Fig. 4. Lignin markers obtained on CuO oxidation. Top: stem of Bt line Novelis T, bottom: stem of near-isogenic non-Bt line Nobilis. Data in parentheses: molecular mass of the free phenol (in Dalton). Peaks referred to identical internal standard (IST) (deuterated dimethylphenol; target molecular mass ion: m/z = 125 amu). GC–MS: free fatty acid phase (FFAP) stationary phase. Data presentation: Extracted ions (full scan data acquisition mode).