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  • 1995-1999
  • 1990-1994  (2.299)
  • 1970-1974
  • 1993  (2.299)
  • Analytical Chemistry and Spectroscopy  (1.600)
  • Atomic, Molecular and Optical Physics  (301)
  • Physical Chemistry  (218)
  • Biochemistry  (180)
  • Nuclear reactions
  • Theoretical, Physical and Computational Chemistry
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  • 1995-1999
  • 1990-1994  (2.299)
  • 1970-1974
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  • 101
    ISSN: 0886-9383
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 102
    ISSN: 0886-9383
    Schlagwort(e): Kalman filter ; Multivariate calibration ; Condition number ; Prediction error ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The usefulness of the Kalman filter as an algorithm for calibration in a real system is shown. Results are compared with classical least squares and pure component calibration. The prediction of four priority pollutant chlorophenols in binary, ternary and quaternary mixtures was also carried out by Kalman filtering. The condition number, standard deviation and prediction error have been employed to choose the most suitable wavelength range. Comparison of the standard error of prediction in the validation set shows significant differences between the evaluated chlorophenols, the best results being obtained with Kalman multivariate calibration.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 103
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 7 (1993), S. 255-265 
    ISSN: 0886-9383
    Schlagwort(e): Multicomponent calibration ; Non-linearity ; Selectivity ; Wavelength selection ; Graphical diagnostics ; Outliers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Modern scanning infrared reflectance/absorption spectroscopes measure absorptions or reflectance at a sequence of around 1000 wavelengths. Training data may consist of 10-100 carefully designed sample mixtures whose true compositions are either known by formulation or accurately determined by wet chemistry. In future, one wishes to predict the true composition of a newly presented sample from its spectrum. Varying compositions of a mixture of three sugars in water are used for illustration of several different graphical techniques; the spectral measurements here are near-infrared (NIR) absorbances, but there is nothing exclusively infrared about the methodology. Graphs display the adequacy of a linear explanation of absorbance variability at each wavelength by wavelength linearity plots. These highlight regions of the spectrum where non-linearities and interaction effects are substantial. By selecting out these substantially non-linear regions, one can concentrate on linear formulae for prediction with resultant robust linear modelling. Such selections are further aided by plots which identify the component sugar for which each wavelength is most selective. Such plots offer rather natural pre-screening as an alternative or supplement to the wavelength selection method of Brown.We also display prediction diagnostics (R, Rx) which on a sample-by-sample basis may diagnose a particularly unusual presented spectrum. These diagnostics are shown to have predictive import for a validation data set.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 104
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 7 (1993), S. 305-340 
    ISSN: 0886-9383
    Schlagwort(e): Stem & leaf display ; Histogram ; Boxplot ; Quantile plot ; Scatterplot ; Regression ; Smoothing ; 3D rotation ; Scatterplot matrix ; OMEGA strategy ; Dimension reduction ; Stability of structure ; Resampling ; Interpretation of structure ; Prediction models ; Variables selection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Exploratory data analysis (EDA) is a toolbox of data manipulation methods for looking at data to see what they seem to say, i.e. one tries to let the data speak for themselves. In this way there is hope that the data will lead to indications about ‘models’ of relationships not expected a priori. In this respect EDA is a pre-step to confirmatory data analysis which delivers measures of how adequate a model is. In this tutorial the focus is on multivariate exploratory data analysis for quantitative data using linear methods for dimension reduction and prediction. Purely graphical multivariate tools such as 3D rotation and scatterplot matrices are discussed after having introduced the univariate and bivariate tools on which they are based. The main tasks of multivariate exploratory data analysis are identified as ‘search for structure’ by dimension reduction and ‘model selection’ by comparing predictive power. Resampling is used to support validity, and variables selection to improve interpretability.
    Zusätzliches Material: 29 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 105
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 7 (1993), S. 15-43 
    ISSN: 0886-9383
    Schlagwort(e): Curve resolution ; Multicomponent analysis ; Latent projections ; Local factor analysis ; Chlorophyll degradation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: High-performance liquid chromatography with diode array detection (HPLC--DAD) is used to characterize mixtures from chlorophyll a degradation experiments. Overlapping chromatographic peaks are resolved by means of the heuristic evolving latent projections (HELP) method. The HELP method is a self-modelling curve resolution method. No assumptions are made about spectral and/or chromatographic peak shape. In the first step the method establishes the real noise level in the data by use of the so-called zero-component regions. This information is used to reveal selective chromatographic information and the number of chemical species at every retention time in unresolved chromatographic peaks. Utilising the selective chromatographic regions in combination with the zero-concentration windows, unique resolution into concentration profiles and spectra of the pure chemical species is accomplished. HPLC-DAD data from six chlorophyll a degradation experiments were analysed. Consistent results were obtained even with very similar spectra for six or seven overlapping chemical components.
    Zusätzliches Material: 25 Ill.
    Materialart: Digitale Medien
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  • 106
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 7 (1993), S. 99-115 
    ISSN: 0886-9383
    Schlagwort(e): Classification ; Appreciation function ; Regularized discriminant analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Regularized discriminant analysis has proven to be a most effective classifier for problems where traditional classifiers fail because of a lack of sufficient training samples, as is often the case in highdimensional settings. However, it has been shown that the model selection procedure of regularized discriminant analysis, determining the degree of regularization, has some deficiencies associated with it. We propose a modified model selection procedure base on a new appreciation function. By means of an extensive simulation it was shown that the new model selection procedure performs better than the original one. We also propose that one of the control parameters of regularized discriminant analysis be allowed to take on negative values. This extension leads to an improved performance in certain situations. The results are confirmed using two chemical data sets.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 107
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 7 (1993), S. 149-150 
    ISSN: 0886-9383
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 108
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 7 (1993), S. 165-176 
    ISSN: 0886-9383
    Schlagwort(e): Measurement error ; Outliers ; Environmental ; Quality control ; Multivariate kurtosis ; Generalized distance ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Environmental data are usually multivariate, with the variables conforming to some correlation structure. Occasionally, measurements which do not conform in structure or magnitude may occur in one or more variables. It is important (1) to characterize these discordancies in terms of the disturbed variables and the direction and magnitude of the anomalous error and (2) to associate each discordant observation with a specific cause of measurement error in order to prevent further mismeasurement. We describe a procedure for identifying suspected causes of discordant observations in otherwise multinormal data sets. Variables are assigned to groups, each of which is associated with a specific cause of measurement error. Discordant observations are identified with the generalized distance test or the multivariate kurtosis test. Suspected causes of measurement error are identified by repeating the tests with one of the groups of variables omitted in each analysis. The procedures are evaluated with simulated data sets having a correlation structure similar to that of a large environmental data set.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 109
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 7 (1993), S. 393-425 
    ISSN: 0886-9383
    Schlagwort(e): Preprocessing ; Closure ; Normalization ; Ratioing ; Constant sum transformation ; Constant length transformation ; Maximum value transformation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The geometric properties of three common object-preprocessing transformations (constant sum, or closure; constant length, or normalization; and maximum value, or ratioing) are investigated. An argument is made for using absolute values in the constant sum and maximum value transformations. In general, each transformation distorts the shape and dimensionality of patterns in the data: transformed data lie on (C-1)-dimensional surfaces in the original C-dimensional space. A data set that has been closed by one of these transformations can be reopened if a vector containing the constant sums, constant lengths or maximum values of the original objects was retained. Transformed data sets may be freely interconverted among these three transformations without the loss of information.
