bluuebunny/crossref_metadata_2025 huggingface dataset:
Fused silica capillary GC/MS coupling: A new, innovative approach
Authors: Friedli F.
Published: May 2005

A novel fused silica capillary GC/MS direct coupling is described which ensures quantitative transfer of sample from the point of injection to the ion source of a mass spectrometer without contacting any surfaces other than the column wall. This device permits GC analysis of highly labile substances. Aflatoxin B1, previously considered unassayable by GC, can now be determined by GC/MS.
Comparative study of efficiency and reproducibility of two high‐performance gel permeation chromatography columns with microparticulate packings
Authors: Rand W. G. , Mukherji A. K.
Published: May 2005

Two kinds of commercially available, microparticulate silica columns have been studied for their efficiency and reproducibility in gel permeation chromatography measurements. Results are provided for column plate height measurements, dispersity, and specific resolution as a function of flow rate. The influence of injection volume and slice width on these measurements is also presented. Reproducibility studies on polystyrene and styrene‐n‐butyl methacrylate copolymer are reported.
Capillary columns with immobilized stationary phases. Part 4: A moderately polar phase, OV‐1701
Authors: Grob K. , Grob G.
Published: May 2005

Whereas the immobilization of apolar silicone phases is essentially understood and mastered, the corresponding treatment of even moderately polar phases remains problematical. Upon attack by peroxide radicals, these phases respond by forming active transformation products rather than by bonding to the support surface or to neighboring molecules. OV‐1701 is at present the most polar stationary phase which can reasonably be immobilized. An essential feature of the practical procedure is the prevention of film breakage after coating the inert support surface and before immobilization. Two ways of overcoming this problem are presented.
Analysis of nitrated polycyclic aromatic hydrocarbons by glass capillary gas chromatography using different detectors
Authors: Ramdahl Th. , Kveseth K. , Becher G.
Published: May 2005

Glass capillary gas chromatography has been investigated as a method for the analysis of nitrated polycyclic aromatic hydrocarbons (nitro‐PAH) using both splitless and on‐column injection techniques. The nitro‐PAH showed good chromatographic performance and thermal stability under the GC conditions used. Retention times and response factors of several nitro‐PAH were compared to those of conventional PAH.

Simultaneous flame ionization and thermionic nitrogen selective detection was used to facilitate identification of nitro‐PAH in complex samples. The feasibility of the method is demonstrated on two samples of commercial carbon black. Besides 1‐nitropyrene several isomeric dinitropyrenes have been identified.
Application of the Hall™ electrolytic conductivity detector for the analysis of chloroanilines and chloronitroanilines in POTW sludges
Authors: Lopez‐Avila V. , Northcutt R.
Published: May 2005

Simultaneous detection with a 700‐A Hall™ and an NPD detector is an effective technique for characterizing chloro‐and chloronitroanilines in highly complex Publicly Owned Water Treatment Works (POTW) sludges. The utilization of a modified Varian effluent splitter and a SE‐54 fused silica capillary column permitted the detection of mid‐picogram quantities of the polar chloroanilines without sacrificing peak shape. The response of the Hall™ detector in the halogen mode was roughly proportional to the number of chlorine atoms present, while the response of the Hall™ in the nitrogen mode and the NPD was less predictably influenced by the presence of one or more nitro groups. When combined with retention time data, the ratio of the NPD response to the Hall™ response has been found to substantiate the presence of chloro‐ and chloronitroanilines in sludge extracts.
Influence of solvent strength in possible optimization of adsorption thin‐layer chromatography
Authors: Różyło J. K. , Chojnacka G. , Kolodziejczyk H.
Published: May 2005

Considerations of TLC process optimization have been based on the thermodynamic theory of adsorption from multicomponent solvents using experimental and theoretical RM1, 2 = f (Φ1) relationships. It was found that a relationship exists between the Az parameter (log k where k is the partition coefficient of the substance chromatographed) of the above theory and pKa values of substances as well as the solubility parameter δ of the mobile phase components. Analysis of the Az values of substances shows that a slight variation therein is associated with lower selectivity of chromatographic separation.
A comparative study of microbore reverse‐phase columns
Authors: Vadukul N. K. , Loscombe C. R.
Published: May 2005

