bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimization of conditions for high temprature capillarary gas chromatography using a split‐mode programmable temprature vaporizing injection system
Authors: Tipler Andrew , Johnson Greg
Published: May 2005

This paper discribes an investigation into the effects of various operating conditions applied in a PTV‐based gas chromatographic system on the performance observed in high temperature analyses. The work comprises a combination of physical and chromatographic measurements, and conclusions are drawn as to the most effective way of using the equipment under evaluation.
Microcolumn chromatography for the analysis of detergents and lubricants. Part 1: High temperature capillary gas chromatography (HT‐CGC) and capillary supercritical fluid chromatography (CSFC)
Authors: Sandra Pat , David Frank
Published: May 2005

High Temperature Capillary GC and Capillary SFC have been applied to the analysis of non‐ionic lubricants, i.e. alkylphenol polyethoxylates (APnEO), ethoxylated alcohols (nEOAIc), polyethylene glycols (PEG), and ethoxylated triethanolamines (nEOEA); to the analysis of anionic lubricants, i.e. alkylbenzene‐sulfonates (ABS), alkylsulfonates (AS), and ethoxylated phosphoric acids (nEOPhA); and to the analysis of cationic lubricants, i.e. quaternary ammonium salts (Quats). Both techniques are compared in terms of resolution and analysis time. The importance of derivatization in HT‐CGC and CSFC is illustrated.
An on‐column capillary gas chromatographic method for the analysis of synthetic pyrethroid residues on fish eggs
Authors: Bolygó Elek , Hadfield Stephen T.
Published: May 2005

A sensitive and reproducible residue method is described for the determination of cypermethrin and deltamethrin in fish eggs. The limit of determination of 0.0005 mg kg−1 is achieved using only a very small sample size; typical sample weights lie in the range of 0.1‐1 g of fathead minnow or trout eggs. The method involves tissue homogenization (tube homogenizer) followed by hot acetonitrile extraction, then sequential C8, aluminum oxide, and silica gel clean‐up. The clean‐up is carried out in glass columns using cotton wool plugs in order to minimize potential sample contamination by plasticizers. Residues are determined by capillary chromatography using automated on‐column injection with electron‐capture detection. Confirmation of residues by gas chromatography‐mass spectrometry using selected ion monitoring (SIM), is also described.
CGC enantiomer separation on diluted cyclodextrin derivatives coated on fused silica columns
Authors: Schurig Volker , Jung Martin , Schmalzing Dieter , Schleimer Martin , Duvekot Jan , Buyten Jan C. , Peene Jürgen A. , Mussche Philippe
Published: May 2005

High‐resolution capillary gas chromatographic separation of enantiomers, belonging to different classes of compounds on cyclodextrin derivatives is described. The solutions of heptakis (2,3,6‐O‐trimethyl)‐β‐cyclodextrin (Phase I), heptakis (2,6‐O‐dimethyl‐3‐O‐trifluoro‐acetyl)‐β‐cyclodextrin (Phase II) and heptakis (2,6‐O‐dimethyl‐3‐O‐heptafluorobutyryl)‐β‐cyclodextrin (Phase III) in the moderately polar polysiioxane OV‐1701 were coated onto deactivated fused silica capillaries furnishing columns of high efficiency. The three phases show different enantioselectivities for various racemic mixtures.
Reversed‐phase LC‐GC with a nitrogen‐phosphorus detector using a loop‐type interface combined with a sandwich‐type phase separator
Authors: van Zoonen Piet , van der Hoff G. René , Hogendoorn Elbert A.
Published: May 2005

Reversed phase LC is coupled to capillary GC by means of an on‐line extraction of the LC eluent. The extract is transferred to a loop‐type LC‐GC interface equipped with an early vapor exit. Using a phase switch from an aqueous reversed‐phase (RP)LC solvent to an organic solvent facilitates the introduction of the analyte in the GC system, since organic solvents such as hexane, pentane, and dichloromethane are more appropriate for the GC‐injection technique used in this study. As the partition coefficient of an organic solvent/aqueous system is correlated to the retention mechanism of reversed phase LC, the method has a general potential in LC/GC interfacing, viz. the extractability a component from the LC mobile phase eluting above a certain capacity factor from a RPLC column can be expected to be efficient. The method is applied to the determination of residues of the fungicide fenpropimorph in barley, oats, rye, and wheat. Another application of the interface which is feasible is the on‐line extraction of aqueous samples prior to large volume injection on GC‐NPD. The potential of the interface for the determination of residues nitrogen containing herbicides is estimated.
Determination of traces of polychlorinated biphenyls in pigments
Authors: Sistovaris Naoum , Donges Ulrich , Dudek Beate
Published: May 2005

PCB patterns in a new pigment brand are characterized using GC‐MS in the single ion monitoring (SIM) mode. Specific PCBs are then used as external standards for GC‐ECD quantification. The following PCB isomers or groups of isomers have to be determined (CB = chlorobiphenyl): total diCBs, 3,3′ diCB, 2,4,5‐triCB, 2,2′,4,4′‐tetraCB, 2,2′,5,5′‐tetraCB, total pentaCB, total hexaCB. Capillary gas chromatography is performed on preseparated solutions (LC) of pigment. An electron caputure detector (ECD) is used for PCB detection and quantification. Calibration is based on the peak areas of external standards and the PCB isomers in the samples, all normalized for internal standard peak areas. Total concentrations of diCB, hexaCB, or pentaCB in a sample are calculated by summing the individual PCB isomer concentrations within the correcsponding elution ranges. Determination limits lie in the range of 1 mg/PCB‐isomer/kg pigment.
Liquid gas techniques for GC trace analysis
Authors: Dünges Wolfgang , Fooken Cornelia , Wagner Heinz
Published: May 2005

