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Chemical Structure Identification based on Differential Mass Spectra Introduction

The CSI-Diff-ms is a new revolutionary technology, accepted by various academical organizations and subject of actual patents, used to identify the chemical structure of substances with similar mass spectra.

The CSI-Diff-ms software includes powerful tools for mass spectra data import, correction of mass spectra, calculation and visualization of differential mass spectra and correlation with quantum chemical data imported form external sources.

The mass spectrum is a property of each substance and two similar mass spectra recorded under identical conditions correspond in most cases to identical substances. The classical mass spectrometry uses this relationship for the identification of chemical structures using databases with etalon mass spectra. Though the term "differential mass spectrometry" (DIFF MS) is relatively new, the difference between mass spectra of substances is a know method used for the identification process, also the fragmentation pattern is used in actual identification methods.

In all known actual identification methods, in case of substances with similar mass spectra the identification process could lead to errors, like in case of double bond position isomers, many aromatic and aliphatic isomers.

The CSI-Diff-ms technology and software suite solves this specific problem related to the identification of chemical structures having similar mass spectra.

The CSI-Diff-ms technology and software don't include and don't replace the well known "library search method" but enhances this method and can be used to identify:

  • the chemical structure of isomer substances with similar mass spectra
  • the best mathematical model, selected from a number of proposed mathematical models, that describe the kinetics and the thermodynamics of the ionization-fragmentation process inside the mass spectrometry system
  • the best set of heat of formation or activation energy for the analyzed fragmentations, selected from a number of proposed sets calculated with various quantum chemical calculations methods
  • the mass spectrum for a given substance or all mass spectra related to similar substances inside a complex MS measurement with multiple scans using a reference mass spectrum

The CSI-Diff-ms uses three types of differential mass spectra in order to calculate the differences between mass spectra: the ratio of spectra (Pms), the difference of the spectra (Δms) and the percentage difference (Δ%ms).

The CSI-Diff-ms uses up to four algorithms used to identify the isomers related to given mass spectra and up to three find scan algoritms used to identifiy a given scan inside a complex MS measurement with multiple scans.

Please consult the support, white papers and references areas for additional documentation and video tutorials about the CSI-Diff-ms.

The differences between the full and lite version are listed under the topic: Features.

The following snapshots shows the powerful CSI-Diff-ms graphical visualization features used for the analysis of two pesticides, which are aromatic isomers, having similar mass spectra: 2,2',3,6'- tetrachlorobiphenyl and 2,2',3,5'- tetrachlorobiphenyl.

Click on each image in order to enlarge.

Click to enlargeTIC representation
the input data
Click to enlarge2,2',3,6'- tetrachlorobiphenyl
Click to enlarge2,2',3,5'- tetrachlorobiphenyl

The differentiated mass spectra show, with sensibility and accuracy, both the fluctuations of the little peaks as well as the fluctuations of the medium and high peaks. The following snapshot show the differential mass spectra graphical visualization performed by CSI-Diff-ms using the two presented tetrachlorobiphenyl mass spectra and a sub range 100 to 325 m/z from the scan.

Click to enlarge2,2',3,6'-tetrachlorobiphenyl / 2,2',3,5'-tetrachlorobiphenyl

The following snapshot shows the internal CSI-Diff-ms quantum chemical database used to manage the imported theoretical data offered by computational chemistry. Up to two methods for the calculation of both heat of formation or activation energy for the analyzed fragmentations are supported.

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Click to enlarge

The following snapshot shows the CSI-Diff-ms correlation results for an analysis of 5 similar mass spectra and 5 isomers.

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Click to enlarge

The CSI-Diff-ms technology and software suite is based on the correlation between the experimental data obtained through mass spectrometry with theoretical dates offered by computational chemistry for substances with extremely similarly structures, like isomers, and allows the identification of isomer substances based on mass spectra processing.
The usage of external databases with etalon spectra is not needed.