bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of organic mobile phase modifiers in micellar electrokinetic capillary chromatography
Authors: Gorse J. , Balchunas A. T. , Swaile D. F. , Sepaniak M. J.
Published: May 2005

The addition of 1–20% (v/v) of methanol or acetonitrile as organic modifier to the mobile phase in a micellar electrokinetic capillary chromatographic (MECC) system, containing sodium dodecyl sulfate and a buffer, is shown to extend the elution range and thus increase the peak capacity of a given system. Although the net change in the elution range parameter, to/tmc, is essentially the same for both modifiers, the acetonitrile‐modified system exhibits much faster elution times for the polar and non‐polar test solutes employed in this study. Retention, as measured by the capacity factor, is generally decreased with the increase of an organic modifier, just as in conventional reversed phase chromatography. However, changes in selectivity as a function of the added modifiers are noted among polar and non‐polar solutes as well. The efficiency of these MECC systems is increased with the addition of either organic modifier.
Retention characteristics of volatile compounds on tenax TA
Authors: Maier I. , Fieber M.
Published: May 2005

The chromatographic separation properties of long, thin adsorption tubes enable substance‐specific quantitative enrichment and reduction to be achieved when sampling and thermal desorption are carried out in the same flow direction.

The specific retention volumes, and also the breakthrough and peak end volumes, of 69 compounds in the boiling range between‐164 and 126°C and of a relative molecular mass between 16 and 119 were determined at temperatures between 30 and 130°C: normal alkanes, isoalkanes, cycloalkanes, alkenes, polyenes, alkynes, aromatics, ethers, alcohols, aldehydes, ketones, carboxylic acids and their esters, nitroalkanes, O‐heterocycles, S‐heterocycles, chloroalkanes, water, nitrogen monoxide, nitrogen dioxide, carbon dioxide, and sulfur dioxide.

The correlation between adsorbent temperature and specific retention volume of these components, presented in the form of diagrams, permits the required quantity of adsorbent to be determined for a given sample volume. Contrary to literature sources, even extremely volatile compounds such as propane, propene, methanol, formaldehyde, formic acid, and chloromethane can be quantitatively retained on Tenax provided the operating conditions are appropriately selected.
Gas chromatographic separations on packed microcolumns using various 10 μm support particles
Authors: Lagesson V. , Newman J. M.
Published: May 2005

Packed columns using 10 μm HPLC‐packing materials as supports for various liquid phases have been studied. The glass columns used were 80 mm long (o.d. 3 mm and i.d. 1.5 mm), the amount of solid support in the column being approximately 0.15 g. A. wide variety of separation characteristics were obtained by combining support material of various surface areas, chemically bonded surfaces, applied liquid phases, and various liquid phase loadings. This type of column is also characterized by a very short gas hold‐up time, leading to possibilities for relatively fast separations. Other advantages are high sample loading, high sample capacity, and low operating cost.
Residential wood combustion: A source of atmospheric polycyclic aromatic hydrocarbons
Authors: Guenther F. R. , Chesler S. N. , Gordon G. E. , Zoller W. H.
Published: May 2005

Samples were taken of the atmospheric particulate matter over Fairbanks Alaska in the winter of 1985, and from wood stoves burning the major wood types locally available. These samples were then analyzed for polycyclic aromatic hydrocarbon (PAH). A PAH emission profile was determined from the wood stove samples and applied to the atmospheric samples to determine the residential wood combustion contribution to the local atmospheric particulate burden. Emission profiles for coal burning and automobile emissions for PAH were also used to estimate their relative contributions.
Techniques and procedures for preparation of aquatic samples for chromatographic analyses
Authors: Onuska F. I.
Published: May 2005

The measurement of low levels of organic compounds in environmental samples presents the researcher with a number of possible pathways to effectively obtain and analyze samples. Numerous sampling methods, sample preparation techniques, and extraction procedures are available. A number of different approaches to sampling strategy, isolation, concentration, cleanup and fractionation will be discussed.

Objectives for collecting environmental samples differ from those for many other types of samples because reliable measurements at very low levels are frequently required. Often, specific analytes need to be measured at the μg/kg and even ng/kg levels in complex matrices. Advances in analytical methodology continue to lower the levels at which reliable measurements can be made. At these levels, many factors that are of little or no concern in other analytical measurements are of critical importance in influencing the outcome and reliability of environmental analyses.

