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  • 2010-2014
  • 1985-1989  (1,903)
  • 1987  (1,903)
  • Analytical Chemistry and Spectroscopy  (1,177)
  • Chemical Engineering  (726)
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Years
  • 2010-2014
  • 1985-1989  (1,903)
Year
  • 101
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 1 (1987), S. 7-18 
    ISSN: 0886-9383
    Keywords: Kalman filter ; Calibration ; Curve resolution ; Parameter estimation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The application of the Kalman filter to the solution of a variety of problems in analytical chemistry is reviewed. Five examples are selected from the literature to illustrate the use of Kalman filtering techniques for obtaining least-squares estimates fo several parameters of analytical importance. These examples include multicomponent curve resolution and concentration estimation, correction for variable background responses, calibration with drift compensation, and estimation of kinetic parameters for first-order reactions and for heterogeneous charge-transfer reactions. An adaptive Kalman filtering technique is required for the solution of the background correction problem, and the extended Kalman filter algorithm is required for the solution of the nonlinear kinetic problems. For each case, the results that were obtained are summarized, and some advantages of Kalman filtering over traditional least-squares approaches are discussed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 102
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 1 (1987), S. 19-31 
    ISSN: 0886-9383
    Keywords: Calibration ; Indirect calibration ; Multivariate ; Matrix decomposition ; PLS ; PCR ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Partial least squares (PLS) modeling is an algorithm for relating one or more dependent variables to two or more independent variables. As a regression procedure it apparently evolved from the method of principal components regression (PCR) using the NIPALS algorithm, which is similar to the power method for determining the eigenvectors and eigenvalues of a matrix. This paper presents a theoretical explanation of the PLS algorithm using singular value decomposition and the power method. The relation of PLS to PCR is demonstrated, and PLS is shown to be one of a continuum of possible solutions of a similar type. These other solutions may give better prediction than either PLS or PCR under appropriate conditions.
    Additional Material: 4 Tab.
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  • 103
    ISSN: 0886-9383
    Keywords: Principal component analysis ; Singular value decomposition ; Factor analysis ; Rank determination ; Eigenvector analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The distribution of error eigenvalues resulting from principal component analysis is deduced by considering the decomposition of an error matrix in which the errors are uniformly distributed. The derived probability function is \documentclass{article}\pagestyle{empty}\begin{document}$$ P(\lambda ^0 _j) = N(r - j + 1)(c - j + 1) $$\end{document} Where λ0j is the jth error eigenvalue, r and c are the numbers of rows and columns in the data matrix, and N is the normalization constant. This expression is tested and validated by investigations involving model data. The distribution function is used to determine the number of factors responsible for various sets of spectroscopic data taken from the chemical literature (including nuclear magnetic resonance, infrared and mass spectra).
    Additional Material: 1 Ill.
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  • 104
    ISSN: 0886-9383
    Keywords: Curve resolution ; Liquid chromatography ; Accuracy ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The performance of curve resolution and iterative target transformation curve resolution in quantitative liquid chromatography with a diode array detector is evaluated. Quantitative accuracy of the elution profiles obtained for two- and three-component mixtures has been evaluated as a function of spectral similarity, chromatographic resolution and ratio of the peak areas, using a number of simulations analysed by an analysis of variance. The results obtained by simulation are compared and validated with the results obtained for the separation of phenylene diamines in reversed phase liquid chromatography and proteins in gel permeation liquid chromatography. The results that were obtained are summarized and the chromatographic implications are discussed.
    Additional Material: 3 Ill.
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  • 105
    ISSN: 0886-9383
    Keywords: Multi-way array ; Multiorder array ; Principal components ; PLS ; Multivariate calibration ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Lohmöller-Wold decomposition of multi-way (three-way, four-way, etc.) data arrays is combined with the non-linear partial least squares (NIPALS) algorithms to provide multi-way solutions of principal components analysis (PCA) and partial least squares modelling in latent variables (PLS).The decomposition of a multi-way array is developed as the product of a score vector and a loading array, where the score vectors have the same properties as those of ordinary two-way PCA and PLS. In image analysis, the array would instead be decomposed as the product of a loading vector and an image score matrix.The resulting methods are equivalent to the method of unfolding a multi-way array to a two-way matrix followed by ordinary PCA or PLS analysis. This automatically proves the eigenvector and least squares properties of the multi-way PCA and PLS methods.The methodology is presented; the algorithms are outlined and illustrated with a small chemical example.
    Additional Material: 5 Ill.
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  • 106
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    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 1 (1987), S. 73-73 
    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
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    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 1 (1987), S. 75-75 
    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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  • 108
    Electronic Resource
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    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 1 (1987), S. 74-74 
    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 1 (1987) 
    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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  • 110
    Electronic Resource
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    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 1 (1987), S. 77-77 
    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 1 (1987), S. 79-90 
    ISSN: 0886-9383
    Keywords: Numerical deconvolution ; Peak resolution ; Peak separation ; Iterative deconvolution ; Jansson's method ; Super-resolution ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Severely overlapped gas chromatographic peaks can be resolved using Jansson's method. Jansson's method is an iterative nonlinear deconvolution technique and consists of Van Cittert's algorithm with the relaxation factor a function of the kth estimate of the peak shape. The maximum peak amplitude of the instrument and peak non-negativity serve as constraints to improve the peak estimate. Super-resolution is achieved without significantly degrading the chromatogram signal-to-noise ratio. The method only requires a knowledge of the instrument impulse response function and maximum peak height.
    Additional Material: 7 Ill.
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  • 112
    ISSN: 0886-9383
    Keywords: NIR ; Fast Fourier transform ; Principal component analysis ; Discrimination ; Baking quality ; Wheat ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Digitalized continuous near infra-red reflectance (NIR) spectra are composed of a great number of data which must be reduced for microcomputer mathematical treatment. The sequence ‘fast Fourier transform preceding principal component analysis’ was tested to perform data size reduction without a large loss of information. The method was applied on a collection of wheat spectra composed of 351 data. Ten resulting data, which described 99.5% of the total variance, were kept. The relevance of the method was estimated by the ability of the resulting data (i) to regenerate the original signal, and (ii) to discriminate the baking quality of the wheat by stepwise multiple discriminant analysis. The average difference between initial and regenerated spectra was -2.4 × 10-3 log (1/R) units and the standard deviation was 1.16 × 10-3 log (1/R) units. The discrimination treatments gave 89.9% of well classified samples for the calibration test and 90.5% for the prediction test. The application of these mathematical treatments to other continuous signals is discussed.
    Additional Material: 2 Ill.
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  • 113
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    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 1 (1987), S. 91-101 
    ISSN: 0886-9383
    Keywords: Factor analysis ; Retention indices ; Model ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Retention indices for 18 monomeric stationary-phase solvents and 33 organic solutes are factor analyzed. Six factors reproduce the data matrix near experimental error. The solvents diglycerol and zonyl E-7 are shown to be highly unique, whereas none of the solutes behaves uniquely. Combination sets of solvent vectors and of solute vectors from the data matrix lead to models having errors within experimental error. Basic factors which might influence the solute - solvent interactions are identified by the least-squares method of target testing. For the solvents, a number of properties, including McReynolds' constants and molecular weight, test successfully. For the solutes, carbon number and group dipole moment are representative properties which test successfully. The best combination of solvent basic factors gives errors about twice the experimental error. Combination sets composed only of McReynolds' constants do not model the data well.