    Zusätzliches Material: 24 Ill.
    Materialart: Digitale Medien
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  • 110
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 7 (1993) 
    ISSN: 0886-9383
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 111
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 7 (1993), S. 455-475 
    ISSN: 0886-9383
    Schlagwort(e): Biological activity ; Cross-validation ; Exchangeability ; Molecular descriptors ; Prediction ; Relationship ; Structure ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The two parts of this paper form a critique of a variety of statistical techniques of actual or potential use in quantitative structure-activity relationship (QSAR) studies and related fields. Part I explores the statistical thinking that is needed to underpin those techniques. Emphasis as placed on (a) the role of ‘exchangeability’ as an alternative to unrealistic statistical modelling and (b) the use of cross-validation to limit self-deception in the use of any particular technique. The problem of the almost unlimited range of molecular descriptors is seriously addressed. (Part II provides a concise critical review of methods-some well-established and some new.)
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 112
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 7 (1993), S. 543-550 
    ISSN: 0886-9383
    Schlagwort(e): Fragment occurrence data ; Molecular similarity ; Similarity searching ; Standardization ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Substructural fragment occurrence data are widely used as the basis for measures of inter-molecular structural similarity. This paper investigates the effect of standardization on the effectiveness of such measures using eight data sets for which both structural and biological activity data are available. Eight different standardization methods are studied and it is shown that there is no significant difference in the effectivenesses of the various methods; accordingly, any of them can be used for the calculation of intermolecular structural similarity.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
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  • 113
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 27-30 
    ISSN: 0935-6304
    Schlagwort(e): Capillary GC ; Solid phase extraction ; Cold on-column injection ; Antiepileptic drugs ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A simple and quick gas chromatographic method has been developed for the determination of up to six commonly used antiepileptic drugs in human serum. The antiepileptics are isolated from serum by solid phase extraction on to a reversed phase sorbent and recovered with ethyl acetate as eluent. The ethyl acetate eluate is suitable for direct on-column injection on to a phenyl methyl siloxane capillary column; hydrogen is used as carrier gas and the compounds are separated with a two-ramp temperature program. Detection is by FID.The reproducibility of the method varies between 2 and 6% RSD, depending on the drug and the level analyzed; limits of detection were found to be 14-51 pg and minimum assayed concentrations in serum were between 14 and 51 ng/ml.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 114
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 18-26 
    ISSN: 0935-6304
    Schlagwort(e): Column liquid Chromatography ; Serially coupled columns ; Selectivity tuning by changing the flow rate ; Stationary phases of different selectivity ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The tuning of selectivity by changing the flow rate has been investigated in HPLC: two columns with different retention characteristics were coupled in series via a T-piece and the relative retention of components chromatographed on the system were changed by varying the individual flow rates in the coupled columns. The flow rate alteration was performed by adding a second flow after the first column. The flow rate ratio necessary for optimum resolution can be easily calculated on the basis of the capacity factors measured on the individual columns. The performance of this method for adjusting selectivity has been demonstrated by using different column combinations to separate several mixtures containing chlorophenols, nitroaromatic compounds, and aromatic hydrocarbons.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 115
    ISSN: 0935-6304
    Schlagwort(e): On-column injection ; On-line injection ; Large (100 μ) injections ; Precision ; Linearity ; Carry-over ; Discrimination ; Activity ; Polar compounds ; High boiling compounds ; Environmental analyses ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: This report describes an on-line capillary GC injection system which enables on-column injection of a hundred or more microliters, and yields separations comparable with those obtained from on-column injection of 1-2 microliters of solutions a hundred times more concentrated. Precision, carry-over, linearity, and discrimination are comparable with those of classical sample-introduction techniques. A selection of polar and high boiling compounds has been examined, and excellent peak shapes obtained for hundreds of injections. Initial results indicate that maintenance and long-term reproducibility will also be comparable with those of classical techniques.The instrument utilizes a version of the large volume on-column injector with solvent diversion described in an earlier communication, with the addition of a method for independent heating of the retention gap. This modification reduces the effects of activity in the retention gap and improves the capability of the technology to handle complex mixtures. It also increases reliability and system lifetime, fits readily into most GC ovens, is easily automated, and should be compatible with all capillary GC detectors.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 116
    ISSN: 0935-6304
    Schlagwort(e): GC-AED ; Sulfur ; FCC gasoline ; Compound-independent calibration ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The identification and quantification of sulfur-containing compounds in gasoline has become an area of interest because of impending legislation regulating total sulfur levels in these fuels. To study the effects of catalyst type and catalytic conditions on gasoline sulfur distribution, a method has been developed employing both the compound-independent and element-specific response of the atomic emission detector (AED). Calibration and quantification can be accomplished even where standards are not available, owing to the nature of the AED response.Compounds were separated on a thick film polydimethylsiloxane column. An external calibration curve was applied to the area responses of individual sulfur components in the sulfur chromatogram, and the concentrations of each were calculated. Summation of these sulfur concentrations over the gasoline range yields the total sulfur content of the gasoline.The method is applicable to the determination of these compounds in raw crude oils, finished gasolines, fluid cracking catalyst (FCC) unit gasolines, and fluid catalytic cracking “model” compound studies. A prefractionating column was employed to remove heavy (〉C13) materials; prefractionation is not, however, necessary for distilled or commercial gasoline samples. Detection limits, linearity, detector stability, and accuracy are discussed.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 117
    ISSN: 0935-6304
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 118
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 46-51 
    ISSN: 0935-6304
    Schlagwort(e): Capillary GC ; Retention time prediction ; Programmed temperature ; Linear programming ; Chlorobenzenes ; Iterative procedure ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Retention times in linear temperature programmed gas chromatography on narrow bore and megabore capillary columns have been calculated from experimental retention times measured at three isothermal temperatures: an iterative procedure performed by BASIC programs was used to obtain the values of the constants enabling the calculation of the programmed temperature retention times. Different methods of calculation have been compared.
    Zusätzliches Material: 8 Tab.