Analytical measurements are used for determining the composition and the quantities of analytes in the defined system at various concentration levels. Environmental analytical measurements provide data about the transportation and transformation of an environmental contraminant and for determination of its concentration in a sample.
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

In 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

Two 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

The 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

A 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

Fatty 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

An 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

Use 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

A 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

Samples 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

A 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

The 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

A 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

γ‐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

The 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

Hyphenation 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

A 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

Wheat 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

Twenty 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

In 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

We 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

Three 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

A 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

A 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

A 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

The 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.
Stereochemical analysis of constituents of essential oils and flavor compounds by enantioselective capillary gas chromatography
Authors: König Wilfried A. , Krebber Ralph , Evers Petra , Bruhn Gabriele
Published: May 2005

Modified cyclodextrins interact enantioselectively with a great variety of volatile chiral constituents of essential oils by forming diastereomeric inclusion complexes. Capillary gas chromatography is used for resolving the enantiomers of terpenoid hydrocarbons (camphene, α‐pinene, limonene, α‐phellandrene), carbonyl compounds (carvone, fenchone, menthone, isomenthone, piperitone, camphor, myrtenal), and alcohols (trifluoroacetylated β‐citronellol, myrtenol, trans‐pinocarveol, 1‐octen‐3‐ol, and underivatized linalool). The enantiomeric composition of some of these compounds in a variety of essential oils is investigated.
Simultaneous determination of particle size and density in polydisperse colloidal samples by sedimentation field‐flow fractionation
Authors: Koliadima A. , Dalas E. , Karaiskakis G.
Published: May 2005

Sedimentation Field‐Flow Fractionation (SFFF), which is a one‐phase chromatographic system, is shown to be a rapid and convenient method for the simultaneous determination of particle size and density in polydisperse colloidal samples. This can be done by a methodology based on the variation of the carrier solution density using various aqueous glycerol solutions having different concentrations. A polydisperse polyvinyl chloride (PVC) latex sample was used as a model colloid. The average diameters and densities found by the proposed methodology are in good agreement with those obtained from the normal. SFFF procedure using a carrier of constant density or given by the manufacturer. Number average, dN, and weight average, dw, particle diameters were determined for the PVC sample at various carrier solutions containing glycerol up to 40 % (w/w) in order to show whether sample aggregation has occurred or not in the presence of glycerol. In all cases, the ratio dw/dN was found to be constant, showing that PVC aggregation has not occurred. Therefore our results, obtained by the proposed methodology in SFFF, are accurate, showing that this approach has considerable promise for characterizing complex colloidal materials.
Significance of minor components of milk fat
Authors: Mariani C. , Contarini G. , Zucchetti S. , Toppino P. M.
Published: May 2005

In order to establish criteria for the evaluation of the genuineness of milk fat and its derivatives, research has been carried out on some minor components (mono‐ and diglycerides and cholestrol esters). Most determinations of milk fat diglycerides showed significant qualitative and quantitative differences compared with other fat sources, and especially with tallow. In particular, the milk fat diglycerides C30–C32–C34–C36 showed characteristic fingerprints. Moreover, the sterol fractions (free and esterified) have also been evaluated. The cholesterol ester profile in milk lipids includs fatty acides from 10 to 18 carbon atoms, while tallow basically showed only C14–C16–C18. In comparison, phytosteral esters with C16 and C18 fatty acids have been found in vegetable fats. These results lead to the hypothesis of possible use of these methods in addition to those most commonly applied (TG‐FAME). Furthermore, the natural variability of milk fat components makes a final evaluation of these methodologies difficult unless experimental work is extended to more samples and performed by several research groups.
Study on retention behavior of cyclic siloxanes by high resolution pyrolysis‐gas chromatography with a fused silica capillary column
Authors: Fujimoto Shinji , Ohtani Hajime , Yamagiwa Katsuya , Tsuge Shin
Published: May 2005

The general gas chromatographic retention behavior of cyclic methylsiloxanes partially substituted with phenyl or 2‐cyanoethyl groups has been systematically studied, with pyrolysis‐gas chromatography being utilized to form the cyclic siloxanes from the corresponding polysiloxanes at a temperature of 600°C. Kovats retention indices (KI) were determined for the cyclic siloxanes by use of the retention data of the pyrolyzates from polyethylene as standards. The effect of phenyl and 2‐cyanoethyl substituents in the cyclic siloxanes on retention behavior has also been considered.
Possibilities and limitations of coiling induced secondary flow in capillary supercritical fluid chromatography
Authors: Janssen Hans‐Gerd M. , Rijks Jacques A. , Cramers Carel A.
Published: May 2005