Liquid gases (LG), i.e. low boiling compounds with vapor pressures below 5 bar at room temperature, are introduced as solvents for trace analyses. A system for preparin, diluting and handling LG solutions safely and conveniently in 5 to 500 μl amounts was developed as well as a syringe for direct injection of μl‐LG samples into capillary GC. Even technical grade LG are of high purity. GC/FID of LG solutions (starting at −60°C) allows the separation of volatile traces from the solvent peak: e.g., dichloromethane can be measured in the picogram range.
Highly sensitive determination of haloperidol in human serum by capillary gas chromatography using a surface ionization detector
Authors: Nagai Yumi , Arimoto Hiromi , Fujii Toshihiro
Published: May 2005

A method has been developed for highly sensitive determination of haloperidol in human serum involving a simple extraction procedure followed by gas chromatographic separation. Target components were separated from the extracting solvents with a Van den Berg type solventless sample injector before introduction Into a DB‐1 capillary separation column. A surface ionization detector (SID), which has highly selective sensitivity for Substituted amines, was employed for quantitation using bromperidol as an internal standard. Chloroform proved to be the best extracting solvent, yielding a quantitative detection limit of 5 ng/ml (S/N = 2). Comparison of the response to target compounds obtained by the SID, FTD (flame thermionic detector), and FID (flame ionization detector) showed the SID to be superior.
Distorted solvent peaks in capillary GC: A symptom of porous column surfaces
Authors: Grob Konrad , Artho Anna
Published: May 2005

Many uncoated precolumns, and to a lesser extent separation columns, strongly retain some of the solvent. Retarded release of such solvent elevates the baseline after the solvent peak and causes ugly “humps” of eluted solvent as the temperature is increased. The problem is probably a result of retention by a porous surface, e.g. surfaces obtained by leaching or hydrothermal treatment of capillaries prior to silylation. It is assumed that other problems with capillary columns can be explained by the same mechanism, including: a kind of adsorption including apolar compounds, and “ghost” peaks as well as “memory” effects. Fused silica capillaries are superior to glass, but even for these special procedures are required in order to achieve thorough deactivation of the internal surface without introducing porosity.
Automated analysis of volatile halogenated hydrocarbons in rainwater and ambient air by purge and trap capillary gas chromatography
Authors: Fujita Masahiko , Jung Wontae T. , Tatematu Hiroko , Sohn Donghun H. , Maeda Tsuneaki
Published: May 2005

An automated system employing a purge and trap technique with capillary gas chromatography and electron‐capture detection (ECD) has been developed for the analysis of trace levels of volatile halogenated hydrocarbons and applied to the determination of the compounds in environmental samples such as rainwater and ambient air. The operation of the method, its application to environmental samples, and the results obtained are described. Use of the system ensured good chromatographic resolution and high accuracy, even with trace levels of the compounds.
Supercritical fluid solid chromatography using novel porous glassy carbon. Evaluation of retention mechanisms
Authors: Engel Tina M. , Olesik Susan V.
Published: May 2005

The use of a porous glassy carbon (PGC) material as a packed‐column SFC stationary phase has been previously demonstrated [1]. The material is further characterized in terms of its retention characteristics. The effects of variations in mobile phase composition, pressure, and temperature conditions are evaluated. Variation of temperature and pressure yielded expected results, specifically, decreased solute capacity factors with increased mobile phase density. The choice of supercritical fluid mobile phase allows the most notable control of solute retention; this was evaluated by adding low percentages of organic modifiers of varying molecular weights to the supercritical carbon dioxide mobile phase. PGC‐SFC provides reversed phase characteristics similar to those found for PGC‐HPLC. Porous glassy carbon has selectivity characteristics previously unavailable in supercritical fluid chromatography. Use of porous glassy carbon in supercritical fluid chromatography may provide distinct advantages in difficult analytical separations, allowing separations of molecules with only slight structural differences.
Microcolumn liquid chromatography of polycyclic aromatic hydrocarbons and some isomeric compounds on cyclodextrin stationary phases
Authors: Malik Abdul , Jinno Kiyokatsu
Published: May 2005

Preparative‐grade bonded β‐ and γ‐cyclodextrin stationary phases were used as the packing material of liquid chromato‐graphic analytical microcolumns. Although the resulting columns are characterized by relatively low efficiency, the high selectivity of the cyclodextrin phases nevertheless allows their successful use for the separation of different classes of isomeric compounds that are difficult to resolve on conventional LC stationary phases. Examples of baseline (or almost baseline) separations of a number of isomeric compounds, including isomeric polycyclic aromatic hydrocarbons, are presented to demonstrate the analytical potential of such columns. Retention behavior of the separated isomers is discussed based on the structure of the solute molecule and the possibility of its inclusion into the molecular cavity of cyclodextrin stationary phases.
The thermal immobilization of hydroxy‐terminated silicone phases in high‐temperature‐silylated glass capillaries. A study of reaction mechanisms
Authors: Welsch Thomas , Teichmann Ute
Published: May 2005

