bluuebunny/crossref_metadata_2025_split huggingface dataset:
Two dimensional TLC determination of PAH in diluted automobile exhaust gases
Authors: Kraft J. , Hartung A. , Lies K.‐H. , Schulze J. 
Published: May 2005

AbstractA method is described for the determination of polycyclic aromatic hydrocarbons (PAH) in the diluted exhaust gas of diesel vehicles. Sampling is done by drawing off proportional streams from the dilution tunnel. The particulates deposited on filters are sublimed, and the sublimate is purified and prefractionated on silica gel. Further separation and quantitative determination of the PAH is performed by two dimensional TLC in conjunction with In situ fluorescence spectrometry. Results of theoretical considerations and experimental data on the distribution of the emitted PAH between particulate matter and the corresponding gas phase in diluted exhaust are presented. A modified Langmuir adsorption model is used to explain the effects of dilution ratio and sample temperature in the dilution tunnel. Comparison of the emission values for PAH obtained from diluted and undiluted exhaust shows good agreement. Furthermore, the PAH contents of the exhaust gas of several diesel‐engined cars are also compared for various driving cycles.
A system for identification of triglycerides in reversed phase HPLC chromatograms based on equivalent carbon numbers
Authors: Podlaha Oldrich , Töregård Bengt 
Published: May 2005

AbstractA graphical system for tentative identification and prediction of peaks in reversed phase HPLC chromatograms of triglycerides is presented. Straight, parallel lines were found for different homologous series of triglycerides when plotting carbon numbers (CN) against equivalent chain numbers (ECN). ECN, defined as the carbon number of the hypothetical saturated triglyceride, which elutes at the same retention time as the unsaturated triglyceride being studied, are given for common triglycerides in vegetable oils for HPLC systems with propionitrile and acetonitrile/acetone (64/36) as mobile phases. The method is presumably also applicable to homologous series of other compounds such as wax esters.
Two‐dimensional capillary gas chromatography without intermediate trapping. Electron capture detector quantitation of an amino alcohol (KABI 2128) in serum after trifluoroacetylation
Authors: Brötell H. , Rietz G. , Sandqvist S. , Berg M. , Ehrsson H. 
Published: May 2005

AbstractA two‐ dimensional gas chromatograph based on the Deans switching principle is described. The unit comprises two separate ovens, each containing a fused silica capillary column. The columns are joined in a specially designed manifold permitting heart cuts to be performed without significant decrease in efficiency. The switching speed and the retention time stability of the system made it possible to perform heart cuts of only a few seconds' duration. The system has been used under isothermal conditions for the determination of an amino alcohol (KABI 2128) in the low ng/ml range after trifluoroacetylation and with electron capture detection. A much shorter clean‐up procedure could be used in combination with the two‐dimensional gas chromatograph as compared to a method using a single glass capillary column.
Investigation into the analysis of complex environmental samples employing fused silica capillary columns
Authors: Dahlgran J. R. , Abrams L. 
Published: May 2005

AbstractThe use of fused silica SE‐54 columns in the analysis of complex environmental samples by GC/MS was examined. Column performance was evaluated for the analysis of priority pollutant acid extractables on both an “acid conditioned” column and a “base/neutral conditioned” column. The largest change in column performance was noted when a single column was used to analyze B/N extractables followed by acid extractable priority pollutants. There was evidence of peak skewing, tailing, and loss of sensitivity. Nitrophenols could not be successfully chromatographed. The analysis of phenols on an acid conditioned column was within acceptable limits (peak shapes and accuracy).
Retention time in series‐coupled columns: An experimental investigation of the non‐thermodynamic effects
Authors: Buys T. S. , Wagener J. B. 
Published: May 2005

AbstractA previously established model of a system of series‐coupled columns is implemented for the experimental investigation of non‐thermodynamic contributions to the retention time in systems of two series‐coupled columns. The results show excellent agreement between theory and experiment and also stresses the importance of non‐thermodynamic contributions to retention times.
A cold silanization method for preparation of medium polarity capillary columns
Authors: Traitler H. 
Published: May 2005

