Table 5. Py-GC-SIM-MS Relative Abundance of Structural Features within Biomasses and ¹³C Internal Standard (¹³C -IS) on the Basis of RRF Corrected Molar Peak Area^a.

	WS	CS	BS	SCB	13C-ISb
Lignin % (w/w)c	18.5 ± 1.3	19.3 ± 1.0	23.9 ± 0.6	28.5 ± 2.0	−
H	16.3 ± 0.8	42.8 ± 0.8	15.4 ± 0.7	49.0 ± 4.2	17.1 ± 5.0
G	66.2 ± 1.4	47.7 ± 1.1	59.9 ± 1.4	35.8 ± 1.8	60.2 ± 3.9
S	17.5 ± 0.4	9.5 ± 0.2	24.7 ± 0.7	15.3 ± 0.7	22.7 ± 1.2
S/G	0.3	0.2	0.4	0.4	0.4
unsub.	6.2 ± 0.2	5.1 ± 0.1	5.4 ± 0.05	6.8 ± 0.4	4.5 ± 0.3
methyl	2.8 ± 0.1	3.0 ± 0.1	2.5 ± 0.1	4.6 ± 0.5	2.1 ± 0.5
ethyl	0.3 ± 0.01	0.3 ± 0.1	0.2 ± 0.01	0.4 ± 0.05	0.2 ± 0.04
vinyl	40.8 ± 0.9	68.3 ± 1.3	34.8 ± 1.3	59.5 ± 4.2	25.3 ± 5.1
Cα-Od	3.1 ± 0.1	4.0 ± 0.1	3.5 ± 0.06	4.1 ± 0.2	4.3 ± 0.3
Cβ-Oe	1.2 ± 0.03	0.8 ± 0.05	1.4 ± 0.05	1.5 ± 0.1	1.4 ± 0.2
Cγ-Of	42.9 ± 1.4	15.9 ± 0.3	49.4 ± 1.2	17.7 ± 1.7	58.8 ± 3.0
misc.g	2.7 ± 0.04	2.6 ± 0.08	2.7 ± 0.06	5.1 ± 0.2	3.3 ± 0.4

^aStructural classification is shown in Table 1. Average and standard deviation of triplicates. WS: wheat straw, CS: corn stover, BS: barley straw, SCB: sugarcane bagasse.

^bAverage and standard deviation of ¹³C-IS added to all biomasses in triplicate.

^cDetermined by ¹³C lignin IS based py-GC-SIM-MS.

^dC_α-oxygen.

^eC_β-oxygen.

^fC_γ-oxygen.

^gMiscellaneous.