    Additional Material: 6 Tab.
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  • 114
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    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 1 (1987), S. 111-120 
    ISSN: 0886-9383
    Keywords: Principal component analysis ; Submatrix analysis ; Spectroscopy ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the treatment of spectroscopic data by principal component analysis, correct determination of the dimensionality of the data is essential. Submatrix analysis, which involves preliminary analysis of subsets of the data matrix, is described, and shown to be valuable in determining both the size of the factor space and estimates of equilibrium constants in the system, even for data containing abnormally large experimental error.
    Additional Material: 4 Ill.
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  • 115
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    Journal of Chemometrics 1 (1987), S. 135-135 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 116
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    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 1 (1987), S. 136-136 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 117
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    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 1 (1987), S. 121-134 
    ISSN: 0886-9383
    Keywords: Multivariate calibration ; NIR ; Cluster analysis ; Experimental design ; Sample selection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A procedure for selecting samples to use in multivariate calibration, inspired by a paper by Zemroch, is proposed. The method developed is designed for multicollinear data and is based on cluster analysis. It selects among availabe spectra the samples to submit to chemical analysis and calibration. The method is tested on an example from NIR spectroscopy of biscuit dough pieces.
    Additional Material: 11 Ill.
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  • 118
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    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 1 (1987), S. 136-136 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 119
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 1 (1987) 
    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
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    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 1 (1987), S. 137-137 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 121
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    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 1 (1987), S. 157-173 
    ISSN: 0886-9383
    Keywords: Gas chromatography ; Simplex ; Barycentric co-ordinates ; Discriminant analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper proposes an elegant, yet straightforward, model for classifying linear mixtures. A linear mixture is defined as a random vector y in which the variable are a (non-negative) weighted average of corresponding variables, assumed to characterize g component groups. These weights are referred to as ‘mixing proportions’. The model seeks to identify the mixture constituents and estimate the mixing proportions. It is demonstrated within the context of high resolution gas chromatography and the problem of identifying the constituents in polychlorinated biphenyl mixtures.
    Additional Material: 9 Ill.
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  • 122
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    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 1 (1987), S. 175-183 
    ISSN: 0886-9383
    Keywords: Deconvolution ; Jansson's method ; Peak resolution ; Numerical deconvolution ; Super resolution ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In a previous paper,1 Jansson's method was used to deconvolve overlapped gas chromatographic peaks. It was found that this method gave improved performance over conventional techniques such as perpendicular drop and shoulder quantitation.2,3 This paper will present the results of a comprehensive test of Jansson's method using several sample mixtures. These results will be compared to what can be obtained by using shoulder quantitation, perpendicular drop or an instrument with a longer column. A relatively large number of tests will be performed for each of the four mentioned methods of peak resolution, so there will be a reasonable statistical basis for the goodness of Jansson's method to resolve fused gas chromatographic peaks for a given set of instrument conditions. A brief review of Jansson's method and the modeling of a gas chromatographic process will also be presented.
    Additional Material: 6 Ill.
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  • 123
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    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 1 (1987), S. 139-155 
    ISSN: 0886-9383
    Keywords: Chemical information systems ; Machine-readable structure representation ; Registration search ; Structure search ; Substructure search ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper decribes the development and current state-of-the-art in computerized systems for the storage and retrieval of chemical structure information. The main types of machine-readable structure representation  -  fragmentation codes, linear notations and connection tables  -  are described, together with the retrieval algorithms which are used to provide structure and substructure search facilities. Current research work in chemical structure retrieval includes the development of techniques for the representation and searching of the generic structures which occur in chemical patents, for searching files of three-dimensional structures, for ranking searches designed to identify compounds structurally similar to a given query compound, and the use of parallel computers to increase the efficiency of substructure searching. Chemical structure handling techniques are also applicable in a range of application areas, including chemical reaction indexing, computer-aided synthesis design and structure elucidation, and substructural analysis methods for the study of quantitative structure - activity relationships.
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  • 124
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    Journal of Chemometrics 1 (1987), S. 197-197 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 125
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    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 1 (1987), S. 185-196 
    ISSN: 0886-9383
    Keywords: Cross-validation ; Partial least squares ; Two-sample location ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method for statistical analysis of two independent samples with respect to difference in location is investigated. The method uses the partial least squares projections to latent structures (PLS) with cross-validation. The relation to classical methods is discussed and a Monte Carlo study is performed to describe how the distribution of the test-statistic employed depends on the number of objects, the number of variables, the percentage variance explained by the first PLS-component and the percentage missing values. Polynomial approximations for the dependency of the 50 per cent and the 5 per cent levels of the test-statistic on these factors are given. The polynomial for the 50 per cent level is complicated, involving several first-, second- and third-degree terms, whereas the polynomial for the 5 per cent level is dependent only on the number of objects and the size of the first component. A separate Monte Carlo experiment indicates that a moderate difference in sample size does not affect the distribution of the test-statistic. The multi-sample location problem is also studied and the effect of increasing the number of samples on the test-statistic is shown in simulations.
    Additional Material: 3 Ill.
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  • 126
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    Journal of Chemometrics 1 (1987), S. 198-198 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 127
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    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 1 (1987), S. 197-198 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 128
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    Journal of Chemometrics 1 (1987), S. 198-198 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 129
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    Journal of Chemometrics 1 (1987), S. 199-199 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 130
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    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 1 (1987) 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 131
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    Journal of Chemometrics 1 (1987), S. 201-219 
    ISSN: 0886-9383
    Keywords: Multivariate ; Calibration ; PLS ; Regression ; Spectroscopy ; Selectivity ; Outliers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper illustrates some advantages of indirect multivariate calibration over conventional calibration: selectivity enhancement and outlier detection. Partial least squares (PLS) calibration is applied for quantitative analysis in the presence of interferences that would make both conventional single-wavelength calibration and direct multicomponent analysis impossible. The PLS algorithm is illustrated graphically, and the importance of outlier detection is demonstrated.
    Additional Material: 9 Ill.
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  • 132
    ISSN: 0886-9383
    Keywords: Pattern recognition ; SIMCA ; PCA ; Classification ; Bacteria ; Pyrolysis mass spectra ; Recall ; Cross-validation ; Indicator function ; Pseudo random data sets ; Leave-x-out ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: As part of a critical evaluation of the pattern recognition method SIMCA, three data sets containing pyrolysis mass spectra from bacteria were analysed using the SIMCA classifier. Each set consisted of two classes, Pseudomonas and Serratia bacteria, each class containing ten mass spectra and each mass spectrum having 285 spectral features.The results indicate that for these py-MS data sets, with low object/feature ratio, the SIMCA classifier produces satisfactory results at the first classification level. At the second level, however, the classification results are not reliable, even after deleting outliers. A comparison of the cross-validation method and Malinowski's indicator function for the determination of the number of significant principal components showed that the cross-validation method is less stable and therefore less reliable than the indicator function.
    Additional Material: 11 Tab.
