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  • Analytical Chemistry and Spectroscopy  (1,441)
  • Inorganic Chemistry  (732)
  • 1990-1994  (2,173)
  • 1980-1984
  • 1925-1929
  • 1992  (2,173)
Collection
Keywords
Publisher
Years
  • 1990-1994  (2,173)
  • 1980-1984
  • 1925-1929
Year
  • 1
    Electronic Resource
    Electronic Resource
    Artificial intelligence in chemistry: Structure elucidation and simulation of organic reactions, Zdzislaw Hippe, Elsevier Science Publishers, Amsterdam, 1991, ISBN 0-444-98746-0 (Vol. 73), 278 pp., Price 240 f1 (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 286-287 
    Details
    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
    URL: http://dx.doi.org/10.1002/cem.1180060509
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  • 2
    Electronic Resource
    Electronic Resource
    Multiple-correspondence analysis optical microscopy for determination of starch granules (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 163-175 
    Details
    ISSN: 0886-9383
    Keywords: Multiple-correspondence analysis ; Starch granule description ; Image analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Raw starch is composed botanically of characteristic granules of various sizes and shapes, so that each kind of starch may be characterized by the population of its granules. In the present study ten commercial starch species were studied: wheat, rice, manioc, potato, arrowroot, amylomaize, normal maize, waxy maize and two different banana species. Six variables measuring the size and shape of granules were obtained by image analysis. The objective was to find a method to describe and compare the granule populations of the ten species. For such a study, multiple-correspondence analysis (MCA) was applied. MCA makes it possible to draw similarity maps of categories and objects. For each starch species the frequency distributions (histograms) of the six variables were assessed and each granule was characterized by its species and the classes of histograms to which it belonged. MCA was applied to the granule table and a description of the histogram classes and the granules was obtained. From the variables description a general typology of the granules was deduced. The similarity maps showed considerable scatter of the granules for all species except rice. A particular species could therefore not be identified by a single granule, but the granule distribution seemed to be characteristic. MCA was an appropriate method to analyse these data because it points out non-linear relationships between quantitative and qualitative variables.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180060307
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  • 3
    Electronic Resource
    Electronic Resource
    Estimation of prediction error for samples within the calibration range (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 177-188 
    Details
    ISSN: 0886-9383
    Keywords: PLS ; Prediction error ; Background constituents ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A modification of a technique proposed by Lorber and Kowalski for the estimation of prediction errors is presented. The method is applied to five data sets. The results show that for some data sets the estimated prediction errors are close to the actual prediction errors for samples within the calibration range, while samples outside the calibration range must be background corrected before quantification of the prediction error.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180060403
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  • 4
    Electronic Resource
    Electronic Resource
    MARS: A tutorial (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 199-216 
    Details
    ISSN: 0886-9383
    Keywords: MARS ; Splines ; Multivariate calibration ; Non-linear ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This tutorial paper presents a simplified view of one of the more recently published multivariate calibration methods particularly suited to dealing with non-linear data sets. The method is referred to as MARS and stands for multivariate adaptive regression splines. Simple examples are provided to explain the workings of the method.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180060405
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  • 5
    Electronic Resource
    Electronic Resource
    Software news (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 229-229 
    Details
    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
    URL: http://dx.doi.org/10.1002/cem.1180060409
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  • 6
    Electronic Resource
    Electronic Resource
    Chemometrics: Applications of mathematics and statistics to laboratory systems, R. G. Brereton, Ellis Horwood, Chichester, ISBN-0-13-131350-9, 307 pp., £54.50, (1990) (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 228-228 
    Details
    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
    URL: http://dx.doi.org/10.1002/cem.1180060408
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  • 7
    Electronic Resource
    Electronic Resource
    Masthead (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992) 
    Details
    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
    URL: http://dx.doi.org/10.1002/cem.1180060501
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  • 8
    Electronic Resource
    Electronic Resource
    Diary (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. i 
    Details
    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
    URL: http://dx.doi.org/10.1002/cem.1180060502
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  • 9
    Electronic Resource
    Electronic Resource
    Data analysis with minimal assumptions (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 247-255 
    Details
    ISSN: 0886-9383
    Keywords: Analysis of variance ; Assumptions ; Graphics ; Models ; Validation of model ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The computer has made it possible to scrutinize data rapidly by means of graphics. This should be done prior to the application of any model to the data, since the model must be validated before using it as a means of analyzing the data. The procedure is illustrated in terms of two examples of real experimental data.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180060504
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  • 10
    Electronic Resource
    Electronic Resource
    On the integration of kinetic models using a high-order taylor series method (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 231-246 
    Details
    ISSN: 0886-9383
    Keywords: Integration methods ; Taylor series method ; Optimization methods ; Kinetic mechanisms ; Kinetic determinations ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A general equation to derive kinetic models up to any order is given. This equation greatly facilitates the application of the Taylor series method to the integration of kinetic models up to very high orders. When dealing with non-stiff models, computing time is always reduced by increasing the integration order, at least up to the 20th order. When the model is stiff, the integration order should be optimized; however, a twelfth order is recommended to integrate weakly stiff models. The use of an algorithm which permits the immediate calculation of the integration step size required to maintain a given accuracy leads to further reductions in computing time. When implemented as recommended here, a high-order Taylor series method is more rapid and accurate than Runge-Kutta and predictor-corrector methods and can be advantageously used in combination with optimization methods to perform mechanism studies and in multicomponent kinetic determinations.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180060503
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  • 11
    Electronic Resource
    Electronic Resource
    Weighted analysis of principal components: Two approximations to statistical weightsPart of the Master of Science Thesis by D.P. (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 257-266 
    Details
    ISSN: 0886-9383
    Keywords: Principal factor analysis ; Factor analysis ; Eigenvalue analysis ; Multivariate analysis ; Weighted factor analysis ; Procrustean analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two approximate methods for weighted principal components analysis (WPCA) were devised and tested in numerical experiments using either empirical variances (obtained from replicated data) or assumed variances (derived from unreplicated data). In the first (‘spherical’) approximation each data vector was assigned a weight proportional to the geometrical mean of its variances in all dimensions. The arithmetical mean of variances was used instead in the other approximation. Both the numerical experiments with artificial data containing random errors of various kinds (constant, proportional, constant plus proportional, Poisson) and the analysis of two sets of Raman spectra clearly indicated the necessity of introducing statistical weights. The spherical approximation was found to be slightly better than the arithmetical one. The application of statistical weighting was found to improve the performance of PCA in estimation problems.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180060505
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  • 12
    Electronic Resource
    Electronic Resource
    Genetic algorithms as a strategy for feature selection (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 267-281 
    Details
    ISSN: 0886-9383
    Keywords: Genetic algorithms ; Feature selection ; Multivariate analysis ; Optimization methods ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Genetic algorithms have been created as an optimization strategy to be used especially when complex response surfaces do not allow the use of better-known methods (simplex, experimental design techniques, etc.). This paper shows that these algorithms, conveniently modified, can also be a valuable tool in solving the feature selection problem. The subsets of variables selected by genetic algorithms are generally more efficient than those obtained by classical methods of feature selection, since they can produce a better result by using a lower number of features.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/cem.1180060506
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  • 13
    Electronic Resource
    Electronic Resource
    Masthead (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992) 
    Details
    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
    URL: http://dx.doi.org/10.1002/cem.1180060601
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  • 14
    Electronic Resource
    Electronic Resource
    Masthead (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992) 
    Details
    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
    URL: http://dx.doi.org/10.1002/cem.1180060101
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  • 15
    Electronic Resource
    Electronic Resource
    Simple validatory tools for judging the predictive performance of parafac and three-way PLS (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 11-28 
    Details
    ISSN: 0886-9383
    Keywords: Three-way PLS ; PARAFAC ; Unfolding ; Validatory tools ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The methods PARAFAC and three-way PLS are compared with respect to their ability to predict reversed-phase retention values. Special attention is paid to simple validatory tools, the meaning and use of which are explained.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180060103
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  • 16
    Electronic Resource
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    Mathematical model for the optimization of the reaction between 2,3-bis(m-tolyl)quinolizinium bromide and piperidine using a factorial design (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 1-10 
    Details
    ISSN: 0886-9383