Differently pretreated glass capillaries were coated with hydroxy‐terminated methyl or methyl‐phenyl polysiloxane gum phases and cured at 340–360°C for several hours. The volatile reaction products formed during the baking procedure were analyzed and the retention behavior of various polar test compounds were investigated both before and after the heat treatment. The findings were used to establish a reaction scheme which explains crosslinking and surface bonding of hydroxy‐terminated silicone phases in high‐temperature‐silylated glass capillaries. The principle has been extended to the immobilization of common endcapped silicone phases by mixing them with hydroxy‐terminated phases.
Analysis of low molecular weight constituents of polypropylene and other polymeric materials using on‐line SFE‐SFC
Authors: Cotton Nicholas J. , Bartle Keith D. , Clifford Anthony A. , Ashraf Sameena , Moulder Robert , Dowle Christopher J.
Published: May 2005

Additives and oligomers from polymers were quantitatively extracted and separated using on‐line SFE and capillary SFC. Conditions were found which extracted the additives selectively and separated them from the co‐extracted oligomers.
Comparison of micro‐LC and capillary zone electrophoresis for the analysis of thiols
Authors: Ling B. Lin , Baeyens W. R. G. , Dewaele C.
Published: May 2005

Micro‐LC and capillary zone electrophoresis (CZE) are two of the most rapidly developing, miniaturized separation techniques in analytical science. In the present paper, both techniques were comparatively evaluated for the determination of several important thiols derivatized with the fluorogenic reagent SBD‐F. Different parameters, such as selectivity, sensitivity, analysis time and efficiency, influence of column length, CZE buffer concentration, and voltage were thus analyzed and discussed. Both techniques are recommended for the analysis of thiols in biological samples.
Fluorescence detection with an immersed flow cell in capillary electrophoresis
Authors: Kurosu Yasuyuki , Sasaki Toru , Saito Muneo
Published: May 2005

An immersed flowcell has been developed for fluorescence detection in capillary electrophoresis (CE) by modifying an ordinary HPLC spectrofluorimetric detector flowcell. The minimum detectability obtained for riboflavine was about 4 fmol. The use of the flowcell to measure a fluorescence spectrum by the stopped‐flow method of shutting down the DC high voltage during a wavelength scan, has also been achieved successfully.
High performance separations of nucleic acids using capillary electrophoresis and high‐performance liquid chromatography
Authors: Baba Yoshinobu , Tsuhako Mitsutomo , Enomoto Shigeru , Chin A. Michael , Dubrow Robert S.
Published: May 2005

High resolution separations of nucleic acids have been performed using high performance capillary electrophoresis (HPCE) and high performance liquid chromatography (HPLC). Electropherograms showing HPCE separations of single and double stranded DNA are presented and compared with HPLC separations. Single base resolution of poly(dA) oligonucleotides in the size range of 12 to 60‐mers was achieved in 35 min using HPCE. Plate numbers for HPCE are in the hundreds of thousands and reproducibility is about 1–2 % (RSD). In comparison with HPLC separations, the resolution of nucleic acids obtained using HPCE is much better than that using HPLC, while reproducibility of HPCE is comparable with that of HPLC.
Optimization of supercritical fluid chromatographic separation of nitroaromatics by the overlapping resolution mapping scheme
Authors: Ong Chye P. , Chin Kiat P. , Lee Hian K. , Li Sam F. Y.
Published: May 2005

The use of an interpretative optimization method to predict optimum conditions for the supercritical fluid chromatographic separation of nitroaromatics is demonstrated. The scheme utilizes the overlapping resolution mapping (ORM) procedure for multivariate prediction of the pressure gradient and temperature in order to separate eight nitroaromatics. Using the ORM scheme, only seven experiments were conducted before a global optimum was revealed. All the peaks were satisfactorily separated using experimental conditions derived from the scheme.
Preparation and evaluation of phenylpropyl‐treated porous glasses for high performance liquid chromatography
Authors: Okamoto Mitsuyoshi , Nobuhara Kazunori , Jinno Kiyokatsu
Published: May 2005

The retention and selectivity behavior of some aromatic hydrocarbons and alkylbenzenes on phenyl‐ or phenylpropyl‐modified glasses have been studied by high performance liquid chromatography. From elemental analysis data for carbon, the maximum number of accessible phenyl or phenylpropyl surface groups per 100 Å2 of glass (mean pore diameter, 157 Å; specific surface area, 213 m2/g) in the phenyl and phenylpropyl modified glasses were calculated to be 1.93 and 1.97, respectively. Using 60:40 methanol‐water mixtures as eluents, the aromatic hydrocarbons or alkylbenzenes were separated on the glasses studied, but with different degrees of resolution.
Optimization of a high speed countercurrent chromatograph for analytical separations
Authors: Oka Hisao , Ikai Yoshitomo , Kawamura Norihisa , Yamada Masuo , Hayakawa Junko , Harada Ken‐Ichi , Nagase Kazuko , Murata Hideaki , Suzuki Makoto , Ito Yoichiro
Published: May 2005

