## 3 Experimental Results  
VOCs produced by normal colonic mucosa and adenomatous polyp specimens were analyzed and monitored by HS- and DI-SPME-GC-MS procedures for seven days under ex vivo conditions. The analyses showed that both tissues of the same patient produced a similar VOC pattern but with different fingerprints. Figure 1 shows two typical HS-SPME-GC-MS chromatograms obtained analyzing the tissues of the same patient at time zero. Thirty-two different VOCs were identified by inspecting the acquired chromatograms with those reported in the library of the NIST. The list of the compounds identified with their retention times (RT), the characteristic ions (\(m/z\)) used to recall the XIC, the numbers for each of them in the hit list (i.e., match factor and probability) created by NIST library for the identification of their chemical structures, the confirmation of identity by standards, and the frequency of appearance in the acquired HS- and DI-SPME-GC/MS chromatograms are reported in Table 2, which clearly shows that benzaldehyde, ethylbenzene, indole, methylbenzene, phenol, octanal, and oxime methoxy-phenyl are the most frequently detected compounds in chromatograms (Frequency > 50%). Benzaldehyde and oxime methoxy-phenyl were also found in chromatograms obtained from the culture medium (control) and their basal values were subtracted from those of tissues, indicating that all tissues exhale and/or metabolize these compounds. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**\#**} & \multirow{2}{*}{**RT (min)**} & \multirow{2}{*}{**Compound**} & \multirow{2}{*}{**Characteristic Ions (\(m/z\))**} & \multirow{2}{*}{**Match**} & \multirow{2}{*}{**Prob. (\%)**} & \multirow{2}{*}{**Standard Identity**} & \multirow{2}{*}{**Frequency (\%)**} \\ \cline{5-6}  & & & & & & & **HSI** & **DI** \\ \hline
1 & 2.02 \(\pm\) 0.04 & Dimethyl chloroacetal & 47 & 782 & 75.5 & & 3.1 & 3.1 \\ \hline
2 & 2.21 \(\pm\) 0.09 & Acetaldehyde oxime & 14, 59 & 962 & 37.3 & & 12.5 & 28.1 \\ \hline
3 & 3.03 \(\pm\) 0.02 & 2-Butanone,4-hydroxy & 43, 61 & 674 & 39.1 & & 3.1 & 0 \\ \hline
4 & 3.30 \(\pm\) 0.08 & 1-Butanol & 41, 56 & 827 & 40.0 & & 5.6 & 3.1 \\ \hline
5 & 5.54 \(\pm\) 0.05 & Acetal & 73, 103 & 849 & 77.0 & & 12.5 & 6.3 \\ \hline
6 & 6.06 \(\pm\) 0.07 & 1-Butanol,3-methyl & 41, 55 & 867 & 20.5 & & 0 & 3.1 \\ \hline
7 & 6.19 \(\pm\) 0.09 & Disulfide, dimethyl & 45, 79 & 939 & 97.1 & & 9.4 & 12.5 \\ \hline
8 & 6.84 \(\pm\) 0.07 & Methylbenzene & 91 & 979 & 60 & yes & 93.8 & 96.9 \\ \hline
9 & 8.82 \(\pm\) 0.08 & Ethlybutanoate & 43, 71 & 877 & 90.0 & & 3.1 & 3.1 \\ \hline
10 & 8.98 \(\pm\) 0.07 & Ethyl 2-methyl butanoate & 57, 102 & 851 & 76.8 & & 18.8 & 3.1 \\ \hline
11 & 9.10 \(\pm\) 0.08 & Ethyl 3-methyl butanoate & 88, 115 & 824 & 88.5 & & 12.5 & 3.1 \\ \hline
12 & 9.29 \(\pm\) 0.09 & Ethylbenzene & 91, 106 & 954 & 71.6 & yes & 68.8 & 31.3 \\ \hline
13 & 9.53 \(\pm\) 0.10 & xylene & 91, 106 & 908 & 61.5 & yes & 46.3 & 3.1 \\ \hline
14 & 10.07 \(\pm\) 0.09 & xylene & 91, 106 & 788 & 30.2 & yes & 46.9 & 9.4 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Lists of compounds, RT, characteristic ions (\(m/z\)), match factor, probability, standard identity confirmation, and frequency of appearance in the acquired HS- and DI-SPME-GC-MS chromatograms related to secreted compounds by normal colonic mucosa and adenomatous polypoid lesion. Figure 1: HS-SPME-GC-MS chromatograms of VOCs released by colon normal mucosa (N) and adenomatous polyp (P) tissues from the same patient (n\({}^{\circ}\) 2) at time zero. For benzaldehyde, ethylbenzene, indole, and methylbenzene, clear differences were found between healthy and adenomatous tissue of the same patient when evolution over time was followed, ex vivo, by SPME-GC-MS. Figure 2 shows the typical time-dependent monitoring (0, 1, 4, and 7 days) of the seven selected compounds by DI-SPME-GC-MS in tissue samples from one of the patients (n\({}^{\circ}\) 2).