Electrochemically modulated liquid chromatography of polymers
Analytical Chemistry
Final Report Abstract
The project „electrochemically modulated liquid chromatography of polymers” was concerned with the development of new liquid chromatographic methods for the characterization of polar polymers (plastics). Therein, primarily water-soluble polymers were studied. It was intended to research, if electrochemically modulated liquid chromatography (EMLC) is suitable to develop new selectivities for the separation of such polymers. Of particular interest were separations according to end-groups, tacticity and the composition of copolymers. Information about these parameters is not suitably accessible using current methods. A core initial aspect of the project was the construction of a suitable chromatographic column (EMLC column). This was because the method and corresponding analytical equipment are not yet commercially available. In the course of the project, this step proved to be more complicated than initially anticipated, which had a significant impact on the development of the project. Finally, a new design concept for an EMLC column could be realized and tested in practice. In order to evaluate the EMLC approach, the question had to be answered, if an electrical voltage applied to the column influences the time it takes for polymer molecules to traverse the column (retention time). In liquid chromatography, the differing retention times of different molecules allow the separation of said molecules. By varying individual parameters (solvent composition, temperature, flow velocity, …), it is attempted to separate molecules with different properties (separation parameters) as good as possible from one another. In this manner, it is possible to evaluate the frequency of occurrence and relative distribution of these properties. To achieve as good a separation as possible, the molecules are supposed to traverse the column on very time scales. In the course of the project, it was observed that it is possible to influence the retention time of polymer molecules during an EMLC separation by varying an electric voltage. The influence of said voltage was, however, too small and not reproducible enough to be of sufficient use in the development of a new separation method. Further research is necessary to elucidate how a stronger influence can possibly be achieved.