The analytical capability of the high speed countercurrent chromatograph model 4000 (HSCCC‐4000) has been improved by optimizing the dimensions of the multilayer coiled column. Using a two‐phase solvent system of n‐hexane – ethyl acetate – methanol – water (1:1:1:1) and a set of indole auxins as test samples, a series of studies was conducted to evaluate performance of coiled columns with i.d.s ranging from 0.1 to 0.55 mm. The studies on the stationary phase retention indicated that multilayer coils of 0.55 mm and 0.30 mm i.d. provide satisfactory retention of the stationary phase while the 0.10 mm i.d. column fails to yield reproducible retention. The best partition efficiencies were obtained from the 0.30 mm i.d. multilayer coil with a 6 ml capacity which produced theoretical plate numbers ranging from 5500 to 10500 with a resolution factor of 2.30. The feasibility of interfacing the HSCCC‐4000 with a mass spectrometer is briefly discussed.
Unusual peak defocusing in capillary GC on hexakis(2,6‐diO‐pentyl‐3‐O‐acetyl)‐α‐cyclodextrin stationary phase
Authors: Schmarr Hans‐Georg , Maas Birgit , Mosandl Armin , Bihler Stephan , Neukom Hans‐Peter , Grob Konrad
Published: May 2005

An unusual peak defocusing effect influencing chromatographic performance over a limited range of elution temperatures is described for hexakis(2,6‐di‐O‐pentyl‐3‐O‐acetyl)‐α‐cyclodextrin stationary phase. Since this phenomenon is likely to be dependent on minor details of the cyclodextrin molecule, full assignment of the 1H‐ and 13C‐NMR‐spectra are given.
Capillary gas chromatography of lower aliphatic C2C5 aldehydes in the free form as a group of pungent odorants in air
Authors: Hoshika Yasuyuki , Muto Giichi
Published: May 2005

The capillary gas chromatography of the C2‐C5 lower aliphatic aldehydes (e.g.,acetaldehyde, propionaldehyde, n‐ and i‐butyraldehydes, n‐ and i‐valeraldehydes) which, in the free form in air, have unpleasant odors and low threshold odor values, has been studied using cold‐trap preconcentration with liquid oxygen. The capillary column outlet was connected to enable simultaneous detection by FID, ECD, FPD AND FTD (SID).
Determination of congeners of polychlorinated biphenyls in reference materials
Authors: Anderson Jerry W.
Published: May 2005

Aroclor reference materials from the United States Environmental Protection Agency repository are proposed for use as secondary standards for the congener‐specific analysis of polychlorinated biphenyls in environmental samples. Representative samples of the materials have been analyzed using a gas chromatograph equipped with photo‐ionization and electron capture detectors. The elution pattern of the congeners was determined for a DB‐17 capillary column.
Coupled LC‐GC: The capacity of silica gel (HP)LC columns for retaining fat
Authors: Grob Konrad , Kaelin Iren , Artho Anna
Published: May 2005

Many applications of coupled LC‐GC in food analysis require that LC separates large quantities of triglycerides from the components of interest. The capacities of silica gels to retain triglycerides have been determined for n‐hexane as mobile phase as well as some eluent mixtures. Conclusions are drawn for practical applications.
Molecular diffusivity of sample solutes in a number of eluents and the implications with regard to the design of capillary chromatographic systems
Authors: Korenaga Takashi , Izawa Miyoko , Fujiwara Takashi , Takahashi Teruo
Published: May 2005

The properties of sample solutes and eluents injected into capillary tubes were studied in order to develop improved chromatographic instrumentation technology. Use of a new apparatus to determine molecular diffusion coefficients (D) of solutes in both aqueous and organic eluents under laminar flow conditions provided results more rapidly than older methods. The experimental results obtained were in agreement with theoretical predictions and will be useful in the design of chromatographic systems.
Capillary columns in series for GC analysis of volatile organic pollutants in atmospheric and alveolar air
Authors: Clair Pascal , Tua Mireille , Simian Hervé
Published: May 2005

Analysis of volatile organic compounds in air samples requires high resolution capillary gas chromatography. When the sample contains both polar and non‐polar compounds, use of only one type of stationary phase can be unsuitable if it leads to the preferential separation of one kind of component having the same polarity at the expense of the separation of other classes of component.

This paper describes the coupling of fused silica capillary columns of different polarity and length in order to achieve the separation of such complex mixtures. The combination is evaluated with a 42 component standard mixture and then applied to various atmospheric air samples and alveolar air of exposed subjects to demonstrate the capabilities of the complete sampling and separation technique.
Comparison by capillary SFC and SFC‐MS of soxhlet and supercritical fluid extraction of hamster feces
Authors: Pinkston J. David , Delaney Thomas E. , Bowling Donald J. , Chester Thomas L.
Published: May 2005

Components of hamster feces ranging from low molecular weight fatty acids through the expected range of triglycerides have been eluted in a single SFC run with simultaneous pressure and temperature programming. Temperature programming from 140°C to 240°C was required to provide optimum conditions for separation of the fatty acids and to move the elution region of the sterol esters away from that of the triglycerides. Data from chemical ionization and electron impact mass spectrometry of compounds separated by SFC were used to confirm identities suggested by retention measurements and to provide tentative identities of unknown compounds.

SFC with flame ionization detection was used to compare Soxhlet extraction, off‐line supercritical fluid extraction (SFE), and on‐line SFE of the feces. Although samples obtained by Soxhlet extraction and SFE produced very similar chromatograms, SFE required far less time and consumed much smaller quantities of organic solvent.
The effects of the column pressure drop on retention and efficiency in packed and open tubular supercritical fluid chromatography
Authors: Janssen Hans‐Gerd , Snijders Henri M. J. , Rijks Jacques A. , Crarners Carel A. , Schoenmakers Peter J.
Published: May 2005

The effects of the pressure drop across the column on retention and efficiency in SFC have been studied. Numerical methods are described which enable the prediction of hold‐up time and pressure drop in both packed and open tubular columns. Predictions of both hold‐up time and pressure drop are in good agreement with experimental data.