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  • 133
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    Journal of Chemometrics 1 (1987), S. 221-230 
    ISSN: 0886-9383
    Keywords: Pattern recognition ; SIMCA ; PCA ; Classification ; Recall ; Cross-validation ; Indicator function ; Leave-x-out ; Pseudo random data sets ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The SIMCA pattern recognition method has been evaluated with pseudo random data sets. The number of objects varied from 5 to 50 and the number of features from 5 to 300.First, the determination of the significant number of PCs in the SIMCA models by the cross-validation method was compared with the indicator function. The results showed that for the lower dimensions (≤ 15 objects or ≤ 15 features) the indicator function produces more reliable results.Second, the classification results with SIMCA were analysed for data sets with two equally sized classes and a varying number of objects and features, using the recall function as the evaluation criterion. The results showed that the SIMCA classifier produces reliable results at the first classification level, even for a low object/feature ratio (5/300). However, at the second level the classification performance of SIMCA decreases rapidly with an increasing number of features, even when the data set consists of two very well separated classes and little random error.
    Additional Material: 6 Ill.
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  • 134
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    Journal of Chemometrics 1 (1987), S. 243-245 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 135
    ISSN: 0886-9383
    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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    Journal of Chemometrics 1 (1987), S. 246-247 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: STATA: VERSION 1.5, available from Computing Resources Center, 10801 National Boulevard, Los Angeles, CA 90064, U.S.A. Telex: 263199 STATAPC. Published by the Computing Resources Center, 1986. Basic version, for data management, data presentation, statistical testing, estimation, including linear regression, ANOVA and ANCOVA, with two program collections (written in the STATA programming language ) for (1) parametric and non-parametric tests and (2) generation of statistical graphs. Price: $395 in North America, $470 elsewhere (academic discount price in North America: $265).STATE GRAPHICS MODULE, for high-resolution statistical graphics, including one-way and two-way scatter plots, scatter-plot matrices, box plots, bar and pie charts, multiple imaging and overlays. Price: $195 in North America, $270 elsewhere (academic discount price in North America: $130).
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  • 137
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    Journal of Chemometrics 1 (1987), S. 248-249 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 138
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    Journal of Chemometrics 1 (1987), S. 250-254 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 139
    ISSN: 0886-9383
    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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    Biological Mass Spectrometry 14 (1987) 
    ISSN: 0887-6134
    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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    Biological Mass Spectrometry 14 (1987), S. i 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 142
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Amino acids can be identified unambiguously in form of their dansylated methyl esters by combination of thin-layer chromatography on polyamide and subsequent mass spectrometry without prior substance elution from the chromatographic polyamide carrier. The evaporation intensity of the amino acid derivatives is sufficient to get excellent mass spectra with significant structural information also with very small amounts of starting material (picomole level), which guarantee a high separation power in the TLC step. Besides the methylester derivatives, in part, products additionally methyl substituted at the sulfonamide nitrogen could be separated.
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  • 143
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The simple combination of thin-layer chromatography on polyamide with subsequent mass spectrometry of the separated compounds together with the carrier material has been employed for unambiguous identification of individual dipeptides in a mixture. The dipeptides were analysed in the form of their dansyl methyl ester derivatives. The appearance of molecular ions in the electron impact mass spectra simultaneously with the ions dans-NH=CHR⌝+ indicating the corresponding N-terminal amino acid residue enables a rapid and sensitive structure elucidation of the dipeptides. The chromatography and mass spectrometry can be performed with 0.2-0.3 nmol dipeptide.
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  • 144
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fast atom bombardment (FAB) followed by collisional activation (CA) mass spectrometry was used for structural analysis of steroidal oligoglycosides, containing two to four sugar units. In the molecular ion region of the FAB mass spectra of these underivatized natural products, intense protonated molecular ions were observed. The collisional activation spectra of these mass selected ions yield more sequence information than FAB mass spectra and are not contaminated with interfering peaks originating from impurities or matrix.
    Additional Material: 6 Ill.
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  • 145
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A highly sensitive (subpicomole level), structure-specific method of analysis has been developed for characterizing and quantitating the dinucleotide thymidylyl(3′ → 5′)thymidine methyl phosphotriester by desorption chemical ionization tandem mass spectrometry. The methodology can be applied to related compounds such as the parent dinucleotide and employs either positive or negative ionization mass spectra or daughter spectra. The procedure allows specification of the site of methyl attachment.
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  • 146
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Treatment of peptides containing methionine and/or tryptophan with dimethylsulfoxide/hydrochloric acid/acetic acid resulted in oxidation of these amino acids respectively to methionine sulfoxide and oxyindolalanine. This reaction was monitored by fast atom bombardment mass spectrometry using a dithiothreitol/dithioerythritol liquid matrix. Under these conditions, only methionine and tryptophan were oxidized. Comparison of mass spectra of a sample before and after oxidation should provide a rapid screening procedure for determination of these residues in peptides.
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  • 147
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Picolinyldimethylsilyl (PICSI) derivatives of long-chain fatty alcohols were prepared either in a two stage sequence involving reaction of the alcohol with an excess of bis(diethylamino)dimethylsilane followed by 3-pyridylcarbinol or by direct reaction with diethylaminodimethylsilyl-3-pyridylcarbinol. The mass spectra of the resulting PICSI derivatives were characterized by very abundant (base peak) molecular ions and a series of abundant radical-induced cleavage ions the masses and abundances of which gave information on the presence and position of double bonds from both mono- and poly-unsaturated alcohols.
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  • 148
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An analytical method, based on a selective extraction and pyrolysis gas chromatography/mass spectrometry assay of arsenocholine and acetylarsenocholine in aquatic organisms, is described. Characteristic fragmentation patterns were obtained from pyrolytically demethylated compounds. The molecules were rearranged in unique pathways which differed from those of corresponding nitrogen analogues. Qualitative determination of arsenocholine and acetylarsenocholine was achieved by gas chromatographic as well as mass spectrometric analysis of the thermal degradation products (trimethylarsine, dimethylvinylarsine and the demethylated arsenocholine or acetylarsenocholine). Arsenocholine and acetylarsenocholine in fish from industrially polluted water were isolated and identified. Massfragmentographic quantification of the arsenic compounds in fish was carried out by use of deuterium labelled analogues of arsenocholine and acetylarsenocholine as internal standards. The method showed a high sensitivity.
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  • 149
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    Biological Mass Spectrometry 14 (1987) 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 150
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    Biological Mass Spectrometry 14 (1987), S. 149-153 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conditions for normal phase high performance liquid chromatrography-chemical ionization mass spectrometry of underivatized glycosphingolipids with the use of a moving belt transport interface were investigated. Chromatography was performed on a 2 mm ID × 3 cm column packed with 5 μm spherical silica. A gradient of increasing methanol and water in methylene chloride was used to resolve mono-, di-, tri-, and tetraglycosylceramides and sulfatides in less than 15 min. A polyimide belt was used to transport the sample residues to the mass spectrometer where ammonia chemical ionization mass spectrometry was used to obtain spectra. One to 5 μg of each component was sufficient to obtain full spectral scans. Mono- and dihexosylceramide spectra showed [M + H]+ ions of good abundance, while the higher glycosphingolipids have molecular weights that exceed the range of the mass spectrometer utilized. All glycosphingolipids gave ions characteristic of their ceramide, fatty acid, long chain base and carbohydrate components. Sequence information which reflected the relative position of hexose and N-acetylhexosamine residues was also obtained.
