# Analytical Pyrolysis and Mass Spectrometry to Characterise Lignin in Archaeological Wood
## 3 Results and Discussion
### Direct Exposure Mass Spectrometry (DE-MS)
\begin{table}
\begin{tabular}{c c c c} \hline \hline \(m/z\) & **Molecular Origin** & **Wood Component** & **References** \\ \hline
107 & alkylphenols & L & [52,83] \\ \hline
110 & 1,2-dihydroxybenzene; 1,4-dihydroxybenzene; 5-methyl-2-furaldehyde; 2-acetylfuran & L/C & [54,82,83,84] \\ \hline
123 & 4-methylcatechol; 4-methylguaiacol; dihydrocaffeic acid & L & [52,54,83,84] \\ \hline
124 & guaiacol; 4-methylcatechol; coniferyl alcohol & G & [38,52,54,83,84] \\ \hline
137 & 4-ethylguaiacol; 4-propylguaiacol; coniferyl alcohol; dihydroconfieryl alcohol; & G & [38,52,54,83,84] \\  & alcohol; guaiacylacetone, homovanillin & G & [38,52,54,83,84] \\ \hline
138 & 4-methylguaiacol & G & [38,52,54,83,84] \\ \hline
150 & 4-vinylguaiacol & G & [38,52,54,83,84] \\ \hline
151 & vanillin; acetovanillone; vanillic acid methyl ester; & G & [38,52,54,83,84] \\  & propiovanillone;guaiacyl vinyl ketone; vanillic acid & G & [38,52,54,83,84] \\ \hline
152 & 4-ethylguaiacol; vanillin; coniferyl alcohol & G & [38,52,54,83,84] \\ \hline
154 & Syringol & S & [38,52,54,83,84] \\ \hline
164 & eugenol; isoeuegenol (E and Z); p-coumaric acid & G & [38,52,54,83,84] \\ \hline
166 & acetovanillone; 4-propylguaiacol & G & [52,54,83,84] \\ \hline
167 & 4-ethylsyringol; 4-propylsyringol; sinapyl alcohol; dihydroosinapyl & S & [38,52,54,83,84] \\  & alcohol; syringacetone & S & [38,52,54,83,84] \\ \hline
168 & vanillic acid; 4-methylsyringol & G/S & [38,52,54,83,84] \\ \hline
178 & Coniferylaldehyde & G & [38,52,54,83,84] \\ \hline
180 & coniferyl alcohol, 4-vinylsyringol; guaiacylacetone; propiovanillone & G/S & [38,52,54,83,84] \\ \hline
181 &
\begin{tabular}{c} syringaldehyde; acetosystemingone; syring acid methyl ester; \\ propiosystemingone; syring vinyl ketone; syring acid \\ \end{tabular} & S & [38,52,54,83,84] \\ \hline
182 & 4-ethylsyringol; syringaldehyde; dihydroconiferyl alcohol; vanillic acid & S/G & [52,54,83,84] \\  & methyl ester; dihydrocaffeic acid; sinapyl alcohol & S/G & [52,54,83,84] \\ \hline
194 & 4-(1-properly)syringol, 4-(2-propenyl)syringol (E and Z); & S & [38,52,54,83,84] \\  & 4-allyysringol; ferulic acid & S & [38,52,54,83,84] \\ \hline
196 & acetosystemingone; 4-propylsyringol & S & [38,52,54,83,84] \\ \hline
198 & Syringic acid & S & [38,52,54,83,84] \\ \hline
208 & Sinapylaldehyde & S & [38,52,54,83,84] \\ \hline
210 & sinapyl alcohol; syringacetone; propiosystemingone & S & [38,52,54,83,84] \\ \hline
212 & dihydroasinapyl alcohol; syring acid methyl ester & S & [52,54,83,84] \\ \hline
272 & stilbene-type dimer & G-G dimer & [38,52] \\ \hline
302 & stilbene-type dimer & G-S dimer & [38,52] \\ \hline
332 & stilbene-type dimer & S-S dimer & [38,52] \\ \hline
358 & \(\beta\)-resinol type dimer & G-G dimer & [38,52] \\ \hline
388 & \(\beta\)-resinol type dimer & G-S dimer & [38,52] \\ \hline
418 & \(\beta\)-resinol type dimer & S-S dimer & [38,52] \\ \hline \hline \end{tabular}
\end{table} 
Table 2: _Cont._The peaks at \(m/z\) 137 and \(m/z\) 167 are commonly present in the mass spectra of sound wood and are generated by the fragmentation of \(p\)-substituted guaiacyl or syringyl compounds, respectively. The first one corresponds to the 4-methylguaiacol ion and is present in the mass spectra of 4-ethylguaiacol, 4-propylguaiacol, coniferyl alcohol, and dihydrocniferyl alcohol. The latter corresponds to the 4-methylsyringol ion and is present in syringyl derivatives, listed in Table 2.  
The oxidation processes occurring in the lignin fraction of archaeological wood can be monitored through the characteristic fragments formed by compounds with carbonyl or carboxyl functionalities such as \(m/z\) 151 from guaiacyl units and \(m/z\) 181 from syringyl ones.