Treatment of the extractive-free bark samples with 1 percent NaOH to remove interfering phenolic compounds impacted the lignin contents determined by the Klason method, but not those determined by the acetyl bromide method.
Lignin contents were also determined by the acetyl bromide method (Morrison 1972) using an extinction coefficient of 23.7 liters [g.sup.-1] [cm.sup.-1] (Johnson et al.
Alternatively, analyses of extractive-free samples by the acetyl bromide method gave even lower lignin contents.
Acetyl bromide lignin analyses, infrared spectroscopic analyses, and density changes of 30 [micro]m-thick sections of peracetic-acid-treated samples, as a function of depth from the wood surface, suggested that a partial delignification had occurred that diminished with depth.
Acetyl bromide lignin analysis as a function of depth
(27), (28) To determine lignin content in small wood samples, an acetyl bromide procedure and a spectrophotometer were used.
Two procedures (thioglycolate and acetyl bromide) also rely on the complete solubilization of lignin, but in this case the lignin in solution is measured.
(1961) developed a method to dissolve lignin in a solution of acetyl bromide and acetic acid.
In addition, we analyzed subsamples of initial litter for total N and P using Kjeldahl digestion followed by colorimetric analysis on an Alpkem autoanalyzer (Alpkem, a division of OI Analytical, Wilsonville, Oregon); for cations (K, Mg, and Ca) using nitric acid digestion followed by analysis with atomic absorption (Perkin-Elmer Corporation, Norwalk, Connecticut); and for lignin using acetyl bromide digestion (Iiyama and Wallis 1990), with National Bureau of Standards pine as a standard (% lignin = 21.8; J Pastor and B.
Initial concentrations of acetyl bromide lignin were lower at Kauni than they were at Thurston and Laupahoehoe, and fertilization with P significantly reduced acetyl bromide lignin concentrations at Thurston (Table 2).
Also, Saxena and Stotzky (2001) reported very large increases (33-97%) in acetyl bromide lignin concentration for lower stem internodes of nine Bt maize hybrids compared with isolines.
Because lignin procedures are known to provide different estimates of lignin concentration, we compared the acid detergent, Klason, and acetyl bromide methods.