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  • 151
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    Biological Mass Spectrometry 14 (1987), S. 167-172 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Alcophosphamide was identified in urine obtained from Sprague-Dawley rats treated with a 1:1 mixture of cyclophosphamide and β-(2H4)cyclophosphamide using chemical ionization mass spectrometry and the ion cluster technique. This compound was also quantified in rat plasma using gas chromatographic-mass spectrometry under ammonia chemical ionization following administration of cyclophosphamide. Apparent terminal half life of 76.2+/-13.7 min and area-under-the concentration-time curve value of 24.8+/-8.6 μg min/ml were obtained for derived alcophosphamide following iv bolus administration of cyclophosphamide. Following co-administrations of unlabeled and β-(2H4)cyclophosphamide via iv/po and iv/ip routes, apparent terminal half-lives of 68.4+/-16.4 and 71.8+/-10.1 min were found for the iv portions and 106.7+/-25.2 and 73.9+/-5.2 min for the non-iv portions, respectively, for the derived alcophosphamide. Phosphoramide mustard was found to be a major circulating and urinary metabolite in the rat following iv administration of preformed alcophosphamide which gave a plasma half-life of 1.9 h.
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  • 152
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The current methods for the qualitative and quantitative control of cosmetologically active triterpenic saponins in raw plant extracts and in cosmetic formulations are far from satisfactory in terms of specificity and sensitivity. Here we describe a method for the simultaneous detection and quantification of Hedera helix L. saponins directly using crude extracts from plant and cosmetic matrices. The first is achieved by conventional EI-mass spectral analysis (direct DEI conditions); the second by CAD MIKE spectrometry (collisionally activated decomposition mass-analysed ion kinetic energy spectrometry) of the EI-induced fragmentation product at m/z 248, which is common to the three saponins of Hedera helix L. (α-hederin, hederacosides B and C). The method is sensitive (sub ppb level), specific and since it is rapid it might be conveniently employed for the routine quality control of these active constituents in plant extracts and in cosmetic formulations.
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  • 153
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The gas chromatographic and mass spectrometric properties of the methyl, trifluorethyl, pentafluoropropyl and hexafluoroisopropyl esters of the pentafluoropropionyl and heptafluorobutyryl derivatives of twelve important acidic metabolites of biogenic amines have been investigated. The optimum derivatization conditions for the different classes of metabolites have been established and the byproducts formed in some of the derivatizations have been identified. Under certain derivatizing conditions, back-exchange of deuterium in the labelled internal standards was observed. No single derivative appears to be ideally suitable for the simultaneous quantitative analysis by GC/MS of all twelve metabolites, so extracts of plasma and urine were split and a combination of the methyl or trifluoroethyl esters of the pentafluoropropionyl derivatives were used.
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  • 154
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: β-Lipotrophin (62-77) or Ac-gastrin releasing peptide was incubated with immobilized carboxypeptidase Y or aminopeptidase M. Subsequent aliquots of each incubation mixture were analysed by fast atom bombardment mass spectrometry using a dithiothreitol/dithioerythritol liquid matrix. The use of immobilized enzymes and volatile buffers for exopeptidase digestions enabled rapid and facile separation of enzyme from digestion products. This approach to mass spectral peptide analysis reduced spectral background arising from a glycerol matrix, buffer salts, or enzyme proteins and contaminants, enabling analysis of as little as 200 picomoles of a suitable peptide.
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  • 155
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    Biological Mass Spectrometry 14 (1987), S. 263-270 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A publically distributed data base of evaluated electron ionization mass spectra is formed by selecting certain mass spectra from a much larger archive collection. The selection process is automated and a single spectrum for each substance is selected from multiple spectra of the same substance with the aid of a quality index (QI). The quality index is evaluated for efficacy in selecting the best spectrum, some modifications of the QI definition are made, and the redefined QI is used to select a new data base.
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  • 156
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    Biological Mass Spectrometry 14 (1987), S. 271-274 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Installation of a commercially available capillary-to-capillary column switching system in an otherwise unmodified gas chromatograph/mass spectrometer instrument is described. The first column is monitored via the jet separator, the second being connected directly to the ion source. This arrangement obviates the need for an auxiliary detector. A single gas chromatographic oven is adequate for many purposes.
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  • 157
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    Biological Mass Spectrometry 14 (1987), S. 281-287 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fragment ion spectra obtained from collision-induced decomposition of protonated molecular ions have been used to determine amino acid sequences of several physalaemin-like peptides which were recently purified from rabbit stomach. This technique was chosen because the peptides were available in microgram quantities and were anticipated to contain pyroglutamate as the blocked N-terminal residue. Such spectra of several synthetic analogs of the naturally occurring peptides were obtained and analyzed to confirm the veracity of this peptide sequencing strategy. In addition, methyl ester derivatives of these synthetic peptides provided a crucial test for the spectral interpretation via the mass shifts thus induced.
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  • 158
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    Biological Mass Spectrometry 14 (1987), S. 301-302 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 159
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    Biological Mass Spectrometry 14 (1987) 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 160
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    Biological Mass Spectrometry 14 (1987), S. 473-477 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Analysis of reports in the world's literature suggests that average sperm densities for groups of unselected males were relatively constant at about 108 million cells per ml prior to 1950. Subsequent to that time mean sperm densities appear to have declined. Regression analysis indicates the existence of significant negative correlations between mean sperm densities and production of synthetic organic chemicals among other parameters. Phthalate esters are one class of large volume organic chemicals that are known to disturb testicular function in laboratory animals. These compounds are also the most abundant man-made chemicals in the environment. Plots of the concentration of dibutylphthalate in the cellular fraction of ejaculates against either the sperm density or the total number of sperm for the same ejaculates gave two clusters of points. These clusters suggest the existence of two or more populations vis à vis phthalate metabolism; both of which show a negative correlation between phthalate concentration and sperm production.
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  • 161
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dinucleoside monophosphates bearing usual protecting groups at the exocyclic amino functions of the heterocyclic bases, the 5′-hydroxy group, the phosphate moiety and the O-6-position of the guanine ring have been analysed by FAB mass specrometry in the negative ion mode. These non-charged key intermediates for oligodeoxynucleotide synthesis exhibit very simple spectra in the mass range of m/z 400-1500 using tetra-ethylene glycol as matrix. Most of the observed ions could easily be assigned. Apart from deprotonated molecular ions sequence specific ions arising from C-O-P bond cleavage and ions derived from loss of protecting groups were observed. The simplicity of spectra interpretation makes FAB mass spectrometry to a rapid and valuable tool for unambiguous identification of dimeric synthons for oligonucleotide synthesis.
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  • 162
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    Biological Mass Spectrometry 14 (1987), S. 141-142 
    ISSN: 0887-6134
    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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    Biological Mass Spectrometry 14 (1987), S. 131-140 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mixtures of both synthetic and naturally occurring (human plasma) cholesteryl esters have been examined by capillary gas chromatography/mass spectrometry (GC/MS). A magnetic sector mass spectrometer was used and a variety of ionization modes were assessed with a view to obtaining structural information on intact cholesteryl esters. By employing ammonia as reagent gas, with negative ion scanning, spectra were produced from which the nature of steryl and fatty acyl moieties could be readily deduced. Analyses were performed at an ion source temperature of 300°C in order to maintain the integrity of the gas chromatographic profile. The technique described is of general use for the GC/MS analysis of steryl esters, particularly in conjunction with magnetic sector instruments.
