bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrophoresis versus electrochromatography
Authors: Everaerts F. M. , van de Goor A. A. A. M. , Verheggen Th. P. E. M. , Beckers J. L. 
Published: May 2005

AbstractIn separation techniques, such as Liquid Chromatography and Capillary Zone Electrophoresis, separation is performed on the basis of differences in velocity of the various separands, making use of differences in k′ and/or effective mobility.While in chromatography the flow of the eluent is elementary, in electrophoretic techniques the electroosmotic flow is generally suppressed in order to avoid disturbing of the sample zone boundaries, which migrate with a maximal velocity of 10−3 m s−1. This holds especially for isotachophoretic separations, where separands migrate in consecutive zones with minimal detectable lengths of about 0.1 mm.If electroosmotic flow is applied as a transport mechanism, using capillaries as small as about 50 μm, linear velocities of the liquid flow can reach about 2 × 10−3 m s−1. Especially for ionic species with a low effective mobility, this velocity can be a multiple of the electrophoretic migration velocity in the separation compartment. Therefore, anionic, non‐ionic, and cationic separands can migrate in the same direction.Depending on whether repulsive or attractive forces are operative, the electrophoretic separation power can be counteracted or favored. The separation mechanisms making use of (quasi)stationary phases are studied.Plotting the chromatographic behavior versus the electrophoretic shows transition areas to exist between the “purely” electrophoretic techniques and the “purely” chromatographic techniques.It must be stated that most of the recent publications in CZE, especially those with very narrow bore capillaries, can be allocated to the transition areas, sometimes with a strong chromatographic retention component.
New methodologies in trace analysis of volatile organic compounds
Authors: Roeraade J. , Blomberg S. 
Published: May 2005

AbstractTwo methods for sampling and concentration of volatile organic compounds are reported. In the first method, traps coated with a very thick film (ca. 100 μm) of cross‐linked silicone stationary phase are employed. Such thick films can be prepared with a modified dynamic coating procedure, which is briefly described. The low phase ratio traps can be utilized for enrichment of volatiles from gaseous as well as aqueous matrices.The second technique is based on chromatographic evaporation of a solvent in a capillary tube, where the process is sustained by a repeated sample injection and a cyclic flow reversal. In this way, large solvent volumes can be handled by a small volume system. Under optimal conditions, when using a solvent barrier, quantitative recovery is possible even for compounds of comparatively high volatility. Another important application of the technique is extraction of trace components from gases such as headspace samples, polluted air, etc.
Characterization of fatty oils by pattern recognition of triglycerides profiles
Authors: Das Neves H. J. Chaves , Vasconcelos A. M. P. 
Published: May 2005

AbstractThe triglyceride profiles for corn, soybean, sunflower, grapestone, olive and olive husks oils were obtained by high temperature capillary gas chromatography on HT‐FS capillary columns coated with OV‐17‐OH. The data were treated by methods of computerized pattern analysis, involving principal component analysis, discriminant analysis, and hierarchical clustering. A graphical representation of results as “star symbol plots” allows prompt visual recognition of the characteristic profiles and straightforward qualitative identification of unknowns as well as recognition of adulterations.
Concentration of volatile organic compounds from solvents by sustained chromatographic evaporation
Authors: Blomberg S. , Roeraade J. 
Published: May 2005

AbstractA system for quantitative concentration of volatile organic trace compounds present in organic solvents is described. Evaporation of the solvent is carried out inside a glass capillary tube by the action of a carrier gas, and large volumes can be reduced by a repeated sample injection and a cyclic flow reversal. Best recovery is obtained when a barrier of pure solvent is maintained ahead of the sample during concentration. Four rotary valves are employed for sample and solvent injection and direction of the gas flow. In principle, indefinite sample volumes can be handled, the limit being set by system contaminants.The process was evaluated both off‐line and on‐line to a gas chromatograph. Concentration of compounds like methylcyclopentane, hexane, and cyclohexane present in pentane in the low nanogram range and subsequent on‐line transfer to a gas chromatograph could be performed with a quantitative recovery. The technique was applied to analysis of trace volatiles in drinking water. Detection limits were estimated to be approximately 0.02 ng/L for normal hydrocarbons (FID detection) when concentration of a pentane extract from a one litre water sample was carried out.
A fatty acid methyl ester (FAMES) analyzer
Authors: Horman I. , Traitler H. , Aeschlimann J. 
Published: May 2005

