bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of compounds of environmental concern: II. Diphenyl ethers
Authors: Lopez‐Avila Viorica , Benedicto Janet , Baldin Emi , Beckert Werner F.
Published: May 2005

Nineteen halogenated and/or nitrated diphenyl ethers (currently listed in EPA Method 8111) have been separated on a DB‐5/ DB‐1701 column pair connected to an inlet splitter and separate electron capture detectors. Retention times are included for 10 additional compounds evaluated for their suitability as internal standards or surrogate compounds for incorporation into Method 8111. Method reproducibility and linearity are discussed, and results are presented for extracts of two real samples spiked with the 19 diphenyl ethers and analyzed using the dual‐column dual‐detector arrangement.
Simulated distillation of wax samples using supercritical fluid and high temperature gas chromatography
Authors: Thomson J. S. , Rynaski A. F.
Published: May 2005

Simulated distillation boiling range distributions have been compared for high boiling petroleum wax samples using high temperature gas chromatography and supercritical fluid chromatography. Midpoint (50 % off) temperature differences were small, and average differences between the two types of analyses were less than 6° Details of optimization of the HTGC and SFC systems and injection techniques used are reported.
Rapid analysis of coke oven gas by capillary gas chromatography
Authors: Havenga Willem J. , Rohwer Egmont R.
Published: May 2005

A porous layer open tubular (PLOT) column has been used for monitoring the light hydrocarbons and permanent gases produced in coking plants. The method, which offers a simple alternative to traditional multi column techniques, entails a single injection on to a Carboplot 007 capillary column and simultaneous thermal conductivity and flame ionization detection. The simplified approach proposed is restricted to coke oven gas analysis: application to other gas mixtures has not been considered.

The reliability of this procedure compares favorably with that of traditional methods; the technique is also much less time‐consuming: seven individual gases can be determined on‐line every fifteen minutes. Primary and secondary gas standards were used to determine response curves for the gases.

The method also facilitates reliable calculation of heat values associated with the burning of the fuel gas mixtures.
Sample evaporation in conventional split/splitless GC injectors. Part 3: Retaining the liquid in the vaporizing chamber
Authors: Grob Konrad , De Martin Mirelia
Published: May 2005

As most sample liquids tend to pass through an empty injector insert at a speed which is too high to enable complete evaporation, movement of the liquid must be arrested before it reaches the column entrance. Stopping the liquid means deposition on to a surface; this, however, is possible only after the temperature of the surface has been cooled to (or below) the boiling point of the liquid (solvent).

The performance of different means of stopping the liquid has been tested visually (by the method described in Part 2). Baffles on the wall of the injector insert had hardly any effect on evaporation: the band of liquid leaving the syringe needle performed a perfect slalorn around them. The inverted cup proved more efficient, but the best performance was obtained from a light plug of glass wool: owing to its low thermal mass, the first fibers to be met by the liquid are immediately cooled to the solvent boiling point, allowing the liquid to wet it. The sample liquid is sucked up by the glass wool, from where the sample evaporates relatively slowly, often over a period of several seconds.
Compressibility effects in packed and open tubular gas and supercritical fluid chromatography
Authors: Janssen Hans‐Gerd , Snijders Henri , Cramers Carel , Schoenmakers Peter
Published: May 2005

The influence of the pressure drop on the efficiency and speed of analysis in packed and open tubular supercritical fluid chromatography (SFC) is described: methods previously developed to describe the effects of mobile phase compressibility on the performance of open tubular columns in SFC have been extended to packed columns.

The Horvath and Lin equation has been used to elucidate the influence of variations in velocity, diffusivity, and capacity factor along the column on the overall efficiency of packed column SFC. In packed columns, in contrast with the situation in open tubular columns, because the increase in velocity is no longer compensated by an increase in diffusion coefficients, the increase in both linear velocity and capacity factor which result from a significant pressure drop cause the plate height to increase along the column.

The effect of fluid decompression along the length of the column on the speed of analysis in SFC has been studied and numerical expressions derived which enable calculation of compressibility correction factors for the plate height. Both the f1 and f2 correction factors remain very close to unity for acceptable pressure drops, which means that the pressure drop has virtually no effect on the number of plates generated per unit time for an unretained component. For retained species, the decompression of the mobile phase across the column causes the capacity factor to increase and hence leads to increased analysis times.
Use of headspace capillary GC to study the development of volatile compounds in fresh fruit
Authors: Rizzolo Anna , Polesello Andrea , Polesello Stefano
Published: May 2005

The composition of volatile compounds produced by fruit during growth and post‐harvest storage and ripening has been studied and the different headspace methods compared. Static and dynamic headspace sampling have been compared and evaluated according to their capacity to collect and concentrate volatiles from the atmosphere surrounding the fruits, and FID, MSD, and organoleptic detection have been compared. The results emphasize that the headspace sampling procedure selected is crucial to the performance of subsequent analysis.
The separation of enantiomers on modified cyclodextrin columns: Measurements and molecular modeling
Authors: de Vries N. Koen , Coussens Betty , Meier Robert J. , Heemels Gerlie
Published: May 2005

The enantiomers of 2‐chloropropionic acid methyl ester, cis‐pinane, 2‐bromoethylbenzene, 2‐bromobutane, 2‐hydroxybutane trifluoroacetyl ester, and styrene oxide have been resolved on an octakis‐(3‐O‐butyryl‐2,6‐di‐O‐pentyl)‐γ‐cyclo‐dextrin capillary column, and the separation of the styrene oxide enantiomers has also been studied on columns coated with octakis‐(3‐O‐trifluoroacetyl‐2,6‐di‐O‐pentyl)‐cyclodextrin, octakis‐(2,3,6‐tri‐O‐pentyl)‐γ‐cyclodextrin, heptakis‐(3‐O‐trifluoroacetyl‐2,6‐di‐O‐pentyl)‐β ‐cyclodextrin, and heptakis‐(2,3,6‐tri‐O‐methyl)‐β‐cyclodextrin.