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  • 164
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermospray spectra on a magnetic sector mass spectrometer, by definition measured at high accelerating voltages, are seen to be highly fragmented. This is rationalised in terms of the necessity to accelerate ions through a region of high pressure in the vicinity of the ion-collecting orifice at the spray volume, where ions may be energized by ion molecule collisions. In this region, a high percentage of the parent ion current is lost through the dispersion of the ion beam and by the collisional activation of molecular ions resulting in extensive fragmentation. The investigation of means by which these effects may be minimized has led to the construction of an improved sector thermospray source. Comparative results for gramicidin S demonstrate that its fragmentation is reduced and that the intensity of the protonated molecular ion is greatly enhanced.
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  • 165
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    Biological Mass Spectrometry 14 (1987), S. 183-185 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Acetates of 12 positionally isomeric tetradecenols (Δ2-Δ13) have been prepared and their mass spectra measured without any prior chemical modification. Comparison of spectra of all the isomers has shown the variation in intensities of some predominant fragments with the position of the double bond on the 14 carbons chain. The mass spectra were interpreted in terms of the relative intensity ratio of the fragment ion peaks to locate the double bond positions. A procedure for elucidation of the positional isomerism of tetradecenyl acetates is given.
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  • 166
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    Biological Mass Spectrometry 14 (1987) 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 167
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    Biological Mass Spectrometry 14 (1987) 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 168
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    Biological Mass Spectrometry 14 (1987), S. 535-541 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A moving belt interface was used to identify budesonide metabolites, obtained from rat and mouse liver incubations, by liquid chromatography/mass spectrometry (LC/MS). The metabolites were separated on a small-bore C18 column with an ethanol/water gradient as mobile phase at a flow rate of 0.2 ml min-1. A spray device was used for deposition of the aqueous solvent on to the belt. Chemical ionization mass spectra were obtained with methane as the reagent gas. Deuterium-labelled budesonide, which was used to facilitate metabolite identification by the isotope cluster technqiue, was found to be slightly separated from the unlabelled analogue on the LC column. Incubations were also performed under 18O2 to elucidate the mechanism of a new metabolic pathway (16α, 17α-acetal splitting) and to confirm the oxidative nature of reactions leading to hydroxylated metabolites. The moving belt LC/MS technique afforded higher sensitivity, and gave more abundant MH+ ions of the compounds studied, than previously found by direct probe mass spectrometry. Phthalate ester background, partly from the polymide belt, complicated the identification of minor metabolites.
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  • 169
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    Biological Mass Spectrometry 14 (1987), S. 563-572 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Male Wistar rats were exposed to 2000 ppm n-hexane or were treated with a single dose of 2,5-hexanedione (200 mg kg-1). Analysis of the urine collected after both treatments revealed the formation of 4,5-dihydroxy-2-hexanone via 5-hydroxy-2-hexanone or 2,5-hexanedione, respectively. Identification of this new n-hexane metabolite included enzymatic hydrolysis of the excreted glucuronide, derivatization of the keto group with O-methylhydroxyl-amine, and subsequent GC-MS analysis. The chemical structure derived from the mass spectra obtained was confirmed by further analysis of the methoxime-TMS derivatives and of deuterated 4,5-dihydroxy-2-hexanone excreted after treating rats with 2,5-[2H10]-hexanedione. 4,5-Dihydroxy-2-hexanone is proposed to be identical with a urinary constituent that is excreted by rats after n-hexane exposure and is converted to 2,5-dimethylfuran or 2,5-hexanedione, respectively, depending on the conditions of urine treatment prior to GC-MS analysis.
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  • 170
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    Biological Mass Spectrometry 14 (1987), S. 587-588 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 171
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    Biological Mass Spectrometry 14 (1987), S. 599-602 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method is described for the quantification in plasma of CP-55,940, a new non-opiate oral analgetic agent, using capillary gas chromatography/mass spectrometry. After extraction, derivation of the drug and a structural analog internal standard is carried out with trifluoracetyl imidazole. The derivative exhibited excellent gas chrornatographic properties. Electron impact yielded an abundant high mass ion whose monitoring permitted the sensitive and specific determination of CP-55,940 down to 0.5 ng ml-1.
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    Biological Mass Spectrometry 14 (1987), S. 613-616 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method is described for the quantification of tulobuterol in human plasma, based upon selective extraction and high resolution capillary gas chromatography-mass spectrometry. The mass spectrometric determination is based on selected ion monitoring of two fragment ions derived from the N,O-heptafluorobutyryl derivatives of tulobuterol and its internal standard, deschlorotulobuterol. The plasma work-up procedure consists of extraction of 1.0 ml alkalinised plasma with dichloromethane, back-extraction into an acidified aqueous phase, followed by a final extraction with dichloromethane after realkalinisation. The method gave interference-free and linear results. The between-assay variability is 4.7% CV at the 3.0 μg l-1 plasma concentration level. The assay permitted quantitative measurements down to 170 ng tulobuterol per litre of plasma and hence provided sufficient sensitivity for quantification of plasma levels after therapeutic doses.
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    Biological Mass Spectrometry 14 (1987), S. 627-632 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In phytochemical and chemotaxonomic research work mass spectrometry plays an outstandingly important role. Using gas chromatography/mass spectrometry (GC/MS) we established the chemotaxa of Tanacetum vulgare L. Chemotypes with essential oils countaining 60-90% of artemisia ketone, carveol, dihydrocarvone, myrtenol, umbellulone, terpinen-4-ol, davanone, and Tagetes species containing various essential oils can be clearly distinguished by their spectra; we examined many variations of Tagetes erecta, T. lucida, T. minuta, T. patula and T. tenuifolia. We have identified α-β-pinene-, 1,8-cineol-, linalool-, camphor-, nerol-, geraniol- and γ-gurjonene as components of Achillea distans L. Injecting the essential oil direct from the oil-secreting organs of T. minuta plants we identified using GC/MS 6-10 and 16% eugenol from the involucral bract and hypsophyll, respectively, as well as β-ocimene, dihydrotagetone, tagetone, Z- and E-ocimenones. In the course of studies on essential fatty acids Borago officinalis and Lappula squarrosa were selected from 70 species of the family Boraginaceae to obtain seed oil as a source of γ-linolenic acid, and for the PG synthesis we isolated several grams of γ-linolenic acid, as well as C18:4, i e. octadecatetraenic acid, from L. squarrosa on the basis of the mass spectra. From the seed oil of Aquilegia vulgaris C18:3 (5) from the oil of Limnanthes dougloasii C20:1 (5) and from the seed oils of Delphinium consolida and of Tropaeolum species (T. majus, T. minus, T. peregrinum) C20:1 (11) fatty acids were identified on the basis of spectra.
