Bruno Weimann

Siscom — a new library search system for mass spectra

Abstract SISCOM is a library search system for mass spectrometry which is based on a new method of coding spectra by selecting the most important peaks within homologous ion series, and on a multiple factor assessment of the result. Examples demonstrate the ability of the system to identify various compounds, even from mixtures or by reference spectra which differ from those measured. SISCOM is especially suitable for detecting structural similarities like common substructures, even in cases where no similarity can be recognized by visual comparison of patterns or by human interpretation of the spectrum.

Optimization of search algorithms for a mass spectra library

Abstract The SISCOM mass spectra library search is mainly an interpretative system producing a “hit list” of similar spectra based on six comparison factors. This paper deals with extension of the system; the aim is exact identification (retrieval) of those reference spectra in the SISCOM hit list that correspond to the unknown compounds or components of the mixture. Thus, instead of a similarity measure, a decision (retrieval) function is needed to establish the identity of reference and unknown compounds by comparison of their spectra. To facilitate estimation of the weightings of the different variables in the retrieval function, pattern recognition algorithms were applied. Numerous statistical evaluations of three different library collections were made to check the quality of data bases and to derive appropriate variables for the retrieval function.

Computer-aided identification of compounds by comparison of mass spectra

Abstract A new identity-orientated search procedure for mass spectral libraries (IDS) was developed by extending the similarity search system SISCOM. The aim of IDS is an exact identification of pure compounds and mixtures on the basis of their mass spectra. The concepts and methods applied, e.g., filtering, feature selection and optimization with pattern recognition, are described. Chracteristics of IDS are summarized and demonstrated for several examples.

Organometallic complex compounds, part 51. Ligand property controlled CO-insertion in nickel complexes: Separation of electronic and steric effects

SummaryThe influence of twenty phosphorus-containing ligands on the CO insertion with four-coordinated Ni11 complexes as starting reagents is reported. Quantitative separation of the electronic and steric effects by a multilinear regression analysis (55% electronic and 45% steric influence) is presented together with a three dimensional representation. An increase in donor-capacity favours CO insertion and an increase in steric hindrance leads to a decrease in the fraction of the corresponding ketone.

Colachrom, a command language for chromatographic data processing

Abstract A command language for the interactive computer processing of chromatograms is described. Report data files, resulting from a peak evaluation program, are processed with single-line commands. Reference peaks for quantitative evaluation or for retention index calculations can be specified, compound names or response factors be assigned, etc. Customer-specific reports can be generated. Several commands operate on the unreduced digitized chromatograms, e.g., repeat peak evaluation with modified peak search parameters or with a user-corrected baseline. Commands can be combined into procedures for semi-automatic processing of series of chromatograms. Various forms of interactive graphical presentations supplement the command language.

Influence of the Particle Size of Silica Support on the Kinetics and the Resulting Polymer Properties at the Polypropylene Polymerization with Heterogeneous Metallocene Catalysts; Part II: Development of a Model as Well as a Mathematical Simulation

In heterogeneous olefin polymerization, the influence of monomer mass transport in the growing particle and the fragmentation of the support have been comprehensively modeled for conventional Ziegler catalyst but the simulation of the polymerization process of silica supported metallocene catalyst was calculated only by few authors. The expansion and modification of the existing ‘particle growth model’ for the catalytic system SiO2/MAO/rac-Me2Si[IndR2]2ZrCl2 of Bonini et al. is presented. Especially the influence of the catalyst particle size on the kinetics and the fragmentation behaviour was modeled. It was observed experimentally that the maximum polymerization rate as well as the polymer properties depend on the average particle size of the catalyst pellet. In our calculations we were able to demonstrate that the propagation rate and the chain transfer rate alter relative to the varying pellet radius due to the different gradients of [MAO]/[metallocene]-ratios from the particle surface to the granule center.

A computer system for measuring fast-scan lowresolution mass spectra

A microprocessor-based satellite computer system (MASDAT) controls a low-resolution, fast-scan mass spectrometer for the measurement of series of spectra. Special digitization hardware (logarithmic A/D converter) and software algorithms are necessary to achieve a dynamic range (ratio of highest to lowest intensity) of about 105 in peak heights. Up to three MASDAT satellites can be connected to a host computer. Synchronized parallel programs in the host system communicate with the operator, calibrate the mass scale, print an interscan report, and store final spectra and, optionally, unreduced data on mass storage devices. Host software is described for a RSX11M and for a VAX/VMS operating system.

Interactive processing of chromatograms with display terminals

SummaryThe use of display terminals for the interactive processing of gas chromatographic data in the Mülheim Computer System is described and discussed.The stepwise and flexible evaluation of chromatograms as they are especially met in research and development laboratories is facilitated considerably.1.The correlation of analogue and digital presentations of chromatographic results can easily be performed by the operator at the display screen via peak numbers or retention parameters.2.Chromatograms can be investigated in more detail by fast plotting of any desired section of the total chromatogram in any desired scales of coordinates.3.The fit of software constructed baselines to the chromatograms can be studied, baseline and solvent peak subtraction methods can be performed easily.