Procedures for the Detection of Lignin

The procedures described below comprise a representative sampling of test methods in which use of the principal types of color-forming reagents is illustrated. Prior to performing the color reaction, the lignified material should be extracted in a Soxhlet apparatus with ethanol-benzene (1 2 v/v) and then with water to remove extractives that otherwise might interfere with the test. 

The reactions are usually performed by treating the extracted sample in a test tube or on a porcelain spot test plate. When an organic reagent is part of the test, the reaction is conducted with a 1% solution of the reagent in 3M hydrochloric acid or sulfuric acid at room temperature. The colors formed generally are stable for several hours. 

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