The density gradient along the column can be calculated using the numerical methods and a procedure is described which enables the calculation of the overall capacity factors of the solutes from the density profile in the column. Significant variations of the capacity factor are observed along the column.

The effect of the density gradient along the column on local diffusivity and dispersion is studied. The column efficiency in systems with significant pressure drops is affected by changes in: the linear velocity of the mobile phase; the diffusion coefficients; and the capacity factors of the solutes along the column. The overall efficiency of the chromatographic system can be calculated if, as is the case for open tubular columns, adequate plate height equations are available.
A different operational mode for addressing the general elution problem in rapid analysis gas chromatography
Authors: Rubey Wayne A.
Published: May 2005

The task of chromatographically separating a complex mixture containing constituents with a wide range of molecular weight has been referred to in the past as the “general elution problem”. A different operational mode for conducting gas chromatography, thermal gradient programmed gas chromatography, presently in the developmental stage, has been investigated and is proposed as a means whereby such separations might be accomplished rapidly. The inherent versatility of the technique for conducting rapid analyses (50 to 300 s duration) of complicated samples containing constituents with a wide range of volatility is considered in terms of the possibility of achieving the maximum amount of analytical information per unit time.
On the complementary nature of CGC‐MS, CGC‐FTIR, and CGC‐AED for water pollution control
Authors: David Frank , Sandra Pat
Published: May 2005

Unequivocal identification of unknown pollutants is very difficult if only one dimension of information is used. Combining different hyphenated techniques can, on the other hand, lead to more reliable identification. Combination of the data provided by the different techniques is more important than on‐line combination of the techniques themselves.
Estimation of the size of liposomes by modified HDC
Authors: Molina F. J. , Vila A. O. , Llácer C. , Martos M. J. , Figueruelo J. E.
Published: May 2005

Internal calibration in modified hydrodynamic chromatography has been realized by the approach of Prieve and Hoysan, i.e. the use of polystyrene monodisperse latexes to evaluate the equivalent capillary radius, R. The value obtained has been used to estimate the average sizes of a variety of liposome samples from egg yolk lecithin.
Capillary gas chromatography of tert‐butyldimethlysilylamino acids with PTV injection
Authors: das Neves H. J. Chaves , Vasconcelos A. M. P.
Published: May 2005

The programmable temperature vaporizing injector (PTV) has been used to study the effects of injection temperature and initial heating period on the FID response factors of TBDMS derivatives of 17 protein amino acids. The relative response factors were calculated for injection temperatures of 50°C, 90°C, 160°C, 220°C, and 260°C with different initial heating periods (1 s, 5 s, and 10 s) and the results compared with the values obtained for the calculated response factors obtained under classical split injection conditions (300°C, continuous). Except for expected peak broadening effects, the initial heating period does not seem to have significative effects on relative peak areas. The response to the derivatives of alanine, glycine, α‐aminobutyric acid, valine, proline, methionine, cysteine, phenylalanine, asparagine, and arginine was only slightly affected by increasing the injection temperature whereas the response factors for the derivatives of serine, threonine, glutamic acid, lysine, histidine, tyrosine, and tryptophan were strongly dependent upon initial injection temperatures, decreasing rapidly at temperatures above 160°C. The cold split‐splitless injection is clearly advantageous over the classical hot injection techniques for the analysis of this type of aminoacid derivative.
Multiple headspace extraction‐capillary gas chromatography (MHE‐CGC) for the quantitative determination of volatiles in contaminated soils
Authors: Maggio A. , Milana M. R. , Denaro M. , Feliciani R. , Gramiccioni L.
Published: May 2005

A multiple headspace extraction‐capillary gas chromatographic method for the quantitative, accurate, and rapid determination of volatiles in multicontaminated soil samples has been developed. A thick film fused silica column has been used and a nine‐step multiple headspace extraction (MHE) determination performed. Calibration was achieved by introducing 1 μl of a standard solution of mixed volatiles into empty headspace vials, the presence of the matrix being unnecessary in multiple headspace extraction. Accuracy of determination by MHE‐CGC and a simple method employing standard additions have been compared.
The use of alternative fluids in on‐line supercritical fluid extraction – capillary gas chromatography
Authors: Levy Joseph M. , Storozynsky Eugene , Ravey Robert M.
Published: May 2005

A key feature differentiating analytical supercritical fluid extraction (SFE) from conventional liquid extraction is the possibility of varying the solvent strength of a supercritical fluid to achieve selective extractions of specific target compounds, or functional classes of compound, from complex matrices. This can be accomplished by using supercritical fluids other than carbon dioxide, for example, sulfur hexafluoride, nitrous oxide, or sulfur hexafluoride‐modified carbon dioxide. The use of these fluids will be demonstrated by the characterization of complex environmental and petroleum matrices by directly coupled SFE – capillary GC. On‐line SFE‐GC involves the decompression of pressurized extraction fluid directly into the heated, unmodified capillary split injection port of the chromatograph. This paper will also show how, by adjustment of the extraction temperature and pressure, SFE selectivity may be further enhanced.
Analysis of nucleic acid derivatives by micellar electrokinetic capillary chromatography
Authors: Lecoq Anna‐Francesca , Leuratti Chiara , Marafante Erminio , Di Biase Sebastiano
Published: May 2005

The use of micellar electrokinetic capillary chromatography (MECC) for the analysis of the major nucleobases, nucleosides, and nucleotides, and their chemically modified derivatives, has been developed and refined. The dimensions of the separating capillaries, the composition of the buffering systems, and the conditions used for electrophoresis were investigated in order to obtain the best performance.