    Materialart: Digitale Medien
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  • 119
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 31-38 
    ISSN: 0935-6304
    Schlagwort(e): Efficiency, erosion of ; Non-uniform chromatography ; Linear chromatography ; Plate height, uniform ; Solute velocity ; Capacity ratio, variation ; SFC pressure drop ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In linear chromatography (i.e. chromatography performed in the absence of sample overloading), when the plate height of a column is roughly uniform along its length, variations in the velocities of solutes are the only possible causes of erosion of efficiency. The sources of these variations (variations in capacity ratio and in the density of the mobile phase, etc.) play no direct role in the erosion of efficiency except through their effect on solute velocities. In other words, what eventually causes the erosion of efficiency is merely variation in the time required for solutes to traverse equally small segments of a column. Significant erosion can only arise from abrupt and deep deceleration of solutes in one or several relatively small segments of a column.If erosion of efficiency caused by pressure gradients in linear SFC is to be large, the depth and the sharpness of the deceleration of a solute must go beyond that hitherto confirmed experimentally. Many relevant examples are analyzed graphically.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 120
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 175-181 
    ISSN: 0935-6304
    Schlagwort(e): Enantioselective gas chromatography ; 2,6-di-O-methyl-3-O-pentyl-β- and y-cyclodextrins ; α and β hydroxy acids ; Branched carboxylic acids ; Non-steroidal anti-inflammatory drugs ; Abscisic Acid ; Epoxides ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The wide range of application of 2,6-di-O-methyl-3-O-pentyl-β-and y-cyclodextrins is demonstrated by the resolution of the enantiomers of the methyl esters of chiral carboxylic acids: α and β hydroxy acids with up to 18 carbon atoms, hydroxy di- and tricarboxylic acids, and alkyl/aryl-substituted carboxylic acid methyl esters, including the plant hormone abscisic acid, insect juvenile hormones, and some non-steroidal anti-inflammatory drugs can be resolved with generally large separation factors. The new cyclodextrin derivatives also exhibit high selectivity for epoxides.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 121
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 192-193 
    ISSN: 0935-6304
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 122
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 188-191 
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; Thermostable WCOT columns ; PLOT columns ; Stainless steel ; Silicon layer for deactivation ; Simulated distillation ; PNA analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A layer of elemental silicon has been deposited on the surface of stainless steel tubing by means of chemical vapor deposition (CVD). Two kinds of capillary column were prepared from the deactivated tubing: cross-linked, silanol-terminated polydime-thylsiloxane wall coated open tubular (WCOT) columns and molecular sieve 13X porous layer open tubular (PLOT) columns. Unlike fused silica capillary columns, stainless steel WCOT and PLOT columns can be operated at temperatures in excess of 400°C. High temperature simulated distillation has been performed successfully with a macro bore WCOT column and rapid PNA (paraffin, naphthene, and aromatic) analysis with a multidimensional gas solid chromatographic (GSC) system using PLOT columns.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 123
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 193-193 
    ISSN: 0935-6304
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 124
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 194-195 
    ISSN: 0935-6304
    Schlagwort(e): Open-tubular liquid chromatography ; Liquid-liquid chromatography ; Electrochemical detection ; Phenols ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 125
    ISSN: 0935-6304
    Schlagwort(e): Supercritical fluid chromatography ; Supercritical fluid extraction ; Poly(vinyl chloride) ; Dimethyltin mercaptide ; Formic acid ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 126
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 52-52 
    ISSN: 0935-6304
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 127
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 53-55 
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; Plant extract ; Photochemical degradation ; Insecticides ; Volatile compounds ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 128
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 55-57 
    ISSN: 0935-6304
    Schlagwort(e): Liquid chromatography, HPLC ; Cyanopropyl phase ; Simple lipids ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 129
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 57-59 
    ISSN: 0935-6304
    Schlagwort(e): HPLC ; Fluorescence emission detection ; Specific dual detection ; Amperometric oxidation detection ; Polymeric reagent ; Derivatization ; Aliphatic amines ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 130
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 59-61 
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; Glass capillary micropacked columns ; SPE sorbents ; Aliphatic hydrocarbons ; Aromatic hydrocarbons ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 131
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 65-66 
    ISSN: 0935-6304
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 132
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 73-84 
    ISSN: 0935-6304
    Schlagwort(e): Sample introduction ; Injection ; Supercritical fluid chromatography ; Supercritical fluid extraction ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: New strategies for sample introduction in supercritical fluid chromatography are reviewed. Both open tubular and packed column systems are examined as the injection demands of each column type are addressed. In addition to advances made in solvent injection methods, supercritical fluid extraction (SFE) is discussed as a solventless injection technique for supercritical fluid chromatography.
    Zusätzliches Material: 19 Ill.
    Materialart: Digitale Medien
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  • 133
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 85-89 
    ISSN: 0935-6304
    Schlagwort(e): Fullerenes ; Liquid chromatography ; Mass Spectrometry ; LC-MS ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Fullerene-rich soot generated by resistive heating of graphite has been gently extracted with toluene, in order to remove some C60 and C70 compounds, followed by extraction with boiling 1,2,4-trichlorobenzene at 214°C. After filtration and removal of the solvent, the residue was re-dissolved in dichloromethane and characterized by non-aqueous reversed phase liquid chromatography coupled on-line with atmospheric pressure chemical ionization mass spectrometry. Several novel fullerenes were detected, including C72, C80, C86, and C88 as well as other fullerenes up to C108 and higher. The results indicate that chromatographic separation of large fullerene molecules can be achieved with low boiling point solvents and conventional liquid chromatographic techniques.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 134
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 95-100 
    ISSN: 0935-6304
    Schlagwort(e): Capillary GC ; Biscyanopropyl siloxane phases ; Temperature program optimization ; Computer simulation (Drylab GC) ; Fatty acid methyl esters ; Electronic pressure control ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The selectivity of capillary columns coated with biscyanopropyl siloxane stationary phases for the separation of fatty acid methyl esters has been optimized by means of computer-assisted column temperature optimization software. Temperature programming rates yielding the highest resolution in the shortest analysis time were selected for split, splitless, and on-column injection operated in the constant pressure and pressure programmed modes.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 135
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 90-94 
    ISSN: 0935-6304