AbstractFatty acids, as their methyl esters (FAMES), are routinely analyzed from a wide variety of plant and animal tissues and fluids. Samples have mainly been analyzed to date using capillary GC with FID detection. However, FID detection is non‐specific, and open to misinterpretation. This is particularly important in the analysis of minor lipid components from, e.g. organ tissues, plasma and other body fluids, where non‐FAMES impurities or contaminants can be present in relatively high amounts. This suggests that even for routine work, a mass spectral detector is necessary for the unambiguous identification–or rather, recognition–of FAMES. The FAMES analyzer we propose consists of three components: an automatic injector; a medium polarity, high‐temperature stable capillary column; a mass spectrometric detector, in our case the Finnigan–MAT ion trap detector (ITD 800). Here, on‐column injection allowed controlled sample transfer even for low absolute concentrations of lipids, and a column effluent splitter gave simultaneous qualititative and quantitative analysis. For automatic routine analysis, a mass spectral library routine using a tailor‐made library of FAMES spectra of the most common naturally occurring fatty acids, plays an essential role. Library comparison parameters used in the standard ITD software usually give “first hit” recognition over a wide sample dynamic range (ca. 2 pg to > 200 ng in the best cases). This gives an absolute recognition even of minor lipid components, especially when combined information from mass spectra and GC retention data is used. By analogy with the now well known concept of the Amino Acid Analyzer, we propose the system described as a FAMES Analyzer. Mass spectrometers like the Finnigan MAT ITD 800 are inexpensive, reliable, sensitive, and easy to operate. Unlike the Amino Acid Analyzer, the FAMES Analyzer needs the specific detection offered by mass spectrometry because the number of acids to be analyzed, including isomers, is much greater.
Identification and quantitative analysis of nitrogen‐containing polycyclic aromatic hydrocarbons in sediments
Authors: Onuska F. I. , Terry K. A. 
Published: May 2005

AbstractAn integrated analytical methodology has been developed for determining nitrogen‐containing polycyclic aromatic hydrocarbons, which enables quantitation of individual contaminants as low as 1 μg/kg in sediment samples. A cross‐sectional profile from the Hamilton Harbour sediment samples was analyzed for azaarenes. These contaminants were separated by Soxhlet extraction, and pH adjustment allowed their isolation from different classes of neutral and acidic components. Separation and identification of the organic bases in each sample were achieved by using open tubular column gas chromatography with thermionic detection and HRGC‐mass spectrometry. Organic bases present in the samples included mostly azaarenes such as acridines, benzacridines, azafluorene, benzoquinolines, azapyrenes, etc. Quantitation and environmental significance of these compounds are discussed. Recoveries of individual azaarenes at two different levels were evaluated. Data presented indicate that detection limits of this method are between 1 and 10 μg/kg. Recovery azaarenes from bottom sediment samples at concentration levels between 1 to 100 μg/kg is 81 ± 17%.
Early solvent vapor exit in GC for coupled LC‐GC involving concurrent eluent evaporation
Authors: Grob Konrad , Schmarr Hans‐Georg , Mosandl Armin 
Published: May 2005

AbstractUse of early solvent vapor exits for concurrent eluent evaporation with the loop‐type interface has two purposes: protection of the GC detectors from large amounts of solvent vapors and more efficient discharge of the vapors to accelerate eluent evaporation and help avoiding broad solvent peaks. Use of a retaining pre‐column after the uncoated pre‐column can rule out losses of solute materials that form sharp peaks.
Rapid cleanup of natural organic extracts for the recovery of plyacyclic aromatic hydrocarbons by solid phase extraction
Authors: Garrigues Ph. , Bellocq J. 
Published: May 2005

AbstractA rapid cleanup procedure has been tested and applied routinely in our laboratory to petroleum and sediment extracts for the recovery of polycyclic aromatic hydrocarbons. Solid‐phase extractsion (SPE) on Florisil cartridges yields a fast and good recovery of neutral aromatic compounds which has been checked by normal‐phase high performance liquid chromatographic (HPLC) analysis with UV‐absorption detection.
Reversed phase high performance liquid chromatographic determination with photodiode‐array detection of nitroaromatics from former ammunition plants in surface waters
Authors: Feltes J. , Levsen K. 
Published: May 2005

