Dynamische Ionenaustauschchromatographie reaktiver Aluminium-Komplexe

A new approach for the simulation of dynamic chromatograms has been developed. The simulation program is based on a Python-script. A numerical solution of the phase transfer rate of the analytes between mobile and stationary phase is used to calculate on-column analyte concentration profiles at different states of the separation process. Second order on-column reactions can be taken into account due to the known concentration profile of each analyte. Because of the modular script, combined reactions with different reaction orders can be simulated independent of the separation techniques used. As a proof for accomplishment dynamic chromatograms generated by ion exchange chromatography and ICP-MS-detection of different aluminum-species ([Al(edta)F]2− , [AlOx3]3− ,[AlCit2]3− , [AlF2]+) has been successful analyzed. The outcome of this method are the determination of the species distributions in the samples as well as the relevant reactions and related reaction rates on the chromatographic timescale at different temperatures. Second order formation reactions of citrate-, oxalate- and fluoride-complexes have shown a strong effect on the resulting chromatograms. Further investigations revealed that reaction rates are dependent on the retention factor of the reactant. It has been proven that mentioned observation is based on different reaction rates in the mobile and stationary phase of the column. The decomposition rate of the complex [Al(edta)F]2− was measured with 10 times higher rate in the mobile phase and [AlCit2]3− shows a 50 times higher rate compared to the stationary phase reaction. However for the decomposition rate of [AlOx3]3− the differences between the mobile and stationary phase reaction are neglectable. Furthermore the dependency of pH values and observed reaction rate was investigated. For all measured complexes the decomposition rates increased with lower eluant pH values. In addition to mentioned homoleptic complexes the decomposition rates of the complex [AlCit(HOx)2]2− has been measured. It shows that this complex in combination with [AlOx3]3− and [AlCit2]3− are essential in detoxification of plants like buckwheat. Dynamic ion exchange chromatography with ICP-MS detection in combination with the simulation program developed in this study is a powerful analytical method for aluminum species determination. The new methode is also useful for the investigation of reaction rates of reactive analytes in general.