AbstractSilane‐coupling agents, commonly used for fiberglass reinforced plastics (FRP), were applied for deactivation of silanol sites in glass capillary columns prior to coating with mediumpolarity phases such as Carbowax and Superox. The columns, prepared in a two‐stage process in the case of glass (acidic leaching and drying, dynamic cold silanization followed by static coating with the phase) or a one stage process in the case of fused silica, gave the best results when deactivation and hence wettability were induced by glycidoxypropyltrimethoxy silane.
Strategies for compound identification and quantification using fused silica capillary column GC/MS
Authors: Colby B. N. , Ryan P. W. , Wilkinson J. E. 
Published: May 2005

AbstractA test mixture containing 28 compounds plus their stable isotopically labeled analogs was analyzed on a daily basis for one month during a series of routine fused silica capillary column GC/MS analyses in order to establish the precision with which retention times and responses were produced. These long‐term precision data were evaluated to determine how to best predict retention times and how to best reproduce quantification. Results clearly indicate that relative retention times should be calculated using the reference compound eluted most closely to the target compound and that quantification should be based on relative response using a chemically “similar” compound.
Reversed‐phase high‐performance liquid chromatographic analysis of endogenous purine ribonucleotide pools in BHK monolayer cultures
Authors: Debetto P. , Bianchi V. 
Published: May 2005

AbstractA rapid, sensitive, and reproducible separation of purine bases, nucleosides and nucleotides by reversed‐phase high‐performance liquid chromatography is described. A multi‐step gradient of acetonitrile in 0.1 M potassium phosphate was used to detect picomole amounts of each compound within 22 min. The high sensitivity of the method made it suitable for the analysis of purine nucleotide pools extracted from 1‐‐2 × 106 hamster fibroblasts grown as monolayer (BHK line) and for the detection of purine bases and nucleosides leaked form the cells into the incubation media. The chromatographic procedure was applied to study the effects of hexavalent chromium (potassium dichromate) on purine metabolism. Several steps are affected by this treatment, causing a marked unbalance of both the guanylate and adenylate pool, which was seen as a strong decrease in the level of triphosphates and accumulation of their precursors.
Capillary columns with very thick coatings
Authors: Grob K. , Grob G. 
Published: May 2005

AbstractIt has become common practice with capillary columns to call film thicknesses of 0.1 – 0.3 μm regular or standard, whereas 0.3 – 1.0 μm is considered to denote thick films. Consequently, films with thickness beyond 1μm (we have explored the range up to 8.0 μm) may be termed very thick. Increasing film thickness, at least to about 5 μm, brings important additionl advantages primarily in terms of loading capacity. Columns with very thick coatings may replace the traditional SCOT columns thanks to at least equivalent loading capacity combined with higher separation efficiency, and better stability characteristics. Additional advantages are increased retention, essential for the analysis of very volatile substances, and increased elution temperature, providing a basis for direct water injection.We observe that TZ (the separation number) drops to roughly 50% when the film thickness is increased by a factor of 300 from 0.025 to 8.0 μm, provided TZ is measured with a standard flow of hydrogen. The reduction is only 30% when the thick‐film colums are run with individual optimization with nitrogen as a carrier gas. In contrast to standard columns, very thickly coated columns show slightly increased separation efficiency with nitrogen at drastically reduced flow rate. The HETP increases very slightly in the indicated range of flim thickness. This contradicts widespread theoretical expectations, which probably account for the fact that very thick coatings have so far been neglected. Since the preparation of very thick coatings involves some deviations from the standard procedure, complete and detailed instructions are given.
High resolution liquid chromatography with a packed micro glass capillary column
Authors: Hirata Y. , Jinno K. 
Published: May 2005

AbstractSingle, long columns (1–5 m) can be prepared efficiently using reversed phase packings (3–10 μm particle diameter). 1‐m columns packed with 3 and 10 μm packing provide 110 000 and 50 000 theoretical plates, respectively. Very efficient columns can resolve highly complex mixtures and difficult‐to‐separate compounds. Temperature gradient elution is a powerful technique for LC with microbore columns.
Thin‐layer chromatography with high‐boiling mobile phase. part 2: Effect of temperature on retention characteristics in TLC with high‐boiling mobile phases
Authors: Berezkin V. G. , Bolotov S. L. 
Published: May 2005