    Schlagwort(e): On-column injection ; Large (100 μl) injections ; Heated retention gap ; Sample preparation ; Extraction efficiency ; Linearity ; Limit of detection ; Polynuclear aromatic hydrocarbons (PAHs) ; Industrial Waste ; Water analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: An automated large volume on-column injection technique for capillary gas chromatography (GC) with solvent divert and heated retention gap technology has been utilized to determine polynuclear aromatic hydrocarbons (PAHs) in samples of industrial plant process water. Injecting large sample volumes on-column enabled the sample preparation procedure to be simplified and provided a fast, labor-saving technique for screening water samples. Diverting approximately 95% of the solvent away from the analytical column and the detector enabled chromatography to reflect classical capillary loading and detector conditions.Simplifications include significant reduction of sample and eluent volumes used during extraction and the elimination of Kuderna-Danish evaporative concentration. System performance, such as linearity and limit of detection, were evaluated for selected PAHs. Spiked water samples were prepared in the lower μ/L range to determine extraction efficiency. Results are compared with those obtained by a reputable contract laboratory following EPA Method 625.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 136
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 101-105 
    ISSN: 0935-6304
    Schlagwort(e): Enantioselective LC (GC) analysis ; β-Cyclodextrin chiral LC-phase ; Heptakis(2,3-di-O-methyl-6-TBDMS)-β-cyclodextrin ; Chiral dihydrofuranones ; Enantiomer eluate sniffing ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The odor impression of the pure enantiomers of various chiral dihydrofuranones which are important flavor compounds has been evaluated by sniffing the well separated optical antipodes in the GC eluate from heptakis(2,3-di-O-methyl-6-TBDMS)-β-cyclodextrin as the chiral phase for capillary gas chromato-graphic separation. Liquid chromatographic separation has been achieved by the use of bonded β-cyclodextrin as the chiral stationary phase and methanol-water as eluent. Enantiomer separation in the latter was improved by addition of triethylammonium acetate to the eluent.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 137
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 116-119 
    ISSN: 0935-6304
    Schlagwort(e): Carbon layer open tubular (CLOT) columns ; Adsorption/partition separation mechanism ; Van Deemter curves ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Capillary columns coated with Carbopack materials, which provide separation by a mixed partition/adsorption mechanism or by adsorption alone, have recently been developed. The reproducibility of the columns is demonstrated and applications shown in which they provide separations which are either unique or are faster than can be achieved with the wall coated open tubular capillary columns currently available.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 138
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 113-115 
    ISSN: 0935-6304
    Schlagwort(e): Capillary GC ; GC-MS ; Headspace ; Milk ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Twenty compounds have been determined by GC-MS in polystyrene used for milk packaging. The major components identified in milk were styrene and its dimer at concentrations of 13 and 43 mg/kg, respectively. The detection limit for styrene by the equilibrium headspace method was 0.29 mg/kg. Another method used to determine the concentration of styrene and its dimer in milk was the use of acetone to precipitate the proteins and extract both the fat and the residues from the plastic packaging. The solution obtained was then directly injected into the GC. The detection limits were found to be 0.16 mg/kg for styrene and 0.28 mg/kg for the dimer. The solution injection method thus proved to be much more sensitive.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 139
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 120-120 
    ISSN: 0935-6304
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 140
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 258-261 
    ISSN: 0935-6304
    Schlagwort(e): Nomenclature ; Chromatography ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The background of the new Unified Nomenclature for Chromatography just accepted by the International Union of Pure and Applied Chemistry (IUPAC) is explained and selected highlights of the new rules are elaborated.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
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  • 141
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 262-262 
    ISSN: 0935-6304
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 142
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993) 
    ISSN: 0935-6304
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 143
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 275-278 
    ISSN: 0935-6304
    Schlagwort(e): Element-specific GC detection ; Spectrometric detection ; Microwave-induced plasma ; Detector instability ; Solvent effect on detector stability ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Capillary gas chromatography coupled to microwave-inducedplasma detection furnishes sensitivity adequate for trace analysis when the signal is monitored at a carbon emission line. Work performed with one of these systems at high electronic gain for the carbon signal has revealed solvent band widths in excess of four minutes; these impeded quantification of peaks eluting after the solvent. This report discusses two phenomena which could be related to the unexpected intensity of this solvent response: photomultiplier tube saturation and carbon deposits in the quartz plasma discharge tube.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 144
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 121-122 
    ISSN: 0935-6304
    Schlagwort(e): Sample liquid pulled out of syringe needle ; Accuracy of sample volume ; On-column injection ; Speed of injection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 145
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 123-125 
    ISSN: 0935-6304
    Schlagwort(e): Sex pheromone ; Isomeric identification ; Capillary gas chromatography ; Mass spectrometry ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 146
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 126-128 
    ISSN: 0935-6304
    Schlagwort(e): Capillary GC ; Substituted anilines ; Phenylurea herbicides ; Nitrogen selective detector (NPD) ; Water analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 147
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 129-130 
    ISSN: 0935-6304
    Schlagwort(e): HPLC ; Stationary phase ; Internal surface reversed phase (ISRP) ; One-step clean-up ; Human milk ; PCDDs ; PCDFs ; PCBs ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 148
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 130-134 
    ISSN: 0935-6304
    Schlagwort(e): Supercritical fluid chromatography ; Packed columns ; Modifiers ; Formic acid ; Formamide ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 149
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 135-136 
    ISSN: 0935-6304
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 150
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 148-152 
    ISSN: 0935-6304
    Schlagwort(e): On-line SFE-GC ; Polychlorinated biphenyls ; Human milk ; Human blood serum ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: On-line coupled supercritical fluid extraction and gas chromatography (SFE-GC) has been utilized for the determination of PCBs and other organochlorine compounds in human milk and blood serum. The procedure involved preconcentration of the sample on C18-silica sorbent in an extraction cell: after precipitation of the proteins up to 20 ml of human milk was concentrated on 0.5 g of sorbent. Serum (up to 5 ml) was applied to the C18 material without pretreatment. Basic alumina was utilized as a selective adsorbent for lipids in the on-line SFE-GC system. The method was used to analyze milk and serum spiked with 0.5 and 10 ng of Aroclor 1260 and the results compared with those obtained by liquid-liquid extraction of serum.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 151
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 289-298 
    ISSN: 0935-6304
    Schlagwort(e): Enantioselective GC ; Polysiloxane-anchored cyclodextrin stationary phase ; Chirasil-Dex-TFA ; Immobilized 2,6-di-O-alkyl-3-O-acyl-cyclodextrin ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Heptakis(2,6-di-O-methyl-3-O-trifluoroacetyl)-†-cyclodextrin has been chemically bonded to a polydimethylsiloxane via an octamethylene spacer and subsequently immobilized on to the surface of fused silica capillaries, the first time a cyclodextrin derivative with mixed substituents has been immobilized in this way. The enantioselectivity of the new chiral stationary phase has been investigated as a function of the cyclodextrin content. It was found to be higher than that reported for heptakis (2,6-di-O-methyl-3-O-trifluoroacetyl)-†-cyclodextrin or hepta-kis(2,6-di-O-methyl-3-O-acetyl)-†-cyclodextrin dissolved in polysiloxane (e.g. OV-1701). The degree of immobilization was over 90 %. The temperature stability is, however, inferior to that of Chirasil-Dex (a permethylated cyclodextrin): the maximum operating temperature is approximately 200 °C.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 152
