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  • 1990-1994  (7,464)
  • 1980-1984  (4,319)
  • 1975-1979  (3,254)
  • Analytical Chemistry and Spectroscopy  (15,035)
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Year
  • 101
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994), S. 147-154 
    ISSN: 0886-9383
    Keywords: RAFA ; GRAM ; Eigenvalue problem ; Complex solution ; Degenerate solution ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rank annihilation factor analysis (RAFA) is a method for multicomponent calibration using two data matrices simultaneously, one for the unknown and one for the calibration sample. In its most general form, the generalized rank annihilation method (GRAM), an eigenvalue problem has to be solved. In this first paper different formulations of GRAM are compared and a slightly different eigenvalue problem will be derived. The eigenvectors of this specific eigenvalue problem constitute the transformation matrix that rotates the abstract factors from principal component analysis (PCA) into their physical counterparts. This reformulation of GRAM facilitates a comparison with other PCA-based methods for curve resolution and calibration. Furthermore, we will discuss two characteristics common to all formulations of GRAM, i.e. the distinct possibility of a complex and degenerate solution. It will be shown that a complex solution-contrary to degeneracy-should not arise for components present in both samples for model data.
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  • 102
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 103
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994), S. 179-180 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 104
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994), S. 287-292 
    ISSN: 0886-9383
    Keywords: Rank annihilation ; Principal components ; Procrustes rotation ; Multivariate analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that the DATa ANalysis (DATAN) algorithm can be expressed in terms of rank annihilation factor analysis (RAFA). Subsequent advances in RAFA are applied to DATAN to eliminate the problems and restrictions associated with DATAN. The extension of DATAN in terms of the trilinear decomposition algorithm is discussed.
    Additional Material: 1 Ill.
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  • 105
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 106
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994) 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 107
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994), S. 365-370 
    ISSN: 0886-9383
    Keywords: Censored data ; ECM and EM algorithms ; Incomplete data ; Maximum likehhood ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The purpose of this short communication is to illustrate the use of conditional maximization (CM) in chemometric applications. The CM algorithm is useful in reducing the computational complexity when a high-dimensional and complicated maximization problem arises from fitting chemometric models. It can also be efficiently combined with the expectation-maximization (EM) algorithm for handling incomplete data, a problem that sometimes arises when only a part of the intended data can be collected. Three models from fluorescence spectroscopy are used for illustration.
    Type of Medium: Electronic Resource
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  • 108
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994) 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 109
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994), S. 423-437 
    ISSN: 0886-9383
    Keywords: Resolvability ; Evolutionary factor analysis ; Variable selection ; Window factor analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method for selecting variables in the non-sequential direction of a two-way data matrix (e.g. wavelength in diode array HPLC) is described. Composition 1 and 2 resolvability indices are calculated according to the size of eigenvalues of uncentred data matrices as a window is moved along the sequential direction. A double-window technique is then performed where resolvability indices are calculated as a window is moved along the non-sequential direction. Some regions have higher resolvability indices and hence are more useful for resolution. Variables are ranked according to resolvability. Two simulations are analysed and it is shown that it is possible to obtain good resolution on a small subset of the original variables.
    Additional Material: 5 Ill.
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  • 110
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994), S. i 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 111
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994), S. 45-63 
    ISSN: 0886-9383
    Keywords: GRAM ; GSVD ; Propagation of errorS ; Correlated noise ; Uncorrelated noise ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effects of correlated and uncorrelated random errors on the precision of predicted quantitative and qualitative information obtained by analysis with the generalized rank annihilation method (GRAM) are shown. These are discussed in terms of propagation of errors through the algorithm. The effects of colinearity, noise level and noise distribution are compared and discussed.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 112
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994), S. 97-98 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 113
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994) 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 114
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994), S. 155-168 
    ISSN: 0886-9383
    Keywords: Trilinear models ; Tensorial resolution ; PARAFAC ; Swamps ; Two-factor degeneracy ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The alternating least squares PARAFAC algorithm is a useful tool for resolving trilinear three-way data arrays. Occasionally, however, it becomes bogged down for many iterations in the vicinity of a poor quality resolution before moving on to a much superior optimum fit. We investigate this behavior in a simulation study and suggest ways of overcoming the obstacles it presents.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 115
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994), S. 205-219 
    ISSN: 0886-9383
    Keywords: Fractional factorial design ; Significant effects ; ANOVA ; Probability plotting ; Bayes plot ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper presents a method for identifying significant effects in fractional factorial designs. The method is based on comparing functions of the estimated effects with a scale invariant reference distribution. The method is illustrated and compared with alternative techniques on a dataset from processed cheese production. The method corresponded well to other methods (probability plotting and Bayes plot) that do not make use of error estimates. These methods were better than F-tests with few (two or four) degrees of freedom for error.
    Additional Material: 2 Ill.
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  • 116
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994) 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 117
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994), S. 245-261 
    ISSN: 0886-9383
    Keywords: Factor analysis ; Spectral resolution ; Two-dimensional luminescence ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A factor analysis algorithm that estimates the spectra of mixture components using the set of most dissimilar rows and/or columns is described and illustrated. This algorithm uses the distance as a measure of spectral similarity and is suitable for application to a variety of the bilinear matrix-formatted data types produced by hyphenated and multidimensional analytical techniqes. The algorithm requires that the data matrix contain at least one row or column that corresponds to the pure spectrum of each component to effect accurate spectral resolution. The performance of the method is illustrated using the resolution of excitation and emission spectra of up to four components from experimental fluorescence excitation-emission matrices (EEMs). In the case of the EEM, characteristic bands in an emission spectrum effect resolution of the excitation spectrum of the corresponding component, while characteristic bands in an excitation spectrum lead to resolution of the corresponding emission spectrum. The use of the set of most dissimilar rows and columns to evaluate the degree of overlap in the component spectra and compare the quality of row and column solutions is also described.
    Additional Material: 6 Ill.
