Removing non-lignin components
Klason Lignin (sulfuric acid lignin): Wood meal is extracted with alcoholbenzene
which is employed to remove materials, such as waxes, fats, some
resins, and possibly some portions of wood gums, then stirred at room
temperature and hydrolysis with 64 to 75% sulfuric acid. The Klason lignin is
obtained after removing the polysaccharides, and refluxed with dilute acid; then
the Klason lignin or sulfuric acid lignin is filtered, dried, and weighed. This
procedure serves as a method for determination of lignin in wood and other
plant materials. But this method is able to change the structure of lignin during
the hydrolysis. (López et al. 2010)
Willstätter Lignin: wood meal is extracted and hydrolyzed with concentrated
hydrochloric acid, and produces an insoluble lignin residue, this is so-called
Willstätter lignin.
Periodate Lignin: mild oxidation of extracted wood meal with periodic acid (HIO3)
dissolved nonlignin components by hot-water hydrolysis, there is less alteration
in lignin structure. Degraded carbohydrates are dissolved, finally obtain anCuproxam Lignin: substantially all carbohydrate components in extracted wood
meal may be dissolved with cuprammonium hydroxide with alternate dilute acid
hydrolysis, and this is the basis for preparation of Freudenberg of Cuproxam
lignin (Glennie & McCarthy 1962).