Ultraviolet (UV) spectra of a 1 N NaOH solution
of TGAL prepared from bamboo (Phyllostachys
heterocycla) milled wood lignin (Nakatsubo et al. 1972;
Nakamura and Higuchi 1978) and from rice were
recorded in a 10 mm quartz cell with a UV-1600PC
spectrophotometer (Shimadzu). For plotting calibration
curves, 1–5 mg dried bamboo milled wood lignin was
weighed and the TGAL solution was prepared as above.
The solution was diluted 50-fold with 1 N NaOH and
absorbance at 280 nm was recorded in a 10 mm quartz
cell with a UV-1600PC spectrophotometer and in a UVStar
96-well plastic microplate (Greiner) containing
200 ml of the diluted TGAL solution in each well on a
SH1000Lab microplate reader (Corona Electronics).
Lignin concentration was determined by dividing the
amount of lignin calculated based on the calibration
curve by the dry weight of the sample after the methanol
extraction