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  • 118
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994), S. 293-294 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 119
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994), S. 295-296 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 120
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994), S. 303-303 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 121
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994), S. 373-373 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 122
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994), S. 445-446 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 123
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 17 (1994), S. 15-19 
    ISSN: 0935-6304
    Keywords: HPLC ; Surfactants ; Sorbitan esters ; Span ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Sorbitan ester surfactants are very complicated mixtures. An improved and simple reversed phase high performance liquid chroma tographic (HPLC) method employing a C18 column has been developed for the rapid separation of sorbitan ester surfactants and the quantitative determination of the distribution of sorbitan mono-, di-, tri-, and tetraester fractions. The sorbitan ester distribution of the six Span and Arlacel surfactants studied was calculated using relative response factors obtained from analysis of pure glycerides of fatty acids. The effects of mobile phase composition on the accuracy and reliability of the distribution values calculated for the sorbitan esters were investigated.
    Additional Material: 3 Ill.
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  • 124
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 17 (1994), S. 22-24 
    ISSN: 0935-6304
    Keywords: High resolution gas chromatography, HRGC ; Sulfur chemiluminescence detection (SCD) ; Sulfur gases ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three different types of SCD combustion source have been evaluated for use in the chromatographic analysis of atmospheric sulfur compounds. The conventional FID source and the newer inverted burner source were found to be less sensitive and less stable than the flameless design. Overall, the flameless source was superior for use with HRGC-SCD.
    Additional Material: 4 Ill.
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  • 125
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 126
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 127
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 17 (1994), S. 53-55 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 128
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 17 (1994), S. 49-50 
    ISSN: 0935-6304
    Keywords: Supercritical fluid chromatography ; Automated injection ; Solvent venting ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 129
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 17 (1994) 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 130
    ISSN: 0935-6304
    Keywords: Supercritical fluid chromatography (SFC) ; Edible oils ; Traditional Chinese medicines ; Characterization ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A home-made supercritical fluid chromatograph fitted with a capillary micropacked column and equipped with FID detection has been used to separate the components of silicone DC-200, beeswax, tea oil, cod-liver oil, rancid butter, and several traditional Chinese medicines such as Honghua oil, Jiuxin oil, and Wanhua oil.
    Additional Material: 9 Ill.
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  • 131
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 17 (1994), S. 91-94 
    ISSN: 0935-6304
    Keywords: Capillary GC ; Thermal cold trapping (TCT) ; Volatile compounds ; Experimental design ; Optimization ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A central composite design has been used to improve the extraction performance of a dynamic headspace method; extraction yield was evaluated on a homogeneous sample of cheese powder. The volatile compounds were stripped from the sample with nitrogen and adsorbed on a Tenax trap, analysis being performed with a thermal cold trapping injector connected directly to a capillary GC. Three variables (sample temperature, extraction time, and nitrogen flow rate) were investigated, and a quadratic model with interactions was postulated. Twenty experiments was performed, each producing five responses. It was shown that the best conditions for the extraction procedure were those characterized by the highest values of the three variables investigated.
    Additional Material: 4 Ill.
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  • 132
    ISSN: 0935-6304
    Keywords: Capillary SFC ; Solid phase extraction ; Quantitative analysis ; Salt-water ; Surfactants ; Span surfactants ; Sorbitan esters ; Hydrophilic-lipophilic balance (HLB) ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A rapid, simple and quantitative approach to the separation and identification of sorbitan ester surfactants has been developed using capillary supercritical fluid chromatography (SFC). The sorbitan ester surfactants were well separated into five groups: starting materials and mono-, di-, tri-, and tetraesters, with each group consisting of a number of peaks representing different isomers. High purity glycerides of fatty acids were employed to estimate the relative response factors of sorbitan esters, and reliable group-wise integration served for quantitation of the distribution of sorbitan fatty acid esters. A very important parameter, hydrophilic-lipophilic balance (HLB), which describes the hydrophilic and hydrophobic characteristics of surfactants, could be correlated with the distribution of the sorbitan esters. A combination of solid-phase extraction (SPE) and SFC was used to separate, concentrate, and analyze Span-20 from salt-water samples. In comparison with the HPLC method, capillary SFC broadens the scope of the technique to encompass high molecular weight sorbitan polyesters while maintaining high separation efficiency.
    Additional Material: 2 Ill.
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  • 133
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 17 (1994), S. 99-101 
    ISSN: 0935-6304
    Keywords: Capillary zone electrophoresis (CZE) ; Chiral separation ; Separation of enantiomers ; Cyclodextrins ; β-Blockers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 5 Ill.
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  • 134
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 17 (1994), S. 116-118 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 135
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 17 (1994), S. 119-119 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 136
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 17 (1994), S. 20-21 
    ISSN: 0935-6304
    Keywords: Capillary GC ; GC-MS ; Gorse pyrolytic oil ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermochemical conversion of biomass produces solid charcoal, gaseous fuels, and condensable oils. Because these oils vary widely in composition depending on the cellulosic feedstock and the operating conditions used, analysis of the oils is necessary in order to determine the best ways of utilizing or disposing of them. The major components of the organic oil from pyrolysis of gorse have been characterized by capillary gas chromatography - mass spectrometry. A qualitative study of the aqueous oil from the same source has also been attempted.
    Additional Material: 2 Tab.
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  • 137
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 17 (1994), S. 25-30 
    ISSN: 0935-6304
    Keywords: GC ; Dynamic headspace analysis ; Capillary columns ; Flavor ; Volatile flavor compounds ; Dairy products ; Cheese ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The aim of this study was to test the suitability and performance of various stationary phases and column dimensions for dynamic headspace gas chromatography of food aromas. The trials were performed using an aqueous test mixture containing thirty seven volatile flavor components of intense aroma, and a sample of ripe Swiss Emmental cheese.The best performance with both samples was obtained with a capillary column coated with a thick film of polydimethylsiloxane. This column resolved the greatest number of compounds in the cheese sample and resulted in the overlapping of one pair of peaks only from the test mixture. Because of its other advantages, i. e. high capacity owing to its film thickness, and insensitivity to the high moisture content of some samples or traces of oxygen in the carrier gas, the polydimethylsiloxane column appears suitable for the analysis of the volatile and highly polar compounds present in complex mixtures such as food aroma.
    Additional Material: 2 Ill.
