Herstellung und Charakterisierung von elektrochemisch regenerierten Membransuppressoren für die Anionenaustauschchromatographie
Abstract
The preparation of mesh based membrane suppressors for ion exchange chromatography was investigated. Sulfonation of polymeric meshes resembles the foundation of this component of chromatographic systems. Transfer of sulfonation techniques for the functionalization of polyolefinic and polyaromatic meshes was examined. Aromatic sulfonation showed advantages regarding sulfonation selectivity and preservation of mesh structure. Variation of operating and design parameters allowed the identification of influencing factors within membrane suppressors and enabled the description of critical variables. These factors include electrode dimensioning, ion exchange capacity, and the cation exchange membrane. The membrane exerts a multi-layered influence, including the conductivity of the suppressors respectively the electric resistance, the mechanical stability and the transport of ions. Across all parameters, the applied voltage was identified as critical variable and has a significant influence on signal broadening and shift of retention times. Transport of ions was investigated with regard to suppression efficiency. Membrane suppressors showed a characteristic coelution of system cations and analytes originating from incomplete removal of cations, leading to a reduced suppression efficiency. Coelution is influenced by the suppression current as well as the meshes and membranes. In addition, the transport of anionic analytes was investigated. A loss of analytes was observed for anions of weak acids, which is based on the transport of undissociated species through the membrane. The loss is influenced by the membrane and the electrical parameters of suppression.
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