Fig. 5. Lignin markers obtained by CuO oxidation; sample subjected to BF3/methanol methylation (see Materials and Methods). Top: Novelis T, Bt stem; bottom: Nobilis, non-Bt stem. Acids S6 and G18 (see Fig. 1) in methylated form. Presentation as superposition of three ion traces. GC–MS conditions: see caption to Fig. 4.