AbstractSamples containing nitroaromatics have been taken from brooks and ponds in former ammunition production areas in Hessia (FRG) and Lower Saxony (FRG). The compounds were extracted by solid/liquid partition using Amberlite XAD 2/4/8 resins and elution with dichloromethane. The samples were analyzed by reversed phase high performance liquid chromatography and detected at their optimum wavelength with a photodiode‐array detector. The resulting UV‐spectra and the retention times were compared with those of reference materials to identify the unknown compounds. The recoveries ranged from 85–105%. The detection limit for the method was at about 50 ng/I depending on the compound while the detection limit for the detector ranged from 0.9–1.4 ng. Mononitrotoluenes, dinitrotoluenes, and 2,4,6‐trinitrotoluene, as well as nitrotoluidines, have been identified in concentrations ranging from 0.1–20 μg/I.
Analysis of C10‐C20 hydrocarbons in natural gas by solid phase extraction and CGC
Authors: David F. , Nikolai A. , Sandra P. 
Published: May 2005

AbstractA method is described for the determination of C10‐C20 hydrocarbons in natural gas. Enrichment by solid phase extraction on ODS followed by liquid desorption was found to give better results than adsorption on Tenax or charcoal followed by liquid or thermal desorption.
Enhancement of sensitivity in capillary supercritical fluid chromatography through optimization of injection and detection techniques
Authors: Munder A. , Chesler S. N. 
Published: May 2005

AbstractThe reproducibility of peak areas as a function of the technique used for sample injection was investigated in capillary supercritical fluid chromatography (SFC). An injection technique has been developed to increase the volume of sample introduced into the capillary column. Using a modified time‐split injection technique, long injection duration times were successfully applied to achieve lower detection limits. Analytes were effectively focused at the head of the analytical column using a unique pressure trap program. Because this on‐column focusing was performed only by pressure and temperature programming, no instrumental modifications were necessary. Up to 1.0 μL of sample solution was injected onto 50 μm i.d. columns using this technique, with no observable peak splitting. Dual detection using ultraviolet (UV) absorption and flame ionization detection (FID) was performed in series, thereby avoiding the necessity of splitting the column effluent. For the compounds investigated (five nitroaromatics and one phthalate ester), the absolute sensitivity of the UV detector was significantly greater than that of the FID.
Fully automated column‐switching HPLC determination of aflatoxin M1 in milk using dialysis as sample preparation
Authors: Th. Tuinstra L. G. M. , Kienhuis P. G. M. , Traag W. A. , Aerts M. M. L. , Beek W. M. J. 
Published: May 2005

AbstractA procedure has been developed for the automated determination of aflatoxin M1 in decreamed milk, by using on‐line dialysis and subsequent trace enrichment on a reverse phase column. After foreflush to the analytical column the determination is performed with fluorescence detection. Fully automated analysis within 10 min is thus possible with reproducible dialysis recoveries above 50% (CV is 3.3%, n = 20) and detection levels of 50 ng/kg.
Cyclodextrins as chiral stationary phases in capillary gas chromatography. Part V: Octakis(3‐O‐butyryl‐2,6‐di‐O‐pentyl)‐γ‐cyclodextrin
Authors: König W. A. , Krebber R. , Mischnick P. 
Published: May 2005

Abstractγ‐Cyclodextrin with 3‐O‐butyryl and 2,6‐di‐O‐pentyl residues is a very versatile chiral stationary phase for enantiomer separation. Most of the common and many uncommon amino acids can be separated as well as α‐ and β‐hydroxy acids, chiral alcohols, diols, triols, ketones, bicyclic, and tricyclic acetals, amines, alkyl halides, lactones, and functionalized cyclopropane derivatives.
Determination of bioconcentration factors of isomeric polycyclic aromatic hydrocarbons in polychaete worms by HRGC on selective liquid crystalline stationary phases
Authors: Fernández P. , Bayona J. M. 
Published: May 2005