A procedure for packing reverse‐phase microbore columns using moderate pressure is described. Columns packed from different manufacturer's tubing are compared with commercially available columns. A method for coupling the column to the injection valve is suggested. The effect of detector cell volume on overall efficiency of the system is also examined.
Optimization of binary solvents in thin layer chromatography
Authors: Nurok D. , Becker R. M. , Richard M. J. , Cunningham P. D. , Gorman W. B. , Bush C. L.
Published: May 2005

ΔRf, the separation between a pair of compounds on a thin layer chromatographic plate, can be predicted as a function of solvent composition for certain binary systems. This allows the prediction of optimum solvent composition for separating a mixture of compounds by thin layer chromatography. A new solvent polarity ranking, based on calculation of ΔRf is described.
Development and evaluation of wall coated open‐tubular columns for GC analysis of individual polychlorinated biphenyl isomers
Authors: Moseley M. A. , Pellizzari E. D.
Published: May 2005

The present article describes the development and testing of capillary columns for analysis of individual isomers of polychlorinated and polybrominated biphenyls, pesticides, and other halogenated hydrocarbons of environmental and biological importance.
Polysiloxane deactivated fused silica capillaries containing immobilized stationary phases
Authors: Moseley M. A. , Pellizzari E. D.
Published: May 2005

This article describes a method of preparing immobilized stationary phases which has arisen from the authors' work on polysiloxane deactivation of fused silica capillaries. Although acid treatment is often omitted with fused silica capillaries, there are good reasons for hydrothermal treatment of this column material. Use of Grob's peroxide method gave immobilized 0.25 μm films of SE‐54; lowering of the immobilization temperature permitted immobilization of 0.1 μm films of the same phase.
Two dimensional TLC determination of PAH in diluted automobile exhaust gases
Authors: Kraft J. , Hartung A. , Lies K.‐H. , Schulze J.
Published: May 2005

A 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

A 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

A 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

The 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

A 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

Silane‐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

A 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

A 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

It 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

Single, 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

A 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

Capillary 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

There 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

A 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

The 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

Residue 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

Analyses 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

A 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

A 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

Crosslinked 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

Various 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

A 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

Fused 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

In 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

Fused‐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

The 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.
A CP‐MAS NMR study of some deactivation methods in capillary gas chromatography
Authors: Rutten G. , van de Ven A. , de Haan J. , van de Ven L. , Rijks J.
Published: May 2005

The effect of temperature, water content, and the type of reagent on the silylation of fused silica capillaries was studied by 29Si and 13C CP‐MAS NMR. Fumed silica (Cab‐O‐Sil M5), which is essentially a highly dispersed vitreous quartz with a surface comparable to that of fused silica capillary columns, was selected as a model material.

Hexamethyldisilazane (HMDS) and 1,2‐diphenyl‐1,1,3,3‐tetraphenyldisilazane (DPTMDS), which were used as silylation reagents, yielded trimethyl‐ and dimethylphenylsilyl surface groups respectively at lower temperatures (< 350°C and <250°C respectively). At higher temperatures, increasingly more dimethylsilyl groups are formed, with the silicon bound to two oxygen atoms. This process occurs for DPTMDS at a considerably lower temperature than for HMDS. The formation of silyl groups on the surface and the disappearance of hydroxyl groups are followed independently. The 13C NMR and GC‐MS of the reaction products showed that with DPTMDS, the formation of two Si‐O‐Si links is accompanied by a loss of phenyl groups rather than of methyl groups.

After the Cab‐O‐Sil had been dried over P2O5, the formation of these double links occurred for HMDS only at temperatures above 460°C and for DPTMDS at 400°C. Thus we concluded that water supplies oxygen atoms for double Si‐O‐Si links (possibly crosslinks) necessary for efficient deactivation. This may explain the less successful silanization of fused silica capillaries because their water content is lower than that of glass capillaries.
Changes in peak width and concentration at the inlet and outlet of a chromatographic column
Authors: Conder J. R.
Published: May 2005

The original plate model of chromatography is extended to the sorption process occurring at the column inlet and the desorption process at the column exit. At the column inlet it is shown that sufficiently wide feed bands undergo no change in concentration but a fall in band width, i.e., the volume of mobile phase occupied by the solute band is reduced. The reduction factor is (1 + k) where k is the mass distribution ratio (capacity factor). Narrower bands suffer partial reduction in both band width and concentration. On desorption at the outlet, however, the change is always in band width and not concentration. A perfect detector registers the true concentration‐time profile of the band in the column if the solute mass fraction in the stationary phase is below 10−3 at the column outlet. The risks of stripping the stationary phase at high solute concentrations in analytical and preparative or production gas chromatography are compared.
Factors affecting the reversed‐phase liquid chromatographic separation of polycyclic aromatic hydrocarbon isomers
Authors: Wise S. A. , Sander L. C.
Published: May 2005

