Hydrophobic Interaction Chromatography in 2 D Liquid Chromatography Characterization of Lignosulfonates

Lignosulfonates are bulk-scale byproducts of industrial sulfite pulping. Their amphiphilic character plays a central role in their successful application in large-scale materials production. As an inherent feature of the chemical structure, this amphiphilic character poses a major analytical challenge. In this study, the amphiphilic behavior of an industrial lignosulfonate was investigated by hydrophobic interaction chromatography (HIC). This technique exploits hydrophobic regions present on the surface of lignosulfonates. Extensive characterization of the obtained fractions from preparative HIC, in terms of elemental composition, functional-group content, chemical structure, and molecular weight distribution, revealed a detailed picture of the chemical composition distribution. The charge-to-size ratio, that is, differences in the degree of sulfonation, was the dominant factor governing separation in HIC. A combination of HIC with size exclusion chromatography showed good orthogonality of separation and demonstrated the power of this 2 D liquid chromatography approach for an in-depth characterization, in general, and amphiphilicity, in particular.