    Keywords: Derivatization reaction ; Factorial design ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A number of nucleophiles have been successfully identified and quantified using the Kröhnke reaction with 2,3-diphenyl derivatives of quinolizinium salts. Optimization of the reaction conditions by means of a mathematical model involving analysis of the response surface has led to a better understanding of the factors exerting an influence on the above reaction.The parameters chosen were temperature, reaction time, base concentration, water concentration and nucleophile concentration. The reaction was developed in polar aprotic solvents (acetone, acetonitrile). To facilitate the nucleophilic attack, the presence of an organic base (triethylamine) was necessary, although concentrations in excess of 0·15M did not alter the development of the reaction. Since pharmaceutical solutions are often aqueous, the influence of water on the reaction was studied. Low water volumes have no significant influence on the opening of the quinolizinium ring by the nucleophilic reagent. However, when the water proportion exceeded that of the organic solvent, the fluorescence intensity was lower than expected. Development of the fluorescent reaction product was first detected 5 min after the reaction started. The fluorescence intensity reached its optimum value after 138 min.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/cem.1180060102
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  • 17
    Electronic Resource
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    Editorial (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 63-64 
    Details
    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
    URL: http://dx.doi.org/10.1002/cem.1180060204
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  • 18
    Electronic Resource
    Electronic Resource
    A new receptor model: A direct trilinear decomposition followed by a matrix reconstruction (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 65-83 
    Details
    ISSN: 0886-9383
    Keywords: Trilinear decomposition ; Receptor modeling ; Source identification ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In many cases, monitoring data for ambient airborne particles can be organized in the form of a three-way data table with one way for chemical species, one for sampling periods and one for sites. A direct trilinear decomposition followed by a matrix reconstruction (DTDMR) is developed to analyze such a data table as a whole. The three-way data set is composed into three two-way matrices by a direct trilinear decomposition (DTD). The column vectors of each of the matrices are called ‘source profiles’, ‘emission patterns’ and ‘site coefficients’ respectively. Particulate sources are identified by examining both their source profiles and emission patterns. After the sources have been identified, emission patterns and site coefficients are used to produce a three-way matrix that gives estimates of mass contributions of sources to the samples collected at every site in every period. By simulation study, not only has the method been verified, but a good indicator has been found that shows the number of factors (i.e. sources) in the system. Unlike other receptor models, DTDMR does not require source profile data and does not involve trial-and-error procedures. Since DTDMR identifies sources based on variations in two dimensions, it has a higher potential to distinguish two sources that have similar chemical compositions. The DTDMR model has provided excellent results with simulated data and has been applied in a real world three-way data set.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180060205
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  • 19
    Electronic Resource
    Electronic Resource
    Computer-generated multicomponent calibration designs for optimal analysis sample predictions (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 85-96 
    Details
    ISSN: 0886-9383
    Keywords: Optimization ; Calibration ; Simulated annealing ; Experimental design ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper utilizes variable step size generalized simulated annealing (VSGSA) to design multicomponent calibration samples for spectroscopic data. VSGSA is an optimization procedure which is capable of converging to exact positions of global optima located on multidimensional continuous functions. On the basis of analysis sample response vectors, optimally designed calibration concentration matrices are obtained assuming knowledge of components present. The complexity of response surfaces established by the optimization criteria is described.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/cem.1180060206
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  • 20
    Electronic Resource
    Electronic Resource
    Ranking principal components to reflect group structure (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 97-102 
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    ISSN: 0886-9383
    Keywords: Between-group variances ; Canonical variate criterion ; Eigenvalues ; Eigenvectors ; Orthogonal projection ; Within-group variance ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Canonical variate analysis is the appropriate descriptive technique for multivariate data which have an a priori group structure, but problems arise with this technique when there are more variables than within-group degrees of freedom because of singularity of matrices. In such cases it is shown through illustrative examples that principal component analysis is a viable substitute provided that the principal components are ranked according to the canonical variate criterion (ratio- of between- to within-group variances) rather than the usual criterion of total variance. This ranking can also be used to select components for subsequent discriminant analysis.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/cem.1180060207
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  • 21
    Electronic Resource
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    Masthead (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992) 
    Details
    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
    URL: http://dx.doi.org/10.1002/cem.1180060301
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  • 22
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    Diary (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. i 
    Details
    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
    URL: http://dx.doi.org/10.1002/cem.1180060302
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  • 23
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    Design and optimization in organic synthesis, Rolf Carlson, Elsevier, Amsterdam ISBN 0-444-89201-X, No. of pages: 552, price: 330 f1 (1992) (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 284-285 
    Details
    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
    URL: http://dx.doi.org/10.1002/cem.1180060508
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  • 24
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    Masthead (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992) 
    Details
    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
    URL: http://dx.doi.org/10.1002/cem.1180060401
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  • 25
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    Diary (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. i 
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    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
    URL: http://dx.doi.org/10.1002/cem.1180060402
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  • 26
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    Which principal components to utilize for principal component regression (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 217-225 
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    ISSN: 0886-9383
    Keywords: Principal component regression ; Calibration ; Optimality ; Principal component selection ; Quantitative structure-activity relationship ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Principal components (PCs) for principal component regression (PCR) have historically been selected from the top down for a reliable predictive model. That is, the PCs are arranged in a list starting with the most informative (PC associated with the largest singular value) and proceeding to the least informative (PC associated with the smallest singular value). PCs are then chosen starting at the top of this list. This paper discusses an alternative procedure of treating PC selection as an optimization problem. Specifically, without any regard to the ordering, the optimal subset of PCs for an acceptable predictive model is desired. Five data sets are analyzed using the conventional and alternative approaches. Two data sets are spectroscopic in nature, two data sets deal with quantitative structure-activity relationships (QSARs) and one data set is concerned with modeling. All five data sets confirm that selection of a subset without consideration to order secures the best results with PCR. One data set is also compared using partial least squares 1.
    Additional Material: 7 Tab.
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    URL: http://dx.doi.org/10.1002/cem.1180060406
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  • 27
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    Sequential simplex optimization, Fredrick H. Walters, Lloyd R. Parker Jr., Stephen L. Morgan and Stanley N. Deming, CRC Press, Boca Raton, FL, 1991, 325 pages, ISBN-8493-5894-9, $49.95 (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 227-227 
    Details
    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
    URL: http://dx.doi.org/10.1002/cem.1180060407
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  • 28
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    Diary (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. i 
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    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
    URL: http://dx.doi.org/10.1002/cem.1180060202
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  • 29
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    Announcements (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. i 
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    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
    URL: http://dx.doi.org/10.1002/cem.1180060203
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  • 30
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    The chemometrics group, University of Bergen, Norway (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 113-116 
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    ISSN: 0886-9383
    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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    URL: http://dx.doi.org/10.1002/cem.1180060209
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  • 31
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    The effect of mean centering on prediction in multivariate calibration (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 103-111 
    Details
    ISSN: 0886-9383
    Keywords: Mean centering ; Preprocessing ; Multivariate calibration ; Error propagation ; Principal component regression (PCR) ; Partial least squares (PLS) ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Traditionally, one form of preprocessing in multivariate calibration methods such as principal component regression and partial least squares is mean centering the independent variables (responses) and the dependent variables (concentrations). However, upon examination of the statistical issue of error propagation in multivariate calibration, it was found that mean centering is not advised for some data structures. In this paper it is shown that for response data which (i) vary linearly with concentration, (ii) have no baseline (when there is a component with a non-zero response that does not change in concentration) and (iii) have no closure in the concentrations (for each sample the concentrations of all components add to a constant, e.g. 100%) it is better not to mean center the calibration data. That is, the prediction errors as evaluated by a root mean square error statistic will be smaller for a model made with the raw data than a model made with mean-centered data. With simulated data relative improvements ranging from 1% to 13% were observed depending on the amount of error in the calibration concentrations and responses.
