Extraction and isolation of lignin for utilization as a standard to determine lignin concentration using the acetyl bromide spectrophotometric method

Lignin extracted with acidic dioxane was investigated as a possible standar d for quantitatively determining lignin content in plant samples using the spectrophotometric method employing acetyl bromide. Acidic dioxane lignins were analyzed for carbohydrate, total protein, nitrobenzene oxidation produ cts, and UV spectral characteristics. Total carbohydrate content of isolate d lignins ranged from 2.21 to 5.70%, while protein ranged from 0.95 to 6.06 % depending upon the plant source of the original cell wall sample. Nitrobe nzene analysis indicated differences in the amount of guaiacyl and syringyl units making up the lignins, but this did not alter the UV spectrum of lig nin solubilized in acetyl bromide. Regression equations developed for the a cetyl bromide method using the isolated lignins for all the plant samples w ere similar to each other. Lignin values obtained by the acetyl bromide met hod were similar to the lignin values obtained as acid insoluble residues f ollowing a Klason lignin procedure.