Reversed‐phase liquid chromatography (LC) on C18 stationary phases provides excellent selectivity for the separation of polycyclic aromatic hydrocarbons (PAH). Recent studies have shown that several factors affect selectivity for the LC separation of PAH including phase type (monomeric or polymeric), pore diameter and surface area of the silica substrate, and surface density of the C18 ligands. In this paper the separation of eleven PAH isomers of molecular weight 278 is used to further illustrate the effect of stationary phase characteristics and shape of the solute (length‐to‐breadth ratio, L/B) on retention and selectivity. Only polymeric C18 phases with a high C18 surface coverage provided separation of all eleven isomers and the elution order of these isomers generally followed increasing L/B values. The effect of solute nonplanarity on reversed‐phase LC retention was investigated on both monomeric and polymeric phases using a series of planar and nonplanar PAH pairs. For each solute pair, the nonplanar solute eluted earlier than the planar solute, the largest selectivity factors being observed on the C18 phase with the highest percent carbon load. Based on these studies, a model is proposed to describe the retention of PAH on polymeric C18 phases.
Immobilized stationary phases on the basis of polyethylene glycol
Authors: Horká M. , Kahle V. , Janák K. , Tesařik K.
Published: May 2005

The preparation of the immobilized stationary phase based on Carbowax 20 M is described. Bifunctional isocyanates were used for cross‐linking. The properties of the prepared stationary phase were studied.
Analysis of mono‐, di‐, and triglycerides by capillary supercritical fluid chromatography
Authors: White C. M. , Houck R. K.
Published: May 2005

The separation of mixed mono‐, di‐, and triglycerides by capillary supercritical fluid chromatography is described. The separations were performed at low operating temperatures, using a carbon dioxide mobile phase, a conventional flame ionization detector, and two different stationary phases, DB‐5 (95% dimethyl‐(5%)‐diphenylpolysiloxane) and DB‐225 (50% cyanopropyl‐methyl‐(50%)‐methylphenylpolysiloxane). Because the separations were performed at low operating temperatures, no thermal degradation of the glycerides was observed. Even under these mild operating conditions, trinervonin, a triglyceride having a molecular weight over 1100 amu, was readily eluted. When rapid pressure programming of the carbon dioxide mobile phase was employed, trinervonin was eluted in less than two minutes. On DB‐5, the mono‐, di‐, and triglycerides eluted in order of increasing molecular weight. A graph of t′r (on DB‐5) versus molecular weight is linear. When DB‐225 was used as the stationary phase, triglycerides eluted in the order of increasing unsaturation. Thus, the order of elution on DB‐225 was tristearin, triolein, trilinolein, and trilinolenin.
Modified flame ionization detector for the analysis of large molecular weight polar compounds by capillary supercritical fluid chromatography
Authors: Richter B. E.
Published: May 2005

The modifications made to a flame ionization detector (FID) to facilitate the detection of large molecular weight polar compounds analyzed by capillary supercritical fluid chromatography are described. Some specific examples are given to demonstrate that polar compounds can be effectively eluted using deactivated fused silica capillary columns and supercritical carbon dioxide at 40°C.
The application of gradient saturation in unidimensional planar chromatography of polar lipids. Part 1: Presentation of the HPTLC system
Authors: Kolarovic L. , Traitler H.
Published: May 2005

A thermostated HPTLC system was assembled to test the influence of gradient chamber saturation upon resolution of polar lipids chromatographed on boric acid‐impregnated silica gel plates. Inexpensive mixtures of nonacidic (14 component peaks) and acidic (8 component peaks) lipids were prepared from soya lecithin by a simplified procedure involving DEAE‐Sephadex liquid column chromatography to monitor performance of the system using a readily available reference material. The system requires ca. 5 min chamber presaturation after which the polar lipids are chromatographed in less than 30 min. Retention times (tR) as well as peak area % values of all component peaks and measured by scanning photodensitometry to demonstrate the influence of different modes of chamber saturation upon the resolution of polar lopids.
Column switching applied to capillary gas chromatography/fourier transform infrared spectroscopy
Authors: Smith S. L.
Published: May 2005

