A comprehensive two-dimensional liquid chromatography system was developed to precisely describe the molecular heterogeneity of fatty alcohol ethoxylates. The end-group functionality was analyzed by gradient HPLC while ethylene oxide oligomer distributions were characterized by liquid adsorption chromatography. A baseline separation of all functionality fractions irrespective of the ethylene oxide oligomer chain length was achieved on nonpolar X-Terra C(18) with a methanol-water gradient, whereas an isocratic flow of isopropanol-water on a polar Chromolith Si column gave a separation according to the oligomer chain length without interference of the end-group distribution. The combination of these two methods to conduct online two-dimensional liquid chromatography experiments resulted in a comprehensive two-dimensional picture on the molecular heterogeneity of the sample.

The free-radical copolymerisation of various acrylates and methacrylates resulting in complex copolymers for cosmetic applications were investigated using different chromatographic techniques including HPLC and on-line coupled two-dimensional (2D) liquid chromatography. The complete separation of all polymerisation products was achieved by gradient HPLC. A computated optimisation procedure, using the Polymer Chromatographic Model allowed us to design a step mobile phase gradient to improve resolution of homopolymer chromatographic separation. By combining gradient HPLC and SEC (Size Exclusion Chromatography) in a fully automated two-dimensional chromatography setup, the complex distributions of chemical composition and molar mass could be simultaneously described and fingerprinted.

Liquid chromatography of polymers is traditionally a slow technique with analysis times of typically 30 min per sample. To adapt liquid chromatographic techniques to combinatorial materials research the sample throughput must be significantly increased. Preferably, the analysis time per sample is to be reduced to a few minutes. Short analysis times can be achieved using high resolution stationary phases, high flow rates, and fast gradients. The present work demonstrates that gradient HPLC of polymethacrylates can be accomplished in less than 2 min. The fast separation of poly( methyl methacrylate), poly(i-propyl methacrylate), poly(n-butyl methacrylate), poly(t-butyl methacrylate), and poly(n-decyl methacrylate) is conducted on a short monolithic stationary phase using a flow rate of up to 7 mL/min. The optimization of the gradient is conducted by running a number of linear gradients and by simulating an optimum step gradient. Further modification of the simulated gradient results in the desired short analysis times.

Liquid chromatography of polymers is traditionally a slow technique with analysis times of typically 30 min per sample. For the application of liquid chromatographic techniques in combinatorial materials research the analysis time per sample must be reduced considerably. For fast high performance liquid chromatography (HPLC) small columns and new stationary phases with improved separation efficiencies can be used. HPLC separations of poly(ethylene oxide)s with different end groups can be conducted in less than 4 min. Accordingly, with new column technology and optimized separation methods time savings of more than 90% can be achieved as compared to conventional technology.

Gradient chromatography was applied in order to calculate the composition at elution for different methacrylates on normal phase columns. In addition the composition at elution was determined for polyethyleneoxide on a reverse phase column. It is shown that high molar mass polymers elute for a given homopolymer irrespective of their molar mass at the same eluent composition, which varies only slightly with gradient slope. In general the composition at elution in gradient chromatography is expected to be slightly lower than the true critical composition. For high molar mass polymers we found this composition to be close to the critical composition determined by isocratic experiments. The difference between the composition at elution and the true critical composition for a variety of polymethacrylates and for polyethyleneglycol was found to be only between 0.2 and 5%. Thus, after estimating the composition at elution, only a small number of additional isocratic experiments is needed to find the exact critical composition.

The application of HPLC-NMR for the analysis of a mixture of fatty alcohol ethoxylates (FAEs) is described. The use of the new generation, cryogenically cooled probes is investigated in respect of the sensitivity advantage that they provide. The FAE mixture is separated using liquid chromatography at the critical point of adsorption. The ability of the method to differentiate between the different end groups and the degree of polymerization of the mixture constituents is investigated. Both on-flow and stop-flow HPLC-NMR techniques were used together with two-dimensional NMR spectroscopy. The results are compared with those obtained by using an evaporative light scattering detector for the HPLC.