The objective of this experiment was the extraction of lignin and its use in the calibration curves to determine lignin concentration in vegetable plants. Among the analytical methods for measuring lignin concentration, there is the "acetyl bromide soluble lignin -ABSL" method, were solubilized lignin in 25% solution of acetyl bromide in glacial acetic acid is read at 280 nm. However, any spectrophotometric method requires a reliable standard to which optical density readings are compared; in this experiment, the standard was obtained through extraction with acetyl bromide reagent. Lignin was quantified in four forage samples, at two maturity stages, and also in two wood samples, comparing the obtained data with two other analytical methods for lignin (acid detergent lignin - ADL and potassium permanganate lignin - PerL). The three techniques yielded different values for the same samples; in general, the ABSL method showed higher lignin concentrations than the two other methods. For each sample it was made a standard curve and a 240-320 nm ultraviolet scanning. Analyses of such curves and scannings indicated qualitative differences among samples, not only related to plant species, but also to maturity stage of vegetable samples.
chemical analysis; forages; lignin; spectrophotometric analysis
