Extraction and Isolation of Lignin for Utilization as a Standard to Determine Lignin Concentration Using the Acetyl Bromide Spectrophotometric Method (original) (raw)

Lignin content in plant samples was determined by using the spectrophotometric method acetyl bromide soluble lignin. As any spectrophotometric method, a reliable standard was required; in this project, lignin extracted with an acidic solution of dioxane was investigated as a possible standard for quantitatively determining lignin content in plant samples. Acidic dioxane lignins were analyzed for carbohydrate, total protein (these values were discounted from the dioxane lignin weight before building the calibration curve), nitrobenzene oxidation products, and for UV spectral characteristics. Total carbohydrate content of isolated 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. Nitrobenzene analysis indicated differences in amount of guaiacyl and syringyl units making up the lignins but this did not alter the UV spectrum of lignin solubilized in acetyl bromide. Regression equations developed for the acetyl bromide method using the isolated lignins for all the plant samples were similar to each other. Lignin values obtained by the acetyl bromide method were similar to the lignin values obtained as acid insoluble residues following a Klason lignin procedure.