AbstractThe bioconcentration factors (Kb) of parent and alkylated PAHs isolated from polychaete worms collected in coastal sediments were determined for the first time. Capillary gas chromatography using a polymeric liquid crystalline (MPMS) and SE‐54 stationary phases coupled to FID, MS and concurrent elution with authentic standards permitted positive identifications of parent PAHs. The Kb values of 18 compounds were accurately determined on the liquid crystalline column and the those of mono‐ and dialkyl‐phenathrene, ‐pyrene and ‐chrysene were determined by GC‐MS on a SE‐54 coated column. The experimental Kb values exhibited a moderate correlation (r=0.7–0.8) with the reported octanol‐water partition coefficients (Kow) for these compounds. Consequently, kinetic considerations, i.e. biouptake‐release and enzymatic activity seem to be relevant, in addition of biota‐media equilibrium. Therefore, integrated bioconcentration models are needed.
Packed microcolumn SFC coupled with photodiode array UV detector and inductively coupled plasma detector (SFC‐photodiode array UV‐ICP)
Authors: Jinno K. , Mae H. , Fujimoto C. 
Published: May 2005

AbstractHyphenation of packed microcolumn SFC, a photodiode array UV detector, and an inductively coupled plasma spectrometer has been developed in order to evaluate the stability of acetylacetone complexes under supercritical conditions.
Dual capillary column supercritical fluid chromatography
Authors: Raynor M. W. , Moulder R. , Davies I. L. , Kithinji J. P. , Clifford A. A. , Bartle K. D. , Hall J. E. 
Published: May 2005

AbstractA chromatograph equipped with one injection valve, two capillary columns with different selectivities, two flame ionization detectors and two electrometers is used to perform simultaneous dual capillary supercritical fluid chromatography. Two sets of retention times and indices are obtained for a mixture of polycyclic aromatic hydrocarbons, from one injection, enabling positive identification. The system is also used to rapidly select a stationary phase for separating hop and beer bittering acids.
Characterization of lignocellulosics by pyrolysis‐gas chromatography‐ion trap detection
Authors: Piccaglia R. , Galletti G. C. , Traldi P. 
Published: May 2005

AbstractWheat straw lignins obtained by HF, H2SO4, HCL, NaOH, and dioxane/water extraction methods and native wheat straw were subjected to pyrolysis‐gas chromatography (Py‐GC). Pyrolytic fragments were tentatively identified by mass spectrometry using an on‐line Py‐GC‐Lon Trap Detector (Py‐GC‐ITD) and their origin could be attributed to polysaccharides and lignin. Quantitation of fourteen main peaks common to all pyrograms showed statistically significant differences depending on lignin preparation. Pyrograms of typical lignin preparations, native wheat straw, and pure cellulose and ITD mass spectra are reported.
Determination and distribution of polycyclic aromatic hydrocarbons in native vegetable oils, smoked fish products, mussels and oysters, and bream from the river Elbe
Authors: Speer K. , Steeg E. , Horstmann P. , Kühn Th. , Montag A. 
Published: May 2005

AbstractTwenty eight native vegetable oils were analyzed for polycyclic aromatic hydrocarbons. Generally PAH concentrations were low, but olive oils showed significantly higher contamination by light PAH ranging from 53 to 105.6 μg/kg. Muscle and liver samples of bream from the river Elbe contained little or no detectable amounts of PAH, whereas fresh and canned oysters and mussels showed higher contaminations. Highest PAH concentrations have been determined in “smoked oysters in oil” with 75.8 μg/kg benzo[a] pyrene for the oil and 12.2 μg/kg for the oyster meat.
High resolution‐GLC of carbohydrates as their dithioacetal‐trimethylsilylates and ‐trifluoroacetates
Authors: Englmaier Peter 
Published: May 2005

AbstractIn the recent past, GLC separation of carbohydrates has significantly decreased in importance as a routine method compared with high resolution HPLC analysis. The reason for this is the handicap of most of the conventional derivatization procedures for GLC, i.e., formation of multiple derivatives with reducing sugars. Mercaptalation, the only method yielding a single derivative with each component, was rather complicated and therefore unpopular for routine work. In this paper a simplified mercaptalation is described which can be followed either by a trimethylsilylation or a trifluoroacetvlation and yields stable assays for chromatography. The combination with an optimized separation on megabore capillary columns results in a universally suited method, useful even with complex sample compositions. The separation power and speed of this method is at least comparable with high resolution HPLC analyses.
The performance and application of a multidimensional system for gas chromatography
Authors: Johnson G. L. , Tipler A. , Crowshaw D. 
Published: May 2005