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 328-328 
    ISSN: 0935-6304
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 153
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 312-323 
    ISSN: 0935-6304
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 154
    ISSN: 0935-6304
    Schlagwort(e): Capillary electrophoresis ; Isotachophoresis preconcentration ; Nonaqueous buffer ; Metabolism ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 155
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 157-160 
    ISSN: 0935-6304
    Schlagwort(e): HPLC ; Inductively coupled plasma MS ; Coal extracts ; Gallium porphyrins ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The HPLC-ICPMS determination of gallium porphyrins in various coal extracts is described. The HPLC-ICPMS results are compared with results obtained by HPLC-UV/VIS. The presence of gallium has been confirmed in all the porphyrin macrocycles.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 156
    ISSN: 0935-6304
    Schlagwort(e): Capillary GC ; Mycobacterium ; Single colony ; Trimethylsulfonium hydroxide (TMSH) ; Fatty acid methyl esters (FAMEs) ; Mycolic acid cleavage products (MACPs) ; Secondary alcohols ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Trimethylsulfonium hydroxide (TMSH) reproducibly converts fatty acids bound in, e.g., biomolecules such as phospholipids and/or glycerides, into the corresponding fatty acid methyl esters (FAMEs). The transesterification can be performed at room temperature in a fast single step reaction. Surprisingly, secondary alcohols and mycolic acid cleavage products (MACPs) are also released from mycobacteria under these conditions.The complex reaction mixtures containing FAMEs, MACPs, and secondary alcohols can easily be separated by high resolution temperature-programmed capillary GC. Different species of mycobacteria give rise to characteristic chromatographic patterns and the amount of lipids from a single colony of mycobacteria is sufficient for reliable identification of the bacteria. The profiles of the chromatograms match well those obtained from other sample preparation techniques.The TMSH method of identification of mycobacteria from the patterns of the gas chromatograms is faster and more sensitive than conventional methods, which also involve transesterification. The identification of mycobacterial species by microbiological culture techniques is difficult to perform and requires several weeks.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 157
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 182-187 
    ISSN: 0935-6304
    Schlagwort(e): PTV injector ; Liner design ; On-line LC-GC interfacing ; Large volume sample introduction ; Programmed temperature injection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Programmed temperature sample introduction is an attractive technique both for the introduction of large volumes of dilute samples in capillary gas chromatography and for LC-GC interfacing.In this study a new type of liner containing a porous bed of sintered glass is introduced and evaluated. Solute recoveries achieved with this liner are compared with those obtained from liners packed with Tenax TA and Thermotrap TA. An open liner containing baffles and a small plug of silanized glass wool in its upper section was used as a reference.The maximum speed of sample introduction allowable using the new liner is ca one order of magnitude higher than for the standard liner. For similar liner operating conditions the trapping efficiency is substantially improved: at a liner temperature of -30°C components with a volatility lower than or equal to that of n-tridecane are trapped quantitatively.Liners packed with trapping materials such as Tenax TA or Thermotrap TA also provide significantly improved trapping efficiencies, even when used at relatively high temperatures.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 158
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 166-168 
    ISSN: 0935-6304
    Schlagwort(e): Supercritical fluid extraction, SFE ; Complexation ; High temperature capillary GC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: It has been demonstrated that calcium montanate (a mixture of aliphatic hydrocarbons, fatty acid esters of C28-C32 acids, the calcium salts of these fatty acids, and the acids themselves) can be selectively extracted with supercritical fluids. By use of carbon dioxide, carbon dioxide containing 10% methanol, and carbon dioxide containing 10% methanol and citric acid (as a further additive), the various compound classes could be isolated with high selectivity. The addition of citric acid results in the complexation of Ca2+ and the simultaneous formation of the free fatty acids, which are soluble in the extractant.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 159
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 738-740 
    ISSN: 0935-6304
    Schlagwort(e): GC-MS ; Vitamin K1(20) ; Phylloquinone ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 160
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 741-741 
    ISSN: 0935-6304
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 161
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 685-685 
    ISSN: 0935-6304
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 162
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 62-64 
    ISSN: 0935-6304
    Schlagwort(e): Capillary electrophoresis ; Hollow fiber ; Polypropylene ; Capillary dynamic coating ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 163
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993) 
    ISSN: 0935-6304
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 164
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 69-69 
    ISSN: 0935-6304
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 165
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 215-223 
    ISSN: 0935-6304
    Schlagwort(e): Enantioselective capillary (open-tubular) SFC ; Polysiloxane-anchored cyclodextrin stationary phase ; Immobilized Chirasil-Dex ; Separation of cyclodextrin derivatives by SFC ; Non-steroidal anti-inflammatory drugs (NSAIDs) ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Immobilized polysiloxane-anchored permethyl-β-cyclodextrin (Chirasil-Dex) with a cyclodextrin content of approximately 30 % by weight, previously employed as a versatile chiral stationary phase for the separation of enantiomers by GC, has been used for the separation of enantiomers by capillary supercritical fluid chromatography (SFC). A considerable number of racemates could be resolved, e.g. aromatic alcohols, amino alcohols (TFA derivatives), and underivatized acids. Many pharmaceutical compounds were among those analyzed, including several NSAIDs (e.g. ibuprofen and ketoprofen), a steroidal drug (nor-gestrel), a barbiturate (hexobarbital), and others.Among the racemates resolved were many which cannot be analyzed by GC owing to low volatility or decomposition at elevated temperatures. For two racemates, analysis temperature and mobile phase density were systematically varied to give constant analysis times or capacity factors k. Low temperatures (ca 60 °C) yielded the best separation in term of separation factor, α, or resolution, Rs, even though higher densities had to be used. In comparison with GC, capillary SFC was able to furnish higher separation factors and similar resolution. The applicability of capillary SFC for the analysis of mixtures of cyclodextrin derivatives, e.g. those used in the synthesis of Chirasil-Dex, was, furthermore, demonstrated.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 166
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 229-233 
    ISSN: 0935-6304
    Schlagwort(e): Column liquid chromatography ; Chlorophylls and carotenoids ; Marine algae ; Polymeric ODS phase ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A method employing a wide pore polymeric reversed phase column has been developed for the separation of most of the chlorophylls and related compounds previously described as occurring in marine microalgae. The high selectivity toward molecular shape of this kind of stationary phase has enabled compounds of very similar structure, such as chlorophylls c1, c2 and Mg-divinylpheoporphyrin a5 monomethyl ester, and chlorophyll a and the phytol-substituted chlorophyll c-like pigments, which commonly coelute on monomeric bonded phases, to be resolved in a single run. Some of these pigments, formerly thought to be a single compound, have, in fact, been demonstrated to be groups of two or more. The method has been successfully applied to both algal cultures and natural sea water samples. When visible light absorbance detection was used, the method proved suitable for separation of various carotenoids.
    Zusätzliches Material: 5 Ill.