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  • 138
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 17 (1994), S. 31-36 
    ISSN: 0935-6304
    Keywords: Capillary GC ; Graphitized carbon black ; Carbon layer open tubular columns ; Column polarity ; Retention times prediction ; Programmed temperature GC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polarity of carbon layer open tubular (CLOT) columns coated with a layer of non-porous graphitized carbon black (Carbopack B) modified with an appropriate amount of polar polyglycol liquid phase has been evaluated and compared with that of standard polar (Supelcowax-10) and non-polar (SPB-1) bonded phase open tubular columns. The efficiency and selectivity were measured at various temperatures and the polarity of the columns was evaluated by use of McReynolds' constants and the difference in apparent carbon number, ΔC of linear alkanes and alcohols. The polarity of the CLOT column was found to depend on temperature, and changing the analytical conditions therefore enabled the separation of compounds of different polarity whose reciprocal position and resolution were affected by temperature. The application of calculation methods which enable programmed temperature retention times to be predicted from isothermal data was also found to be possible when the polarity of the CLOT column changes with temperature.
    Additional Material: 7 Ill.
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  • 139
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 17 (1994), S. 47-48 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 140
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 17 (1994), S. 48-48 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 141
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 17 (1994), S. 184-186 
    ISSN: 0935-6304
    Keywords: Chiral capillary GC ; Linalyl acetate ; Bergamot ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 142
    Electronic Resource
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 17 (1994) 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 143
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 17 (1994), S. 197-202 
    ISSN: 0935-6304
    Keywords: GC and GC-MS ; HPLC ; SFC ; TLC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Practically all the conventional chromatographic techniques are used in the characterization of the highly complex mixtures of organic compounds occurring in fuels, heavy fractions, and crude oils. This paper surveys the techniques employed for class determination, preparative fractionation of the main classes, and determination of subgroups after class fractionation.
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  • 144
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 17 (1994), S. 217-222 
    ISSN: 0935-6304
    Keywords: Size exclusion chromatography ; Gas chromatography - atomic emission detection ; Sample pretreatment ; Metalloporphyrins ; Crude oil ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Size exclusion chromatography (SEC) has been demonstrated to be an effective and reproducible sample pretreatment procedure for removal of heavy oil matrices prior to GC-AED analysis of metalloporphyrins, and for the resolution of volatile metal species into clean and defined fractions. This paper also discusses the results obtained by SEC for determination of the distribution of metallopor-phyrins in crude oils and the correlation between total metal, metal-loporphyrin, and total distillable metal content.
    Additional Material: 9 Ill.
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  • 145
    ISSN: 0935-6304
    Keywords: Nitrogen compounds ; Alkylcarbazoles ; Analytical TLC ; Oil migration ; Crude oils ; Petroleum source rocks ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The results are reported of a range of laboratory chromatographic fractionation experiments with synthetic model compounds and a petroleum pyrrolic nitrogen fraction. Reversed phase separation of pyrrolic nitrogen compounds was governed mainly by the number of carbon atoms in the molecule, with little selectivity toward different positional isomers, whereas normal phase separation of the compounds could be explained in terms of steric effects related to alkylation position. Comparison of experimental results from model compounds with observations made previously using sets of natural samples taken from sedimentary basins clearly suggests adsorptive interactions between organic and mineral phases are involved in the compositional fractionation of pyrrolic nitrogen compounds in petroleum during migration. Detailed studies of the effects of petroleum migration on the molecular distribution of petroleum pyrrolic nitrogen compounds may provide useful, quantifiable, migration-related geochemical parameters.
    Additional Material: 7 Ill.
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  • 146
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    Journal of High Resolution Chromatography 17 (1994), S. 245-250 
    ISSN: 0935-6304
    Keywords: Fischer-Tropsch waters ; Alcohols in water ; Carboxylic acids in water ; Aldehydes in water ; Ketones in water ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper describes a quantitative technique for the determination of organic constituents in Fischer-Tropsch by-product waters. Temperature-programmed gas chromatography on derivatized bonded polar capillary columns provides the required separation that permits reliable quantitation of individual compounds. A preliminary combined gas chromatographic-mass spectrometric survey to identify the components present in Fischer-Tropsch by-product waters is presented. The elution order of 58 identified components is tabulated. Components identified in a typical Fischer-Tropsch by-product water include C1-C9 linear and branched alcohols, C3—C8 ketones, C2—C6 carboxylic acids, and C2—C4 linear aldehydes.
    Additional Material: 3 Ill.
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  • 147
    ISSN: 0935-6304
    Keywords: High temperature capillary GC ; SPI injector ; Cold on-column injector ; Paraffin deposition ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: HTHRGC was found essential for optimizing representative preparation of high molecular weight samples and enabling fingerprinting of heavy fractions of crude oils and associated paraffinic deposits in production pipelines. Laboratory experiments aimed at simulating the process of paraffin deposition could also be easily evaluated. A comparative investigation of the performance of cold on-column and SPI (PTV type) injectors, in conjunction with high temperature capillary columns, for analysis of high molecular weight fractions, was also conducted during the course of this work.
    Additional Material: 6 Ill.
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  • 148
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    Journal of High Resolution Chromatography 17 (1994), S. 271-276 
    ISSN: 0935-6304
    Keywords: High boiling petroleum fractions ; Polar petroleum compounds ; Compound class separation ; Normal phase HPLC ; On-line LC-MS ; Low voltage electron-impact ionization ; High resolution mass spectrometry ; Deuterated ammonia chemical ionization ; ‘Neutral’ and ‘basic’ nitrogen fractions ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chromatography on Attapulgus clay and on silicic acid has been used to isolate ‘neutral’ and ‘basic’ nitrogen fractions from the 650-1050 °F distillate of an off-shore Californian crude oil. These polar compounds were subjected to on-line liquid chromatography - mass spectrometric (LC-MS) analysis using low voltage electron-impact ionization high resolution mass spectrometry (LVEI HRMS) and deuterated ammonia chemical ionization (ND3 Cl) to determine the molecules' elemental composition and number of exchangeable hydrogen atoms. On-line separation of heavy oils into saturated, 1-4 ring aromatic, and polar compounds was performed by normal phase high performance liquid chromatography (HPLC) on a dinitroanilinopropyl (DNAP) silica column.
    Additional Material: 10 Ill.
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  • 149
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    Journal of High Resolution Chromatography 17 (1994), S. 212-216 
    ISSN: 0935-6304
    Keywords: SFE ; SFC ; Hydrocarbon group separation ; Polynuclear aromatic hydrocarbons ; Total petroleum hydrocarbons ; Simulated distillation ; Polymer additives ; Sulfur chemiluminescence detection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The use of supercritical fluid technology for sample preparation and analysis in the petroleum industry will be described using various examples including: separation of petroleum fuels into hydrocarbon classes, determination of polynuclear aromatic hydrocarbon in soils and petroleum fuels, characterization of fuel-contaminated soil, assessment of fuel boiling point distribution, determination of polymer additives, and characterization of shale rock and drilling mud.
