Caroline Collette

Comparison of the Internal Energy Distributions of Ions Produced by Different Electrospray Sources

The internal energies of the emitted ions can be modulated in an electrospray source through different experimental conditions. However, the fragmentation pattern depends also on conditions that cannot be controlled by the operator, e.g. the geometry of the source or the mode of transfer of the ions. These differences make difficult the comparison of the electrospray mass spectra obtained with different mass spectrometers. A method for the calibration of the internal energies of ions produced by an electrospray source has been presented previously to study the influence of experimental conditions on the internal energies of the ions. The method permits the calibration of individual working conditions. In this work, new results were obtained with modified values of fragmentation energy taking into account the kinetic shift of the thermometer ions. The internal energy distributions are compared for different instruments with different geometries, and are measured under different accelerating and focusing conditions.

Calibration of the Internal Energy Distribution of Ions Produced by Electrospray

The internal energy deposited in the ions in the source of a mass spectrometer governs their fragmentation and therefore the content of the spectra. When the ionization conditions are well defined and reproducible, e.g. in electron impact, the elaboration of databases benefits the use of the method. In electrospray, however, the source conditions are not strictly defined. The elaboration of spectra databases therefore requires a calibration of the internal energy of the ions that is valid for all types of spectrometers. A method for the calibration of the internal energy of ions in electrospray is presented, developed using the fragmentation reactions of a set of probe ions (benzylpyridinium salts) under various conditions (the voltage on the sampling cone, the nature of the collision gas, the composition of the mobile phase). The influence of the experimental conditions on the internal energy of the ions permits the calibration of individual working conditions.

Qualitative Comparison between the Quantum Calculations and Electrospray Mass Spectra of Complexes of Polyammonium Macrotricyclic Ligands with Dicarboxylic Acids

The host—guest interactions play a very important role in chemical and biological processes. It is therefore important to be able to characterize these complexes. Electrospray mass spectrometry can be used to characterize the complex formation. It provides information on the mass and the charge of these ionic complexes. In this article, we show that the use of ab initio and semiempirical calculations, in addition to the results obtained by electrospray mass spectrometry, reveal to be a promising tool for the study of these noncovalent complexes. In this article, host—guest complexes formed by macropolycyclic polyammonium host molecules and dicarboxylic acids are studied.

On the Determination of the Ion Internal Energy in an Electrospray Source

Electrospray ionisation (ESI) is a “soft” ionisation method which produces ions from solution by nebulisation in an electric field. It allows the direct analysis of samples in solution with a mixture of usual solvents (H2O, CH3OH, CH3CN), and has rapidly become an essential method for the analysis of biological compounds (peptides, proteins, organometalics, organic salts).