AbstractWe have previously described [1] the design of a simple heart‐cuttings device based on the Deans' principle of remote pressure switching [2]. Since that time, further work has been conducted to refine the design of the heart‐cutting device and to develop complementary backflushing and cryofocusing units. This paper describes the results obtained from an intensive evaluation of the three modules in various combinations and considers parameters critical to the practical application of multidimensional gas chromatography (MDGC).
Evaluation of sample treatment procedures for the routine identification and determination at nanogram level of O6‐monoacetylmorphine in urine by capillary GC and dual NPD‐FID
Authors: Vu‐Duc Trinh , Vernay André 
Published: May 2005

AbstractThree methods were evaluated for the determination of O6‐monoacetylmorphine (6‐MAM), the specific metabolite of heroin in human urine, by GC‐NPD‐FID. The procedure devised for a hydrophobic cation exchange column showed superior performances over the liquid‐liquid extraction technique and solid phase extraction with C18. 6‐MAM can be analyzed in random urines at the 2 ng/mL concentration with classical equipment for the differentiation between heroin intake and opiates from various origins. The procedure was also applied to enzymatic and acid hydrolyzates of urines. The simultaneous presence of morphine and codeine are useful in the interpretation of results.
Multidimensional HRGC for sample components with a wide range of volatilities and polarities
Authors: Wu Shaowen , Chatham William H. , Farwell Sherry O. 
Published: May 2005

AbstractA diverse mixture of volatile headspace analytes containing compounds with boiling points covering a range from −196°c to 145°c can be separated in approximately 40 minutes by multidimensional HRGC. The described provisional MD‐HRGC Systems employ cryogenic sample collection, four 0.53 mm FSOT columns, and multi‐ramp temperature programming of either one or two ovens. Enhanced sensitivity for organic species and minimal interference from water vapour in the samples can be obtained by a MD‐HRGC configuration that uses separate ovens, appropriate column switching operations, and TCD + FID detection.
A standard test mixture for assessing enantioselectivity of chiral phase capillary GC columns – CHIRAL‐Test I for amide phases
Authors: Aichholz Reiner , Bölz Uwe , Fischer Peter 
Published: May 2005

AbstractA test mixture is proposed which allows assessment of the enantioselective separation potential of chiral amide phase capillary columns. This CHIRAL‐Test I includes a range of chromatographically problematical substrates, covering the temperature range from 100–200°C. One test component, the N‐pivaloyl leucine methyl ester enatiomers, may be used exemplarily to calculate chiral resolution (chirale Auflösung, cR). Unlike separation factors α, cR values take account of peak shape as well as of relative retention time of both enantiomers, and thus are a measure of affective chromatographic separation. In combination with the Grob test, the CHIRAL‐Test may be used for characterizing the chromatographical properties of columns coated with chiral amide phases.
Cooperative trial studies on the analysis of ethyl carbamate using capillary gas chromatography
Authors: Dennis M. John , Massey Robert C. , Pointer Mark , Willetts Paul 
Published: May 2005

AbstractA design for cooperative study of analytical methods is described which involves the analysis of spiked samples and evaluation of the results using a linear regression technique. Two examples are described involving the study of ethyl carbamate in whisky at levels from 40–170 μg/L and in beer at levels <1–20 μg/L. Most participating laboratories used capillary gas chromatography with variations in sample preparation and detection methods. Acceptability criteria were defined as: intercept ±2 standard deviations of the group mean, slope 0.9 to 1.1, individual analyses of duplicates within ±10% of the mean and correlation coefficient better than 0.99. In the whisky trial, four of the seven laboratories taking part met these criteria, while for the beer trial all of the laboratories taking part were sufficiently close to these standards to be considered satisfactory given that the analyses were being performed close to the detection limit of the methods.
Screening of trihalomethanes by direct aqueous injection using electron capture detection
Authors: Carmichael Duncan , Holmes William 
Published: May 2005

AbstractThe disinfection of drinking water with chlorine produces carcinogenic by‐products called trihalomethanes or (THM's). These compounds are formed when the chlorine reacts with the organic matter in the raw water. The four major THM's are chloroform, bromodichloromethane, dibromochromethane, and bromoform. Direct aqueous injection is used for the rapid screening THM's and other volatile organic compounds (VOC's) in water by direct on column injection of the water sample in to wide bore capillary columns, to which is attached an electron capture detector.