Table 2.
Comparison of sedimentation equilibrium (SE) and alkaline size exclusion chromatography (SEC) methods to determine the weight average molar masses (Mw) of P1000 soda lignin from mixed wheat straw/sarkanda grass and Indulin AT Kraft softwood lignin.
| Lignin/lignin fraction | Weight average molar mass, Mw (kDa)* | ||
|---|---|---|---|
| SE | SEC | ||
| From M* extrapolation | From hinge point | ||
| Soda P1000 | 3.0 | 2.8 | 2.2 |
| F01 ethyl acetate | 1.0 | 1.0 | 1.3 |
| F02 MEK | 1.2 | 1.3 | 1.9 |
| F03 methanol soluble | 3.7 | 3.2 | 3.3 |
| F04 acetone/water (4:1) | 10.2 | 9.0 | 6.8 |
| F05 residual fraction | 8.9 | 7.3 | 28.3 |
| Indulin AT Kraft | 4.2 | 4.1 | 3.5 |
| F01 ethyl acetate | 1.2 | 0.9 | 1.0 |
| F02 MEK | 1.1 | 1.0 | 1.4 |
| F03 methanol soluble | 6.5 | 6.5 | 2.8 |
| F04 acetone/water (4:1) | 11.1 | 9.5 | 5.3 |
| F05 residual fraction | 11.9 | 9.5 | 8.4 |
Solvents used to derive fractions F01-F04 are shown. F05 is the residual fraction remaining after the four-step solvent extraction with ethyl acetate, MEK, methanol and acetone:water (4:1). Sedimentation equilibrium (SE) analysis was carried out at 20.0 °C as described in Methods. Mw data were derived using the Sedfit-MStar suite of programmes.
*Standard error is 3–5%. Size exclusion chromatography was performed as described in Methods. MEK: methyl ethyl ketone.