    Additional Material: 5 Ill.
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  • 150
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    Journal of High Resolution Chromatography 17 (1994), S. 223-229 
    ISSN: 0935-6304
    Keywords: Atomic emission detection ; High temperature GC ; GC-AED ; Microwave-induced plasma ; Metalloporphyrins ; Selective detection of metals ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: High temperature gas chromatography-atomic emission spectroscopy is used for the detection of vanadyl, nickel, and iron porphyrins in crude oils. The operational variables are investigated with regard to the effects on performance in high temperature GC-AED. Under optimal conditions, the method provides charactersitic metal distributions for oils from different sources. The method is also advantageous in the study of decomposition of petroleum metal species. Several crude oils were analyzed for the content of the distillable metals in comparison with total metals as determined by a direct spectroscopic method.
    Additional Material: 10 Ill.
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  • 151
    ISSN: 0935-6304
    Keywords: Enantioselective GC ; Sesquiterpene hydrocarbons ; Cyclodextrin derivatives ; Essential oils ; Liverworts ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A number of sesquiterpene hydrocarbons commonly occurring in essential oils has been prepared as racemic mixtures by chemical synthesis. Preparative gas chromatography with selectively per-O-alkylated cyclodextrins has been employed for the isolation of enantiomeric mixtures or pure enantiomers from the essential oils of higher plants and liverworts (Hepaticae). The enantiomers of α-curcumene, α- and β-bisabolene, β-elemene, δ-elemene, α-copaene, δ-cadinene, cis- and trans-calamenene, and bicyclogermacrene could be resolved by enantioselective gas chromatography on capillary columns coated with cyclodextrin derivatives. The enantiomeric composition of these sesquiterpene hydrocarbons in various essential oils was determined.
    Additional Material: 7 Ill.
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  • 152
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    Journal of High Resolution Chromatography 17 (1994), S. 335-338 
    ISSN: 0935-6304
    Keywords: Capillary GC ; Specific detectors ; ECD:NPD response ratio ; ECD:FPD response ratio ; Retention indices ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ratio of the responses of two different specific detectors to a single compound has, when used in conjunction with the compound's retention index, been investigated as an identification criterion for the compound. The ECD:NPD and ECD:FPD response ratios have been used for the identification of some pesticides. Analyses were performed with a single column - dual parallel detection - personal computer system.The reliability of the detector response ratio (DRR) was demonstrated by the consistency of detector response with time, and the influence of the quantity of analyte and of the chromatographic operating conditions. These factors were selected in the expectation that the technique could be used for routine trace analysis.
    Additional Material: 2 Ill.
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  • 153
    ISSN: 0935-6304
    Keywords: Multidimensional enantioselective GC ; Stable atropisomeric polychlorinated biphenyls (PCBs) ; Chirasil-Dex ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 5 Ill.
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  • 154
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    Journal of High Resolution Chromatography 17 (1994), S. 354-354 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 155
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    Journal of High Resolution Chromatography 17 (1994), S. 369-369 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 156
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    Journal of High Resolution Chromatography 17 (1994), S. 407-410 
    ISSN: 0935-6304
    Keywords: High resolution capillary GC (HRGC) ; Coupled GC-GC-MS ; Hydrocarbon distillate ; Alkylbenzenes ; Alkenylbenzenes ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper describes the use of multidimensional capillary gas chromatography for analysis of individual components in a C9—C10 aromatic hydrocarbon pyrolysis distillate containing substantial amounts of aromatic olefins. By coupling this GC-GC system on-line to a mass spectrometer difficulties in identifying overlapping compounds were overcome. No coelution of different types of compound was observed, but a few isomeric compounds such as methylstyrenes were poorly separated.
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  • 157
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    Journal of High Resolution Chromatography 17 (1994), S. 411-414 
    ISSN: 0935-6304
    Keywords: Size exclusion chromatography ; Gas chromatography ; Coupled LC-GC ; Cleanup and analysis ; Automation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A fully automated on-line sample cleanup system based on the coupling of size exclusion chromatography to high resolution gas chromatography is described. The transfer technique employed is based on fully concurrent solvent evaporation using a loop-type interface, early vapor exit and co-solvent trapping. Optimization of the LC-GC transfer was done visually via an all-glass oven door. To circumvent the problem of mixing within the injection loop, an adaptation was made to the standard loop-type interface. The determination of a series of additives in a polymer matrix is presented as one example of the vast range of applications opened up by this technique.
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  • 158
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    Journal of High Resolution Chromatography 17 (1994), S. 325-334 
    ISSN: 0935-6304
    Keywords: Capillary electrophoresis ; Repeatability of electroosmotic flow ; Silica capillary tubes ; Column pretreatment ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of a number of factors, such as the nature of the buffer, the presence of additives therein, the manufacturing conditions, and the pretreatment of the capillary, on the magnitude and repeatability of the electroosmotic flow (EOF) in silica capillary tubes has been investigated. It was established that the nature of the buffer plays the most significant role in respect of the stability and magnitude of EOF, whereas the conditions used for manufacture and pretreatment of the tubing are less important. The EOF obtained using buffers consisting of tris(hydroxymethyl)aminomethane and ethylenediamine was more repeatable than that obtained using pure phosphate buffers. Buffer additives such as sodium dodecylsulfate, 1-butanol, sodium salts of 1-pentanesulfonic acid and 1-heptanesulfonic acid, altered the magnitude of the EOF only, not its repeatability.
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  • 159
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    Journal of High Resolution Chromatography 17 (1994), S. 343-346 
    ISSN: 0935-6304
    Keywords: High performance thin layer chromatography ; Platinum metal 8-hydroxyquinolinates ; Polar stationary phases ; Retention, effect of mobile phase ; Sample preparation ; Optimization ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: High performance thin layer chromatography has been used to separate all the platinum metal 8-hydroxyquinolinates on polar stationary phases. The dependence of Rf values on the composition of mobile phases prepared from chloroform - tetrahydrofuran or chloroform - alcohol mixtures has been investigated. Retention was found to be partially dependent on alcohol chain length in chloroform - alcohol systems. The results obtained from TLC are dependent on the method of sample preparation used for the analyte.