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  • 174
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polynuclear aromatic hydrocarbons are ubiquitous pollutants that may become highly carcinogenic during their metabolism by organisms. Benzo(a)pyrene is an example of such a compound. Benzo(a)pyrene metabolite standards, which are labile, polar compounds, have been used to evaluate high performance liquid chromatography-mass spectrometry as an analytical technique for polynuclear aromatic hydrocarbon metabolites. The chromatography used microbore (1 mm i.d.) C18 columns with acetonitrile/water as the elution solvent which became the reagent/moderator gas. A direct liquid introduction interface was used and characteristic spectra were obtained in the negative chemical ionization mode. Molecular or pseudomolecular ions were obtained for five phenols (m/z 268 and m/z 267) and three trans-dihydrodiols (m/z 286, m/z 285, m/z 284). Useful spectra were also obtained for a tetrahydrotriol, four tetrahydrotetrols and three conjugated metabolites. Fragmentation usually involved loss of water and anions at m/z 284 and m/z 268 were common to most of the spectra. Variations in the source/desolvation chamber temperature between 175°C and 275°C caused significant alterations in the relative abundance of molecular and fragment ions. Dissociative electron capture was the dominant ionization process.
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  • 175
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fast atom bombardment mass spectrometry (FAB MS) and fast atom bombardment mass spectrometry-mass spectrometry (FAB MS/MS) were used to study the monovalent glycoside polyether antibiotics maduramicin α, β and δ and the maduramicin α salts, their derivatives and degradation products. Also, representative compounds from three major classes of polyether antibiotics were studied: the monovalent polyethers, nigericin and monensin A, the divalent polyether lasalocid A and the monovalent glycoside polyethers septamycin, BL580 δ, etheromycin and carriomycin. The respective FAB fragment and decomposition ions were correlated with the known structures. The FAB spectra of all the polyethers contained metal-adduct molecular ions. Protonated molecular ions were absent. All the polyethers having a β-hemiketal carboxylic acid group produced an abundant ion, often the base peak of the spectra, 62 daltons less than the corresponding metal-adduct molecular ion. The gas phase mechanism proposed for the formation of this fragment ion is an unusual unimolecular reaction which is initiated by an intramolecular proton transfer from the carboxylic acid to the hydroxy group of the β-hemiketal, and, then followed by the concerted losses of water and carbon dioxide to produce the corresponding polyether olefin.
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  • 176
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    Biological Mass Spectrometry 14 (1987), S. 343-354 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Primary effluent from a municipal wastewater treatment plant was used as the feed in bench scale activated sludge systems. These systems were spiked with disperse azo dyes at 1 mg l-1 and 5 mg l-1 levels and were sampled at various points in the process. Samples were analysed by high performance liquid chromatography with UV = visible detection and by thermospray ionization MS and tandem mass spectrometry (MS/MS) using direct injection or via column chromatography. The tandem mass spectrometry techniques were used both for method development purposes and for the specificity and extra information these techniques can provide. The investigation of the fate of disperse azo dyes in the activated sludge process was a major feature of this study. Major degradation products have been identified by tandem mass spectrometry analyses of these wastewaters. Precision and accuracy data generated by the thermospray tandem mass spectrometry technique are compared to those derived from the high performance liquid chromatography /UV-visible method.
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  • 177
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    Biological Mass Spectrometry 14 (1987), S. 357-362 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several classes of environmentally significant compounds were introduced into an ion trap detector (ITD) by capillary column gas chromatography, and the performance of the device as a gas chromatography/mass spectrometry (GC/MS) system was studied. The experiments conducted included studies of the precision of selected ion monitoring (SIM) measurements, the precision of relative ion abundance measurements in full mass range scans, the sensitivity and instrument detection limits in SIM and full mass range data acquisition, and the linear range of concentration calibration. It was observed that resolution may be lost and saturation may occur under certain conditions, and that the data system can report artifact ions under these conditions.
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  • 178
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    Biological Mass Spectrometry 14 (1987), S. 591-598 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Laser desorption mass spectrometry has been employed for the structural determination of lipid A components derived from the lipopolysaccharides (LPS) of gram-negative bacteria. Mass spectra were obtained for methylated monophosphoryl lipid A from Neisseria gonorrhoeae and Rhodopseudomonas sphaeroides, for diphosphoryl lipid A from Escherichia coli and for the intact LPS from the Re Mutant of E. coli consisting of triphosphoryl lipid A and two KDO (2-keto-3-deoxyoctonate) units. Fragmentation of the phosphate (or pyrophosphate) on the reducing glucosamine is followed by fragmentation of acyl-linked fatty acids. Also observed are fragmentions which correspond to the distal portion of the molecule.
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  • 179
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    Biological Mass Spectrometry 14 (1987), S. 623-625 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The use of thermospray LC/MS for quantitative analysis using isotope dilution is reviewed. Assays for acetylcholine, glucose, sorbitol, cortisol, testosterone and 1,25-(OH)2-vitamin D in biological fluids are discussed.
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  • 180
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    Biological Mass Spectrometry 14 (1987), S. 639-641 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Branched-chain hydrocarbon-induced nephropathy in male rats was examined using 2,3,4-trimethylpentane. Lesions are elected only in male rats, not in females or in controls. Mechanisms of nephropathy may be the interaction of metabolites with the male rat-specific protein alpha 2u globulin. The identified urinary metabolites of 2,3,4-trimethylpentane in male rats given the hydrocarbon by gavage are 2,3,4-trimethyl-1-pentanol, 2,3,4-trimethyl-2-pentanol and 2,3,4-trimethyl-1-pentanoic acid. Of the C8-isomers, 2,3,4-trimethylpentane dosing leads to the highest incidence of kidney damage in male rats.
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  • 181
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    Biological Mass Spectrometry 14 (1987), S. 659-662 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method for simultaneous quantitative determination of erythromycin 2′-ethylsuccinate and erythromycin in human plasma is described. After extracting the deuterium-labelled internal standards and analytes from alkalinized plasma to diethyl ether the extracts were analysed by fast atom bombardment mass spectrometry. The quantification limit for 2′-ethylsuccinate ester was 50 ng ml-1 and for erythromycin 100 ng ml-1. The calibration curves were linear up to 5 μg ml-1 for both. The precision of the method at higher concentration was less than 2% and at the quantification limit ∼6% for both analytes.
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  • 182
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    Biological Mass Spectrometry 14 (1987) 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 183
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An automated capillary column gas chromatography electron-impact mass selective detection method has been developed for the determination of a major tranquilizing agent, fluphenazine. Using a new purification method and incorporating a deuterated internal reference, a limit of quantitation of 50 pg per ml of plasma was obtained.
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  • 184
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Direct analysis of unpurified urine from patients with β-ketothiolase deficiency and glutaryl-coenzyme A dehydrogenase deficiency was carried out by methylation and fast atom bombardment mass spectrometry. Previously unidentified signals consistent with unusual acylcarnitines were detected. In the former disease, thermospray liquid chromatography/mass spectrometry analysis confirmed the identification of tiglylcarnitine and differentiated it from a biological isomer, 3-methylcrotonylcarnitine. In glutaric aciduria, glutarylcarnitine was confirmed by detection of glutaric acid liberated upon base hydrolysis of a purified acylcarnitine fraction. The discovery of these metabolites suggests that L-carnitine therapy might be beneficial for the enhanced excretion of toxic metabolites that accumulate in patients with these disorders.