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    In memoriam: Herman Wold, pioneer of PLS (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 117-118 
    Details
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/cem.1180060303
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    Classification of mass spectra (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 119-133 
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    ISSN: 0886-9383
    Keywords: Mass spectra ; Classification ; Structure description ; Fragmentation ; Ion series ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In order to investigate correlations between the functionality of compounds and the classification of their mass spectra, low-resolution spectra of monofunctional compounds have been classified by four supervised classification methods. The new classes are characterized by structural features and the correlation between functionality and classification is explained by fragmentation rules. Systematic misclassifications show that low-resolution mass spectra alone are not suitable for reliable identification of functionality.
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    Wavelength selection in multicomponent near-infrared calibration (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 151-161 
    Details
    ISSN: 0886-9383
    Keywords: NIR spectroscopy ; Wavelength selection ; Interaction effects ; Multicomponent mixtures ; Partial least squares ; Generalized least squares ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Modern scanning (near-)infrared reflectance/absorption (NIR) spectroscopes measure the absorptions or reflectances at a sequence of around 1000 wavelengths. Training data may consist of 10-100 carefully designed sample mixtures for which the true composition of the mixture is either known by formulation or accurately determined by wet chemistry. In future one wishes to predict the true composition from the spectrum. In this paper we compare a simple wavelength selection approach with methods which retain all the wavelengths. It offers a powerful yet simple technique for choosing those wavelengths that are specific to each pure component as against the other components (including the medium) for the varying compositions. In the presence of a defined range of ingredients in thus chooses wavelengths which are highly selective for each particular component. It has the added advantage of selecting wavelengths which are little effected by interaction effects and consequent non-linearities.The calibration data used consist of 125 observations of three sugars, each varying at five levels in a full 53 design. The validation set consists of 21 further samples specially selected to have compositions outside the range of the training sample. The selection methods perform much better on this prediction set than methods which retain all the wavelengths, 700 in this case. The leave-one-out cross-validation internal to the calibration data would point to the opposite finding and suggests that such crossvalidations may be overly flattering to techniques such as partial least squares and may encourage overfitting. After selection, simple straightforward least squares methods may be used, eschewing the need for ‘shrinkage’ methods such as partial least squares or ridge regression.
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    Quadratic PLS regression (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 307-334 
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    ISSN: 0886-9383
    Keywords: Non-linear PLS ; Quadratic regression ; Non-linear models ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We treat here an extension of linear PLS regression to include regression on quadratic PLS components. The quadratic regression can be viewed as a natural extention of linear PLS regression to quadratic PLS according to the H-principle of mathematical modelling. The numerical implementation is treated in detail. It is shown that this approach can be used for models with large numbers of variables. Some modelling strategies are discussed depending on the purpose of the modelling. Applications of this approach are treated.
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    Predictive ability of regression models. Part II: Selection of the best predictive PLS model (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 347-356 
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    ISSN: 0886-9383
    Keywords: GOLPE ; PLS ; Regression ; SDEP ; Variable selection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A procedure called GOLPE is suggested in order to detect those variables which increase the predictivity of PLS models. The procedure is based on evaluating the predictive power of a number of PLS models built by different combinations of variables selected according to a factorial design strategy. Examples are given of the efficiency of this variable selection procedure, which shows how these predictive PLS models are better than those obtained by all variables and better than the corresponding ordinary regression models.
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    Predictive ability of regression models. Part I: Standard deviation of prediction errors (SDEP)Presented in part at the Euchem Conference held in Trieste, 1988, and at the Symposium on Chemometrics held in Holmsund, 1989. (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 335-346 
    Details
    ISSN: 0886-9383
    Keywords: Predictive ability ; Regression ; PLS ; SDEP ; Cross-validation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The standard deviation of prediction errors (SDEP) is used to evaluate and compare the predictive ability of some regression models, namely MLR, ACE and linear and non-linear PLS, the last being the best one. The parameter is determined by a cross-validation approach as an average of several runs obtained on forming groups in a random way. The variation in SDEP with the number of latent variables in PLS is also discussed.
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    Software Review (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 357-357 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/cem.1180060606
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    A robust PLS procedure (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 189-198 
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    ISSN: 0886-9383
    Keywords: Robust regression ; Partial least squares ; QSAR ; Perturbation study ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A robust partial least squares (PLS) regression algorithm is developed. This is achieved by substitution of the univariate regression steps in the iterative PLS2 algorithm by a robust alternative. The angle between loading vectors from both perturbed and unperturbed solutions is used as a measure of robustness. By means of a perturbation study on a structure-activity data set, it is demonstrated that the stability of the robust method is superior to standard PLS.
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    Multivariate analysis of 2D surfaces: Folding and interpretation (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 135-150 
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    ISSN: 0886-9383
    Keywords: 2D surface ; Multivariate analysis ; Non-congruent ; Unfolding ; Folding ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The use of latent variable projection for analysis of non-congruent 2D surfaces is presented. We give a formal description of the folding/unfolding process. A simulated 2D oscillator evolving in time is studied in detail to illustrate interpretation aspects of the method.
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    A review of three-dimensional chemical structure retrieval systems (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 289-305 
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    ISSN: 0886-9383
    Keywords: Chemical structure database ; Conformational searching ; Similarity searching ; Substructure searching ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper presents a review of the rapid developments that have taken place over the last few years for the searching of databases of three-dimensional (3D) molecules. The geometric arrangement of the atoms in a 3D molecule is described by an interatomic distance matrix. This is a form of labelled graph that can thus be searched using the subgraph-isomorphism algorithms that are widely used for searching databases of two-dimensional (2D) molecules. Several in-house and commercial systems have been developed for 3D database searching that are based on such techniques. These systems are reviewed and their effectiveness demonstrated by examples of their use in the discovery of novel, biologically active molecules. Current systems represent a molecule by one or a small number of low-energy conformations and there is hence much interest in the development of representational techniques and searching algorithms that account for the full set of geometric arrangements that can be adopted by a flexible molecule.
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    Three-dimensional chemical structure handling, Peter Willett, Research Studies Press, Taunton, Somerset, UK, 1991, ISBN 00 86380 121 8 (Wiley Inc. 0 471 93108 X), 241 pp (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 283-284 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/cem.1180060507
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    Window factor analysis: Theoretical derivation and application to flow injection analysis data (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 29-40 
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    ISSN: 0886-9383
    Keywords: Factor analysis ; Window factor analysis ; Multicomponent analysis ; Flow injection analysis ; Self-modeling curve resolution ; Bismuth chloride complexes ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Window factor analysis (WFA) is a self-modeling method for extracting the concentration profiles of individual components from evolutionary processes such as flow injection, chromatography, titrations and reaction kinetics. The method takes advantage of the fact that each component lies in a specific region along the evolutionary axis, called the window. Theoretical equations are derived. The method is used to extract the concentration profiles and spectra of seven bismuth species from data obtained by Gemperline and Hamilton, who injected bismuth perchlorate into a flowing stream of hydrochloric acid.
