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United States Department of Agriculture

Agricultural Research Service

Title: Using the Acetyl Bromide Assay to Determine Lignin Concentrations in Herbaceous Plants: Some Cautionary Notes

item Hatfield, Ronald
item Grabber, John
item Ralph, John

Submitted to: International Symposium on Wood and Pulping Chemistry
Publication Type: Abstract Only
Publication Acceptance Date: June 9, 1997
Publication Date: N/A

Technical Abstract: The acetyl bromide method was developed to provide a rapid and sensitive method for quantifying lignin in wood species. The original procedure cautioned against prolonged reaction times and advised keeping the reaction temperature at 70 deg C to prevent excessive carbohydrate degradation that would skew the absorption spectra. We have found that xylans, a prominent group within all plants, are easily degraded by the acetyl bromide reagent resulting in increased absorbance in the 270 to 280 nm region. The degradation of xylans is dependent upon temperature and is exacerbated by the addition of catalytic amounts of perchloric acid. Degradation of the xylans is minimized by lowering the reaction temperature to 50 deg C and increasing the reaction time to 2 h to 4 h for complete lignin solubilization.

Last Modified: 4/21/2015
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