A dual oven gas chromatograph incorporating a micro, mechanical switching valve has been interfaced to an FTIR spectrometer. With this system, each oven can be operated with independent temperature control. Complete choice of the columns' type and capacity gives flexibility in the separation prior to spectroscopic evaluation. An application which demonstrates some of the advantages of column switching in GC/FTIR is presented. Minor sample components have been successfully analyzed by heart‐cutting the appropriate section of the separation from a high to a low capacity column. In this way, the dynamic range of the technique is effectively increased while an efficient chromatographic inlet to the FTIR is maintained.
Modified GC‐phases for the enantiomeric separation of optically active compounds: Crosslinking experiments with polymeric chiral compounds
Authors: Schomburg G. , Benecke I. , Severin G.
Published: May 2005

Crosslinking experiments for immobilization of the well‐known chiral stationary phases XE 60‐L‐valine‐(S)‐ and XE 60‐L‐valine‐(R)‐α‐phenylethylamide within capillary columns have been successfully carried out. Crosslinking was also obtained with mixtures of the chiral compound acrylyl‐L‐valine‐(S)‐α‐phenylethylamide and the polyethylene glycol Carbowax 20M. Immobilization of 75% to 90% was achieved by crosslinking the polymeric chiral phases, but sometimes up to 100% of these phases remained within the columns after the usual subsequent solvent treatment. The crosslinking of Carbowax 20M with acrylyl‐L‐valine‐(S)‐α‐phenylethylamide led to a chiral polymer of a polarity different from that of the common siloxane type chiral phases.
Analysis of light hydrocarbons (C2C6) at PPT levels by high resolution gas chromatography
Authors: Schmidbauer N. , Oehme M.
Published: May 2005

An analytical technique is described which allows the determination of C2C6 hydrocarbons in the ppt‐range from up to 21 air samples after removal of air humidity. Preconcentration is carried out on a two stage cryotrap system. The compounds are separ ated on a temperature‐programmed capillary coated with Al2 O3. Detection limits (S/N 2:1) of 1.5 to 5 ppt were obtained for air samples from the Arctic. The reproducibility of the method was about 3% at the 50–100 ppt level. Practical problems are discussed in detail.
Analysis of essential oils by direct sampling from plant secretory structures and capillary gas chromatography
Authors: Bicchi C. , D' Amato A. , Frattini C. , Nano G. M. , Cappelletti E. , Caniato R.
Published: May 2005

It is of fundamental importance to know the true composition of the essential oil produced by the secretory structures of a plant, both from a biogenetic and a chemotaxonomic point of view. This paper considers a method which combines direct sampling with on‐column CGC and studies the oils directly from the secretory structures: some examples are given (Humulus lupulus L., Tagetes erecta L., and Tagetes patula L.). For each plant, the composition of the distilled oil is compared to that obtained by direct sampling, and a photograph of the secretory structures taken by electroscanning microscopy is given.
Dicholorbenzyl alkyl ether homologs as retention index markers and internal standards for the analysis of environmental samples using capillary gas chromatography
Authors: Wells D. E. , Gillespie M. J. , Porter A. E. A.
Published: May 2005

A homologous series of 2,4‐dichlorobenzyl alkyl ethers (DCBEs) have been synthesized and purified for use as retention index calibrants and internal standards. They are stable, sensitive to ECD and FID and ideal for GC‐MS, with base peaks at m/z 159/161. The retention index calibration against the n‐alkanes for a linear temperature program (LTP) series is given and recommendations made for the most suitable members of the DCBE series for use as internal standards in organochlorine (OC) residue analysis.
On‐line multidimensional chromatography using packed capillary liquid chromatography and capillary gas chromatography
Authors: Cortes H. J. , Pfeiffer C. D. , Richter B. E.
Published: May 2005

The introduction of selected fractions from a liquid chromatograph into a gas chromatograph has been described; however, analyses were performed by off‐line experiments requiring collection and reinjection of the separate fractions or by on‐line procedures where disadvantageously, only a fraction of the separated peak or a well resolved component in a mixture could be introduced into a gas chromatograph. This disadvantage is overcome by the apparatus and method described in this paper, which utilizes a multidimensional chromatography system employing a high efficiency, packed capillary LC column coupled on‐line to a capillary gas chromatograph.

