AOAC Official Method 932.01 Lignin in Plants Direct Method
First Action 1932
Final Action 1965
A. Preparation of Test Sample
Grind test sample in mill to pass No. 80 sieve and dry at 105°C. Extract weighed test portions (5–10 g) 30 h in Soxhlet apparatus with alcohol–benzene solution (32 parts alcohol and 68 parts benzene by weight). Dry material in oven to free it from solvents and place in flask of suitable size. Add 150mLH2O/g sample, and reflux 3 h. Filter mixture while still hot, preferably through weighed fritted glass crucible, and transfer extracted material to flask. Add 1% HCl (111 g concentrated HCl + 3890 mL H2O) in proportion of 150 mL acid solution/g plant material, and reflux 3 h. Filter mixture while still hot through fritted glass crucible previously used, wash with H2O until acid-free, dry at 105°C, and weigh. Calculate percent total loss due to successive extraction with alcohol–benzene solution, hot H2O, and 1% HCl. (With test samples not especially rich in carbohydrates and proteins, extraction with hot H2O may be omitted.)