AbstractA study has been undertaken on the effect of temperature on retention characteristics in thin‐layer chromatography (TLC) with low‐volatility mobile phases (MP). It is shown that temperature variations in TLC in melts bring about variations in both the relative retention values and, in some cases, in the order of migration of the chromatographic zones across the layer. The variation in the capacity factor k' with temperature agrees well with Martin's equation. To explain the temperature dependence of Rf one must, in general, take into account the variations with temperature in both the partition coefficient and the phase ratio. To describe the variation in Rf with temperature in TLC with low‐volatile MP one can use an approximate equation in which In Rf is a linear function of 1/T. The experiments indicate that temperature is a major factor in TLC in melts.
Applications of capillary gas chromatography in routine toxicological analyses
Authors: Anderson W. H. , Stafford D. T. 
Published: May 2005

AbstractCapillary columns offer the toxicologist several advantages over packed columns. We have presented a highly reproducible screening procedure based on the retention index system and have shown the use of capillary columns for routine quantitation. We are currently expanding the use of these columns in our laboratory and predict that they will be in routine use by most toxicologists in the near future.
Azo compounds for free radical crosslinking of polysiloxane stationary phases
Authors: Richter B. E. , Kuei J. C. , Park N. J. , Crowley S. J. , Bradshaw J. S. , Lee M. L. 
Published: May 2005

AbstractThere has been much effort spent in recent years developing the technology for free radical crosslinking of polysiloxane polymers to prepare capillary columns coated with thermally stable and nonextractable stationary phases. Organic peroxides have been used extensively as the free radical initiators for the in situ polymerization of the stationary phases. However, these peroxides adversely affect the phase polarity and column activity. Seven azo compounds were studied for crosslinking efficiency. Azo compounds can be used as free radical initiators to prepare nonextractable stationary phases without the adverse effects caused by peroxides.
Evaluation of electron capture cell designs for use in high resolution capillary column gas chromatography
Authors: Wells G. , Simon R. 
Published: May 2005

AbstractA comparison of the effects on peak shape is made between a 350 and 100 microliter displaced coaxial and a 350 microliter concentric cylinder electron capture cell. Peaks as fast as W1/2 = 0.5 second were detected using electronics operating in the constant current mode. The measured peak shapes are compared to those obtained by computer simulation assuming either complete mixing or plug‐like flow within ECD cell. The advantage of controlling the flow pattern through the cell to obtain plug‐like flow is demonstrated. Differences in peak shape between the displaced coaxial and concentric cylinder cells of the same volume are explained in terms of the electrostatic fields within the cells.
Injection temperature effects using On‐column and split sampling in capillary gas chromatography
Authors: Wang F.‐S. , Shanfield H. , Zlatkis A. 
Published: May 2005

AbstractThe effect of sample injection temperature on quantitation is examined for on‐column and conventional split modes of sampling in capillary gas chromatography. Discrimination effects can be observed even with on‐column injection if the injection temperature is too far above the boiling point of the solvent (or that of a major low boiling constituent(. This is attributed to higher boiling components being left behind in the syringe needle, and a set of simulation experiments are described to illustrate this effect. Various discrimination patterns using conventional split injection were observed, depending on temperature of injection. Apart from syringe needle effects, discrimination is probably due to the preferential venting of higher boiling components as liquid sample droplets, which can have a lifetime greater than the time of transit to the splitter. With such a two‐phase system, involving variable droplet size, the flow distribution in the splitter will be critical to uniform sampling. The use of combination on‐column/split sampling, with the appropriate temperature control to provide sample uniformity to the splitter is discussed as an advantageous alternative to conventional split sampling.
Capillary gas chromatography of pesticide residues in foods: Application of a split/splitless inlet system
Authors: Daft J. L. 
Published: May 2005

AbstractResidue mixtures of pesticides in foods which were difficult to separate by packed‐column gas chromatography were determined by capillary gas chromatography and electron capture detection. Manual injections of sample and reference standard were made with a 10 μL syringe on a septum‐enclosed, split/ splitless inlet system. Optimal peak height repeatability (± 3%( was achieved with three‐μL injections which were made within time periods of four hours or less. The average linearity coefficient (slope( obtained for detector response as a function of solution concentration was 1.1.
Recent contributions of high resolution gas chromatography to the analysis of environmental hydrocarbons
Authors: Bayona J. M. , Grimalt J. , Albaigés J. , Walker W. , de Lappe B. W. , Risebrough R. W. 
Published: May 2005