    Additional Material: 7 Ill.
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  • 160
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; Atomic emission detector ; Organotin compounds ; Organolead compounds ; Organomercury compounds ; Grignard derivatization ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: As part of a continuing evaluation of new analytical and sample preparation techniques conducted by the US Environmental Protection Agency (EPA), the use of capillary gas chromatography with atomic emission detection (GC-AED) for the simultaneous determination of organotin, organolead, and organomercury compounds in environmental samples was investigated. Pentylmagnesium bromide was used to pentylate ionic organotin, organolead, and organomercury compounds; the pentyl derivatives were then separated by GC and determined by AED. Several important GC-AED parameters, including the type of injector inlet, carrier gas flow rate, and helium make-up gas flow rate, were optimized for the simultaneous determination of these organometallic compounds. Their minimum detectable concentrations were approximately 1.0 to 2.5 ng/mL using a 0.5-μL on-column injection. The calibration curves exhibited good linearity between 2.5 and 2500 ng/mL for organotin and organolead compounds, and between 2.5 and 10000 ng/mL for organomercury compounds.
    Additional Material: 5 Ill.
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  • 161
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    Journal of High Resolution Chromatography 17 (1994), S. 549-552 
    ISSN: 0935-6304
    Keywords: GC/MS ; Crude oils ; Monoaromatic steroids ; Triaromatic steroids ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Series of C-ring monoaromatic steroid hydrocarbons (C21, C22, C27 — C29) and triaromatic steroid hydrocarbons (C20, C21, C26 — C28) have been recognized in the aromatic hydrocarbon fraction of Alamein crude oil from the western desert, Egypt. Detection of these compounds were based on mass fragmentography of the key ions m/z 253 and m/z 231 and comparison of the mass spectra and relative retention times with literature data. The predominance of the C29 monoaromatic steroids and C28 triaromatic steroids provide further evidence for a land plant origin of Alamein oil. The results substantiate previous evidence of the occurrence of an aromatization process with increasing maturation and indicate a moderate maturity level for Alamein oil.
    Additional Material: 5 Ill.
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  • 162
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    Journal of High Resolution Chromatography 17 (1994), S. 556-556 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 163
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    Journal of High Resolution Chromatography 17 (1994), S. 559-560 
    ISSN: 0935-6304
    Keywords: Capillary electrophoresis ; Scutellariae Radix ; Flavonoids determination ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 164
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    Journal of High Resolution Chromatography 17 (1994), S. 567-568 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 165
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    Journal of High Resolution Chromatography 17 (1994) 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 166
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    Journal of High Resolution Chromatography 17 (1994), S. 593-596 
    ISSN: 0935-6304
    Keywords: High Temperature Gas Chromatography (HTGC) ; Bis(trimethylsilyl)trifluoroacetamide ; Ethoxylated alcohols ; Ethoxylated alcohol sulfates ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conversion of ethoxylated alcohols to trimethylsilyl derivatives and subsequent high temperature gas chromatography allowed for the determination of alkyl chain distribution, mole average degree of ethoxylation and weight percent distribution of several commercial mixtures. Repetitive derivatizations and analyses of a mixture with a vendor specified mole average degree of ethoxylation of 3.0 (Neodol 23-3), yielded an experimental result of 2.93 ± 0.05 (n = 6). Mixtures with different alkyl chain distributions and higher degrees of ethoxylation provided similar accuracy. Extension of the method to the analysis of ethoxylated alcohol sulfate raw materials and ethoxylated alcohol sulfates in dishwashing liquids is discussed.
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  • 167
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    Journal of High Resolution Chromatography 17 (1994), S. 607-608 
    ISSN: 0935-6304
    Keywords: Ion Chromatography, IC ; Interference ; Fluoride ; Carbonate ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
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  • 168
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    Journal of High Resolution Chromatography 17 (1994), S. 609-612 
    ISSN: 0935-6304
    Keywords: Capillary zone electrophoresis (CZE) ; Chiral separation ; Separation of enantiomers ; Acidic chiral compounds ; Dextrins ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 7 Ill.
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  • 169
    ISSN: 0935-6304
    Keywords: Crude oils ; Organic sulfur ; Desulfurization ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Five crude oils with varying sulfur contents (0.1 - 4.7%) were characterized on a molecular level for organically-bound sulfur. Aromatic fractions were analyzed by GC-(MS) and asphaltene and polar fractions were analyzed by flash pyrolysis-GC-(MS). The polar fractions were also desulfurized with Raney Ni and the hydrocarbons formed were analyzed by GC-MS. Major sulfur compounds in the aromatic fractions were identified as alkylbenzo- and alkyldiben-zothiophenes. The flash pyrolyzates of the asphaltene contained alkylthiophenes and alkylbenzothiophenes as major compounds, depending on the thermal maturity of the oil. Generally, the sulfur-rich crude oils contained relatively more sulfur compounds. The flash pyrolyzates of polar fractions contained a variety of sulfur compounds (alkylthiolanes, alkylthianes, terpenoid sulfides, alkylbenzothiophenes) with substantial differences between different crude oils. Raney Ni desulfurization of the polar fraction yielded hydrocarbons dominated by n-alkanes, but isoprenoid alkanes, n-alkylcyclohexanes, mid-chain methylalkanes, tricyclic terpanes, hopanes and steranes were also present. These hydrocarbons show a potential to fingerprint crude oils since their distribution patterns are more characteristic than those of the hydrocarbons present in the saturated hydrocarbon fraction.
    Additional Material: 15 Ill.
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  • 170
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    Journal of High Resolution Chromatography 17 (1994), S. 537-542 
    ISSN: 0935-6304
    Keywords: Metal-ammonia complexes ; Electroosmosis ; Field strength ; Diuretics ; Resolution ; Capillary length ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The counter ion in CZE separation systems affects resolution, effective field strength and electroosmosis. Alkali metals (lithium, sodium, potassium, and cesium), the ammonium ion, and several complexes of metals with ammonia ([Ag(NH3)2]+, [Cu(NH3)4]2+, [Zn(NH3)4]2+, [Cd(NH3)4]2+, [Ni(NH3)6]2+, and [Co(NH3)6]2+) have been studied for their effect on the separation of diuretics. With the alkali metals the electroosmotic flow velocity decreased and the effective field strength and resolution increased as the hydrated radius of the alkali metal decreased.All the metal-ammonia complexes except that with silver greatly reduced the electroosmotic flow velocity (Veo) and had only a slight effect on the effective field strength (Eeff). Because these complexes had a negligible effect on the ionic strength of the buffer, they enabled high separating power to be maintained during the separation, and hence the use of more energy in the separation system. This yielded better resolution of the compounds, but the analysis time was then compromised.A simultaneous reduction in capillary length and Veo while maintaining the high voltage enabled increased resolution without an increase in analysis time. The ability to control Veo by adding small concentrations (〈 100 μM) of metal complexes to the buffer solution makes it possible to adjust the analysis time and capillary length independently while employing high separation power.