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  • 185
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    Biological Mass Spectrometry 14 (1987), S. 207-211 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Eight normal subjects ingested 125 mg of p-tyramine-β,β-2H2 hydrochloride and the 3 h and following 21 h urine collections were analysed by mass spectrometry with selected ion monitoring for the deuterated metabolites: free and conjugated p-tyramine-β,β-2H2, free p-octopamine-β-2H1, free and conjugated p-hydroxyphenylacetic acid-α-2H1 and -α,α-2H2, and free p-hydroxymandelic acid-α-2H1. These metabolites accounted for 72% of the ingested label, of which conjugated p-tyramine and free p-hydroxyphenylacetic acid constituted 90%. Approximately 50% of the total deuterated tyramine and 70% of the total deuterated p-hydroxyphenylacetic acid were excreted in the first three hours, although there was considerable variation between individuals. The presence of a small amount of p-hydroxyphenylacetic acid-α-2H1 suggests that some exchange of deuterium occurred at the intermediate p-hydrophenylacetaldehyde stage.These results, based as they are on metabolites labelled with the stable isotope deuterium, ought to be more reliable than earlier studies in which unlabelled tyramine was ingested with the resultant metabolites, indistinguishable from their endogenous metabolic counterparts, being measured by fluorimetry or gas chromatography.
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  • 186
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    Biological Mass Spectrometry 14 (1987), S. 221-227 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Human exposure to aromatic amines may be monitored by measuring the amount of sulfinamide adduct bound to hemoglobin. In order to develop a sensitive and selective method for measuring aromatic amines present in low concentrations the mass spectra of the pentafluoropropionamide derivatives of a series of aromatic amines were determined under various ionization conditions. With electron ionization the aromatic amine derivatives typically yield intense molecular ions with fragmentation leading to elimination of C2F5 and COC2F5. Higher molecular weight polycyclic aromatic amines, e.g., 6-aminochrysene, give prominent molecular ions as well as intense ions corresponding to M-174 (loss of CNHCOC2F5). With positive chemical ionization using methane as reagent gas the derivatives give protonated molecular ions as the base peaks, as well as the associated ions at M + 29 and M + 41. Negative ion chemical ionization yields, primarily, peaks corresponding to the loss of HF from the molecular anions. Negative ion chemical ionization with selected ion monitoring is generally more suitable than positive chemical ionization or electron ionization for the quantitative analysis of aromatic amines present in biological samples in the mid femtomolar range. Exposure of human subjects to aromatic amines was determined via basic hydrolysis of the isolated sulfinic acid amide hemoglobin adducts. Analysis of the derivatized extracts by gas chromatography/negative ion chemical ionization/mass spectrometry demonstrated the presence of aniline, ortho-, meta-, and para-toluidine, 2-naphthylamine, and 4-aminobiphenyl. The hemoglobin adduct levels of these amines in both cigarette smokers and nonsmokers were determined. The mean values of the adduct levels of ortho- and para-toluidine, 2-naphthylamine, and 4-aminobiphenyl were higher in smokers than in nonsmokers, while the mean adduct values of aniline and meta-toluidine were similar in both groups. Adducts of 2-, 3-, 4-ethylaniline, 2,3-, 2,4-, 2,5-, 2,6-dimethylaniline, and 3-aminobiphenyl have been detected in smokers' blood. 1-Aminoanthracene, 9-aminophenanthrene, and 6-aminochrysene have not been detected. GC/MS procedures were also used to determine the extent of binding of aniline-2,3,4,5,6-d5 to hemoglobin in rats administered aniline-d5.
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  • 187
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    Biological Mass Spectrometry 14 (1987), S. 97-102 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dicyclopentadiene, a waste product of manufacturing at the Rocky Mountain Arsenal near Denver Colorado, has been detected in ground water at this facility. Ground water extracts were analysed by gas chromatography-mass spectrometry (GC/MS) to determine if derivatives of dicyclopentadiene were present in addition to dicyclopentadiene and other chemical wastes. The derivatives thus identified were characterized by GC high resolution MS, deuterium exchange for active hydrogen in the chemical ionization source of the mass spectrometer, and GC/MS following on-column base catalyzed deuteration of enolizable hydrogen. Two ketone derivatives of dicyclopentadiene were identified by comparison with synthetic standards.Ground water derivatives of dicyclopentadiene were compared with mammalian enzymatic metabolites produced in vitro by incubation with immobilized rabbit liver cytochromes P-450. The metabolites were analysed by GC/MS and by GC/MS following derivatization and deuterium labelling. Although not found in ground water samples, the two metabolites were identified as monoepoxides of dicyclopentadiene by comparison with compounds synthesized in the laboratory.
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  • 188
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    Biological Mass Spectrometry 14 (1987), S. 275-280 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Twenty-one organosulphur compounds were detected in a survey of water, industrial effluent, sediment and fish samples, using automated gas chromatography/mass spectrometry developed for the identification of forty target semi-volatile and volatile organosulphur compounds. The compound classes detected in the environmental samples are three allotropes of sulphur, three thioethers, five sulphones, six thiophenes, one thiol, two sulphonamides and one thiazole. The compounds were detected in the approximate concentration range 0.1 to 2000 parts per billion (ppb). α,α-Dichlorodimethyl sulphone was detected in environmental samples subjected to biodegradation and chemical treatment.
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  • 189
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    Biological Mass Spectrometry 14 (1987), S. 295-299 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 190
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Field desorption mass spectrometry was applied to a series of underivatized anthracycline, cosmomycins, to obtain fragment ions which were mass analysed using the linked scan technique without using collision activated dissociation. The daughter spectra of the various protonated compounds contain sugar sequence information which is in the mass spectra. The mass spectrometric data make it clear that field desorption tandem mass spectrometry can become a valuable additional technique for the structural analysis of anthracyclines.
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  • 191
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The gas chromatographic and mass spectrometric properties of leukotriene B4, 20-hydroxy-leukotriene B4 and 20-carboxy-leukotriene-B4 were investigated as their methyl ester trimethylsilyl, methyl ester allyldimethylsilyl and methyl ester tert-butyldimethylsilyl ethers. The gas chromatographic properties of the trimethylsilyl and tert-butyldimethylsilyl ether derivatives were good with respect to peak shape and sensitivity, whereas the allyldimethylsilyl ether derivative gave a lower sensitivity. The sensitivity defined as the quantity that could be passed through the gas chromatographic column.The three derivatives showed a mass spectrometric fragmentation pattern with cleavage of the C12—C13 bond as an important feature. Particularly, the allyldimethylsilyl ether derivative of the three compounds studied exhibited a high tendency for C12—C13 bond cleavage resulting in a fairly intense ion at m/z 435. However, the mass spectra indicated multiple fragmentation pathways due to the presence of double bonds, leading to decreased intensities of the high mass ions. A quantitative analysis by selected ion monitoring of the most intense high mass ions in the respective mass spectrum demonstrated that neither derivative would allow measurements in the low picogram range. Catalytic hydrogenation of the double bonds was performed and the methyl ester trimethylsiyl, methyl ester allyldimethylsilyl and methyl ester tert-butyldimethylsilyl ether derivatives of the reduced compounds were prepared. Saturation of the double bonds increased the gas chromatographic sensitivity for the three derivatives as well as the intensities of the high mass ions in their mass spectra. The high sensitivity that can be obtained by measurement of such high mass ions was demonstrated by quantification of leukotriene B4 in lung tissue samples by selected ion monitoring.