AbstractAnalyses of hydrocarbon fractions from different areas of the marine environment are described to illustrate the possibilities and limitations of high resolution gas chromatography (HRGC) in the analysis of environmental samples. Examples are given of dissolved, particulate, and sedimentary hydrocarbons and organochlorine compounds; the importance of an adequate sampling of the marine environment is stressed. HR chromatographic profiles obtained in two columns of low and high polarity (SE‐52 and PEG 20M) permit the sources and transport pathways of both natural and anthropogenic hydrocarbons to be traced. Analysis of tissues of marine mammals, which metabolize or excrete many of the biogenic and petrogenic hydrocarbons present in other areas of the marine environment, may provide an opportunity to obtain relatively clean profiles of many anthropogenic compounds of interest. The plotting of mass chromatograms from data compiled by COM‐GC‐MS remains the most appropriate method for the conclusive indentification of these compounds.
Separation of (3R, 3′ R)‐, (3R, 3′ S; meso)‐, (3S, 3′ S)‐ Zeaxanthin, (3R, 3′ R, 6′ R)‐, (3R, 3′ S, 6′ S)‐ and (3S, 3′ S, 6′ S)‐Lutein via the dicarbamates of (S)‐(+)‐α‐(1‐naphthyl) ethyl isocyanate
Authors: Rüttimann A. , Schiedt K. , Vecchi M. 
Published: May 2005

AbstractA method is described for the qualitative and quantitative determination of configurational isomers of zeaxanthin (=3,3′ ‐dihydroxy‐β, β ‐carotene) and lutein (=3,3′ ‐dihydroxy‐α ‐cartotene). It is based on the reaction of these zeaxathin and lutein isomers with (S)‐(+)‐α‐(1‐naphthyl) ethyl isocyanate to afford diastereomeric dicarbamates, which are analyzed by HPLC.
Determination of acetylsalicylic acid and salicylic acid in blood and plasma by HPLC
Authors: Nieder M. , Jaeger H. 
Published: May 2005

AbstractA method is described for the determination of acetylsalicylic acid and salicylic acid in human whole blood and plasma which uses liquid chromatography with UV detection. The enzymatic degradation of acetylsalicyclic acid in blood and plasma is examined. Addition of potassium fluoride as enzyme inhibitor and deep freezing after plasma preparation allows storage of plasma for one week. A mixture of acetonitrile and diluted acetic acid as mobile phase give the best peak shape. Traces of iron lead to slight peak broadening; addition of EDTA results in excessive tailing. The detection limit for acetylsalicylic acid and salicylic acid is about 250 ng/ml for a 1.0 ml primary sample. The method is sensitive enough for the monitoring of both drugs in bioavailability studies.
Use of crosslinked polysiloxane stationary phases in open‐tubular capillary liquid chromatography
Authors: Takeuchi T. , Kitamura H. , Spitzer T. , Ishii D. 
Published: May 2005

AbstractCrosslinked polysiloxane stationary phases were prepared on soda‐lime glass capillaries and applied to the separation of polynuclear aromatic hydrocarbons and of phthalates in reversedphase liquid chromatography. Preparation procedures and chromatographic performance of these columns are described.
Selective and non‐selective sampling from precolumn separations—with emphasis on the sampling of aqueous solutions
Authors: Schomburg G. , Bastian E. , Behlau H. , Husmann H. , Weeke F. , Oreans M. , Müller F. 
Published: May 2005

AbstractVarious methods of gas chromatographic analysis at high resolution and low detection limits in aqueous solutions are described with regard to sampling techniques, column technology, and the application of coupled pre‐columns, also including multidimensional methods. Immobilized polyethylene glycol (Carbowax 20 M) columns have also been produced and used successfully.
Chromatographic terminal band lengths
Authors: Saxton Wilbur L. 
Published: May 2005