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    Principal variations in the chemical composition of peat: Predictive peat scales based on multivariate strategies (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 41-56 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The principal properties, here called the ρ-scales, of peat have been calculated on the basis of chemical analysis. The scales were derived from quantitative contents of carbohydrates, Klason lignin, amino acids, amino sugars and conventional chemical peat measurements. The variation in the chemical parameters was compressed using principal component analysis (PCA). Partial least squares (PLS) regression was used for prediction of botanical, microbial, physical and dewatering data. A rapid estimation of the scales has been made from near-infrared (NIR) spectroscopy and offers, indirectly, rapidly obtainable, chemically interpretable, biological information. A reduced scale based on carbohydrate data was also tested. The ρ-scales offer an interface between different areas of peat research. Strategies are outlined for the selection of a subset of chemical measurements among the variables used for characterization. A multivariate strategy based on these ideas is discussed.
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    Masthead (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992) 
    Details
    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
    URL: http://dx.doi.org/10.1002/cem.1180060201
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    The relationship of closure, mean centering and matrix rank interpretation (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 57-62 
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    ISSN: 0886-9383
    Keywords: Closure ; Baseline ; Mean centering ; Rank ; Exploratory data analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper describes an investigation into the relationship of closure, a baseline offset and mean centering to the interpretation of matrix rank. The equivalence of a certain type of closure to a constant baseline (i.e. a simple numerical offset which may vary between response channels but is constant over all samples) is demonstrated. A systematic approach to the interpretation of the rank of a matrix is given.
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    Ionspray mass spectrometry of marine toxins. IV. Determination of diarrhetic shellfish poisoning toxins in mussel tissue by liquid chromatography/mass spectrometryNRCC 3303. (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 121-127 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: An Improved liquid chromatographic/mass spectrometric (LC/MS) method utilizing gradient elution and ion-spray ionization is described for the sensitive determination of okadaic acid and dinophysistoxin-1, the principal toxins implicated in cases of diarrhetic shellfish poisoning. The method was used to confirm the presence of both toxins, together with a recently identified isomer of okadaic acid, dinophysistoxin-2, in various samples of cultivated blue mussels (Mytilus edulis) from Canadian and European Waters. The method provided a mass detection limit of 0.4 ng for each toxin, thus allowing detection of 40 ng per g of whole mussel tissue (or approximately 10 ng/g if only the digestive glands were used in the assay). Quantitative results obtained by LC/MS were in good agreement with those obtained by derivatization and high-performance liquid chromatography with fluorescence detection.
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    Characterization of [C6H7N]+· radical cations by tandem mass spectrometry (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 135-139 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Collisional Activation, charge-stripping and neutralization/reionozation mass spectra allow the identification of six [C6H7N]+· isomers, namely the molecular ions of the three isomeric picolines, 1+·-;3+·, ionized 2- and 4-methylene dihydropyridines, b - c, and ionized pyridinium methylide, a. The implication of the distonic forms a and b in some fragmentation reactions of funct of onalized (position 2) pyyridines is briefly discussed. Molecular orbital calculations indicate the b〉a〉1+· stability sequence.
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    Recent events (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 158-158 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
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    URL: http://dx.doi.org/10.1002/rcm.1290060216
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    Protein structural effects in gas phase ion/molecule reactions with diethylamine (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 159-165 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The relationship between gas-phase protein structure and ion/molecule reactivity is explored in comparisons between native and disulfide-reduced aprotinin, lysozyme, and albumin. Reactions are performed in the reactions with equal concentrations of diethylamine, multiply protonated molecules generated by electrospray ionization (ESI) of ‘native’ proteins shifted to lower charge states than did multiply protonated molecules from ESI of the disulfide-reduced counterparts, suggesting that the disulfide-reduced protein ions are less reactive than native protein ions of the same charge state. Differences in reactivity may arise from protonation of different amino acid residues and/or differences in the proximites of charge sites in two molecules. These results suggest that the reactivity of multiply charged proteins can be significantly affected by their gas-phase structure.
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    Dyanmic ion trapping for Fourier-transform ion cyclotron resonance mass spectrometry: Simultaneous positive- and negative-ion detection (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 166-172 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The conventional static electric potential used to trap ions fro fourier-transform ion cyclotron resonance (FTICR) mass spectrometry has been replaced by a low-amplitude [as low as Vac≍0.5 V for N2+] alternating (17.5kHz) electric field applied to the end caps of an ICR ion trap. Ion z-motion is then governed by a Mathieu equation, whose solution leads to a z-stability diagram for which optimal results are obtained at z-stability parameter, qz = 4qλV ac/(mω2)≍0.5, in which m/q is the ion mass-to-charge ratio, Ω is the RF frequency, and λ=2.7737/d2 for a cubic trap of edge length, d. A triangular waveform appears to be more effective than sinusoidal modulation. We demonstrate experimentally three major additional advantages of RF trapping for FTICR mass spectrometry: (a) both positive and negative ions may be trapped and detected simultaneously; (b) Magnetron motion is eliminated, along with the electrostatic radial field-induced ICR frequency shift and sidebands; and (c) mass calibration follows a simpler law (m=a/v, in which a is a constant and v is the measured ICR orbital frequency) than for electrostatic trapping (m=a/v+b/v2, in which a and b are constants). All prior FTICR mass spectrometric capabilities are preserved, except that (as in an RF-only quadrupole ion trap) optimal sensitivity is observed only for 0.4≤qz≤0.7, so that the mass-to-charge ratio range for a single FTICR mass spectrum is limited accordingly.
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    Modification of a commercial thermospray interface controller to improve ion-current stability (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 179-183 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The stability of the ion beam in a thermospray interface is largely dependent on the control of the vaporizer temperature. The original time-proportional vaporizer control circuit provides inadequate temperature stabilization. Modification of the circuit by repositioning the thermocouple amplifier and replacing the time proportional part of the circuit with a phase-angle controller greatly improves the temperature stability and hence th ion-current stability. The improvement in performance was demonstrated using terbutaline as a test substance.
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    Masthead (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992) 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
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    URL: http://dx.doi.org/10.1002/rcm.1290060401
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    A compact time-of-flight mass spectrometer for the structural analysis of biological molecules using laser desorption (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 242-248 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A compact laser-desorption time-of-flight mass spectrometer using a 600 ps nitrogen laser and 1 Gsample/s transient recorder is described. The instrument incorporates two electrically-isolatable, reflecting flight tubes designed for subsequent configuration of the mass spectrometer as a tandem instrument. In this first report, we compare mass resolution in the laser-desorption mass spectra of an organic dye, sinapinic and caffeic acid matrices, and sevesral small peptides. For directly desorbed ions, peak widths are generally of the order of 11 to 13 ns, so that mass sesolutiojn increases with increasing mass. For peptide ions in the range of 500 to 1000 u, formed by matrix-assisted desorption, peak widths range from 9.5 to 17.6 ns and increase with mass. However, better than unit mass resolution (1600 to 2400) is maintained throughout this range. Mass measurement accuracy is better than 0.1 u using a single calibration peak and a prompt start trigger pulse. Prospects for extending mass range and resolution are discussed.
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    Electron impact and chemical ionization mass spectrometry of heterocumulenes produced by flash vacuum pyrolysis (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 249-253 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Heterocumulenes such as ketenes, propadienones and comulogs of isocyanates are produced by flash vacuum pyrolysis of Meldrum's acid. Real-time monitoring of the pyrolysis products is performed by methods of tandem mass spectrometry. In particular, chemical ionization is show, for the first time, to generate protonated moleculular ions of these kinetically unstable neutral molecules which can be identified by collisional activation experiments.
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    Observation of the fullerene anions C60- and C70- by electrospray ionization (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 254-256 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Mass spectsrometric investigation on the fullerence C60 and C70 was performed using electsdrospray ionization. C60-, C60O2-, C70-, and C70O2- ions were detected by reducing C60 and C70 using Nak amalgam in benzene + dimethoxyethane solvent. C70- was found to be much more reactive than C60- in solution.
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    Negative-mode electrospray-mass spectrometry using nonaqueous solvents (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 265-268 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Nonaqueous solvents suitable for negative-mode electrospray-mass spectrometry were investigated. Mixtures of methanol with benzene and with carbon tetrachloride were found to be the best solvents. Negative ions of 10-9 M concentrations of surface-active agents in these solutions could be detected.