    Additional Material: 5 Ill.
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  • 171
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    Journal of High Resolution Chromatography 17 (1994), S. 543-548 
    ISSN: 0935-6304
    Keywords: GC-FTIR-MS ; Polyunsaturated fatty acids ; Methyl esters ; Oxazolines ; cis/trans isomers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Identification of cis/trans isomers of unsaturated fatty acids cannot usually be achieved by GC-MS (gas chromatography-mass spectrometry) without reference substances. In this study a GC-FTIR-MS system (gas chromatography-Fourier transform-mass spectrometry) was used to identify fatty acid methyl esters (FAMEs) and differentiate between the cis/trans isomers. Besides methyl esters, 2-alkenyl-4,4-dimethyloxazoline derivatives (DMOX), which have been used to locate double bond positions of unsaturated fatty acids, were examined with respect to their suitability for cis/trans differentiation.A combined GC-FTIR-MS system with a wide band (4000-550 cm-1) mercury cadmium telluride (MCT) detector was used in series and parallel to identify 31 reference unsaturated fatty acids, including 7 pairs of cis/trans isomers. Serum samples of healthy persons and commercially available fish oil were analyzed as examples of complex mixtures. Using splitless injection the detection limit for the less sensitive IR detector was 25 ng/μl in case of the weak cis and trans bands.In the FTIR spectra cis/trans isomers were identified by analysis of bands arising from C—H out-of-plane (oop) bending: for both the FAME and DMOX derivatives cis-1,2-disubstituted double bonds give a strong band near 720 cm-1 and the corresponding trans isomers near 967 cm-1. cis Isomers could be identified further by a band at 3012 cm-1. With the combined data of the GC-FTIR-MS system it is now possible to identify polyunsaturated fatty acids with regard to the discrimination of cis/trans isomers.
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  • 172
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    Journal of High Resolution Chromatography 17 (1994), S. 557-559 
    ISSN: 0935-6304
    Keywords: Open tubular liquid chromatography (OTLC) ; Inertness ; Protein analysis ; Ultraviolet detection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 173
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    Journal of High Resolution Chromatography 17 (1994), S. 565-566 
    ISSN: 0935-6304
    Keywords: Micellar electrokinetic chromatography ; Solid phase extraction ; Cycloheximide ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 174
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    Journal of High Resolution Chromatography 17 (1994), S. 573-576 
    ISSN: 0935-6304
    Keywords: Capillary supercritical fluid chromatography ; Mass spectrometry ; On-line combination ; Polymer additives analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A standard direct introduction capillary interface is used for the SFC-MS analysis of polymer additives. The system is optimized with respect to the position of the restrictor, probe tip temperature, and ion source temperature. El-like charge-exchange spectra are obtained. Cl using ammonia as the reagent gas is used for the quantitative analysis of a real world sample.The experimental capillary SFC-MS spectra obtained show a good similarity with those recorded using the direct insertion probe. The influence of the experimental conditions on the mass spectra obtained is evaluated statistically.
    Additional Material: 5 Ill.
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  • 175
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    Journal of High Resolution Chromatography 17 (1994), S. 589-592 
    ISSN: 0935-6304
    Keywords: Silica gel fractionation ; GC-MS ; Industrial waste water analysis ; Biological water treatment ; Tannery waste water ; Dissolved organic compounds ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The separation of the components of complex industrial waste water extracts according to their functional groups has been accomplished by use of small silica gel columns eluted with a hexane - dichloromethane - methanol gradient. The six fractions obtained covered a polarity range from aliphatic fatty acids to (aromatic) polyhydroxy and polyether compounds. Recovery of model compounds was between 75 and 105%.Used prior to GC-MS analysis this fractionation substantially enhances chromatographic resolution and facilitates peak identification. The procedure was exemplarily applied to an extract of anaerobically treated tannery waste water. Phenols, aromatic acids, and aromatic and aliphatic (poly)hydroxy acids, in the low ppm range, were determined as main constituents. Since fractionation extends the range of detection, trace substances such as chlorocresol, dichlorobenzoic acid, mercaptobenzothiazole, and mercaptoacetic acid were also detectable at the ppb level.
    Additional Material: 3 Ill.
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  • 176
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    Journal of High Resolution Chromatography 17 (1994), S. 603-606 
    ISSN: 0935-6304
    Keywords: Supercritical fluid chromatography ; Lanthanide β-diketonates ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chromatographic behaviors of lanthanide chelates of acetylacetone (ACAC), trifluoroacetylacetone (TFA), thenoyltrifluoroacetone (TTA), dipivaloylmethane (THD), 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedione (FOD), and the thenoyltrifluoroacetonepyridine (TTA·Py) adduct were investigated using packed column supercritical fluid chromatography. Mobile phases consisting of neat and alcohol modified CO2 were used with a phenyl packed stationary phase. Lanthanide complexes of ACAC, THD, and FOD were shown to have better chromatographic performance compared to the corresponding chelates with TFA, TTA, and TTA·Py. In particular, TTA complexes such as Eu(TTA)3 showed characteristic thermal decomposition in the mobile phase at elevated temperature. In addition, retention behavior was found to be a temperature dependent function of volatility and solubility for all chelates studied.
    Additional Material: 4 Ill.
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  • 177
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    Journal of High Resolution Chromatography 17 (1994), S. 616-618 
    ISSN: 0935-6304
    Keywords: HPLC ; MEKC ; Diode-array detection ; Flavonoid analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 5 Ill.
