Table 2 Lignin-derived monomeric products in water-soluble portion and their retention times, structures, and MS fragments for GC–MS analysis

1

Guaiacol

G

124, 109, 89, 81

2

Methylguaiacol

G–C

138, 123, 95, 77

3

Vinylguaiacol^b

G–C=C

150, 136, 107, 78

4

Eugenol

G–C–C=C

164, 149, 134, 104, 77

5

Vanillin

G–CHO

152, 123, 109, 77

6

trans-Isoeugenol

G–C=C–C

164, 150, 104

7

Homovanillin

G–C–CHO

166, 138, 123

8

Unknown

162, 148, 120, 92

9

Acetovanillone

G–CO–C

166, 152

10

Guaiacylacetone^c

G–C–CO–C

180, 137

11

Unknown

178, 150, 90, 78

12

2-Methoxy-4-(prop-1-en-3-one)phenol^d

G–CO–C–C

178, 151

13

Homovanillic acid

G–C–COOH

182, 152

14

3-4-Hydroxy-3-methoxyphenyl-1-propanol

G–C–C–C–OH

182, 138

15

cis-Coniferyl alcohol

G–C=C–C–OH

180, 163, 138, 124, 78

16

Hydroferulic acid

G–C–C–COOH

196, 137

17

trans-Coniferyl aldehyde

G–C=C–CHO

178, 164, 149

18

trans-Coniferyl alcohol

G–C=C–C–OH

180, 164, 138

19

Ferulic acid

G–C=C–COOH

194, 167, 138