminated, polysiloxane phases PS 086 and OV‐225‐OH. The paper gives detailed working directions for the preparation of the high temperature GC/MS‐interface, and of the high temperature stable OV‐225‐OH columns (max. working temperature 390°C).
The preparation of immobilized stationary phase fused silica capillary columns with OV‐1701‐vinyl deactivation
Authors: Arrendale R. F. , Martin R. M. 
Published: May 2005

AbstractA new simplified method was developed for the preparation of immobilized stationary phase fused silica capillary columns coated with OV‐1‐vinyl, SE‐54, and OV‐1701‐vinyl. This methodology includes the application of the moderately polar stationary phase OV‐1701‐vinyl as a surface deactivation agent that may also participate in the dicumyl peroxide initiated free radical immobilization process. Practical details of the procedure are presented and applications of the laboratory‐produced columns are illustrated with capillary gas chromatographic separations of standard mixtures. Possible contributions of the OV‐1701‐vinyl deactivation layer to both crosslinking and surface bonding in the immobilization process are discussed.
Short capillary column for the separation and identification of mononitrofluoranthene and mononitropyrene isomers present in air and emission samples
Authors: Ciccioli P. , Cecinato A. , Brancaleoni E. , Liberti A. 
Published: May 2005

AbstractA 15 m DB‐17 fused‐silica capillary column has been used to achieve the separation of all mononitrofluorarthene and mononitropyrene isomers. Linear Retention Indices and Relative Retention times for each component have been measured and the values were compared with those observed on DB‐5 columns, commonly used for this separation. Increased polarity of the liquid phase results in better separation of some key isomeric pairs (such as 2‐, 3‐nitrofluoranthene and 1‐nitropyrene, 8‐nitrofluoranthene), difficult to resolve on DB‐5 columns. Practical applications are reported. They include the analysis of extracts from emission samples (diesel exhaust and particles emitted by a factory manufacturing carbon electrodes) as well as atmospheric dust sampled in a urban area under different conditions.
Metal selective flame ionization detection after supercritical fluid chromatography
Authors: Morrissey M. A. , Hill H. H. 
Published: May 2005

AbstractThis work describes the construction and operation of a flame ionization detector for the selective detection of metal‐containing compounds after capillary supercritical fluid chromatography. Using optimal conditions for achieving metal sensitive flame ionization responses which have been established for the detector after capillary gas chromatography, initial evaluation of the detector after SFC proved promising. Like the carbon sensitive FID, it appears that the metal sensitive FID is compatible with SFC when pure carbon dioxide is used as the mobile phase. Response characteristics were found to be similar to those observed when the detector is used in gas chromatography.
Device for filling of small diameter capillaries with stationary phase solutions in liquefied gases
Authors: Janák K. , Kahle V. , Horká M. , Tesařík K. 
Published: May 2005

AbstractThis paper describes a high pressure device for filling small diameter capillaries with stationary phase solutions is described. A liquid is forced into the capillary column with the help of high pressure syringe whose needle (provided with a side opening) is tightened in a PTFE seal. The device allows use of liquefied gas as solvent. A detailed procedure is given for filling the capillary with stationary phase solution. The performance of the device was evaluated by filling 12 m × 15 μm i. d. glass capillary with 6.5 % (w/v) SE‐54.
Co‐solvent effects for preventing broadening or loss of early eluted peaks when using concurrent solvent evaporation in capillary GC. Part 1: Concept of the technique
Authors: Grob K. , Müller E. 
Published: May 2005

AbstractThe concept and some first results of a method are described for evaporating large volumes of solvent in a relatively short pre‐column (retention gap) in such a way that solvent trapping retains volatile components in the inlet up to completion of solvent evaporation. The method was developed for transferring large volumes (easily exceeding 1 ml) of HPLC eluent to GC when using on‐line coupled HPLC‐GC, but is equally suited for injecting large sample volumes (at least some 50 μl) and could be particularly useful for introducing aqueous solutions.Concurrent solvent evaporation allows introduction of very large volumes of liquid into GC. However, peaks eluted up to some 40–80° above the column temperature during introduction of the liquid are strongly broadened due to the absence of solvent trapping. On the other hand, previous retention gap techniques involving solvent trapping were not suited for transferring very large volumes of liquid into GC. Using a relatively high boiling co‐solvent added to the sample or the HPLC eluent, advantages of concurrent solvent evaporation can be combined with solute reconcentration by solvent effects, allowing elution of sharp peaks starting at the column temperature during introduction of the sample.
Novel fused silica capillary columns: Surface modification through controlled doping of the preform‐tube
Authors: Anthony L. J. , Soto L. , Heffner S. A. , Holland R. A. , Simpson J. R. , Kosinski S. G. 
Published: May 2005

AbstractA method has been developed for fabricating fused silica capillary columns which have specific surface properties but still retain the excellent strength, flexibility, and resilience of pure fused silica. By using the Modified Chemical Vapor Deposition process (MCVD), typically used for the production of optical fiber lightguides, inorganic dopants such as Al, Nd, Ge, and P can be introduced into the preform‐tube by MCVD. Doped columns have a wide range of specific surface properties, and columns with undoped fused silica prepared by MCVD are more chemically inert and less acidic than columns prepared by conventional methods. This paper describes the method for fabricating capillaries and the initial studies to characterize them.
High‐temperature silylation in the production of inert glass capillary columns. From the first experiments to the chemical mechanism
Authors: Welsch T. 
Published: May 2005

AbstractThis retrospective article describes the beginnings and the development of silylation methods with diverse silazanes and siloxanes at high temperatures, and stresses their role in producing modern capillary columns characterized by a high degree of thermostability and adsorptive and catalytic inertness. Particular emphasis is placed on the outstanding contributions to this field ofKurt Grob, whose persilylation techniques provided the basis for the expansion of high resolution capillary gas chromatography.
HRGC assay of antihistaminic drugs in plasma samples using a nitrogen‐phosphorus detector
Authors: Giachetti C. , Poletti P. , Zanolo G. 
Published: May 2005

AbstractThirteen antihistaminic drugs are separated on a CP‐Sil 5 capillary column and are evaluated by a NP detector after extraction of spiked plasma samples, alkalinized, in a solvent mixture of chloroform, dichloromethane, and methanol. Intra‐ and inter‐assay analyses showed high reliability, therefore this method can be usefully applied in experimental or clinical pharmacokinetic investigations.
Supercritical fluid extraction / capillary supercritical fluid chromatography / Fourier transform infrared microspectrometry of polycyclic aromatic compounds in a coal tar pitch
Authors: Raynor M. W. , Davies I. L. , Bartle K. D. , Clifford A. A. , Williams A. , Chalmers J. M. , Cook B. W. 
Published: May 2005

AbstractThe combination of supercritical fluid extraction, high resolution capillary supercritical fluid chromatography, and Fourier transform infrared microspectrometry is described for the separation and identification of polycyclic aromatic hydrocarbons in a coal tar pitch. The variable solvating power of the supercritical fluid was utilized to selectively fractionate the sample. The fluid extract was decompressed through a frit restrictor into the sample cavity of a cooled microvalve injector, where the analytes were deposited and concentrated for subsequent chromatographic analysis. Several of the analytes separated in the chromatograph were collected on a potassium bromide disc at a solvent elimination inter‐face for subsequent infrared analysis involving the use of an infra‐red microscope accessory. The spectra obtained show the power of this detection technique for distinguishing between isomers.