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  • 178
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    Journal of High Resolution Chromatography 17 (1994), S. 622-622 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 179
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    Journal of High Resolution Chromatography 17 (1994) 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 180
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    Journal of High Resolution Chromatography 17 (1994), S. 643-646 
    ISSN: 0935-6304
    Keywords: High Resolution Capillary GC ; High Resolution GC-MS ; Lemon oil ; Citrus volkameriana ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dependence of the limonene content of lemon (Citrus volkameriana) peel oil on the degree of ripeness of the fruit has been studied by using steam distillation and cold pressing to extract the oils from lemon fruit peel at different stages of maturation (green, greenish-yellow, and yellow-orange peel coloration). Samples of essential oils were analyzed by high resolution GC and GC-MS, using tetradecane as internal standard for quantitation. Forty components were detected; thirty eight were positively identified by comparison of their mass spectra (El, 70 eV) and Kováts retention indexes (determined using a non-logarithmic scale on capillary columns coated with both polar (DB-Wax) and non-polar (DB-1) stationary phases) with those of standards and with data reported in the literature. The limonene concentration reached a maximum level of 79.4% when the fruit was in the intermediate maturation stage characterized by greenish-yellow coloration.
    Additional Material: 4 Ill.
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  • 181
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    Journal of High Resolution Chromatography 17 (1994), S. 639-642 
    ISSN: 0935-6304
    Keywords: Capillary GC ; Chiral stationary phase ; Chirasil-Val ; Cyclodextrins ; Perfluoroacylation ; Enantiomeric separation ; Amino alcohols ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Racemic amino alcohols have been separated as perfluoroacylated derivatives by gas chromatography using either improved Chirasil-Val or heptakis(2,6-di-O-methyl-3-O-pentyl)-β-cyclodextrin as stationary phase. Using Chirasil-Val all the amino alcohols investigated were separated to baseline (α values between 1.03 and 1.08) whereas only a few amino alcohols were resolved on the modified cyclodextrin column. The enantioselectivity obtained on the latter phase was, however, significantly higher.The separations were performed as trifluoroacetyl, pentafluoropropionyl, and heptafluorobutyryl derivatives and the chiral discrimination observed for the different derivatives was significantly different for both stationary phases.In oder to obtain a better understanding of the separation mechanism, the Gibbs-Helmholtz parameters Δ(R,S)ΔH° and Δ(R,S)ΔS° were determined. The most extraordinary result was obtained for the trifluoroacetyl derivative of allo-threoninol. In addition to the order of elution of the enantiomers being the opposite of that for the other compounds, the separation seems to be entropy controlled (the sign Δ(R,S)ΔH° is positive), i.e. the separation improved at higher temperatures.
    Additional Material: 4 Ill.
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  • 182
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    Journal of High Resolution Chromatography 17 (1994), S. 662-664 
    ISSN: 0935-6304
    Keywords: Capillary GC ; Sorbent cartridge ; Medium-chain fatty acids ; Fatty acid ethyl esters ; Beer analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A modification of a procedure by Hage [1] is proposed for the gas chromatographic evaluation of the content of free medium-chain fatty acids and related ethyl esters in beer. The method involves extraction of free fatty acids and ethyl esters by SPE using C18 bonded phase columns, derivatization of free fatty acids and related ethyl esters with diazomethane, and GC analysis using an SP-2340 capillary column. The results obtained have shown the method to be rapid and highly reproducible. The technique has been compared with other methods used for determination of free fatty acids.
    Additional Material: 1 Ill.
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  • 183
    ISSN: 0935-6304
    Keywords: Oxazaphosphorines ; Iphosphamide ; Iphosphamide metabolites ; Electron capture chemical ionization MS ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method is described for the determination of the antitumor agent iphosphamide and seven of its metabolites in the plasma of cancer patients by multiple ion monitoring (MIM) GC-MS, mainly using the electron capture chemical ionization mode, of stable methyl and/or trifluoroacetyl derivatives. The metabolites determined were 2- and 3-dechloroethyliphosphamide, 4-ketoiphosphamide, carboxyiphosphamide, iphosphamide mustard, and two previously undetected metabolites, chloroethylamine and 1,3-oxazolidine-2-one.The isolation of the acidic and neutral metabolites was performed by solid phase extraction on to C18 adsorbent at pH 4. The weakly acidic iphosphamide mustard, isolated under these conditions with a yield of ca 50%, was measured as a stable methyltrifluoroacetyl derivative, in contrast to the corresponding phosphoramide mustard of the isomer cyclophosphamide which decomposes during derivatization. Chloroethylamine and 1,3-oxazolidine-2-one were isolated with high yield by liquid extraction with ethyl acetate at pH 10.Selective measurement of several metabolite derivatives with similar retention times was performed by multiple ion monitoring MS of specific ion masses, using a methyl phenyl siloxane capillary column previously employed in the study of cyclophosphamide metabolites. Quantitation of metabolites in patient plasma samples could be performed in the concentration range 3 ng to 20 μg per ml of original plasma.
    Additional Material: 9 Ill.
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  • 184
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    Journal of High Resolution Chromatography 17 (1994), S. 759-764 
    ISSN: 0935-6304
    Keywords: Supercrirtical fluid extraction (SFE) ; Modified carbon dioxide in SFE ; Liquid trapping ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A polarity test mix consisting of acetophenone, N,N-dimethylaniline, naphthalene, 2-naphthol, and n-tetracosane was spiked onto sand and extracted with carbon dioxide modified with acetonitrile, methanol, or toluene. The extracts were collected in chloroform, hexane, methanol, or a mixed collection solvent consisting of equal parts chloroform-hexane-methanol. The mixed collection solvent which showed excellent recoveries for pure CO2, had the worst recoveries of all the collection solvents with modified CO2. Overall hexane was the best collection solvent studied for these analytes under these extraction conditions.
    Additional Material: 1 Ill.
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  • 185
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    Journal of High Resolution Chromatography 17 (1994), S. 57-57 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 186
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    Journal of High Resolution Chromatography 17 (1994) 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 187
    ISSN: 0935-6304
    Keywords: GC-AED ; High boiling PAC ; Peak splitting in discharge tube ; Additional make-up gas ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Peak splitting of high molecular weight polycyclic aromatic compounds originating from the microwave plasma of an atomic emission detector (AED) coupled to a GC has been described and evaluated. The influence of the solute structure, solute concentration, and physical conditions in the AED (such as detector temperature, make-up gas flow, concentration of reagent gases and distance of column end from the plasma) have been studied. An explanation is presented for peak splitting, which is based on an insufficient solute decomposition and solute mass flow in the discharge tube. Modification of the instrument by introduction of additional make-up gas applied through the transfer line has been shown to improve peak shape and solute response.