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    New gas-chromatographic/mass spectrometric method for the quantitative analysis of primary aromatic amines in main- and side-stream cigarette smoke. I (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 406-409 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A sensitive and accurate method to quantitate 17 primary aromatic amines in tobacco smoke has been set up. two Italian commercial brands of cigarette were smoked in a home-made smoking machine; the amines in the smoke were trapped in dilute hudrochloric acid (containing 2H5-aniline, 13C1-o-toluidine and 2H9-4-aminobiphenyl as internal standards) and, after extraction and purification, derivatized as pentafluoropro-pionamides and measured by gas chromatography/mass spectrometry in the selected-ion-monitoring mode. Our results confirmed that side-stream smoke contains total levels of aromatic amines about 50-60 times higher than those of main-stream smoke of black-tobacco cigarettes is richer in aromatic amines compared to light-tobacco cigarettes.
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    A method for uniform optimization of quadrupole pre-filters (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 459-462 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Novel aspects of utilizing RF-only pre-filters in a quadrupole mass spectrometer are presented. Theoretical considerations converning the optimization of the spectrometer by means of the pre-filter length and the ion entrance velocity are given and are given and are compared with the results of model calculations. Experimental results are shown to illustrate the advantages of the setup constructed according to the proposed optimization method over both the single mass filter and one with a pre-filter of conventional length range. The most effectively focusing pre-filters are shown to have integer multiples of an elementary length. The predictions have only been verified experimentally for helium. Apoproximeately 150% improvement was measured for helium transmission with respect to the single analyser with the suggestede parameters. Since the resolution always inporoves with length at a certain ion velocity, it is preferable to make use of some of the higher local minima of the suggestede optimizing function.
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    Calendar of events (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. i 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290060717
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    Measurement of gas-phase binding energies of crown ethers with metal ions by Fourier-transform ion cyclotron resonance mass spectrometry (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 25-27 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Complexes of the type [crown+M]+ were observed following laser desorption ionization of 18-crown-6 molecules ‘doped’ with K+, Cs+, and Ba+. Laser desorption ionization of 15-crown-5 and 12-crown-4 ‘doped’ with the same metals gave [(crown)]2+[M]+ type sandwich complexes. Binding energies of crown ethers with different metal ions in all such complexes have been estimated from appearance energies obtained in the collisionally-activated dissociation of the corresponding laster desorbed complexes.
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    Dissociation of positively-charged apliphatic epoxides. III. [C4H8O]+· eposides and α, β unsaturated ethersFor Parts I and II, see references 2 and 3. (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 37-45 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Unimolecular dissociation of the molecular cations of 1,2-expoxybutane (1), 1-methoxypropene (2), 2,3-epoxybutane (3), ethyl-vinyl ether (4), 1,2-epoxy-2-methylpropene (5), and 2-methoxypropene (6)have been investigated. Different behaviour of pairs of [C4H8O]+· isomers (1+·/2+·), (3+·/4+·) and (5+·/6+·) have been demonstrated. Isomerization by epoxide ring opening and 1,4-hydrogen migration is suggested to explain the similar unimolecular chemistry observed for the two partners of each pair of isomers.
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    Identification of cyclobutane-type dimers of substituted cinnamic acids by gas chromatography/mass spectrometry (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 46-53 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Substituted cinnamic acids were dimerized, under fluorescent or UV light, as a glassy coating on a vial then subsequently analysed by GC/MS. Mass Spectrometric analysis of the dimers formed by each acid allowed the assignment of the dimer as a truxillic or truxinic structure since these structures had distinctive fragmentation patterns; the breakdown of the truxillic acids involves a McLafferty rearrangment before fragmentation occurs, whereas the truxinic acids, which have both carboxy groups on one side and both aromatic groups on the other, fragment asymmetrically to give characteristic stilbene and dicarboxylate fragments. It is apparent from the results of the dimerization of the lcinnamic acids that, under the conditions used here, if the monomeric acid had the capacity for hydrogen bonding using the ring substituent as well as the carboxy group, the dimerization products would be overshelmingly truxillic in structure. However, if only the carboxy group could hydrogen bond, the products would be almost exclusively traxinic in structure.
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    Structure interconversion in isomeric guanine derivatives at elevated sample temperature (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 62-67 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Guanine derivatives were examined using the tandem mass spectrometry (MS/MS) method. Isomeric structure differences were explored by means of the unimolecular decomposition spectra of the common ion m/z 151 having the empirical formula of the guanine molecular ion. An interconversion of the isomeric structures as the sample temperature is gradually raised, was observed.
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    Mass spectrometer sysrtems and products. An expanded directory of manufacturers and suppliers (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 75-84 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A directory of companies which supply mass spectrometers, components and services is provided. This directory expands on an earlier version.
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    Mass spectrometry of laser-desorbed oligonucleotides (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 365-368 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Various matrices were used for laser-desorption ionization of mixtures of small DNA segments. Parent negative ions of 34-mer as well as other smaller single-stranded oligomers were observed for selected organic acids and dye compounds. Both positive and negative parent ions were observed with very little fragmentation. Effects of various matrices and the potential applications to DNA sequencing are briefly discussed.
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    Development of a condensation technique for thin-layer chromatography/fast-atom bombardment mass spectrometry of non-visible compounds (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 89-94 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: In Order to prevent the diffusion of sample when a matrix is deposited on the sample spot on a thin-layer chromatography (TLC) plate and to obtain constructively high sensitivity in mass spectrometry, we developed a conedensation technique including ‘trapezoid technique’ for TLC/fast-atom bombardment mass spectrometry (FABMS) on both silica gel and C18 plates. For colored samples and colorless samples having a chromophore, the condensation technique previously in use, that condenses the sample towards the center of the spot in a line, using methoanol, was effective. The trapezoid condensation technique has been newly developed for colorless compounds having no chromophore. The mass spectra obtained using this technique clerly showed molecular ion species at relatively lower concentrations of samples, and the technoique can improve the detection limits of molecular ion species in TLC/FABMS by 3-100 times with good reproducibility.
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    Association of the acylium ion of acids with alcohols as an esterification mechanism in chemical ionization (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 623-625 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The reactions between aliphatic acids and alcohols in the gas phase were investigated by chemical ionization (CL) mass spectrometry. The association of the acylium ion of acids with alcohols is suggested as an esterificaion mechanism under CI conditions in addition to the classical nucleophilic addition - elimination pathway.
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    Mass spectrometry of DNA mixtures by laser ablation from frozen aqueous solution (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 631-636 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: We report time-of-fight mass spectra of test mixtures of six single-stranded DNA segments. The segments range in size from 8 to 60 nucleotides (molecular weight range 2413 to 18 602 Da). The best mass spectra were obtained by pulsed laser ablation of thin frozen films of an aqueous solution of the mixture from an oxidized copper substrate. These mass spectra are dominated by the molecular-ion peak for each DNA segment, and show little evidence of fragmentation, peak broadening or cluster formation. In contrast, mass spectra obtained using UV laser ablation from an anthranilic acid matrix yield broad peaks with evidence of fragmentation, and DNA segments longer than 26 nucleotides are difficult to detect.
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    Masthead (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992) 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290061101
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    Unequivocal discrimination between consecutive and competing collisionally induced decompositions in an ion trap (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 641-646 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Discrimination between consecutive and competing collisionally induced decomposition (CID) reactions can easily be obtained by a new pocedure consisting of the collisional activation of a parent ion and the simultaneous ejection of one of its daughter ions in an ion trap. This is done by applying, during a single storage phase, a DC voltage appropriate to induce fragmentation (‘boundary’ activation) of the parent and, at the same time, a ‘tickling’ RF potential, sufficient to eject a selected daughter ion rapidly from the trap. Several examples are reported which illustrate the capabilities of the procedure in establishing fragmentation pathways e.g., to determine whether a daughter ion is formed in a stepwise process involving an intermediate primary fragment rather than from the direct fragmentation of the parent ion. Salient features of this technique are discussed.