The possibility of enhancing radial mass transfer in capillary SFC by tightly coiling the column is discussed. The influence of coiling‐induced secondary flow on the plate height and the speed of analysis in capillary SFC is investigated. It is shown that the experimental plate height in tightly coiled metal or fused silica columns departs from the Golay theory for laminar flow. The effect of the pressure drop associated with the use of higher mobile phase linear velocities is studied. The capacity factors of retained components are used as sensitive probes for pressure drop over the column. Experimental plate heights in coiled columns are compared with values calculated from Tijssen's theory for coiling induced secondary flow. At low velocities a good quantitative agreement was observed between the theory and the experimental results. At intermediate velocities only a qualitative agreement is found. The speed of analysis in coiled columns was found to be up to 5 times higher than in straight capillaries. The largest gain in analysis speed was obtained for solutes with low capacity factors. It is shown that coiling the column can have a positive influence on the detectability. For tightly coiled 210 μm i.d. columns the advantages of coiling‐induced secondary flow could be fully exploited without adverse effects of the column pressure drop. For 50 μm columns the possibility to increase the speed of analysis by coiling was limited due to the high pressure drop.
Review: The usefulness of the headspace analysis‐gas chromatography technique for the investigation of solid samples
Authors: Venema Arnold
Published: May 2005

The scope of the headspace sampling technique for the analysis of solid samples is discussed, and the static and the dynamic headspace methods compared. Theoretical aspects relating to quantification are discussed. The paper considers both instrumental requirements and applications.
Differences in absorbance levels as found in capillary zone electrophoresis under stacking conditions
Authors: Vinther Anders , Everaerts Frans M. , Søeberg Henrik
Published: May 2005

During some capillary zone electrophoresis (CZE) experiments, the baseline UV absorbance signal at 200 nm “jumped” from one stable level prior to the water plug (marking the flow of neutrals) to another stable level after the water plug. The phenomenon was further examined with distilled water as the sample and with different buffers, applied potentials, and salt concentrations in the buffer. It seems that there is an “isotachophoretic effect” on top of the CZE separations when running under stacking conditions. The effect results in a higher pH value of the buffer after the water plug compared to the pH prior to the plug. The nature of the buffer, the salt concentration in the buffer, and the applied potential all affect this phenomenon.
Partition and adsorption in the separation of long chain lipids by normal phase high performance liquid chromatography
Authors: Netting A. G. , Rhodes S. H.
Published: May 2005

Martin's adaption of Raoult's Law has been shown to describe partition phenomena in normal phase HPLC. Thus, in the separation of fatty acid pentaflorobenzyl esters and of triacylglycerols in dichloromethane or acetonitrile in half‐water‐saturated hexane, the natural logarithm of the corrected retention volume is proportional to the number of double bonds that these solutes contain. By extending Martin's adaption of Raoult's Law with activity coefficients, evidence was obtained that deviations observed for the homologous series of saturated fatty acid pentafluorobenzyl esters from C2 to C5 could be accounted for by a diminution of adsorption by the inductive effect. For chain lengths longer than C5, it appeared that there were additional field and inductive effects from the methyl end of the hydrocarbon chains.

Thus, with these half‐water‐saturated solvent systems, the silica surface is probably covered with a bilayer of water which, in the dynamic situation in an HPLC column, attracts several layers of the polar organic component of the mobile phase by dispersive interactions. This stationary phase surface may, then, be considered to be immiscible with the predominantly hexane mobile phase due to these dispersive interactions and thus partition can occur between these two phases. Solutes that enter the stationary phase are then free to interact with the underlying aqueous phase by adsorption.
Optimization of resolution in micellar electrokinetic chromatography
Authors: Rasmussen Henrik T. , Goebel Lisa K. , McNair Harold M.
Published: May 2005

A comparison of separations conducted in sodium dodecyl sulfate (SDS) and SDS modified with Brij 35 indicates that selectivity, in Micellar Electrokinetic Chromatography (MEKC), is governed by the composition of the micellar phase. Beyond selectivity optimization, resolution may be improved by increasing efficiency or decreasing electroosmotic flow. Of these approaches, increasing capillary length (to improve efficiency) should be a more time effective means of improving separation.
Selective detection of volatile nickel, vanadium, and iron porphyrins in crude oils by gas chromatography‐atomic emission spectroscopy
Authors: Quimby Bruce D. , Dryden Paul C. , Sullivan James J.
Published: May 2005