Thermodynamic parameters (ΔG, ΔH, and ΔS) were determined from variable temperature measurements. The inclusion complexes containing styrene oxide were also studied by molecular modeling techniques. It has been found that a combined molecular mechanics–molecular dynamics approach may be a valuable tool for rationalizing the qualitative trends observed in the experimental separation factors. For the inclusion complexes considered here it is shown that the orientation of the guest relative to the cyclodextrin host is determined by the size and polarity of the cyclodextrin.
Determination of the animal of origin of dairy products and raw and cooked meats by GC analysis of the fatty acid methyl esters (FAME) obtained by transesterification
Authors: Matter Lothar
Published: May 2005

It is possible to determine the animal of origin of dairy products and raw and cooked meats by high resolution capillary GC of fatty acid methyl esters. This is demonstrated by several examples.
Determination of organometallic compounds by capillar gas chromatography – inductively coupled plasma mass spectrometry
Authors: Kim Alexander , Hill Steve , Ebdon Les , Rowland Steve
Published: May 2005

The separation and detection of volatile organometallic compounds containing tin, iron, and nickel has been achieved using capillary GC–inductively coupled plasma–mass spectrometry (capillary GC‐ICP‐MS). Detection limits range from 3.0 to 7.0 pg/s. The presence of volatile organotin compounds in a harbor sediment has been confirmed. The retention range of the organometallic compounds analyzed by capillary GC‐ICP‐MS has been extended considerably beyond that possible in earlier studies (retention indices up to 3400).
A monomolecular pseudostationary phase for micellar electrokinetic capillary chromatography
Authors: Palmer Christopher P. , Khaled Maha Y. , McNair Harold M.
Published: May 2005

A highly stable pseudostationary phase has been synthesized and evaluated for use in micellar electrokinetic capillary chromatography (MECC). Sodium 10‐undecylenate has been oligomerized to form a micelle‐like structure following the procedure of Durairaj et al. [1].The stability of this structure renders it suitable for use with mobile phases containing relatively high percentages of organic modifiers, enabling the separation and detection of hydrophobic analytes such as alkyl phthalates and polynuclear aromatic hydrocarbons (PAHs) which are difficult to analyze by conventional micellar electrokinetic chromatography. In addition to demonstrating the utility of this structure for the analysis of hydrophobic analytes, the electrophoretic and chromatographic properties of the new phase have been investigated.
Identification of pentacyclic triterpenes by GC‐MS‐MS
Authors: Hazai Istvan , Galvez‐Sinibaldi Alfredo , Philp R. Paul
Published: May 2005

The development of tandem mass spectrometry (MS‐MS) and its combination with gas chromatography (GC‐MS‐MS) has greatly enhanced our ability to analyze exceedingly complex mixtures from a wide variety of sources, including fossil fuels. This paper describes a comparison of the conventional electron impact (El) mass spectral fragmentation patterns, obtained in the MS‐MS precursor – product mode, of three oleanane isomers and one ursene, all of which are used as indicators of higher plant input to the sedimentary environment

Results show that El and collision‐activated dissociation (CAD) spectra are most similar at collision energies between −15 and −20 eV.The presence of methyl substituents in these pentacyclic terpenes plays an important role in the process of ring fragmentation: the daughter spectra of the M – 15 fragments can be used to obtain structural information, such as the positions of the double bonds.
Improved SFE recovery of trace analytes from liver using an integral micrometering valve–SPE column holder assembly
Authors: Maxwell Robert J. , Parks Owen W. , Piotrowski Edwin G.
Published: May 2005

A novel integral restrictor–collector has been designed for use with a conventional supercritical fluid extraction (SFE) apparatus. The assembly reduces the path length between a micrometering valve and collector (a solid phase extraction (SPE) column), obviating the need for the complicated tubing and connectors usually associated with such devices. Also described is a heating‐block assembly which encases the micrometering valve and provides uniform heating of the valve during extraction.

The valve–SPE column assembly was part of a system used to perform the first reported SFE multi‐residue drug recovery from fortified liver. Extractions used carbon dioxide pressurized to 690 bar as the supercritical fluid. Flow rates of expanded gas through the SPE columns were 3–4 L/min with concomitant quantitative trapping of the analytes on the sorbent bed. After SFE the three nitrobenzamide antimicrobial drug residues from the liver were eluted from the SPE columns by off‐line analysis. The results demonstrated that losses of trace level analytes in tissue may be significantly reduced by including an integral metering valve‐collector assembly as part of the SFE apparatus.
The effects of inlet liner configuration and septum purge flow rate on discrimination in splitless injection
Authors: Hinshaw John V.
Published: May 2005