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    Secondary-ion and electron production from surfaces bombarded by large polyatomic ions (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 147-157 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Heavy molecular ions with energies in the range 10-20 keV and masses from 276 u to 132 000 u, produced by matrix-assisted laser desorption, were used as primary projectiles to produce secondary-ion spectra from a variety of surfaces ina tandem time-of-fight mass spectrometer. In the negative mode the ratio of electron emission to secondary-ion emission was found to decrease rapidly with increasing projectile mass. Ion emission was found to dominate for primary ions larger than ∼ 10 000 u. Positive or negative molecular ions and cations were observed from several organic targets of masses up to 1140 u (gramicidin S) for incident projectiles up to mass 132 000 u, i. e., for projectile speeds down to ∼7000 m/s. Other ions characteristic of the target were also observed for these projectiles. Thus, large polyatomic ions can cause secondary-ion desorption even at very low velocity. The background ions of both polarities are similar to those found in keV particle bombardment by monatomic projectiles. The same ions are observed for all the projectiles; most can be identified with hydrocarbon background. The relative intensities of the background positive ions are largely independent of projectile, and for both polarities the ratio of the ions characterizing the target to those forming the background is approximately constant for all the projectiles. These results strongly suggest that the background ions come from the usual layer of organic impurities attached to the target surface. No direct evidence for surface-induced dissociation was observed in this mass and energy range.
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    Masthead (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992) 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
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    Improvements in ion-trap chemical-ionization performance (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 449-453 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Ion-trap chemical-ionization performance has been imporved by application of a modified scan function for the rejection of the undesired electron-ionization-like (EI-like) ions formed at the beginning of the reaction ionization period. The net effect of this software modification to the automatic reaction control is to produce chemical ionization (CI) spectra that are no longer adulterated with conventration-dependent EI-like ions. Under such improved conditions, CI spectra from an ion trap can now be dirctly compared with CI spectra produced on conventional quardrupole and magnet-scanning instruments.
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    How are ions formed from electrosprayed charged liquid droplets? (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 463-468 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The dependence of ion intensities on capillary position has been investigated for electrosprayed solutions of 5 × 10-6M (CH3)4 NBr and 10-3M CH3COOH in CH3OH+H2O+CCI4. It was found that the efficiencies for desorption from the charged liquid droplets into the gas phase are in thE order (CH3)4+〉NH4+〉CH3OH2+. The intensities of ions with higher desorption efficiencies become strong near the periphery of the spray cone, whereas those with lower desorption efficiencies have maxima in the central region of the spray cone. With increase of the vertical distance between the capillary tip and the sampling orifice, the distribution of the space-charge density becomes nearly uniform in the spray cone due to the space-charge field.
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    Differences in the conformational state of a zinc-finger DNA-binding protein domain occupied by zinc and copper revealed by electrospray ionization mass spectrometry (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 469-473 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Transition metal ions are important in biological regulation partly because they can bind to and stabilize protein surface domain structures in specific conformations that are involved in key molecular recognition events. There are twso C2-C2 type zinc-finger sequences within the highly conserved DNA-binding domain of the estrogen receptor protein (ERDBD). Electrospray ionization (ESI) mass spectrometry has been used to demonstrate that the metal-binding sites within the 71-residue ERDBD can bind either Zn (up to 2) or Cu (up to 4). Evidence for the induction and /or stabilization of a different conformational state with bound Cu is revealed by a characteristic shift in the ESI charge envelope. The 10+ charge state is most abundant for the fully reduced ERDBD apopeptide and the ERDBD-Zn holopeptide (bound Zn does not alter the charge envelope. In contrast, the 8+ charge state is typically the optimjum charge state observed for the ERDBD-Cu holopeptide; indeed, the entire charge envelope is frame-shifted to lower charge states with bound Cu. Interpretation of the altered charge states is simplified because (i) a single type of metal-binding ligand (sulfur) is involved in the case of both Zn and Cu binding, and (ii) the two different metal cations are both divaalent. Thus, it is likely that the dissimilar charge envelopes represent different peptide conformers, each of which is stabilized by a different type of bound metal ion. The covalent bridging or adjacent Cys residues within a peptide is similar to the formation of intramolecular disulfide bonds, a process that we also found to decrease both the optimum and mumber of ERDBD charge states observed by ESI. The existence of distinct conformational states for the ERDBD-Zn and ERDBD-Cu is consistent with the differences in apparent coordinate covalent geometry and stoichiometry for the two bound metal ions. Our findings are aslo consistent with prevous investigations of globular proteins that reveal an increase both in the number of charge states and a shift in the optimum charge state when structure is disrupted by reduction of intramolecular disulfide bonds.
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    Sequence distribution of β-hydroxyalkanoate units in bacterial copolyesters determined by desorption chemicl ionization mass spectrometry (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 702-706 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The sequence distributions of poly(β-hydroxyalknoate) copolymers were determined by analyzing oligomers obtaned by the pyrolysis direct-chemical-ionization (DCI) mass spectrometry technique. Oligomers up to nonamers were identified and the comparison between the experimental and calculated peak intensities makes it possible to calculate repeating unit compositions and sequence distributions. Comparison with other earlier methods are given.
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    Disentangling electrospray spectra with maximum entropy (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 707-711 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Software using maximum entropy (MaxEnt) analysis has been developed, and used to econvolute complete electrospray spectra of protein mixtures. It automatically produces zero-charge mass spectra on a molecular mass scale, along with probabilistic quantification so that the reliability of features in the spectrum can be ascertained. Because maximum entropy is faithful to the experimental data, the results tend to have improved resolution and signal-to-noise ratio. This improved performance, particularly regarding resolution, is demonstrated on a haemoglobin containing two β-globins separated by 12 Da at m/z 15 867 (0.08%). A separation of 12 Da was previously the closest at which mass measurement of two globins was practicable. Also, two hiherto unresolved β-globins from a second haemoglobin, separated by 9 Da (0.06%) were resolved by MaxEnt and their masses accurately measured. These are the first results using rigorous MaxEnt analysis in electrospray mass spectrometry.
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    Investigation of some β-lactam antibiotics by means of 2-35 keV cesium ion bombardment (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 712-716 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A number of commercial β-lactam antibiotics are investigated by means of cesium ion (Cs+) bombardment in the kinetic energy range 2-35 keV. The relative intensities of the protonated molecules, as well as some of the major fragment ions, are monitored as a function of the Cs+ kinetic energy. The dependence of the intact protonated molecule:fragment ion ratios on the primary-ion kinetic energy is evident in some of the spectra investigated. An attempt is made to interpret these results in terms of existing secondary-ion mass spectrometry data which have been obtained in a different kinetic energy range.
