Liquid adsorption chromatography of polyethers: experiments and simulation

The adsorption behavior of poly(ethylene glycol) (PEG) in reversed-phase ch romatography is studied both experimentally and theoretically and a compute r simulation of chromatograms is performed on the basis of these studies. T he experimental conditions were: different reversed-phase adsorbents and a solvent methanol-water system as the mobile phase. At varying mobile phase compositions highly resolved chromatograms of PEG samples were obtained, in which all peaks could be identified, and the dependencies of the distribut ion coefficient on the degree of polymerization for PEG molecules were eval uated by processing these chromatograms. The data were interpreted by using a theory of homopolymers based on a continuum Gaussian chain model of flex ible macromolecules and a slit-like model of pores of stationary phase. The theory proved to describe well the experimental data in the whole range of studied molecular masses, and the thermodynamic parameters characterizing interactions of ethylene oxide repeating units in PEG molecules with the ad sorbent pore walls have been determined from the comparison of the theory w ith the experimental data. The dispersion of chromatographic peaks correspo nding to individual oligomer molecules is also estimated. In the system stu died the peak width occurred to be proportional to the distribution coeffic ient of corresponding macromolecule. The theory is used to develop a comput er-assisted procedure for simulation of chromatograms for samples of linear homopolymers. Using the obtained data on the thermodynamic parameters and the estimates of peak dispersion, chromatograms are simulated for PEG sampl es at two different chromatographic conditions. These simulated chromatogra ms were in good quantitative agreement with the real chromatograms. (C) 200 0 Elsevier Science B.V. All rights reserved.