This report describes the selective detection of volatile nickel, vanadium, and iron metalloporphyrins in crude oil samples. An atomic emission detector (AED) was used for simultaneous detection of these metals using the Ni 301.2 nm, V 292.4 nm, and Fe 302.1 nm emission lines. Detection limits for these metals range from 0.05 to 5 pg/sec. The presence of volatile forms of these metals in several crude oil samples has been confirmed.
GC with LC‐like packed capillary columns
Authors: Takeuchi Toyohide , Watanabe Mototada , Haraguchi Hiroki , Ishii Daido
Published: May 2005

Capillary columns of 0.3–0.35 mm internal diameter and 0.3–7.7 m length, packed with 3 to 30 μm octadecylsilica stationary phases as used for liquid chromatography, were applied to gas chromatographic separation of low boiling hydrocarbons. Van Deemter plots for these columns showed the optimum column efficiency to occur at linear velocities of 4–5 cm/s. A short column was applied to the rapid separation of components of a natural gas and impurities in standard gases, while a long column was applied to the separation of complex mixtures.
Fast separations with open tubular ion exchange capillary columns
Authors: Müller Stephan , Scheidegger David , Haber Carsten , Simon Wilhelm
Published: May 2005

Fused silica columns of 4.6 μm i.d. were coated with 3‐sulfopropylsilane as a cation exchanger and 3‐(2‐aminoethyl‐amino)‐propylsilane as an anion exchanger. Fast separations of cations (< 25 seconds) and of anions (< 35 seconds) were obtained, using a potentiometric microelectrode as a detector. In proceeding towards smaller i.d.s, a mixture of alkali metal cations could be separated successfully in an uncoated fused silica capillary of 2.3 μm i.d. as a result of retention by the surface silanol groups at pH 9.4.
Simultaneous determination of creatinine and uric acid in human plasma and urine by micellar electrokinetic chromatography
Authors: Miyake Mamoru , Shibukawa Akimasa , Nakagawa Terumichi
Published: May 2005

High performance capillary electrophoresis using a buffer solution containing micelles of ionic surfactant (e.g. sodium dodecyl sulfate), called micellar electrokinetic chromatography, has been applied to the separation and simultaneous determination of creatinine and uric acid in human plasma and urine. The sample was introduced into the capillary by siphoning an appropriate volume of untreated plasma or urine spiked with an internal standard (antipyrine). Creatinine, uric acid, and antipyrine were separated mutually, and from other endogeneous components within 18 min. The calibration plots showed good linearity (correlation coefficient > 0.999) over the concentration range needed for clinical analysis. Standard addition tests indicated that the recoveries of creatinine and uric acid from urine samples ranged, respectively, from 97 % to 106 % and 97.4 % to 108 % with a coefficient of variation (C.V.) of 3.3 % (n = 5), and that those from plasma samples ranged, respectively, from 100 % to 112 % and 101 % to 107 % with a C.V. of 4.7 % (n = 5). The results were in agreement with those obtained by conventional methods.
Temperature dependence of equivalent chain length values on capillary columns of different polarity
Authors: Sidisky Leonard M. , Ridley Heloise J.
Published: May 2005

The influence of temperature and capillary column stationary phase polarity on the equivalent chain length (ECL) values of unsaturated fatty acid methyl esters (FAMEs) is discussed. Comparisons are made of a bonded, nonpolar methyl silicone, bonded and nonbonded polyethylene glycols, and a highly polar, stabilized cyanosilicone stationary phase. The change in the ECL values over a 20° temperature range is used to demonstrate selectivity shifts and the influence of temperature on the separation of FAMEs on these phases. The effect of the degree of unsaturation of the FAME components, on the various stationary phases is also investigated.
Mobilities of metal β‐diketonato complexes in micellar electrokinetic chromatography
Authors: Saitoh Koichi , Kiyohara Chikara , Suzuki Nobuo
Published: May 2005

Electrically neutral acetylacetonato complexes of chromium(III), cobalt(III), rhodium(III), and platinum(II) (or palladium(II)) have been separated successfully by capillary zone electrophoresis in a micellar solution of sodium dodecyl sulfate (SDS). The distribution coefficient of each metal complex between the SDS micelle and the aqueous solution surrounding the micelle was calculated from the capacity factor. A linear log‐log relationship was found between the distribution coefficient and the partition coefficient of the complex between dodecane and water. The linear relationship was effectively used for prediction of both the distribution coefficients and the migration times of other metal complexes, such as palladium(II) acetylacetonate and chromium(III) 3‐methyl acetylacetonate.
Effects of the sample matrix on the separation of peptides by high performance capillary electrophoresis
Authors: Satow Takashi , Machida Akiko , Funakushi Kayo , Palrnieri Richard
Published: May 2005