Particular emphasis was placed on the identification of the physiological constituents of nucleic acids and their chemically modified analogs: in vitro studies on calf thymus DNA exposed to genotoxic agents have demonstrated that adducted bases and nucleolides can be identified by MECC.
Determination of lidocaine in human serum by capillary gas chromatography with surface ionization detection
Authors: Arimoto Hiromi , Shiomi Koichi , Fujii Toshihiro
Published: May 2005

A novel analytical method has been developed for the determination of lidocaine (2‐(diethylamino)‐N‐(2,6‐dimethyl)phenylacetamide) in human serum. After solvent extraction from serum the extract was analyzed by gas chromatography employing a van den Berg type solventless injector, a new sensitive and selective detector, the surface ionization detector, and a bonded phase flexible fused silica capillary column. The detection limit was ca. 30–50 ng/ml.
High resolution capillary gas chromatographic hydrocarbon‐type analysis of naphtha and gasoline
Authors: Shiomi Koichi , Shimono Masao , Arimoto Hiromi , Takahashi Seiji
Published: May 2005

A slightly modified, commercially available high resolution capillary gas chromatograph and a PC‐based data processing system running proprietary software (“PONA”) have been employed in the development of a system for petroleum type analysis which would be equivalent or superior to the FIA (fluorescent indicator adsorption) method in terms of ease of use and the speed, variety, and accuracy of the analytical data produced.

The system is capable of performing identification and quantitation of most of the individual components in a complex gasoline sample consisting of more than 230 components and can report weight percentage and/or volume percentage for each component as well as types by carbon number (e.g., isoparaffins, normal paraffins, olefins, naphthenes, aromatic compounds) within a ca. 70 minute analysis cycle.

Precolumn sulfonation to trap olefins and aromatic compounds has been used as an complementary technique to the basic mass spectrometric identification of components of interest. The estimation of correction factors for weight percentage (or volume percentage) calculation are also discussed. Comparisons are made between this system and others, and the results indicate that the proposed method supersedes the conventional method employing FIA.
Influence of intramolecular interaction on the enthalpy and entropy of methylene unit sorption for the homologous series of carbonyl‐containing compounds analyzed by capillary GC
Authors: Golovnya Rimma V. , Grigoryeva Diana N. , Vasilyev Alexei V.
Published: May 2005

The enthalpy and entropy of sorption of methylene units in the homologous series of n‐alkyl acetates; methyl, n‐butyl, and phenyl n‐alkyl ketones; and the methyl esters and chloroanhydrides of n‐aliphatic carboxylic acids have been determined on an SE‐54 capillary column. The enthalpy of sorption of the first methylene unit is anomalously high when the growing n‐alkyl chain is connected directly to a carbonyl group. This effect is a result of intramolecular interaction between neighboring methyl and carbonyl groups. It has been shown by measurement of the enthalpy and entropy of sorption of the difluoromethylene unit in the series of n‐hexyl esters of perfluorinated carboxylic acids that for these compounds the effect is absent.

The intramolecular interaction was found to increase in the order methyl butyl ketone < methyl phenyl ketone < methyl acetate < acetyl chloride < acetone.
Elution order in gas chromatography
Authors: Mehran Mehrzad , Cooper William J. , Golkar Nahid , Nickelsen Michael G. , Mittlefehldt Eric R. , Guthrie Edward , Jennings Walter
Published: May 2005

The retention behavior of a heterogeneous group of solutes has been examined on seven different stationary phases under isothermal and temperature‐programmed conditions. Both ΔHv (enthalpy of solute vaporization from the stationary phase) and ΔSv (entropy of solute vaporization from the stationary phase) values were determined for each solute – stationary phase combination under isothermal conditions. Both program rate and carrier gas velocity were shown to affect solute elution order. Unless these and other experimental factors discussed are controlled, column equivalency studies based on solute elution order have dubious value.
Ozone‐based sulfur chemiluminescence detection: Its applicability to gas, supercritical fluid, and high performance liquid chromatography
Authors: Howard Angela L. , Taylor Larry T.
Published: May 2005

The sensitive detection of sulfur‐containing analytes is of interest in many industrial applications; selective detection is also desirable since these compounds are usually present at trace levels in difficult matrixes. The purpose of this article is to review the use of the Sievers® ozone‐based sulfur chemiluminescence detector, and its coupling with gas chromatography, supercritical fluid chromatography, and high performance liquid chromatography. Detection limits, linearity, response factors, and selectivity are discussed for each of these techniques. Critical operational parameters for the SCD are also described. The use of other sulfur selective detectors for SFC and HPLC is also briefly summarized.
Determination of streptomycin in pharmaceutical preparations by gas chromatography
Authors: Arrowood Susan , Hoyt Arthur M. , Woods Mark W.
Published: May 2005

The antibiotic streptomycin can be reliably quantitated in injectable pharmaceuticals by GC. The manipulations are not difficult, and total analysis time for duplicate samples is less than twenty minutes.