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  • 167
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 239-242 
    ISSN: 0935-6304
    Schlagwort(e): Capillary GC ; Residential furnaces ; Brown coal ; Emission condensate ; PAH derivatives ; PAH retention index ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 168
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 243-246 
    ISSN: 0935-6304
    Schlagwort(e): Toothpastes ; Gas chromatography (GC) ; Capillary electrophoresis (CE) ; Capillary ion analysis (CIA) ; Fluoride, F- ; Monofluorophosphate, FPO32- ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The quantitative CE analysis of fluorine and monofluorophosphate in toothpastes is described. Separation is performed using a Waters CIA-Pak chemistry kit with Waters Electro Osmotic Flow Modifiers on a CE instrument from Spectra Physics (Spectra-phoresis 500) at elevated temperatures up to 40 °C and at a low temperature of 10 °C. The quantitative results and the simplicity are compared for the CE method, the existing standard GC procedure described in the Official Journal of the European Communities, and the procedure employing a fluoride-ion-specific electrode.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 169
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 254-257 
    ISSN: 0935-6304
    Schlagwort(e): Enantioselective LC ; Enantioselective GC ; β-Cyclodextrin chiral LC phase ; ChiraDex® ; Chiraspher® ; Recycling chromatography ; Chiral dihydrofuranones ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Preparative resolution of the enantiomers of several chiral dihydrofuranones, known to be important flavor compounds, has been achieved by combining the use of bonded β-cyclo-dextrin as chiral stationary phase with closed-loop recycling chromatography. The purity of the separated enantiomers has been determined by chirospecific capillary GC analysis, using heptakis(2,3-di-O-methyl-6-TBDMS)-β-cyclodextrin as the chiral stationary phase.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 170
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 247-253 
    ISSN: 0935-6304
    Schlagwort(e): Capillary GC ; Splitless injection ; Mass discrimination ; Septum purge ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: An unmodified split/splitless inlet system using forward-pressure controlled pneumatics was operated in splitless injection mode with several inlet liners under a range of septum purge flow rates. The relative recovery (discrimination) of hydrocarbons ranging from n-C8 to n-C20 depended strongly upon the injected sample volume with open-ended liners at high septum purge flow rates of e.g. 50 mL/min. Little or no discrimination was observed at septum purge flows of 2-3 mL/min. The same inlet was also operated in a back-pressure regulated configuration that produced mass discrimination similar to that observed with the higher septum purge flows in the forward-pressure configuration. An inlet liner with a restricted inlet and outlet gave mass-discrimination levels independent of septum purge flow rate, but in the reverse sense of that observed with open-ended liners. Preferential volatile-component losses out of the inlet liner to the septum purge vent are principally responsible for the observed mass discrimination with openended liners, while mass-dependent losses with doubly-restricted liners seem due to slow sample evaporation.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 171
    ISSN: 0935-6304
    Schlagwort(e): Capillary GC ; Atomic emission detector ; Supercritical fluid extraction ; Organotin compounds ; Complexation ; Grignard derivatization ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The extraction of six tetraalkyltin and seven ionic organotin compounds from spiked topsoil samples with supercritical carbon dioxide and carbon dioxide modified with 5 percent methanol was investigated. Analysis of the soil extracts was performed by gas chromatography with atomic emission detection. Retention times, minimum detectable concentrations, and detector linear ranges are included for nine organotin compounds (seven of the nine compounds were derivatized with n-pentylmagnesium bromide prior to gas chromatographic analysis). A 23 factorial experimental design was used to study the effect of three variables (pressure, temperature, and extraction time) on compound recovery. The results indicate that the tetraalkyltin compounds are extracted from topsoil samples with recoveries ranging from 90 to 110 percent. Recoveries for the ionic organotin compounds ranged from 50 to 75 percent for trimethyltin chloride, triethyltin bromide, and tributyltin iodide; they were below 20 percent for dimethyltin dichloride, dibutyltin dichloride, diphenyltin dichloride, and butyltin trichloride. When sodium diethyldithiocarbamate was added to the soil samples prior to extraction, followed by extraction with carbon dioxide modified with 5 percent methanol, recoveries ranged from 70 to 90 percent for trimethyltin chloride, triethyltin bromide, dimethyltin dichloride, tributyltin iodide, and dibutyltin dichloride; recoveries were approximately 40 percent for butyltin trichloride and diphenyltin dichloride.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 172
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 279-284 
    ISSN: 0935-6304
    Schlagwort(e): Supercritical fluid fractionation ; Supercritical fluid chromatography (SFC) ; High temperature gel permeation chromatography (GPC) ; Differential scanning calorimetry ; High density (HD) polyethylene wax ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: This paper reports on the use of supercritical carbon dioxide to fractionate a low molecular weight, high density polyethylene into very narrow molecular weight distributions (MWDs). A simple extraction system was developed that allowed relatively trouble free extractions of the polyethylene samples. Fractions were collected at successively higher densities of CO2 at constant temperature and then analyzed by capillary supercritical fluid chromatography (SFC), or high temperature gel permeation chromatography (GPC) and/or differential scanning calorimetry (DSC). Fractionations were performed at three different temperatures (60,80, and 100°C). Higher temperatures were found to yield greater recoveries and higher MWDs at any given density. Reducing the increment between successive extraction steps resulted in polydispersities being reduced to nearly “monodisperse” levels. Total recoveries ranged from 12 to 33% depending on the temperature, and the highest molecular weight fraction extracted by the CO2 was centered around 1500.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 173
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 269-274 
    ISSN: 0935-6304
    Schlagwort(e): Supercritical fluid chromatography ; Flow restrictor ; Integral restrictor ; Tapered restrictor ; Frit restrictor ; Polysiloxane ; Polydimethylsiloxane, PDMS ; Polyethylene glycol, PEG ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Proper performance of the flow restrictor is of crucial importance in supercritical fluid chromatography. This is especially the case when the restrictor is the interface between the chromatographic column and a detector operating at lower pressure than the column. The performance of three types of fixed flow restrictor, the “tapered”, the “integral”, and the “frit”, was examined. The test mixtures chosen covered a range of polarities and molecular weights. Polydimethylsiloxane with an average molecular weight of 10,000 was used as a low polarity probe. Two polyethylene glycol mixtures were chosen as higher polarity probes. One consisted of a mixture of polyethylene glycol standards with average molecular weights ranging from 200 to 1450. The other polyethylene glycol mixture had an average molecular weight of 2000. The polydimethylsiloxane standard did not elute when the frit restrictor was used. Satisfactory results were obtained when the tapered and integral restrictors were employed. All three restrictors provided satisfactory results for polyethylene glycol oligomers eluting up to approximately 40.5 MPa (400 atm). However, for oligomers eluting above this pressure, the peaks merged into a broad hump with the frit restrictor, while the tapered and integral restrictors provided satisfactory separations. The integral restrictor produced more evenly spaced, more well resolved peaks at the high-pressure end of the chromatograms than did the tapered restrictor. This is shown to be due to differences in the rates of increase in mobile-phase velocity with increasing pressure for the two restrictors.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 174
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 285-288 
    ISSN: 0935-6304
    Schlagwort(e): Chiral separations ; Inversion of elution order ; Atypical temperature effect ; Atypical solvent effect ; Nonlinear van't Hoff plots ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Typically, reduction of column temperature increases the enantioselectivity of a chiral stationary phase. An instance in which progressive reduction of temperature initially reduces enantioselectivity, then inverts the elution order of the enantiomers, and finally causes enantioselectivity to increase has been observed. This behavior is related to the nature and concentration of the polar modifier in the mobile phase, and requires particular chiral phase-analyte-mobile phase combinations. A rationalization is presented as to the possible origin of this behavior. This rationale may aid in finding other examples of this temperature-dependent elution order of enantiomers and ultimately increase our understanding of chiral recognition processes.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 175