An unmodified split/splitless inlet system using forward‐pressure controlled pneumatics was operated in splitless injection mode with several inlet liners under a range of septum purge flow rates. The relative recovery (discrimination) of hydrocarbons ranging from n‐C8 to n‐C20 depended strongly upon the injected sample volume with open‐ended liners at high septum purge flow rates of e.g. 50 mL/min. Little or no discrimination was observed at septum purge flows of 2–3 mL/min. The same inlet was also operated in a back‐pressure regulated configuration that produced mass discrimination similar to that observed with the higher septum purge flows in the forward‐pressure configuration. An inlet liner with a restricted inlet and outlet gave mass‐discrimination levels independent of septum purge flow rate, but in the reverse sense of that observed with open‐ended liners. Preferential volatile‐component losses out of the inlet liner to the septum purge vent are principally responsible for the observed mass discrimination with openended liners, while mass‐dependent losses with doubly‐restricted liners seem due to slow sample evaporation.
An amylopectin tris(phenylcarbamate) chiral stationary phase for high performance liquid chromatography
Authors: Félix Guy , Zhang Tong
Published: May 2005

Amylopectin tris(phenylcarbamate) has been evaluated as a chiral stationary phase for HPLC; the influence on its cptical resolving capabilities of mobile phase composition and nature of the alcohol used as modifier has been studied. Separation and resolution of twelve arylalcohol racemates were examined. In most instances, the stationary phase exhibited high optical resolving capacity.
Use of modifiers in on‐line and off‐line supercritical fluid extraction
Authors: Levy Joseph M. , Dolata Lori , Ravey Robert M. , Storozynsky Eugene , Holowczak Kathy A.
Published: May 2005

For many applications using supercritical fluid extraction (SFE), modifiers may be required.This paper will present some findings regarding the use of various modifiers including methanol, hexane, acetone, chloroform, dichloromethane, toluene, and tributylphosphate, in on‐line and off‐line SFE with cryogenic adsorbent trapping. The specific applications involved the extractions of petroleum hydrocarbons and pesticides from naturally incurred soils.
Inserts providing complete sample evaporation above the column entrance in vaporizing GC injectors
Authors: Grob Konrad , Wagner Christoph
Published: May 2005

Completeness of sample evaporation in conventional vaporizing injection is a problem for many samples and calls for measures to arrest the sample liquid in the space between the needle exit and the column entrance. A visual testing procedure reveals that a small plug of loose glass or quartz wool ensures complete evaporation in all instances. Obstacles built into the liner also stop liquid, provided they force the sample to pass through narrow channels. Other important design characteristics concern access to the narrow channel. Evaporation in a packed insert usually occurs from a surface, whereas the sample hardly touches surfaces in the instance of an insert with obstacles. Evaporation from a packing is, in fact, more reliable, but creates more problems concerning inertness.
Coupled solid phase extraction–supercritical fluid extraction–on‐line gas chromatography of explosives from water
Authors: Slack Gregory C. , McNair Harold M. , Hawthorne Steven B. , Miller David J.
Published: May 2005

A method has been developed for the quantitative extraction of nitrotoluenes (2,3‐dinitrotoluene, 2,4‐dinitrotoluene and trinitrotolugene) from water using a BakerbondTM phenyl sorbent. The average solid phase extraction recoveries for spiked standards ranged from 80 to 95 percent for reagent water and 52 to 95 percent from well and surface water in the low ppb and ppt levels. After the nitrotoluenes had been trapped on the solid sorbent they were quantitatively eluted using SFE. Adding toluene to the extraction cell increased the rate of extraction, but did not improve analyte recovery versus unmodified CO2. The extracts were analyzed off‐line with GC–ECD using an internal standard. Extraction losses were due to analyte breakthrough, and not from poor SFE recoveries. This demonstrates that supercritical fluid extraction is a suitable elution technique for analytes trapped on solid phase extraction sorbents.

Also, a method for the direct on‐line coupling of SPE to GC, using SFE, has been developed and evaluated. Supercritical CO2 is ideal for directly coupling SPE to GC, since carbon dioxide is a gas under ambient conditions. One potential problem of on‐line SPE–SFE–GC is the presence of residual water trapped on the active sites of the Bakerbond13 phenyl sorbent. This problem was dealt with by using a split interface previously described by Hawthorne. From the results of this study, the relative standard deviation of the on‐line SPE–SFE–GC interface was determined to be between 4 and 10 percent. In addition, there was no significant difference in the precision of the method with or without the use of an internal standard. A calibration curve was also constructed (r2 = 0.995) from spiked controls, demonstrating that the method is quantitative.
An homologous series of benzodiazepine retention index standards for gas chromatography
Authors: Rasanen Ilpo , Ojanperä Ilkka , Vuori Erkki , Hase Tapio A.
Published: May 2005

An homologous series of benzodiazepine retention index standards (the R‐series) has been synthesized and the gas chromatographic behavior of the series investigated on NB‐54 and NB‐1701 capillary columns. The compounds were stable, exhibited symmetrical peak shapes, and fairly linear retention behavior was observed on both columns. The series can be coinjected with every sample to enable the high precision analysis of toxicological samples; screening for 20 benzodiazepine drugs was possible in 23 minutes (including cooling). The R‐series method was compared with a retention index method based on a series of benzodiazepine drugs as standards and with a method employing relative retention times. The precision of the R‐series method was found to be generally better than that of the two other methods in both long‐ and short‐term studies.
Supercritical fluid extraction of nylon 6: An investigation into the factors affecting the efficiency of extraction of caprolactam and its oligomers
Authors: Venema Arnold , van de Ven Henk J. F. M. , David Frank , Sandra Pat
Published: May 2005

