Size exclusion chromatography (SEC) represents the most important and advantageous technique for determination of the molar mass distribution of lignins, due to the ease of implementation and the large choice of commercially available chromatographic columns responding to most demands. There are different SEC systems, which are suitable for analysis of either water-soluble lignins, such as lignosulfonates, or lignins soluble in organic solvents, such as organosolv or kraft lignin (Ringena et al. 2006, Baumberger et al. 2007). The ALICE core facility offers a universal SEC methodology that can cope with all different lignin types in a single system, requiring no special lignin sample preparation or time-consuming derivatization pretreatment. Still, the method requires the lignin to be liberated from its liquor matrix by means of precipitation, ultrafiltration or other approaches. For the most accurate characterization an additional lignin purification by means of solvent extraction can be recommended.
In order to achieve a reliable and reproducible determination of the molar mass distributions of all types of lignins an appropriate set of detectors has to be applied. In addition to the conventional detection techniques, such as ultraviolet-visible (UV-Vis) and refractive index (RI), we apply the most advanced and accurate Multi-Angle Light Scattering (MALS), requiring no instrument calibration and providing absolute molar mass characterization (Zinovyev et al., 2018).
SEC-MALS analysis is performed using an Ultimate 3000 autosampler, column oven, UV detector (all Thermo Fisher Scientific Inc., Waltham, MA, USA) equipped with a Dionex HPLC Pump Series P580 (Dionex Softron GmbH, Germering, Germany), Dawn HELEOS II MALS detectors with lasers operating at either 658 or 785 nm; and an Optilab T-rEX differential refractive index detector, λ = 633 nm (all Wyatt Technology, Santa Barbara, CA, USA). Both MALS detectors are equipped with 18 photodiodes at different measuring angles, with narrow band pass filters (±10 nm for the respective wavelength used, installed on every second photodiode).
Sample amount required: 20 mg.
Baumberger, S., Abaecherli, A., Fasching, M., Gellerstedt, G., Gosselink, R., Hortling, B., Li, J., Saake, B. & De Jong, E. (2007).
Molar mass determination of lignins by size-exclusion chromatography: towards standardisation of the method.
Holzforschung, 61(4), 459-468. doi: 10.1515/Hf.2007.074
Ringena, O., Lebioda, A., Lehnen, R., & Saake, B. (2006).
Size-exclusion chromatography of technical lignins in dimethyl sulfoxide/water and dimethylacetamide.
Journal of Chromatography A, 1102(1-2), 154-163. doi: 10.1016/j.chroma.2005.10.037
Zinovyev, G., Sulaeva, I., Podzimek, S., Rossner, D., Kilpelainen, I., Sumerskii, I., Rosenau, T., Potthast, A. (2018).
Getting Closer to Absolute Molar Masses of Technical Lignins.
Chemsuschem, 11(18), 3259-3268. doi: 10.1002/cssc.201801177