Reaction of the drug with aqueous sodium hydroxide solution generates maltol, which is extracted into chloroform prior to silylation. The silyl ether of maltol is then assayed, using naphthalene as internal standard. Duplicate analyses of twenty pharmaceutical samples showed a relative standard deviation of ±1.3%.
Enantiomeric resolution of underivatized small peptides by HPLC with a chiral crown ether stationary phase
Authors: Esquivel Benjamin , Nicholson Lawrence , Peerey Linda , Fazio Michael
Published: May 2005

Factors influencing the stereoisomeric resolution of underivatized dipeptides and a representative tripeptide on Crownpak (CR) columns have been investigated. The elution order and relative retention suggest that a combination of chiral, steric, and hydrophobic interactions effects the extent of chiral recognition and the retention achieved during separations. Some dipeptides whose amine terminus is located three atoms from the asymmetric center (such as dipeptides of D,L‐glycine) were resolved, but the elution order was the opposite of that expected for the type of Crownpak column used (CR(+)). Peptides containing hydrophobic substituents were strongly retained, but their retention times could be significantly reduced, and detectability improved, by use of gradient elution. Analysis of a commercial sample of D,L‐leucine‐D,L‐alanine revealed the stereoisomers to be present in an unexpected quantitative ratio and demonstrated the utility of these separations for quality assurance and quantitative analyses.
Comments concerning the HPLC separation of acrolein from other C3 carbonyl compounds as 2,4‐dinitrophenylhydrazones: A proposal for improvement
Authors: Dye Christian , Oehme Michael
Published: May 2005

The separation of the toxicologically important aldehyde acrolein from other carbonyl compounds by high performance liquid chromatography after derivatization to 2,4‐dinitrophenylhydrazones is critically discussed on the basis of a selection of published methods. A method is proposed whereby the compounds acrolein, acetone, and propanal may be reproducibly separated to baseline by a reversed phase HPLC procedure employing a ternary mixture of methanol, water, and acetonitrile as mobile phase.
Prediction, optimization of separation, and identification of unknown compounds in capillary gas chromatography
Authors: Guan Yafeng , Zheng Peng , Zhou Liangmo
Published: May 2005

A procedure for the identification and separation of unknown compounds by capillary gas chromatography is described. The procedure involves a live retention time database and optimization of the separation. After initial chromatography of the sample, a rough search lists all the possible compounds it might contain and the analyst then uses his experience to discard those compounds in the list which are unlikely to be present. The multi‐component separation is then optimized over the whole range of defined starting temperatures and programming rates, in order to produce the best possible separation of the sample components, and the chromatography repeated using the results obtained from the optimization procedure. Further search operations within a given search window will then report the compound names, and related information, for each peak.

Since the identification operation is performed at least twice during the procedure, and the optimization of the separation assists the identification by separating possibly overlapped peaks, the confidence of the qualitative analysis is higher than may be obtained using standards alone. If the reproducibility of isothermal indices measured on columns could be guaranteed, this procedure could be used instead of performing chromatography on standards of the compounds contained in the database, regardless of changes in column dimensions, phase ratio, and operating conditions in temperature programmed analysis.
Investigation of the detection limit for the determination, by pyrolysis‐capillary GC, of the thickness of ultra thin PMMA layers coated on to PET film
Authors: Jin Xigao , Oguri Naoki , Onishi Akira , Uchino Sigeki
Published: May 2005

The determination of nanometer thick layers of poly(methyl methacrylate) coated on to the surface of poly(ethylene terephthalate) film has been investigated by high resolution pyrolysis gas chromatography without sample pretreatment or modification of the instrumentation used. A good linear relationship was observed between the quantity of the characteristic pyrolysate and the thickness of the poly(methyl methacrylate) layer; the detection limit was sufficient to enable the quantitation of poly(methyl methacrylate)‐to‐poly(ethylene terephthalate) film thickness ratios of 1:20000 in composite materials.
Improving detection limits in chromatography by signal averaging
Authors: Ghaoui Labib , Rothman L. David
Published: May 2005

Ensemble or signal averaging has been used to increase detection limits in gas chromatography. The sample is injected several times into a gas chromatograph and the chromatograms generated are summed. The resulting chromatogram is treated as a separate chromatogram with the benefit of an improved signal‐to‐noise ratio. Use of the technique enables reliable quantitation, the time invested being used to convert an unacceptable signal‐to‐noise ratio into useful data. A discussion and some applications of the technique are described.
Use of carbon adsorption traps combined with high resolution gas chromatography – mass spectrometry for the analysis of polar and non‐polar C4‐C14 hydrocarbons involved in photochemical smog formation
Authors: Ciccioli Paolo , Cecinato Angelo , Brancaleoni Enzo , Frattoni Massimiliano , Liberti Arnaldo
Published: May 2005

A method has been developed for the collection and analysis of polar and non‐polar C4‐C14 hydrocarbons involved in the formation of photochemical smog. Enrichment of hydrocarbons from both polluted and unpolluted areas has been achieved with three‐stage traps packed with carbon adsorbents of different surface area; the use of a home‐made desorption unit employing cryofocusing then enables the determination of the compounds by HRGC‐FID. Two‐stage traps filled with graphitic carbon have been used prior to GC‐MS identification and quantitation of compounds producing overlapping peaks.