AbstractA terminal band length is defined here as the length of a dispersed solute band as it emerges from the chromatographic column. The number of terminal band lengths per column can be used in the same way that the number of theoretical plates per column is used to measure and compare chromatographic efficiencies, but with greater insight since the proposed unit of measure is an easily visualized, real entity. In addition, the height equivalent to a theoretical plate (HETP) can be regarded as a ratio of the terminal band lenght to sixteen times the number of equivalent terminal band lengths that could be contained in tandem in the column. This concept offers another approach to understanding the meaning of the term, HETP. The terminal band length of a series of homologues is constant and independent of retention time above a certain solute molecular size and column capacity ratio. Within those conditions the correlation between the recorded peak width and retention time during isothermal analysis occurs primarily as a result of change in solute velocity.
Effect of column diameter on efficiency in capillary supercritical fluid chromatography
Authors: Fields S. M. , Kong R. C. , Fieldsted J. C. , Lee M. L. , Peaden P. A. 
Published: May 2005

AbstractFused silica capillary columns with internal diameters from 100 to 25 μm were coated with SE‐54 and evaluated under supercritical fluid chromatographic conditions using carbon dioxide as mobile phase. Experimental results compared well with theoretical predictions. At ten times the optimum mobile phase velocity and for a capacity factor, k of 3, efficiencies of 2300 to 5600 plates m−1 were obtained for column diameters of 100 to 25 μm, respectively.
Length of the flooded zone in the column inlet and evaluation of different retention gaps for capillary gas chromatography
Authors: Grob K. , Neukom H. P. , Riekkola M.‐L. 
Published: May 2005

AbstractIn on‐column or in splitless injection with recondensation of the solvent, the length of the flooded zone in the column inlet depends primarily on the wettability of the internal wall of the inlet. For columns with a coated inlet this explains why peak distortion due to band broadening in space by a certain sample volume is pronounced in one case and hardly observable in another. Glass or fused silica capillaries silylated with diphenyltetramethyldisilazane were found to give optimal retention gaps. They combine thorough and thermostable deactivation with good wettability and low retention power. On the other hand it is very easy to deactivate fused silica capillaries with Carbowax. The resulting retention gaps are suitable for a wide range of applications and are particularly attractive for the analysis of dirty samples which require frequent replacement of the inlet.
Effect of stationary phase film thickness on efficiency in capillary supercritical fluid chromatography
Authors: Fields S. M. , Kong R. C. , Lee M. L. , Peaden P. A. 
Published: May 2005

AbstractFused‐silica capillary columns with internal diameters of 50 μm were coated with 0.25 to 1.0 μm films of SE‐54 and evaluated under supercritical fluid chromatographic conditions using carbon dioxide as mobile phase. Experimental results compared well with theoretical predictions. There was no significant difference in hmin or ūopt for film thicknesses from 0.25 to 1.0 μm over k = 1 to 5. At a film thickness of 1.0 μm, calculations indicate that approximately 10% resolution loss would be expected for solutes with k = 1.
The Analysis of volatile compounds by purge and trap with whole column cryotrapping (WCC) on a fused silica capillary column
Authors: Pankow J. F. , Rosen M. E. 
Published: May 2005

AbstractThe purge and trap (P&T) method of analysis has been interfaced with fused silica capillary column gas chromatography. This interfacing has been accomplished without splitting the P&T trap desorption carrier gas. Thus, 100% of the purged compounds are transferred to the column. The analytes are cryofocussed on the column using whole column cryotrapping (WCC) at −80°C. The resulting P&T/WCC procedure is extremely well‐suited to the analysis of trace purgeable aqueous organic compounds. Samples and standards containing a variety of aromatic standard compounds were analyzed. The standards included benzene, toluene, ethylbenzene, xylenes, C3‐C4‐benzenes, and naphthalene, as well as three P&T internal standard compounds. Chromatographic peak widths were uniformly less than 6 s at the base and excellent precision was obtained in the relative retention time data for all compounds. The chromatogram of a groundwater sample contaminated with aromatic gasoline compounds is also presented. Since P&T/WCC works well with fused silica capillary columns, the full sensitivity and chromatographic efficiency of capillary gas chromatography is made available to P&T analyses.