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 299-311 
    ISSN: 0935-6304
    Schlagwort(e): Capillary gas chromatography ; Derivatized cyclodextrins ; Molecular modelling ; Chiral recognition ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The results of gas chromatographic enantiomeric separations of selected non-polar and polar test solutes (limonene and 1-phenylethanol) using two different derivatives of β-cyclodextrin, permethyl-β-CD and 2,3-dimethyl-tert-butyldimethylsilyl-β-CD (PMCD and TBCD) are interpreted in combination with the conclusions from molecular modelling calculations based on docking experiments. A comparison of the two selectors which were used as solution in a polysiloxane matrix (OV 1701) indicated that the less flexible TBCD which is blocked on one side by the bulky tert-butyldimethylsilyl groups seems to possess advantages for certain chiral separations, especially of the non-polar type. The special properties of TBCD as selector are also demonstrated by chiral separations of other compounds.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 176
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 169-174 
    ISSN: 0935-6304
    Schlagwort(e): Experimental design optimization ; Supercritical fluid chromatography ; Aromatic content ; Petroleum cuts ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A experimental design optimization method is demonstrated for evaluation of the resolution of the performance mixture used in the proposed ASTM test to determine the aromatic content of aviation fuels. The method uses a Doehlert experimental matrix test to optimize the resolution and analysis time by varying the pressure and temperature of the supercritical carbon dioxide mobile phase. The separation between saturated and aromatic compounds was optimized using only seven experiments. With this procedure, the analysis time required for determination of the total aromatic content of more complex samples can be reduced to less than 10 min.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 177
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 645-650 
    ISSN: 0935-6304
    Schlagwort(e): Capillary GC ; Multidimensional gas chromatography ; Heart cutting ; Selectivity optimization ; Retention indices ; Real-time calculation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In chromatography the separation power expressed in terms of peak capacity can be greatly enhanced by multidimensional techniques. The most important aspect of multidimensional chromatography is the precise location of the heart-cut window. Very often the reliability of this positioning is ensured by applying relatively large heart-cuts; this reduces the intrinsic selectivity offered by the technique.The best way of locating peaks in chromatography is by means of retention indices. This technique can also be used in multidimensional chromatography. A method is described whereby the heartcut window in multidimensional gas chromatography (MDGC) can be defined precisely.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 178
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 642-644 
    ISSN: 0935-6304
    Schlagwort(e): Multidimensional GC-MS ; Enantioselective GC ; Flavor analysis ; Theaspiranes ; Theaspirones ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: This paper reports the differentiation between the enantiomers of theaspiranes and theaspirones, potent flavor compounds widely used in the flavor industry. Optically pure reference compounds of isomeric theaspiranes were obtained by enantioselective synthesis. Enantiomerically pure reference theaspirones were isolated from quince fruit; their absolute stereochemistry was assigned by CD spectroscopy. For both types of compounds the order of elution was elucidated by using authentic reference compounds. These data enabled the determination of the enantiomeric distribution of both types of compounds in a variety of plant tissues.Because of the complexity of the natural flavor isolates, compounds were identified by mass spectrometry after multidimensional gas chromatography employing a Sichromat 2 double oven chromatograph. After separation of the target compounds on the first, achiral, column (DB-5), they were transferred to a chiral column (C-Dex B) for determination of the enantiomeric distribution. Multiple ion detection (MID) enabled the determination of the enantiomeric distribution even for complex mixtures containing the target compounds at extremely low levels.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 179
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 663-665 
    ISSN: 0935-6304
    Schlagwort(e): Micro-LC ; Amperometric detector ; Nitrophenols ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: An amperometric-type electrochemical detector is proposed for use in capillary HPLC. Its cell (volume 60 nl) contains a cylindrical working electrode for detecting the presence of electroactive compounds. The noise level is 3-5 pA depending on the potential. The minimum detectable concentrations of the o-, m-, and p- isomers of nitrophenol (after separation of a 20 μl sample on a fused silica column) lies between 4 and 18 ng/l. The relative standard deviation of the height of the chromatographic peaks of phenols present at concentrations of 10 ppb does not exceed 0. 08 (n = 5).
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 180
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 660-662 
    ISSN: 0935-6304
    Schlagwort(e): Atomic emission detection ; Capillary GC ; Environmental analysis ; Element selective detection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Capillary GC coupled to an atomic emission detector (AED) provides a powerful new hyphenated technique for the separation and characterization of complex mixtures and compounds. The AED provides simultaneous and truly specific multi-element detection. The specificity of detection reduces the need for the complex sample pretreatment procedures which are necessary to reduce the interference from co-eluted substances which is experienced with detectors such as the FID and the ECD. A range of environmentally significant problems has been studied, including PCB analysis, the characterization of the reaction products of a novel waste treatment process, and the profiling of sulfur-containing species formed by the pyrolysis of various types of coal.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 181
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 674-676 
    ISSN: 0935-6304
    Schlagwort(e): Capillary GC ; Atomic emission detection ; Absolute measurements ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 182
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 677-678 
    ISSN: 0935-6304
    Schlagwort(e): Capillary GC ; Dihydropyridine ; Calcium antagonist ; Plasma ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 183
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 679-682 
    ISSN: 0935-6304
    Schlagwort(e): GC-ECD ; Sample preparation ; Derivatization ; Acetylation ; Soil ; Chlorobenzenes ; PCBs ; Chlorophenols ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 184
    ISSN: 0935-6304
    Schlagwort(e): Capillary GC ; Derivatized cyclodextrins ; Chiral recognition ; Polysiloxane matrices ; Selector concentration ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The enantioselectivity of three chiral selectors, 6-t-butyldimethyl-silyl-2,3-dimethyl-α-, β- and γ-cyclodextrin (TB-α-CD, TB-β-CD, TB-γ-CD), are compared and discussed for a range of chiral test compounds. TB-β-CD in particular offers high enantioselectivity for a variety of chiral compounds and has the special property of excellent solubility in different alkylpolysiloxanes, including the weakly polar variety, because of its weak self-association. To investigate the influence of the polarity of polysiloxane matrices this selector can be used at a wide range of concentrations in the most suitable polysiloxane matrices and at low separation temperatures without impairment of resolution by peak broadening and symmetry distortion.
    Zusätzliches Material: 10 Ill.
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  • 185
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 708-712 
    ISSN: 0935-6304
    Schlagwort(e): Reversed phase HPLC-GC-MS ; On-line derivatization ; Diazomethane ; MSTFA ; Bromination ; Loop-type interface ; Structure elucidation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Degradation products obtained under severe alkaline stress of the drug substance ENA 713, a compound developed for the treatment of DAT (dementia of the Alzheimer type), have been identified by on-line coupled reversed phase HPLC-GC-MS as 3-hydroxyaceto-phenone and 3-hydroxystyrene. Their structures were proven by mass spectroscopic investigation of the products obtained by on-column derivatization during LC-GC transfer. On-column trimethyl-silylation and bromination of the degradation products during the transfer were achieved by the introduction of the reagent via the loop-type interface. The usefulness of the technique was further demonstrated by the on-column methylation of carboxylic acids with diazomethane solution (using naproxen as model compound). First results are also given of the use of the liquid-liquid extraction unit of the LC-GC interface for extractive derivatization during reversed phase HPLC-GC-MS transfer.
    Zusätzliches Material: 8 Ill.