Caprolactam and oligomers can be efficiently extracted from nylon 6 by use of supercritical fluid extraction with carbon dioxide containing 7.5 % (m/m) methanol as the extraction fluid. The application of a static extraction, using an additional amount of methanol, is necessary to obtain high extraction efficiencies.
Derivatized cyclodextrins for the separation of enantiomers in capillary electrophoresis
Authors: Schmitt Thomas , Engelhardt Heinz
Published: May 2005

The use of cyclodextrin derivatives for the efficient separation of enantiomeric drugs is described. Hydroxypropylation, methylation or carboxymethylation of the cyclodextrin not only result in a better solubility of the cyclodextrin in aqueous solutions, but also favor, via additional hydrogen bonding, the stabilization of one of the cyclodextrin‐analyte complexes. The influence of the background electrolyte on peak shape is also described here. Carboxymethylated cyclodextrin can be used in similar manner to uncharged cyclodextrins at low pH values (below 4). At pH values above 5, however, its charge also allows the separation of uncharged enantiomers as in a micellar‐like system.
Real‐time control of column switching in multidimensional gas chromatography
Authors: Himber Kimmo , Sippola Erkki , David Frank , Sandra Pat
Published: May 2005

In chromatography the separation power expressed in terms of peak capacity can be greatly enhanced by multidimensional techniques. The most important aspect of multidimensional chromatography is the precise location of the heart‐cut window. Very often the reliability of this positioning is ensured by applying relatively large heart‐cuts; this reduces the intrinsic selectivity offered by the technique.

The best way of locating peaks in chromatography is by means of retention indices. This technique can also be used in multidimensional chromatography. A method is described whereby the heartcut window in multidimensional gas chromatography (MDGC) can be defined precisely.
Trapping efficiencies of various collection solvents after supercritical fluid extraction
Authors: Thompson Peter G. , Taylor Larry T. , Richter Bruce E. , Porter Neil L. , Ezzell John L.
Published: May 2005

A polarity test mix consisting of acetophenone, N, N‐dimethylaniline, naphthalene, decanoic acid, 2‐naphthol, and n‐tetracosane was spiked onto sand, and extracted with supercritical carbon dioxide, to evaluate the collection efficiency of various solvents and solvent mixtures. Nine single collection solvent systems and four mixed collection solvent systems were studied. When one‐component collection solvents were employed, quantitative (above 90%) recovery of all analytes was not possible. With mixed collection solvents, recoveries of 90% or better with all analytes studied were possible.
Dual‐column GC analysis of mediterranean fish for ten organochlorine pesticides and sixty two chlorobiphenyls
Authors: Rahman M. S. , Bøwadt S. , Larsen B.
Published: May 2005

The simultaneous analysis of α‐HCH, β‐HCH, γ‐HCH, HCB, p,p′‐DDD, p,p′‐DDT, p,p′‐DDE, o,p′‐DDT, mirex, dieldrin and 62 chlorobiphenyl congeners on two parallel capillary GC columns of different polarity is described for nine Mediterranean fish species. Ten commercially available columns with stationary phases completely characterized in respect of their PCB elution patterns were considered for dual‐column GC‐ECD analysis. The combination of a 60 m × 0.25 mm i.d. column coated with a 0.25 μm film of 50% diphenyl dimethylsiloxane and a series combination of a 25 m × 0.25 mm i.d. column coated with a 0.25 μm film of 5% diphenyl dimethylsiloxane with a 25 m × 0.22 mm i.d. column coated with a 0.10 μm film of 1, 10‐dicarba‐closo‐dodecarborane dimethylpolysiloxane furnished the highest number of separated chlorobiphenyl congeners (104). The dual‐column GC system performed with high stability and reproducibility over a broad concentration range (1–3000 ng/g lipid) of the organochlorine compounds in the investigated fish.
A method for reproducible preparation of chiral polysiloxanes with regular repeat units as stationary phases for capillary gas chromatography
Authors: Abe Iwao , Nishiyama Takako , Frank Hartmut
Published: May 2005

Trifluoroethyl ester‐functionalized polysiloxanes can be prepared by block condensation of 3‐dichloromethylsilyl‐2‐methylpropionic acid 2′,2′,2′‐trifluoroethyl ester with 1,5‐bis(diethylamino)hexamethyltrisiloxane or with disodium tetramethyldisiloxane‐1,3‐diolate. The functionalized polysiloxanes may serve as supports for a variety of selector groups; for instance, nucleophilic displacements with L‐valine‐t‐butylamide or L‐α‐naphthylethylamine lead to chiral polysiloxanes in high yields and with high reproducibility. Imidazole accelerates the rate of nucleophilic displacement. Capillary columns coated with such chiral polysiloxanes exhibit high enantioselectivity and thermostability.
The selectivity and polarity of carbon layer open tubular capillary columns modified with a polar liquid phase
Authors: Castello Gianrico , Vezzani Sonia , Moretti Paolo
Published: May 2005

The polarity of carbon layer open tubular (CLOT) columns coated with a layer of non‐porous graphitized carbon black (Carbopack B) modified with an appropriate amount of polar polyglycol liquid phase has been evaluated and compared with that of standard polar (Supelcowax‐10) and non‐polar (SPB‐1) bonded phase open tubular columns. The efficiency and selectivity were measured at various temperatures and the polarity of the columns was evaluated by use of McReynolds' constants and the difference in apparent carbon number, ΔC of linear alkanes and alcohols. The polarity of the CLOT column was found to depend on temperature, and changing the analytical conditions therefore enabled the separation of compounds of different polarity whose reciprocal position and resolution were affected by temperature. The application of calculation methods which enable programmed temperature retention times to be predicted from isothermal data was also found to be possible when the polarity of the CLOT column changes with temperature.
High performance liquid chromatography on the chiral stationary phase (R,R)‐DACH‐DNB using carbon dioxide‐based eluents
Authors: Gasparrini Francesco , Maggio Francesco , Misiti Domenico , Villani Claudio , Andreolini Franca , Mapelli Gian Pietro
Published: May 2005

Fast and efficient separations of chiral stereolabile compounds were obtained at very low temperature on a π‐acid chiral stationary phase (R,R‐DACH‐DNB) using carbon dioxide‐based mobile phases containing alcoholic polar modifiers.