    Additional Material: 9 Ill.
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  • 188
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    Journal of High Resolution Chromatography 17 (1994), S. 153-159 
    ISSN: 0935-6304
    Keywords: Capillary GC-MS ; Purge and trap GC-MS ; Extraction ; Solid phase extraction ; Fractionation ; Organic contaminants in municipal wastewater ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: High resolution capillary gas chromatography-mass spectrometry has been used in combination with various sample preparation methods to analyze a wide range of low molecular weight organic contaminants in municipal wastewaters. Volatile organic compounds were extracted using a purge and trap concentrator connected directly to a wide bore DB-624 capillary column. Because of the high organic load in wastewater samples, this method was preferred to the more sensitive closed loop stripping technique which suffered from competition effects and insufficient adsorbent capacity. Volatile and semi-volatile base/neutral compounds and acids were extracted with dichloromethane at pH 11 and pH 2, respectively, or were recovered using a simultaneous distillation-extraction procedure. Acidic compounds were subsequently derivatized using diazomethane methylation. Both fractions were separated with a 30m DB-5ms capillary column. Specific ionic substances (LAS, NTA, EDTA) were isolated by solid-phase extraction then derivatized with diazomethane (LAS) or acetyl chloride in n-butanol (NTA, EDTA) before GC-MS analysis.This array of techniques enabled the identification of more than 150 organic contaminants in the influent of a municipal wastewater treatment plant in northern suburban Paris. The individual concentrations of these contaminants ranged from 〈 0.1 μg/l to 5.7 mg/l.
    Additional Material: 8 Ill.
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  • 189
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    Journal of High Resolution Chromatography 17 (1994), S. 169-173 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 190
    ISSN: 0935-6304
    Keywords: Nonaqueous solvent ; Capillary electrophoresis ; CE-electrospray-mass spectrometry ; Drug metabolism ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 191
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography (CGC) ; Enantioselective separations ; (2,3,6-Tri-O-methyl)cyclodextrins ; Enantiomeric excess determination ; 2,3-Isopropylidene-1,2,3-cyclohexanetriol derivatives ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Capillary GC on permethyl α-, β-, and γ-cyclodextrins has been applied to separate and quantify the enantiomers of some 2,3-iso-propylidene-1,2,3-cyclohexanetriol derivatives. Quantitative CGC data are compared to those obtained with chiral shift 1H NMR.
    Additional Material: 2 Ill.
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  • 192
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    Journal of High Resolution Chromatography 17 (1994), S. 98-98 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 193
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    Journal of High Resolution Chromatography 17 (1994), S. 107-108 
    ISSN: 0935-6304
    Keywords: Capillary electrophoresis ; Polyacrylamide ; Hydrophobic interaction ; Electrokinetic chromatography ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 194
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    Journal of High Resolution Chromatography 17 (1994), S. 104-106 
    ISSN: 0935-6304
    Keywords: HPLC ; SFC ; Rapid analysis ; Donor - acceptor chromatography ; Acceptor bonded phases ; C60 fullerene ; C70 fullerene ; Higher fullerenes ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 5 Ill.
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  • 195
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    Journal of High Resolution Chromatography 17 (1994), S. 118-118 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 196
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    Journal of High Resolution Chromatography 17 (1994) 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 197
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    Journal of High Resolution Chromatography 17 (1994), S. 350-352 
    ISSN: 0935-6304
    Keywords: Supercritical fluid extraction ; Supercritical fluid derivatization ; C18 adsorbent ; Capillary GC ; Polar compounds ; Phenoxycarboxylic acids ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 198
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    Journal of High Resolution Chromatography 17 (1994) 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 199
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    Journal of High Resolution Chromatography 17 (1994), S. 373-389 
    ISSN: 0935-6304
    Keywords: GC ; Natural gas analysis ; Sulfur components ; Selective enrighment ; Sulfur selective detection ; Calibration ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: More stringent environmental regulations as well as higher demands presently being imposed on the sulfur content of natural gas feed-stocks for chemical processes necessitate the development of new analytical procedures for sulfur determination in natural gas. Only analytical procedures based on gas chromatography can meet the sensitivity and accuracy requirements dictated by environmental regulation institutions and modern chemical industry. The complexity of the natural gas matrix as well as the extremely low concentration levels at which the sulfur species occur make the development of these analytical methods a true challenge. In this review the three steps common for analytical methods for trace analysis in complex matrices, i.e. pretreatment, chromatographic separation, and detection, are discussed in detail. Possible methods for calibration of the system are discussed in the final section.Various techniques to determine sulfur in natural gas are described. Depending on the application, the most suitable system has to be selected. For example, for on-line application in a hazardous area a simple and rugged system is required, i.e. a simple gas chromatograph with a flame photometric detector, while for laboratory application a more complex instrument including preconcentration, column switching, and more exotic detection systems could be more suitable. Therefore it is crucial to define the requirements of the instrument at an early stage and use the information in this review article to develop/select a dedicated instrument/procedure for the problem at hand.
    Additional Material: 17 Ill.
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  • 200
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    Journal of High Resolution Chromatography 17 (1994), S. 398-406 
    ISSN: 0935-6304
    Keywords: High temperature GC ; Pyrolysis ; Hydrocarbons ; Waxes ; High molecular weight hydrocarbons (C40—C100) ; Asphaltenes ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For the past two or three decades geochemists have been concerned with the analyses and characterization of compounds, generally hydrocarbons, ranging from C1—C40. Significant amounts of information have resulted from these studies which have been extremely useful in many geochemical and environmental studies. However, in the past two or three years the commercial development and availability of high temperature gas chromatography columns has lead to the investigation of the occurrence and distribution of high molecular weight hydrocarbons (HMWHC), and other compounds, in the carbon number range C40—C100, present in oils, waxes, bitumens and rock extracts. The ability to study these compounds represents a major advance in organic geochemistry. In some samples these compounds may represent the bulk of the organic components but prior to development of the high temperature columns it was impossible to study their distributions.This paper will review advances that have occurred in terms of the application of high temperature gas chromatography (HTGC) to the analyses of fossil fuel samples and discuss the possible origin and significance of these compounds that have been identified. In addition, some of the potential problems involved in the analyses of these compounds will also be discussed.
    Additional Material: 5 Ill.
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