Development of Size Exclusion Chromatography/Laser Induced Fluorescence Analysis of Isolated Lignins

Abstract

Size Exclusion Chromatography/Low Angle Laser Light Scattering (SEC/LALLS) has been used to monitor changes in the molecular weight disbribution (MWD) of lignins recovered from alkaline pulping liquors. While developing a method of molecular weight analysis, we discovered that fluorescence was contributing to the detected signal. During the course of the experiments, we realized that this laser-induced fluorescence, could be used to monitor lignin. We modified the filters in the LALLS instrument and sucessfully measured lignin fluorescent properties. We found that fluorescence of lignin increased during the course of pulping with the formation of fluorescent structures excited at the wavelength of the laser (632.8 nm) being uniform throughout the molecular weight range.