High-Performance Size Exclusion Chromatography of Low-Molecular-Weight Lignins and Model Compounds

An experimental high-performance size exclusion chromatographic procedure to obtain apparent molecular weights and their distribution for low-molecular-weight lignins was developed. Polystyrenes and lignin model compounds were utilized for calibration of the molecular weights. Values found in this study for weight and number average molecular weights for steam-exploded aspen lignins agree well with values reported by other workers using different solvent systems and calibration methods for similar lignins. In addition, possible associative effects were estimated by using one model compound with a free phenolic group and a carbonyl group, acetovanillone. The mobile phase and concentration range were optimized to minimize associative effects. The procedure used proved to be reproducible and to give good resolution of paucidisperse components. An examination of the application of Kirkwood-Riseman theory to the elution behavior of low-molecular-weight polystyrenes and lignin model compounds, is also included.