Furthermore, efficient separations of the newly discovered spherical carbon cluster buckminsterfullerene (C60) and the related higher fullerenes (C70, etc.) have been performed on the same stationary phase using eluents based on either n‐hexane or carbon dioxide.
Analysis of sorbitan ester surfactants. Part II: Capillary supercritical fluid chromatography
Authors: Wang Zhendi , Fingas Merv
Published: May 2005

A rapid, simple and quantitative approach to the separation and identification of sorbitan ester surfactants has been developed using capillary supercritical fluid chromatography (SFC). The sorbitan ester surfactants were well separated into five groups: starting materials and mono‐, di‐, tri‐, and tetraesters, with each group consisting of a number of peaks representing different isomers. High purity glycerides of fatty acids were employed to estimate the relative response factors of sorbitan esters, and reliable group‐wise integration served for quantitation of the distribution of sorbitan fatty acid esters. A very important parameter, hydrophilic–lipophilic balance (HLB), which describes the hydrophilic and hydrophobic characteristics of surfactants, could be correlated with the distribution of the sorbitan esters. A combination of solid‐phase extraction (SPE) and SFC was used to separate, concentrate, and analyze Span‐20 from salt‐water samples. In comparison with the HPLC method, capillary SFC broadens the scope of the technique to encompass high molecular weight sorbitan polyesters while maintaining high separation efficiency.
Methodological approach for evaluating operational parameters and the characterization of a popular sorbent for solid‐phase extraction by high pressure liquid chromatography
Authors: Miller Kenneth G. , Poole Colin F.
Published: May 2005

The kinetic and retention properties of a silica‐based octadecylsiloxane bonded phase sorbent used in solid‐phase extraction (SPE) were determined by high pressure liquid chromatography (HPLC). This sorbent had a high bonded phase density resulting in a material with very low intraparticle porosity. This led to favorable retention and mass transfer properties over the normal sampling flow rate range. Typical cartridges for SPE have a low and variable packing density which is recognized as a significant cause of poor sampling performance and, under some circumstances, results in poor repro‐ducibility. The apparent particle size for the sorbent at 55–57 μm is considerably larger than generally indicated in the trade literature but this is not detrimental to its use for SPE since sorbent cartridges are able to function adequately with only a few theoretical plates. Solute size is identified as the primary driving force for sorbent retention under SPE conditions with polar interactions favoring retention in the aqueous mobile phase and a decrease in the breakthrough volume. All parameters required to predict the optimum sampling conditions, breakthrough volume and recovery in SPE can be conveniently obtained from data generated by HPLC. The sampling characteristics of particle‐loaded membranes are compared to those of conventional sorbent cartridges and differences in operating characteristics which affect the sampling efficiency for both devices are discussed.
Capillary SFC‐FTIR – effects of the flow‐cell on chromatographic resolution
Authors: Jenkins Timothy J. , Kaplan Muammer , Davidson George
Published: May 2005

The quantitative effects on chromatographic resolution of FTIR flow‐cells for detection in capillary SFC have been determined. A suitably designed cell with a volume of 500 nl was shown to cause only modest broadening of chromatographic peaks obtained from the surfactant mixture Triton X‐100, showing that subsequent detection methods can therefore be used in a multi‐hyphenated chromatographic ensemble. A larger‐volume (980 nl) cell was found to give satisfactory results with 100 μ columns, but not with 50 μm columns. The practicability of a multi‐hyphenated system was illustrated by a preliminary capillary SFC‐UV‐FTIR‐FID study on a plant extract. Good infrared spectra were obtained, together with well‐resolved UV and (subsequent) FID chromatograms.
Determination of organic acids and ketones in contaminated soils
Authors: Langbehn Arno , Steinhart Hans
Published: May 2005

Hydrocarbons and metabolites from biodegradation in soil have been isolated and separated using Soxhlet extraction, with n‐heptane and dichloromethane, combined with solid‐phase extraction on silica gel and basic aluminum oxide using n‐pentane, dichloromethane, methanol, and sulfuric acid – methanol as eluents. This procedure can be used for determination of metabolites both in laboratory‐prepared soil samples containing mineral oils and in actual contaminated soil.