The methodology has been tested in the urban area of Rome and in a pine forest, and more than 140 different compounds identified and quantitated. Many of the constituents were found to be oxygenated, either formed by photochemical reactions or of anthropogenic origin.
Optimization of an electrolytic conductivity detector for determination of toxic nitrogen‐containing food contaminants separated by open tubular column gas chromatography
Authors: Fehringer Norbert V. , Gilvydis Dalia M. , Walters Stephen M. , Poole Colin F.
Published: May 2005

The combination of open tubular column gas chromatography with electrolytic conductivity detection has been evaluated for the determination of nitrogen‐containing pesticide residues in food extracts. Optimization of the column position at the column‐detector interface was crucial to the successful operation of the detector. The signal‐to‐noise ratio and response stability of the detector are greatly influenced by the composition of the electrolyte solvent. Large volume splitless injections using retention gaps and optimized detector operating conditions enabled pesticide residues in food extracts to be determined at sub parts‐per‐million levels. Although the electrolytic conductivity detector is less sensitive than the thermionic ionization detector, its greater nitrogen selectivity can he crucial to the determination of nitrogen‐containing contaminants in food extracts, particularly in complex mixtures where phosphorus‐containing contaminants or matrix compounds are also present.
Stereoisomeric flavor compounds part. LV: Stereodifferentiation of some chiral volatiles on heptakis(2,3‐di‐O‐acetyl‐6‐O‐tert‐butyldimethylsilyl)‐β‐cyclodextrin
Authors: Dietrich Armin , Maas Birgit , Karl Volker , Kreis Peter , Lehmann Detmar , Weber Bernhard , Mosandl Armin
Published: May 2005

Heptakis(2,3‐di‐O‐acetyl‐6‐O‐tert‐butyldimethylsilyl)‐β‐cyclo ‐dextrin proves to be a versatile chiral stationary phase for the direct differentiation of aroma‐relevant enantiomers.
Enantiomeric composition of the chiral constituents in essential oils. Part 1: Monoterpene hydrocarbons
Authors: König Wilfried A. , Krüger Angelika , Icheln Detlef , Runge Torsten
Published: May 2005

Using a dual column gas chromatograph equipped with two capillary columns coated with heptakis(6‐O‐methyl‐2,3‐di‐O‐pentyl)‐β‐cyclodextrin (6‐me‐2,3‐pe‐β‐CD) and octakis(6‐O‐methyl‐2,3‐di‐O‐pentyl)‐γ‐cyclodextrin (6‐me‐2,3‐pe‐γ‐CD), respectively, all important olefinic monoterpene hydrocarbons occurring in essential oils, including α‐thujene, α‐ and β‐pinene, camphene, sabinene, α‐ and β‐phellandrene, Δ‐3‐carene and limonene can be resolved into enantiomers. With the chromatographic system described the characteristic enantiomeric composition of these monoterpene hydrocarbons in essential oils can be determined.
Sample evaporation in conventional GC split/splitless injectors. Part 1: Some quantitative estimates concerning heat consumption during evaporation
Authors: Grob Konrad
Published: May 2005

During sample evaporation in conventional vaporizing injection, the supply of heat to the evaporating liquid is a problem, first because the amounts of heat consumed are relatively large and, secondly, because the heat must be transferred to the sample within a very short time. Times available for evaporation, required amounts of heat, possible sources of heat, and the time required to transfer the heat to the sample liquid are discussed. It is shown that mixing with carrier gas contributes little heat to the evaporation process, but also that packings with glass wool have too low a heat capacity to deliver the required amount of heat to the evaporating sample. Transfer of heat from the insert wall to the sample easily requires several seconds, even if cooling of the vaporizing zone by 20° is accepted. Thus “flash evaporation” is usually impossible and most liquids must be held in the vaporizing chamber to allow full evaporation.
Development of analytical SFE of a polar drug from an animal food matrix
Authors: Messer Dale C. , Taylor Larry T.
Published: May 2005

The applicability of supercritical CO2 extraction as a quantitative method for recovery of a hypolipidemic drug from an animal food matrix has been evaluated. Off‐line extraction with solid phase trapping and solvent rinsing has been utilized. An optimized method for quantitative extraction of the pure drug was initially developed with high reproducibility. Three drug/rat feed matrices were examined. The as‐received “crystalline matrix” yielded the poorest reproducibility suggestive of a heterogeneous matrix. A laboratory‐prepared crystalline drug/feed matrix and a matrix prepared by spiking the animal feed with a solution of the drug gave ten‐fold better RSDs than the “crystalline matrix”.
Retention behavior of ions in high performance ion chromatography: III effect of the nature of the cation on anion retention
Authors: Daignault Louis G. , Rillema D. Paul
Published: May 2005

The affects of alkali metal cations on the retention behavior of halide ions has been investigated. In general, the retention times of the anions were found to decrease as the size of the metal ion increased, although an inversion was observed for the rubidium and cesium ions. A similar inversion has been reported for calculated anion polarizabilities.
The performance concept: A contribution to the modern theory of capillary GC
Authors: Gaspar Guy
Published: May 2005

An original theoretical approach, the “performance concept” is introduced.

This concept enables the linear carrier gas velocity and column length to be optimized in order to obtain the shortest possible analysis time for a required separation. The optimized gas velocity and column length are expressed as functions of the B and C coefficients of the HETP equation, the extra‐column equipment constant, σ2EC, and the necessary plate number, Nne, determined by the analytical problem. A new equation is given for predicting analysis time as a function of the same parameters.

The validity of the concept is illustrated with an example of such an optimization. The fundamental relationships have been proved experimentally and excellent agreement found between predicted and measured values.