The liquid chromatograph (so designed) can act as a highly efficient clean‐up or chemical class fractionation step prior to introduction into the gas chromatograph, significantly reducing sample preparation times in many applications. Thus minor components in a complex matrix can be determined without prior sample clean‐up, an example of which is the determination of polychlorinated biphenyls in a complex hydrocarbon matrix.
Liquid crystal stationary phases for gas chromatography and supercritical fluid chromatography
Authors: Rokushika S. , Naikwadi K. P. , Jadhav A. L. , Hatano H.
Published: May 2005

Novel monomeric and polymeric liquid crystalline compounds were synthesized as stationary phases for gas chromatography (GC) and supercritical fluid chromatography (SFC). Monomeric liquid crystalline compounds were used in packed column gas chromatography for the separation of isomeric aromatic compounds and insect sex pheromones. Liquid crystalline polymers possess long nematic ranges and a uniform coating was easily achieved in glass and fused silica capillaries, which could stand temperatures up to 250°C in GC and pressures of 200 MPa at 160°C in SFC. The columns provide excellent selectivity and resolution for fused ring aromatic compounds such as the isomers anthracene and phenanthrene or triphenylene and chrysene.
Practical applications of open tubes in liquid chromatography
Authors: Engelhardt H. , Lillig B.
Published: May 2005

The practical applications of open tubes in liquid chromatography as separation columns and as reactors for post column derivatization are discussed. With present technology, the potential efficiency of open tubular columns cannot be fully exploited. As reactors in post column derivatization, these tubes offer many advantages if knitted or stitched to enhance radial mass transfer. The application of open tubes with diameters between 0.12 mm and 0.6 mm as reactors in the selective and sensitive detection of amino acids is demonstrated.
A fast procedure to immobilize polyethylene glycols in glass capillary columns
Authors: Russo M. V. , Goretti G. C. , Liberti A.
Published: May 2005

Polyethylene glycols can be immobilized in glass capillary columns by a new procedure involving covering the glass walls with a layer of graphitized carbon black and by flowing a mixture of the stationary phase and dicumyl peroxide. After curing and conditioning the column is ready for use. Excellent performance is reported for Carbowax 20 M and high molecular weight glycols. For other glycols the immobilized layer is less stable and can be washed out.
On the efficiency of capillary columns coated with medium polarity thick films
Authors: David F. , Proot M. , Sandra P.
Published: May 2005

The efficiency of FSOT columns coated with thick films of polyphenylmethylsiloxane was theoretically and experimentally compared to thin apolar and medium polar coatings and to thick apolar coatings. Experimental hū and TZū plots clearly demonstrate the enormous loss in chromatographic efficiency of thick films of medium polar siloxane stationary phases. The low diffusion coefficient in the liquid phaese is responsible for this behavior. The influence of the temperature and the nature of the solute on the efficiency was also studied.
Enzyme activity determination by radio gas chromatography on capillary columns
Authors: Herkner K. , Schaupal R. , Goedl U.
Published: May 2005

Androgen 5α‐reductase from the foreskin of 48 boys in prepubertal age was analyzed by evaluation of the apparent Km‐and Vmax‐ values after tissue incubation. Reaction rates were calculated after determination of specific radioactivity of distinct metabolites, by comparison to the radioactivity of the precursor. Reaction products were separated by radio gas chromatography on capillary columns. The chromatography system was based on multicolumn equipment with column switching facilities and a variable splitter at the outlet of the separation column. A radioactivity monitor (gas proportional counter) was used for measurement of radioactivity in the column effluents. An electron capture detector was used for mass detection of steroid acyl derivatives.
Packed columns vs. wall coated open tubular columns in quantitative analyses of polychlorinated biphenyls
Authors: Kominar R. J. , Onuska F. I. , Terry K. A.
Published: May 2005

This article describes and critically evaluates a complete method for the quantitation of PCB in sediment samples. The extraction and clean‐up procedure is described. Packed column and capillary column results are compared. Capillary column quantitation yields lower values for total PCB loading. Preferences for capillary column quantitation are discussed and explained. Capillary quantitation is based on the combination of an external Aroclor standard and an internal decachlorobiphenyl standard for normalizing data. In light of the recent report of synthesis of all 209 PCB congeners a suggestion is made to use these as absolute standards to establish a bank of primary standard Aroclors.