After microbiological degradation, organic acids and ketones which were not original components of the diesel fuel and lubricating oil contaminating the soil samples were identified using capillary gas chromatography – mass spectrometry in batch‐soil experiments. Predominantly alicyclic and branched‐chain aliphatic organic acids and diacids, and aromatic ketones, were found to be formed after a few weeks degradation.
System for calculating the linear temperature‐programmed retention indices of polycyclic aromatic compounds
Authors: Shaogang Chu , Xiaobai Xu
Published: May 2005

Theoretical procedures have been used to predict linear temperature‐programmed retention indices for polycyclic aromatic compounds. It is possible to calculate such indices for polycyclic aromatic compounds in some practical situations in which the compounds cannot be eluted during a simple linear temperature program. The theory has been tested for a number of polycyclic aromatic hydrocarbon (PAHs) in single‐ and multi‐plateau temperature‐programmed gas chromatography with SE‐52 as the stationary phase. This method will extend the applicability of linear retention indices for the identification of the isomers of polycyclic aromatic compounds.
HPTLC separation of platinum metal 8‐hydroxyquinolinates
Authors: Wenclawiak Bernd W. , Flemming Michael
Published: May 2005

High performance thin layer chromatography has been used to separate all the platinum metal 8‐hydroxyquinolinates on polar stationary phases. The dependence of Rf values on the composition of mobile phases prepared from chloroform – tetrahydrofuran or chloroform – alcohol mixtures has been investigated. Retention was found to be partially dependent on alcohol chain length in chloroform – alcohol systems. The results obtained from TLC are dependent on the method of sample preparation used for the analyte.
Automated sample cleanup using on‐line coupling of size exclusion chromatography to high resolution gas chromatography
Authors: Blomberg Jan , Schoenmakers Peter J. , van den Hoed Nico
Published: May 2005

A fully automated on‐line sample cleanup system based on the coupling of size exclusion chromatography to high resolution gas chromatography is described. The transfer technique employed is based on fully concurrent solvent evaporation using a loop‐type interface, early vapor exit and co‐solvent trapping. Optimization of the LC‐GC transfer was done visually via an all‐glass oven door. To circumvent the problem of mixing within the injection loop, an adaptation was made to the standard loop‐type interface. The determination of a series of additives in a polymer matrix is presented as one example of the vast range of applications opened up by this technique.
Analysis of amines in petroleum
Authors: Thomson Jane S. , Green John B. , McWilliams Ted B. , Yu Shirley K.‐T.
Published: May 2005

An analytical method for differentiation of primary, secondary, and tertiary amines using exhaustive trifluoroacetylation prior to GC/MS has been developed. Using the conditions described in the report, most primary amines add two and secondary amines add one trifluoroacetyl group. In general, tertiary amines do not react. GC retention indices and relative GC/MS total ion current response factors for 102 trifluoroacetyl derivatives are reported. Examples of the application of the method to petroleum and coal liquid products are provided. Because of the limited thermal stability of the derivatives of primary amines, the method is applicable only to distillates boiling below 370 °C (700 °F).
GC–MS analysis of phenolic compounds in fuels after conversion to trifluoroacetate esters
Authors: Green John B. , Yu Shirley K.‐T. , Vrana Robert P.
Published: May 2005

The GC–MS characteristics of trifluoroacetate esters of phenolic compounds are discussed. Linear temperature programmed retention indices and total ion current MS response factors of over 120 phenolic esters are reported.

The main GC advantages from analysis of trifluoroacetate esters as compared to plain phenols are enhanced volatility and improved resolution. For example, the elution temperature of a given phenol is typically 50 °C greater than that of the corresponding trifluoroacetate ester. Also, while retention of compounds with two trifluoroacetate groups is only moderately greater than mono esters, underivatized dihydroxy compounds are very difficult to elute from any GC column. Complete resolution of isomeric C0‐, C1‐ and C2‐alkylphenol esters is readily achieved on conventional fused silica GC columns; resolution of the corresponding underivatized compounds requires specialized GC columns with low temperature limits.

In general, mass spectra of trifluoroacetate esters are more characteristic of a given structure than those of the corresponding phenols and may be more rigorously interpreted towards structural elucidation. A table in the report summarizes some of the more important spectral features used in compound identification.

Example applications in analysis of coal‐, shale‐ and petroleum‐derived materials are presented. Selected ion monitoring is used to determine individual phenolic components in whole distillates; reconstructed ion chromatograms are used to illustrate distributions of selected species as a function of fuel storage and thermal stress.
Prediction of programmed temperature retention times on linked capillary columns of different polarity
Authors: Gerbino Tomaso C. , Costello Gianrico
Published: May 2005

Systems formed by serial connection of capillary columns of different polarity were studied with methods previously used to predict the behavior of linked capillary columns under isothermal conditions and to obtain programmed temperature gas chromatography (PTGC) retention times of the individual columns starting from isothermal data. The two calculation methods were simultaneously applied in order to predict PTGC retention times of the series system starting from isothermal data obtained on the two individual columns. Experimental retention values measured using different temperature programs on the individual columns and on the series systems were found to agree with those calculated.
Limonene concentration in lemon (Citrus volkameriana) peel oil as a function of ripeness
Authors: Combariza Marianny Yajaira , Tirado Cristian Blanco , Stashenko Elena , Shibamoto Takayuki
Published: May 2005

The dependence of the limonene content of lemon (Citrus volkameriana) peel oil on the degree of ripeness of the fruit has been studied by using steam distillation and cold pressing to extract the oils from lemon fruit peel at different stages of maturation (green, greenish‐yellow, and yellow‐orange peel coloration). Samples of essential oils were analyzed by high resolution GC and GC‐MS, using tetradecane as internal standard for quantitation. Forty components were detected; thirty eight were positively identified by comparison of their mass spectra (El, 70 eV) and Kováts retention indexes (determined using a non‐logarithmic scale on capillary columns coated with both polar (DB‐Wax) and non‐polar (DB‐1) stationary phases) with those of standards and with data reported in the literature. The limonene concentration reached a maximum level of 79.4% when the fruit was in the intermediate maturation stage characterized by greenish‐yellow coloration.
Determination of iphosphamide and seven metabolites in blood plasma, as stable trifluoroacetyl derivatives, by electron capture chemical ionization GC‐MS
Authors: Momerency Guido , Van Cauwenberghe Karel , De Bruijn Ernst A. , Van Oosterom Allan T. , Highley Martin S. , Harper Peter G.
Published: May 2005

