Data processing method for the determination of accurate molecular weight distribution of polymers by SEC/MALDI-MS

Abstract

A novel data processing method for a hyphenated technique, size exclusion chromatography/matrix-assisted laser desorption/ionization-mass spectrometry (SEC/MALDI-MS), has been proposed to determine accurate molecular weight distributions on the basis of the individual oligomer species of a polymer. This method is based on the concept that the individual peak intensities of MALDI mass spectrum observed for every SEC fraction with narrow molecular weight distribution could be adjusted to the quantified values to reveal the accurate molecular weight distribution using the signal intensity of the corresponding fraction on the SEC chromatogram observed with a refractive index detector. At first, the theory of the proposed date processing is described in detail. Then, experimental verification of the method is described. This was performed through the characterization of mixtures of three kinds of monodispersed polystyrene reference materials (weight average molecular weight = ca. 6000, 10000, and 18000) as model samples. An accurate trimodal molecular weight distribution for the individual oligomer species of the sample was obtained without any influence of the chromatographic band broadening observed in the original SEC chromatogram. Moreover, the method for depicting the elution profiles of individual oligomer species during SEC separation was also obtained as a "mass chromatogram" using the data processing procedure.