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V. Weiss:
"Gas-phase electrophoresis of (bio-)nanoparticles on a nES GEMMA instrumentation: hyphenation to orthogonal analysis techniques";
Fakultät für Technische Chemie, 2021.

Nanoparticles can be found in many everyday situations ranging from naturally occurring particles in the nanometer scale to engineered nanomaterials employed e.g. in pharmaceutical, medical or nutritional applications. Due to their high surface-to-volume ratio, characteristics of nanoparticles differ from bulk materials. To allow for an improved risk assessment, number-based particle concentrations are recommended by the European Commission for nanoparticle characterization (2011/696/EU from October 18th, 2011). Gas-phase electrophoresis in this context is a very appealing analytical method.
Gas-phase electrophoresis applying a nano Electrospray Gas-phase Electrophoretic Mobility Molecular Analyzer (nES GEMMA) separates native, surface-dry nanoparticles in the gas-phase on the basis of the size of analytes according to electrophoretic principles. Monodisperse (monomobile) analytes are counted after separation enabling number-based particle detection. Data concerning nanoparticle size, size distribution and particle numbers of the original, polydisperse sample can therefore be obtained. Hyphenation of gas-phase electrophoresis to orthogonal analysis methods (online e.g. to capillary electrophoresis, offline e.g. to mass spectrometry and spectroscopic techniques) adds another dimension to nES GEMMA separations and will improve the portfolio of targetable nanoparticle characteristics. The aim of my habilitation thesis was therefore fourfold:
(i) Improvement of the gas-phase electrophoretic instrumentation itself (especially in terms of possible alternatives to an employed radioactive source necessary for charge equilibration) to allow for a less regulated implementation of the instrument in a standard laboratory setting without any further safety precautions. Corresponding results are presented in section 6.2 of this thesis.
(ii) Characterization of the nES GEMMA method for application in the analysis of additional bionanoparticle classes, e.g. viruses, virus-like particles (VLPs), polysaccharides and liposomes. As an outcome, well-characterized analyte material can be applied for hyphenation strategies. Corresponding results are presented in section 6.3 of this thesis.
(iii) Improvement of analyte preparation and polishing steps (especially necessary for an exemplary virus) to allow for experimental work applying highly pure bionanoparticles. Corresponding results are presented as additional work in section 8 of this thesis.
(iv) On- and offline hyphenation of gas-phase electrophoresis (nES GEMMA instrumentation) to additional analytical methods. Corresponding results are presented in sections 6.4 and 6.5 of this thesis. Furthermore, an outlook to further strategies will be given in section 7.
To conclude, in overall ten key publications and six additional papers are presented in this thesis.