A method is described for the determination of the antitumor agent iphosphamide and seven of its metabolites in the plasma of cancer patients by multiple ion monitoring (MIM) GC‐MS, mainly using the electron capture chemical ionization mode, of stable methyl and/or trifluoroacetyl derivatives. The metabolites determined were 2‐ and 3‐dechloroethyliphosphamide, 4‐ketoiphosphamide, carboxyiphosphamide, iphosphamide mustard, and two previously undetected metabolites, chloroethylamine and 1,3‐oxazolidine‐2‐one.

The isolation of the acidic and neutral metabolites was performed by solid phase extraction on to C18 adsorbent at pH 4. The weakly acidic iphosphamide mustard, isolated under these conditions with a yield of ca 50%, was measured as a stable methyltrifluoroacetyl derivative, in contrast to the corresponding phosphoramide mustard of the isomer cyclophosphamide which decomposes during derivatization. Chloroethylamine and 1,3‐oxazolidine‐2‐one were isolated with high yield by liquid extraction with ethyl acetate at pH 10.

Selective measurement of several metabolite derivatives with similar retention times was performed by multiple ion monitoring MS of specific ion masses, using a methyl phenyl siloxane capillary column previously employed in the study of cyclophosphamide metabolites. Quantitation of metabolites in patient plasma samples could be performed in the concentration range 3 ng to 20 μg per ml of original plasma.
A novel focusing injection technique for chemiluminescent detection of volatile sulfur compounds separated by HRGC
Authors: Burdge Julia R. , Cai Zhong‐tao , Papillon Jay , Farwell Sherry
Published: May 2005

A one meter stainless steel capillary column coated with a 20μm film of polydimethylsiloxane was used to replace the Teflon gas sampling loop of a HRGC – flameless SCD system. This column trap was equilibrated with the gaseous sample and then purged with carrier gas while being sequentially, resistively heated in ten 10 cm sections. The sequential heating of the 10cm sections was timed such that the velocity of the moving heated zone was approximately the same as the velocity of the carrier gas. The thick stationary phase film served to retard the front end of the injection band while the ballistic heating accelerated the back end. The net result was focusing of the injection, which gave rise to a narrower injection profile than that obtained with the original Teflon loop.
Chromatographic properties of zirconia‐based stationary phases for ion exchange chromatography having surface bound cationic functions
Authors: Yu Jim , Rassi Ziad El
Published: May 2005

A series of non‐porous, microspherical zirconia‐based stationary phases with surface bound cationic functions have been introduced and evaluated in ion exchange chromatography of proteins and small acidic solutes. Different surface modification procedures were evaluated in the covalent attachment of weak, strong or hybrid anion exchange moieties on the surface of non‐porous zirconia micropar‐ticles. N,N‐Diethylaminoethanol (DEAE) was used as the weak anion exchange ligand while glycidyltrimethylammonium chloride, which was covalently attached to poly(vinyl alcohol) layer (PVAN) on the zirconia surface, constituted the strong anion exchange moiety. Partially quaternarized poly(ethyleneimine) hydroxyethylated (PEI) was used as the hybrid type of anion exchange coating. DEAE‐zir‐conia microparticles acted as purely cation exchange stationary phases toward basic proteins indicating the predominance of electron donor‐electron acceptor interaction (EDA) with surface exposed zirconium sites as well as cation exchange mechanism via electrostatic interaction with unreacted and unshielded hydroxyl groups. PVAN‐zirconia stationary phase exhibited anion exchange chromatographic properties toward acidic proteins, but EDA interaction has stayed as an important contributor to solute retention despite the presence of a relatively thick layer of poly(vinyl alcohol) on the surface of the zirconia particles. The modification of zirconia surface with partially quaternarized PEI proved to be the most effective approach to minimize Lewis acidic metallic properties of the support. In fact, PEI‐zirconia stationary phase operated as an anion exchanger toward acidic proteins and other small acidic solutes.
Simultaneous HPLC determination of phenylurea herbicides and their corresponding anilines in water after on‐line preconcentration
Authors: Hatrík Štefan , Lehotay Jozef , Tekel' Jozef
Published: May 2005

On‐line preconcentration on a short C18 column, prior to HPLC with UV and electrochemical detection, has been used for determination of some phenylurea herbicides and their possible degradation products, substituted anilines, in water samples. With electrochemical detection the detection limit at a signal‐to‐noise ratio of 3 was 5 ppt for 4‐chloroaniline and 4‐bromoaniline and 7 ppt for 3,4‐dichloroaniline; with UV detection the detection limit was ca 300 ppt for all analytes.
Reversed phase HPLC determination of titanium(IV) and iron(III) with sodium 1,2‐dihydroxybenzene‐3,5‐disulfonic acid
Authors: Nagaosa Yukio , Segawa Shin‐ichi
Published: May 2005