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    Electrospray-ionization mass spectrometry for the detection of discrete peptide/metal-ion complexes involving multiple cysteine (sulfur) ligands (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 308-312 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Conditions have been developed to characterize the reversible interaction of one or more Zn(II) ions with cysteine (sulfur) ligands on metal-binding peptides by electrospray-ionization (ES) mass sspectrometry. A 71-residue peptide with two separate clusters of four cysteine residues was selected as a model to optimize both the solution and electrospray variables most likely to affect the detection of stable cysteine (sulfur) ligland/Zn interactions. By infljusing peptide in water alone, stable elelctrospray and ion signals were produced in both the absence and presence of up to 100 uM zinc sulfate. In the absence of Zn(II), the callculated mass of the fully reduced peptide (8248.5 Da) was observed (8248.4±0.4 Da). In the presence of Zn(II), peptides with zero, one and two bound Zn atoms were detected; all three species were prelsent in several different charge states. The overall charge envelope was typically unchanged in the presence of Zn; the chaarge-state optimum (10+) observed for this peptide dwas apparently unaffected by the dpresence dsof bound Zn. The interaction of Zn(II) ions with sulfur lilgands in this peptide appeared to result in tetracoordinate covalent bonds. In summary, these data suggest that (i) stable electrospray signals can be generated form high conductivity aqueous solutions of meltal ions; (ii) peptides with sulfur ligand/Zn complexas are stable to the ES ionization prolcess; (iii) bound Zn is not the primary source of charge and does not alter the observed charge-envelope optimum; (iv) the relative distribution of peptide without bound Zn, with one bound Zn, and with two bound Zn atoms can be fully resolved in each of several different charge sltates; and (v) various solution factors affecting peptide/metal-ion interaction stoichiomeltry can be investiged by ES. In conclusion, we believe dthat ES mass spectrometry is a powerful new method of evaluating a wide variety of specific biomolecular polymer/metal-ion interactions.
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    High resolution parent-ion selection/isolation using a quadrupole ion-trap mass spectrometer (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 313-317 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The same techniques used to generate high-resolution mass spectra on a quadrupole ion trap can be used for selection or storage of a very narrow mass window with nearly 100% efficiency.
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    URL: http://dx.doi.org/10.1002/rcm.1290060419
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    Usefulness of fast-atom bombardment and collision-activated dissociation linked scan (B/E) mass spectrometry for structural investigation of indole alkaloids (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 318-321 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Positive-ion fast-atom bombardment (FAM) mass sspectrometry was used to ionize two indole alkaloids, namely trinervine and its quaternary metho-salt venecurine containing a hemiketal ring system. Analysis of collision-activated dissociation spectra by the technique of linked scanning at consltant B/E gave sturcturally useful information. Addition of concentratedf acid to the glycerol matrix yielded glycoside-type derivatives from both compounds. These studies Provide further examples of an ‘acid effect’ on the protonation site of polyfunlctional molecules along with the possibility of their undergoing chemical mokification in the FAB matrix.
    Additional Material: 3 Ill.
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    FT-ICR MS: Analytical applications of Fourier transform ion cyclotron resonance mass spectrometry. EDITED BY BRUCE ASAMOTO Publisher: VCH Weinheim, New York, Basel, Cambridge, 1991, pp xii + 306, DM 134, £47 (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 323-323 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
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    URL: http://dx.doi.org/10.1002/rcm.1290060422
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    Bimolecular reactions of ·CH2CH2OCH2+: A comparison with the chemical properties of CH3CH2OCH2+ and ionized trimethylene oxide (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 734-740 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The chemical properties of the distonic radical cation ·CH2CH2OCH2+ are compared with those of its conventional isomer, ionized trimethylene oxide, and its even-electron analog, the ethoxymethyl cation (CH3CH2OCH2+). The rate constants and branching rations have been determined for the gas-phase reactions of the three ions with several neutral reagents in a dual-cell Fourier-transform ion cyclotron resonance device. The reactivity of each ion is found to be quite distinct. Fast electron transfer dominates most of the bimolecular reactions of ionized trimethyleene oxide. The ethoxymethyl cation reacts slowly or not at all with the reagents studied, and the only reaction observed is ethyl cation transfer. The distonic ion ·CH2CH2OCH2+ undergoes vedry fast reactions with all the neutral reagents, and, in sharp contrast to the other two ions, shows remarkably versatile reactivity. This ion rapidly transfers ionized ethylene to most of the neutral molecules studied. Facile electron transfer occurs with some of the neutral reagents while others abstract a pproton from the ion. Abstraction of a radical by the distonic ion-a reaction reported earlier for dimethyl disulfide - is not observed for any other reagent.
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    Location of epoxy rings in a long chain acetogenin by fast-atom bombardment and linked scan (B/E) mass spectrometry of lithium-cationized moleculesPart 15 in the series ‘Acetogenins of Annonaceae’; for part 14 see; B. Figadère, J.-C. Harmange, A. Laurens and A. Cavé, Tetrahedron lett, 32, 7539 (1991). (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 352-355 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Fast-atom bombardment desorption combined with mass spectrometry (using linked scans at constantB/E) of a lithium-cationized long-chain acetogenin was used to determine the position of two epoxy rings in thhe alkyl chain. Analysis of metastable and collision-induced dissociations gave structurally useful information which could not be obtained by other spectroscopic methods such as nuclear magnetic resonance. A direct effect of lithium of thhe observed decomposition pathways was demonstrated.
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    URL: http://dx.doi.org/10.1002/rcm.1290060509
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    C-terminal sequencing of peptides using electrospray ionization mass spectrometry (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 637-640 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A low-flow reactor is described for the on-line monitoring of peptides digested with carboxypeptidase P by electrospray ionization. Two peptides were analyzed using this technique: glucagon (average MW 3482.8 Da), and apomyoglobin (average MW 16 951.5). Both peptides gave interpretable results. The first 19 amino acids of glucagon were successfully sequenced. Apomyoglobin yielded sequence information to the 30th amino acid with some gaps. At 300 nL/min, 50% of the first 30 amino acids were sequenced and at 1μL/min, 67% of the first 30 amino acids were observed.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/rcm.1290061102
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    Product announcements (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. ii 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
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    URL: http://dx.doi.org/10.1002/rcm.1290061216
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    Atmospheric-pressure ionization interface for a bench-top quadrupole ion trap (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 508-516 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A novel interface is described that effects the sampling and mass analysis of ions formed at atmospheric pressure into a Saturn II bench-top quadrupole ion-trap mass spectrometer. The standard high-vacuum pumping system of the system is unchanged, bit a 960L/min rotary pump is incorporated to pump the first vacuum stage of the atmospheric-pressure ion sampling interface. An ‘Electric skimmer’ ion focusing region in the first vacuum turbomolecular pump of the Sasturn II maintains high vaccuum at 4×10-4 Torr in the analyzer region while helium damping gas is introduced. By vaarying the potential difference between selected lenses in the first vacuum region the ‘declustering’ energy may be varied to decluster effectively ion/molecule dissociation mass spectra. The on-line analysis of quaternary ammonium drugs by liquid chromatography of 5 ng and 150 pg, respectively.
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    Improved accuracy of mass measurement with a quadrupole ion-trap mass spectrometer (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 524-527 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Mass Measurement accuracy of better than 0.015% on protonated gramicidin S (nominal chemical average molecular weight 1141.5 Da) and its first three isotopes has been achieved using reasonant ion ejection in the quadrupole ion-trap mass spectrometer operated at unit resolution. Analyte and Calibrant ions are subjected to identical injection and trapping conditions when desorbed by Cs+ ions from a split prone-tip and co-injected into the trap. When the mass analysis scan rate is slowed, enhanced resolution is achieved for all ions but the mass range accessed in a single scan of the digital-to-analog converter, which controls the mass analysis scan, is limited making calibration difficult. A peak-matching procedure is described for use at these higher resolution conditions in which the offset voltage which determines the origin of the RF amplitude ramp is adjusted in such a fashion that the analyte and calibrant ions occur at the same point in the mass analysis scan. This procedure gave an improved mass measurement accuracy of better than 0.007% for the protonated gramicidin S. ions.
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    Charge-state distributuion and electric-discharge suppression in negative-ion electrospray mass spectrometry using/chlorinated solvents (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 536-539 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Solvent effects in electrospray mass spectrometry performed in the negaative-ion mode have been examined, for a series of low-nucleophilicity chlorinated solvents. The charge-state distribution of a test analyte was observed to change radically with the nature of the solvent. Formation of anions of higher charge stae was favored in solvents of higher polarity. The shift in the charge-state distribution has been largely attributed to improved solvation of chaarge sites by increasingly polar solvents. Evidence suggests that valence electrons of the chlorine atoms do not contribute significantly to solvation of acidic protons. Highly chlorinated solvents in teh electrospray bath gas serve to suppress electrical (corona) discharge phenomena. The latter effect was magnified with increasing percent weight of chlorine in the solvent. The observed discharge suppression has been attributed to electron-capture preocesses. This solvent effect was muted when a highly efficient electron seavenger(i. e., SF6) comprised the elctrospray high gas.