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  • 192
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    Biological Mass Spectrometry 14 (1987), S. 355-355 
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    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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    Biological Mass Spectrometry 14 (1987), S. 363-367 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The indoor air quality of the offices of smokers and nonsmokers was surveyed for volatile organic compound identities and concentrations. These results were examined to determine whether environmental tobacco smoke contamination could be distinguished from airborne pollutants outgassing from other sources. It was not possible to positively attribute volatile organic contaminants to environmental tobacco smoke. It was possible to distinguish between smokers' and nonsmokers' offices by determining airborne nicotine levels.
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  • 194
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A study of the binding to human serum albumin (HSA) of caffeine and its deuterated isotopomers, 1-C2H3-, 3-C2H3-, 1,7-(C2H3)2-, 3,7-(C2H3)2- and 1,3,7-(C2H3)3-caffeine, was performed by equilibrium dialysis. Free and bound fractions were measured by gas chromatography/mass spectrometry. Important and significant (Fischer and Student tests) isotope effects were observed on binding parameters: sites total concentration (N = 1732) μM for 1,3,7-(C2H3)3-caffeine versus 822 μM for caffeine; number of sites (n = 3 for 1,3,7-(C2H3)3-caffeine v. 1 for caffeine); and extent of binding (46% for 1,3,7-(C2H3)3-caffeine v. 27% for caffeine).A study of competition for HSA binding between caffeine and its 1,3,7-(C2H3)3- and 3,7-(C2H3)2-isotopomers confirmed the results obtained in direct binding studies. These isotope effects are discussed in terms of (a) tools for molecular pharmacology, (b) precautions to be taken when such labelled drugs are used in clinical pharmacology.
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  • 195
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    Biological Mass Spectrometry 14 (1987), S. 689-697 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For the identification of intact underivatized drug conjugates, the mass spectrometric technique of choice is fast atom bombardment (FAB); the combined use of both positive and negative ion FAB usually provides information on the molecular mass and nature of conjugates under study, while the number of exchangeable hydrogen atoms can be determined using trideuterated glycerol as the FAB-matrix. Electron impact and desorption chemical ionization spectra can be used to study the aglycone part of the conjugated metabolites. With this approach metabolites conjugated with glucuronic acid, sulphuric acid and amino acids have been identified. The identification was supported by analysis of reference compounds, prepared by chemical synthesis. The examples given are selected from current metabolism studies on drug candidates in development within Organon's research.
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  • 196
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    Biological Mass Spectrometry 14 (1987), S. 533-534 
    ISSN: 0887-6134
    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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    Biological Mass Spectrometry 14 (1987), S. 523-531 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Derivatization of prostaglandins and thromboxane B2 using diethyl amino ethyl chloride and diethyl amino ethyl bromide improved thermospray HPLC/MS sensitivity. The derivatization was evaluated for prostaglandin A1, A2, D2, E2, F1α, F2α, and thromboxane B2. The derivatization reaction, thermospray operating conditions, and mode of detection were optimized to produce the most intense [M + H]+ or [M - H]- ions for the derivative. Derivatization was better than 99% complete in 1 hour at 75°C. No thermal degradation of the prostaglandins was observed. Positive thermospray ionization proved the mode most sensitive, enabling detection from 10 to 300 pg of each prostaglandin under multiple ion detection. The thermospray spectra exhibited intense [M + H]+ ions for the derivative with a few fragment ions from sequential losses of water from the [M + H]+ ion. Detection of a prostaglandin metabolite in plasma over the concentration range from 3 ppm to 30 ppb was possible using this derivatization.
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  • 198
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    Biological Mass Spectrometry 14 (1987), S. 669-673 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass of intact and enzymatically derived fragments of cecropin B, an antibacterial protein from the Chinese oak silk moth, Antherea pernyi, have been determined by 252Cf plasma desorption time-of-flight mass spectrometry. As a result, the carboxy terminal amino acid sequence of the protein was established.
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  • 199
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    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The technique of isotope dilution mass spectrometry has been used for the measurement of biogenic amine metabolites in cerebrospinal fluid (CSF). CSF samples were collected from rabbits treated with α2-antagonists. The aim of our study was to determine the specificity of these drugs on the central nervous noradrenergic, dopaminergic and serotonergic activity as measured by the release of corresponding monoamine metabolites. 3-Methoxy-4-hydroxyphenylethylene glycol (MHPG) and vanilmandelic acid (VMA) were used as parameters for the noradrenergic activity, whereas homovanillic acid (HVA) and 5-hydroxyindole-3-acetic acid (5-HIAA) were employed to follow the dopaminergic and serotonergic activity, respectively. For the measurement of the biogenic amine metabolites a published GCMS method has been adapted. Samples of 200 μl CSF were processed. Following addition of deuterated internal standards and acidification, extraction was carried out with ethyl acetate. Preliminary experiments with the analysis of MHPG using diethyl ether for extraction gave rise to emulsion formation and resulted in poor recoveries for MHPG and in irreproducibility problems due to a preferential extraction of non-labelled MHPG, effects which were not observed with ethyl acetate extraction. Derivatization was done with a mixture of pentafluoropropionic anhydride/pentafluoropropanol (or hexafluoroisopropanol) in order to derivatize both hydroxyl and carboxylic acid groups. The derivatization procedure was optimized for the analysis of 5-HIAA by carrying out a second reaction step with pentafluoropropionic anhydride alone in order to complete the derivatization for the indolic NH moiety. The molecular ions of the derivatized products were selected for detection. The methodology has been applied to evaluate the effects of two α2-antagonists, i.e. yohimbine and idazoxan. Yohimbine was found to increase the CSF levels of the noradrenergic metabolites MHPG and VMA and of the dopaminergic metabolite HVA and to have serotonergic effects, whereas idazoxan was shown to exhibit noradrenergic effect only.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 200
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 14 (1987), S. 683-688 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The determination of thyroid hormones is widely used for the diagnosis and therapy control of thyroid disorders. In particular, thyroxine in serum is one of the most frequently determined endocrine parameters. Unfortunately, the results obtained by the use of different commercial test kits vary significantly, and until now there has been no means to decide whether a particular enzyme or radioimmunoassay kit yields accurate results or not. It seemed, therefore, necessary to develop definitive or reference methods for the measurement of thyroxine and to apply this technique for the assessment of target values in control sera for internal and external quality control. In the present investigation, an analytical protocol using the isotope dilution mass spectrometry technique is described which is herewith proposed as a definitive method for the measurement of thyroxine in human serum. The procedure consists of the following steps. (i) Equilibration of endogenous thyroxine in a serum sample with 100 ng [13C2]thyroxine. (ii) Isolation of the thyroid hormones by using a cation exchange resin. (iii) Formation of the methyl ester by reaction with methanolic hydrochloric acid. (iv) Purification of the methyl ester by column chromatography on Sephadex LH-20. (v) Formation of the N,O-bistrifluoroacetyl derivative with trifluoracetic anhydride. (vi) Selected ion monitoring of fragment ions of the thyroxine and the [13C2]thyroxine derivatives at m/z 870 and 872 using a magnetic sector field mass spectrometer with electron impact ionization combined with a capillary gas chromatography column. This method is now used to assign target values in a German quality control scheme. The precision of the method is of the order of 1-2% (coefficient of variation).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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