# Identification by GC-MS Analysis of Organics in Manufactured Articles through a D-Optimal Design
## 3 Results
### GC-MS Analysis
#### 3.2.1 Samples A to F  
In Table 3, the characteristic identified compounds of samples A to F and their derivatives are reported. In the Supplementary Materials (Figure S1), the chromatogram of sample A with the parameters of Experiment 2 (Soxhlet extraction with dichloromethane and time of analysis of 24 min) is reported. From sample A, we can note that the extraction did not completely break the links in the polymer, but only the molecules that were not cross-linked were recovered and analyzed, and as a matter of fact, in sample A1, and more so in A2, there is a minor number of molecules. In sample A2, we did not find characteristic compounds due to both the high curing rate and the fact that at high temperatures, some compounds may have evaporated. In these samples, compounds with phenolic groups or substituted bisphenols were found, confirming the phenolic nature of the resin. Moreover, hexamethylenetetramine and benzoic acid were found, which are a curing agent and cross-linking catalyst, respectively. It is interesting to note that these molecules were not present \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Sample** & **Compound** & **CAS** & **Raw Material** & **t\({}_{\text{R}}\) (min)** & **\# ID** \\ \hline \multirow{8}{*}{W} & phenol & 108-95-2 & A–C & 5.1 & 1 \\  & 2-hydroxybenzaldehyde & 90-02-8 & A & 6.0 & 2 \\  & 4-hydroxybenzaldehyde & 123-08-0 & A & 9.2 & 12 \\  & 2-[(4-hydroxyphenyl)methyl]phenol & 2467-03-0 & A & 14.2 & 7 \\  & 4-[(4-hydroxyphenyl)methyl]phenol & 620-92-8 & A & 14.6 & 8 \\  & 2-methylpropyl hexadecanoate & 110-34-9 & C & 14.9 & 23 \\  & 1-methyl-4-(4-methylphenyl)sulfonylbenzene & 599-66-6 & C & 15.4 & 26 \\  & 3-pentadecylphenol & 501-24-6 & C & 17.0 & 31 \\ \hline \multirow{8}{*}{X} & phenol & 108-95-2 & A & 5.1 & 1 \\  & 2-hydroxybenzaldehyde & 90-02-8 & A & 6.0 & 2 \\  & benzoic acid & 65-85-0 & A & 7.5 & 4 \\  & 4-hydroxybenzaldehyde & 123-08-0 & A & 9.2 & 12 \\  & 2-[(4-hydroxyphenyl)methyl]phenol & 2467-03-0 & A & 14.2 & 7 \\  & 4-[(4-hydroxyphenyl)methyl]phenol & 620-92-8 & A & 14.6 & 8 \\ \hline \multirow{8}{*}{Z} & Phenol & 108-95-2 & C & 5.1 & 1 \\  & hexadecan-1-ol & 36653-82-4 & C & 13.2 & 17 \\ \cline{1-1} \cline{2-5}  & 2-hydroxybenzaldehyde & 90-02-8 & B & 6.0 & 2 \\  & 4-hydroxybenzaldehyde & 123-08-0 & B & 9.2 & 12 \\ \cline{1-1}  & phenylmethoxymethylbenzene & 103-50-4 & B & 11.5 & 14 \\ \cline{1-1}  & hexadecan-1-ol & 36653-82-4 & C & 11.8 & 17 \\ \cline{1-1}  & 2-[(4-hydroxyphenyl)methyl]phenol & 2467-03-0 & B & 14.2 & 7 \\ \cline{1-1}  & 4-[(4-hydroxyphenyl)methyl]phenol & 620-92-8 & B & 14.6 & 8 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Characteristic compounds in samples W–Z. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample** & **Compound** & **CAS** & **t\({}_{\text{R}}\) (min)** & **\# ID** \\ \hline \multirow{8}{*}{F} & heptadecanoic acid & 506-12-7 & 14.4 & 52 \\  & octadec-1-ene & 112-88-9 & 14.5 & 58 \\  & (Z)-octadec-9-enenitrile & 112-91-4 & 14.6 & 59 \\  & octadecanentiffe & 638-65-3 & 14.7 & 60 \\  & (E)-octadec-9-enoic acid & 112-79-8 & 15.0 & 24 \\  & (Z)-octadec-6-enoic acid & 593-39-5 & 15.1 & 61 \\  & octadecanoic acid & 57-11-4 & 15.2 & 25 \\  & hexadecanamide & 629-54-9 & 15.3 & 62 \\  & (Z)-octadec-9-enamide & 301-02-0 & 16.2 & 63 \\  & 3-pentadecylphenol & 501-24-6 & 17.0 & 31 \\ \hline \end{tabular}
\end{table} 
Table 3: _Cont._in A1 and A2, since such molecules are completely consumed during the curing process. These data immediately give us an indication of whether the resin has been cross-linked or still has some non-cured parts. Thus, the presence of some specific molecules (i.e., hexamethylenetetramine) can be considered the first quality indicator of an incomplete curing process.