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    Black canyons for ions stored in an ion-trap mass spectrometer (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 573-578 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Effects from higher order non-linear resonances, ‘black canyons’, have been observed for ions stored within the quadrupole ion-trap mass spectrometer. At specific qz values, higher-order field effects were observed to cause decreased intensity of chemical ionization (CI) reagent ions, due to ineffcient storage, as well as collision-induced dissociation. Efects have been observed, whether or not the CI reagent ions are mass-selected, and exibit increased severity with longer storage times. Previous reports have shown ‘black holes’ due to inefficient storage of product ions in tandem (MS/MS) spectra, but have reported no such effects in normal mass spectra. Without employing resonant excitation, higher-order field effects were investigated and found to occur continuously along iso-βz lines for βz = 1/3, 1/2, and 2/3. Described in this paper are the directs from higher-order fields on ions stored at specific az values, and indirec effects by those ions. Also described in this paper is new evidence for ‘black canyons’ occurring at βz = 1/3 at negative az values.
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    URL: http://dx.doi.org/10.1002/rcm.1290060908
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    Gas phase relative proton affinities from selected-ion flow tube (SIFT) rate constant measurements (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 579-581 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A new method of measuring equilibrium constants of proton transfer gas phase reactions is proposed. The method is based on measuring only the endothermic direction. The expression developed is: K=kexp(BR)kc/{(kc—kexp)k′c}, where kexp is the measured rate constant, BR is the branching ratio of the proton transfer channel, kc and k′c are the forward and reverse collision rates. Two reaction systems were measured: the equilibrium between methanol and chloroacetonitrile and the equilibrium between ethanol and acetaldehyde. Both equilibrium constants were calculated by measuring forward end reverse rate constants and by the new method. There is good agreement between the two methods and with previously published values.
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    Calendar of events (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. ii 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
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    URL: http://dx.doi.org/10.1002/rcm.1290060912
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    Quantitation by fast-atom bombardment mass spectrometry: Assay of cytidine 3′, 5′ -cyclic monophosphate-responsive protein kinase (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 601-607 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A protein kinase, stimulated by cytidine 3′, 5′ -cyclic monophosphate, is conventionally assayed by monitoring the incorporation of radiolabelled phosphate from adenosine triphosphate into a histone substrate. Here the assay of the protein kinase is carried out by positive-ion fast-atom bombardment mass spectrometric analysis of the enzyme incubation mixture after the reaction has been terminated. The data so obtained show good agreement with data obtained by the conventional radiometric assay: the intrinsic advantage of the mass spectrometric assay is the capacity for multiple component monitoring; the ability of the kinase to bind competing cyclic nucleotides togeter with integral adenosine triphosphatase (ATPase) and phosphodiesterase activity can also be assessed.
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    Electron-impact induced fragmentation of spiro-1-pyrazolines (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 626-630 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The positive-ion electron impact mass spectra of twelve spiro-1-pyrazolines have been recorded as 70 eV electron energy and the dat analyzed to elucidate their fragmentation pathways. None of these compounds gave abundant molecular ions (M+) due to the instability of the pyrazoline ring. The first step in the decomposition of M+ ions is the elimination of a nitrogen molecule followed by a rearrangement resulting in the formation of the cation radical [M-28]+, the decomposition of which is discussed in detail. The proposed fragmentation pathways and their mechanisms are supported by high-resolution data, linked-scan measurements at constant B/E and collision-induced dissociation-mass-analyzed ion kinetic energy spectra.
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    URL: http://dx.doi.org/10.1002/rcm.1290061008
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    The correct molecular weight of myoglobin, a common calibrant for mass spectrometry (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 32-36 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Myoglobins from horse heat muscle, horse skeletal muscle and sperm whale are widely used as calibration standards or test compounds for various mas spectrometric methodologies. In all such cases reproted in the literature, a molecular weight value is used (16950.5 and 17199, respectively) which is based on the assumption that amino acid 122 in this 153 amino-acid-long protein is asparagine, overlooking a published suggestion that it is aspartic acid instead. Since the mass assignment accuracy for matrix-assisted laser desorption mass spectrometry is reproted to be ±0.01% and for electrospray ionization ±0.0025%, and error of one mass unit in ∼ 17000 would be significant. The mass-to-charge ration of ions of the tryptic peptide encompassing amino acid 122 derived from commercially available horse heart and horse skeletal myoglobins, the apomyoglobin of the latter, and the tryptic and chymotryptic peptide of sperm whale myoglobin proved that in both proteins amino acid 122 is indeed aspartic acid, rather than asparagine. This finding was further confirmed by the collision-induced dissociation sectra of the [M+H]+ ions of the tryptic peptides from the horse myoglobins and the chymotriptic peptide from sperm whale myoglobin. Thus, the correct molecular weight of horse myoglobinis 16951.49 and that of the sperm whale protein is 17199.91.
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    Negative-ion fragmentations of deprotonated heterocycles. The pyrazole and imidazole ring systems (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 54-57 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Imidazole and pyrazole deprotonate preferentially at the 1-position, and a number of fragmentations are best rationalized as occurring through common ring-opened intermediate -NHCH=CHCN. C-Methylomidazoles and pyrazoles fragment similarly.
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    Are gas-phase processes really responsible for the ionization of cyclic acetals by fast-atom bombardment? (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 85-88 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The mass spectral behavior of a series of substituted 2-phenyl-1,3-dioxolanes has been studied by several ionization techniques in order to gain further insight into the basic ionization mechanisms occurring in the fast-atom bombardment mass spectrometry. The results obtained show that in chemical ionization, ions of the type [M+H]+ are predominant while [M—H]+ ions are observed as important species in electron ionization and fast-atom bombardment. Comparison of the gas-phase hydride-ion affinities of thr chemical ionization reagent gases ammonia and isobutane with those of the loquid matrices glycerol and dithiothereitol/dithioerythritol indicates that the predomionant formation of the [M—H]+ ion observed in fast-atom bombardment by hydride abstraction in the gas phase is improbable. Furthermore, comparison of the electron ionization behavior of the cyclic acetals with that observed under fast-atom bombardment suggests that the origin of [M—H]+ in the latter is not related EI gas-phase processes.
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    Peptide sequencing by matrix-assisted laser-desorption mass spectrometry (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 105-108 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A novel method of peptide sequencing by mass spectrometry is described. Metastable decay of laser-desorbedions, taking place in the first field-free drift region of a reflectron time-of-flight mass spectrometer, has been monitored to get structural information from larger peptides. Fragment ions from metastable decay are mass analysed by adjusting the potentiaals of the ion reflectron according to the kinetic energies of the ions. The features of the technique and its significance for future applications are outlined.
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    Analysis of a mass-analyzed ion kinetic energy profile. I. Analytical expression for a peak shape at a single kinetic energy release (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 115-120 
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    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: An analytical expression has been derived for the mass-analyzed ion kinetic energy spectral profile resulting from a single kinetic energy release in a metastable ion decopmposition. Effects of the Z and Y discriminations and the site of dissociation on the peak-shape have been accounted for. In addition an analytical peak-shape function has been derived for a dissociation occurring in and near the collision cell floated at high voltage. Excellent agreement between the present results and the peak shapes obtained by regorous ion-optical trajectory calculations support the validity of the present method. More importantly, the present method has the advantage of a tremendous reduction in computing time.
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    URL: http://dx.doi.org/10.1002/rcm.1290060209
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