The effects of the sample matrix on the separation of peptides by HPCE has been investigated. Under both acidic and alkaline conditions, use of 25–30 mM salts in the sample zone resulted in much better resolution than did 100 mM salts. Prefocusing effects and acceleration of elution were also observed. These results agree well with the theory developed by Everaerts. In this paper a practical guide for high sensitivity, high resolution separation of salt‐containing peptide mixtures is proposed.
Determination of mono‐, di‐ and tri‐substituted butyltin, phenyltin and methyltin compounds as free halides using gas chromatography with flame photometric detection
Authors: Hashimoto Shinya , Otsuki Akiro
Published: May 2005

A simple chromatographic procedure has been developed for the sensitive determination of mono‐, di‐ and tri‐substituted butyltin, phenyltin, and methyltin compounds as halides. The organotin compounds were separated on a DB‐1 capillary column and detected by flame photometric detection (FPD) equipped with a 611.5 nm filter.

Pretreatment of the capillary column with an ethyl acetate solution of hydrobromic acid, or doping of standard solutions with hydrobromic acid, was found to be necessary if reproducibly sharp peaks of organotin halides were to be obtained. Column treatment and acid doping did not cause any background problems or undesirable degradation of the organotin compounds.

Three different standard solutions in ethyl acetate had to be Jrepared, because undesirable degradation of the organotin halides was observed when all the compounds were dissolved in the same solution. The first, standard solution I, contained tri‐n‐butyltin chloride (TBTCI) and trimethyltin chloride (TMTCI), the second, standard solution II, contained triphenyltin chloride (TPTCI), and the third, standard solution III, contained hydrogen bromide and the other organotin compounds: di‐n‐butyltin chloride (DBTCI), mono‐n‐butyltin chloride (MBTCI), dimethyltin chloride (DMTCI), monomethyltin chloride (MMTCI), diphenyltin chloride (DPTCI), and monophenyltin chloride (MPTCI). An ethyl acetate solution containing hydrobromic acid (20 × 10−3 mol/I) was used for column treatment.
Simplex optimization of a programmed temperature capillary gas chromatographic separation
Authors: Lanças Fernando M. , Francelin Roseli A. , de Souza Ailton J.
Published: May 2005

The modified simplex algorithm proposed by Nelder and Mead has been used to optimize the separation by temperature programmed capillary GC, of volatile compounds present in alcoholic beverages. An adequate objective function, CRF, based on the separation factor of Kaiser has been used for the optimization process.

A factorial design was initially performed to verify the relationship between the several parameters of interest. Following this, the optimization was executed and a surface adjusted within the set of experimental data.
Polymer analysis using pyrolysis‐GC‐FTIR‐MS and GC‐AED
Authors: Oguchi Rimiko , Shimizu Ayako , Yamashita Satoru , Yamaguchi Kenji , Wylie Philip
Published: May 2005

Volatile pyrolysates of a methyl methacrylate‐butadiene‐styrene copolymer (MBS) have been analyzed using a capillary gas chromatograph equipped with a Fourier transform infrared detector in tandem with a mass selective detector, and a gas chromatograph‐atomic emission detector system.

Among the volatile compounds observed were monomers used for synthesis of the polymer. Numerous oligomers of higher boiling point were also found; identification of these could be used to give structural information about the parent polymer.

Combining information from these techniques was found to be extremely useful for the analysis of polymer pyrolysis products. In characterizing each compound it was found particularly helpful to juxtapose feature‐specific chromatograms (e.g., single ion monitoring from the mass‐selective detector and the selected wavelength chromatography from the infrared detector).
Determination of pyrethroids and their degradation productds in indoor air and on surfaces by HRGC‐ECD and HRGC‐MS(NCI)
Authors: Class Thomas J.
Published: May 2005

Air and surface samples taken following indoor applications of natural pyrethrins and pyrethroids have been analyzed by HRGC‐ECD and HRGC‐MS using negative chemical ionization (NCI). It has been found that pyrethroids persist on surfaces as long as sixty hours after application.

Primary pyrethroid degradation products have been characterized by mass spectrometry; their identities and route of formation by ozonolysis have been verified by degradation studies and NMR.