A highly sensitive method has been developed for the determination of titanium(IV) and iron(III) by ion‐pair reversed phase liquid chromatography using sodium 1,2‐dihydroxybenzene‐3,5‐disulfonic acid (Tiron) as a precolumn chelating reagent. The metal ‐ Tiron chelates were separated on a C18 (ODS) column; the mobile phase was a 2:8 (v/v) mixture of acetonitrile and acetate buffer (0.04 mol/L, pH 6.2) containing 2.0 × 10−3 mol/L Tiron, 0.04 mol/L tetrabutylammonium bromide, and 0.1 mol/L potassium nitrate. The detection limits for titanium(IV) and iron(III) are 0.5 and 2.0 μg/L, respectively. The method has been applied to the simultaneous determination of titanium(IV) and iron(III) in river water samples and has furnished highly precise results.
Enantiomer separation by capillary SFC and GC on immobilized octakis(2,6‐di‐O‐methyl‐3‐O‐pentyl)‐γ‐cyclodextrin
Authors: Dönnecke Jürgen , König Wilfried A. , Gyllenhaal Olle , Vessman Jörgen , Schulze Christian
Published: May 2005

Heptakis(2,6‐di‐O‐methyl‐3‐O‐pentyl) (2‐O‐methyl‐6‐O‐oct‐1‐enyl‐3‐O‐pentyl)‐γ‐cyclodextrin was immobilized to narrow‐bore fused silica capillaries after selective modification. One tert‐butyldimethylsilyl group was introduced into octakis‐(2‐O‐methyl‐3‐O‐pentyl)‐γ‐cyclodextrin in order to get a pure monofunctionalized cyclodextrin derivative. During synthesis the tert‐butyldimethylsilyl group was replaced by an anchoring group to bind the cyclodextrin to a polysiloxane. After thermal immobilization of the modified polysiloxane this new chiral stationary phase was applied in GC and SFC. High efficiency separations were obtained in GC. In SFC very polar compounds could be chromatographed at low temperatures resulting in higher separation factors as compared to GC.
Determination of lysinoalanine by high performance liquid chromatography
Authors: Moret Sabrina , Cherubin Susi , Rodriguez‐Estrada Maria Teresa , Lercker Giovanni
Published: May 2005

This work suggests an HPLC method for qualitative and quantitative determination of Nε(2‐amino‐2‐carboxyethyl)‐L‐lysine (LAL). LAL was released from total hydrolysates of various proteins of animal origin and derivatized with dansyl chloride. The performance of two different columns, Spherisorb 3S TG and μ‐Bondapack C18, was compared; better resolution and quantitative response were obtained with the former. The mobile phase was a mixture of 0.01 M phosphate buffer (pH 7) and acetonitrile. Linear response and quantitative repeatability were tested for both detectors used (UV‐Vis set at 254 nm; fluorimetric set at λex(max) = 360 nm and λem(max) = 525 nm).

For LAL standard the minimum detectable amount was 0.05 ng, whereas for LAL in actual samples the amount was 0.5 ng (40 μg/g of analyzed proteins). Good analytical repeatability was obtained, resulting in CV % of 4.7 and 3.8 for UV and fluorimetric detectors, respectively. LAL recovery was determined using both detectors; the values obtained were 94 % (fluorimetric) and 92 % (UV). Greater noise levels were observed with the fluorimetric detector and its higher sensitivity could not, therefore, be fully utilized. The highest amounts of LAL were found in the casein (2816 μg/g) and cooked albumin (615 μg/g) samples.
Evaluation of a low‐resolution near‐IR monochromator for atomic emission detection in capillary gas chromatography
Authors: Pedersen‐Bjergaard Stig , Greibrokk Tyge
Published: May 2005

A single 0.2 m focal length near‐IR monochromator providing a 0.8–3.2 nm effective bandpass was evaluated as spectrometer for F‐, Cl‐, Br‐, I‐, S‐, and P‐selective atomic emission detection in capillary gas chromatography. With optimized plasma conditions and careful wavelength selection, interferences from eluting hydrocarbons were almost eliminated for all the elements studied (element‐to‐carbon selectivities between 1000:1 and 10000:1). For Cl and S, other heteroatoms were found not to cause cross‐interferences. F‐, Br‐, I‐, and P‐selective detection, however, was complicated by this second type of non‐specificity. For these atoms, elemental confirmation was carried out by analyzing the samples also for heteroatoms potentially causing interferences.
On‐line capillary supercritical fluid chromatography‐inductively coupled plasma mass spectrometry for the analysis of organometallic compounds
Authors: Blake Earl , Raynor Mark W. , Cornell David
Published: May 2005

Supercritical fluid chromatography with inductively coupled plasma‐mass spectrometric detection is a new and useful technique for the analysis of organometallic compounds. An interface has been developed for coupling these techniques. The interface is compact, easy to assembel, and causes minimal disruption to either instrument. A series of organotin, organoarsenic, and organorion compounds has been used to evaluate the interface and ICPMS as a detector for SFC. The effect of analyte concentration and restrictor temperature on peak intensity has been investigated and the effect of the mobile phase on the plasma has also been studied to assess background interference from changes in the plasma.
Separation of lipid classes from plant tissues by high performance liquid chromatography on chemically bonded stationary phases
Authors: Christie William W. , Anne Urwin R.
Published: May 2005

The wide range of lipid classes found in plant tissues, including simple lipids, glycolipids, and phospholipids, have been resolved by gradient high performance liquid chromatography with evaporative light‐scattering detection. The lipids from potato tubers were used to optimize the separations. Adsorption chromatography with silica gel gave disappointing results for the plant glycolipids. Much better separations were obtained with chemically bonded stationary phases, e.g. those with propionitrile or polymeric vinyl alcohol as the functional moiety. With careful calibration, good reproducibility was possible. Only highly acidic lipids such as phosphatidylserine still present some problems.