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  • 186
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 725-730 
    ISSN: 0935-6304
    Schlagwort(e): HPLC ; Capillary GC ; Triacyl-sn-glycerol ; Grignard reaction ; Pancreatic lipase ; Fatty acids ; Olive oil ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The triacylglycerol composition of olive oil samples has been determined by stereospecific analysis after partial hydrolysis with ethyl magnesium bromide, derivatization, preparative chiral HPLC, transesterification, and GC quantitation of fatty acid methyl esters. The data obtained for position sn-2 were compared with those from capillary GC analysis of monoacyl sn-2-glycerols after enzymatic lipolysis of triacylglycerols.The determination of triacylglycerols collected by silver ion HPLC and quantified (as fatty acid methyl esters) by GC, together with direct GC analysis on a polar column, have then furnished a comprehensive picture of the triacylglycerol content of olive oil.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 187
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 736-737 
    ISSN: 0935-6304
    Schlagwort(e): Aminophenols ; Ion-pair liquid chromatography ; Electrochemical detection ; Quinobenzoxazine ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 188
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 376-378 
    ISSN: 0935-6304
    Schlagwort(e): Resolution of atropisomers ; Alkylated biphenyls ; Polychlorinated biphenyls (PCBs) ; Dynamic gas chromatography ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Selectively alkylated cyclodextrins have been used to resolve the enantiomers of 2,2′ alkylated biphenyls. The configurational stability of 2,2′-dimethyl and 2,2′-diethyl biphenyls is insufficient for gas chromatographic separation even at ambient temperature. 2-Isopropyl-2′-t-butyl- and 2,2′-di-t-butylbiphenyl are configurationally stable under the conditions applied, whereas 2,2′-diisopropyl- and 2,2′-bis(trifluoromethyl)biphenyl show temperature-dependent interconversion of the enantiomers during chromatography. The gas chromatographic separation of the enantiomers of some ortho trichlorinated biphenyls carrying 4, 5, and 6 chlorine substituents has been demonstrated for the first time.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 189
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 384-385 
    ISSN: 0935-6304
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 190
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 386-387 
    ISSN: 0935-6304
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 191
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 388-390 
    ISSN: 0935-6304
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 192
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993) 
    ISSN: 0935-6304
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 193
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 413-418 
    ISSN: 0935-6304
    Schlagwort(e): On-line extraction-GC ; Phase-switching ; Open-tubular traps ; Stationary phase swelling ; Large volume injection ; PTV ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The applicability of open-tubular trapping columns for on-line extraction-capillary GC analysis is evaluated. The extraction step involves sorption of the analytes from water into the stationary phase of an open-tubular column, removal of the water by purging the trap with nitrogen, and desorption of the analytes with an organic solvent. The effect of swelling of the stationary phase with organic solvents on the retention power of the trap is studied. When using pentane or hexane as swelling agent breakthrough volumes of at least 10 ml can easily be obtained for non-polar compounds. For a number of medium polarity compounds breakthrough volumes of 5 ml can be achieved when chloroform is used as the swelling agent. The required drying time is less than 1 minute. Quantitative desorption requires only 75 μl of organic solvent. Solvent elimination prior to transfer to the GC column is carried out using a PTV injector and a multidimensional GC system. The system is applied for the analyses of river water, urine, and serum samples.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 194
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 422-424 
    ISSN: 0935-6304
    Schlagwort(e): Capillary gas chromatography ; Offset printing ; Residual solvent ; Solvent retention ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A method was developed for measuring the residual solvent content in a dried offset print. The method is based on hexane extraction. The presence of additives and resins in the printing inks necessitated purification of the extract on an aluminum oxide column. In the study concerning the effect of the heatset web offset drying process on print quality, a distinct correlation was found between the residual solvent content of the print and the drying parameters.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 195
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 419-421 
    ISSN: 0935-6304
    Schlagwort(e): Liquid chromatography ; Indirect conductimetric detection ; Cyclodextrin ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Indirect conductimetric detection of cyclodextrins (CDs) was investigated in liquid chromatography (LC). The mobile phase contained an electrolytic substance which maintained high background, and CDs were indirectly detected owing to a depression of the background signal due to dilution of the mobile phase by the analyte molecules. The dynamic reserve, defined as the ratio of the background to its noise level, was (1-2) × 105, and the detection limits at S/N = 3 were 23-40 ng for CDs when a microcolumn LC system was employed.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 196
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 407-412 
    ISSN: 0935-6304
    Schlagwort(e): SFE ; HRGC-MS ; Chlorinated dibenzofurans ; Extraction of fly ash ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A multiresidue supercritical fluid extraction procedure for chlorinated dibenzofurans (PCDFs) has been optimized as an efficient method for the determination of these compounds in fly ash samples. The results were compared with those obtained by Soxhlet extraction. Extracts from the two procedures were analyzed by gas chromatography-mass spectrometry (HRGC-MS) Statistical analysis of the results confirmed that supercritical fluid extraction provides data with a relative standard deviation of less than 10% while Soxhlet extraction data show a much greater spread.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 197
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 425-428 
    ISSN: 0935-6304
    Schlagwort(e): On-line SFE-GC ; Split/splitless interface ; Quantitative aspects ; Discrimination ; Reproducibility ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The quantitative aspects of on-line supercritical fluid extractioncapillary gas chromatography (SFE-GC) with a split/splitless injector as interface were investigated. Special attention was paid to the discrimination behavior and the reproducibility of the split/splitless interface. A simple experimental set-up is proposed that allows accurate quantitation in on-line SFE-split GC. The results obtained in on-line SFE-GC compare favorably with those from conventional GC with split injection. Discrimination was found to be absent when working at sufficiently high interface temperatures. Finally, the effects of the carbon dioxide flow rate, interface temperature and split ratio on both discrimination and reproducibility were studied.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 198
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 429-432 
    ISSN: 0935-6304
    Schlagwort(e): Sample evaporation inside injector ; Injector liners ; Laminar cup splitter ; Glass wool in injector insert ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Completeness of sample evaporation in conventional vaporizing injection is a problem for many samples and calls for measures to arrest the sample liquid in the space between the needle exit and the column entrance. A visual testing procedure reveals that a small plug of loose glass or quartz wool ensures complete evaporation in all instances. Obstacles built into the liner also stop liquid, provided they force the sample to pass through narrow channels. Other important design characteristics concern access to the narrow channel. Evaporation in a packed insert usually occurs from a surface, whereas the sample hardly touches surfaces in the instance of an insert with obstacles. Evaporation from a packing is, in fact, more reliable, but creates more problems concerning inertness.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 199
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 433-436 
    ISSN: 0935-6304
    Schlagwort(e): Capillary electrophoresis ; Miniaturization ; Planar chip technology ; Silicon and glass microstructures ; Small volume optical detector cell ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Miniaturization of separation columns implies equally reduced vol- umes of injectors, detectors, and the connecting channels. Planar chip technology provides a powerful means for the fabrication of micron-sized structures such as channels. This is demonstrated by two examples. An optical absorbance detector chip exhibits the expected behavior of a 1 mm optical path length cell despite its volume of 1 nL. A capillary electrophoresis device allows integrated injections of 100 pL samples, efficiencies of 70,000 to 160,000 theoretical plates in 10 to 20 seconds, and external laser-induced fluorescence detection at any capillary length of choice between 5 and 50 mm.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 200
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 441-444 
    ISSN: 0935-6304
    Schlagwort(e): High resolution capillary gas chromatography ; High resolution gas chromatography-mass spectrometry ; Essential oil analysis ; Ylang-ylang oil composition ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Samples of essential oil from Colombian ylang-ylang trees were analyzed by means of HRGC, HRGC-MS, IR and 1H- and 13C-NMR. 57 components were detected, 51 of which were positively identified. Camphene and anethol were identified in ylang-ylang essential oil for the first time. Among the composition-determining variables studied (extraction time, part of the flower, and flower freshness), the extraction time and the flower condition (fresh versus dry) were found to have the largest incidence in the quality of the essential oil.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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