## 3 Results and Discussion
### Suitability of Sorbent Materials
#### 3.2.3 Sulphur Compounds
Figure 8: Storage stability of sulphur compounds (\(\sim\)100 nmol/mol) on Tenax TA. Figure 10: Storage stability of sulphur compounds (\(\sim\)100 nmol/mol) on Carboxen 1003. Figure 9: Storage stability of sulphur compounds (\(\sim\)100 nmol/mol) on Tenax TA/SulfiCarb. Figure 11: Storage stability of sulphur compounds (-20 nmol/mol) on Tenax TA. Figure 12: Storage stability of sulphur compounds (-20 nmol/mol) on Tenax TA/SulfiCarb. The uncertainty of the RRF was determined by taking into account different sources of uncertainty; the uncertainties due to the gas mixture preparation, the uncertainties due to the sampling procedure, and the standard deviation for the peak area obtained when analysing five sorbent tubes. The targeted compounds behaved differently depending on the tested sorbent materials. Under the conditions for the experiments, H\({}_{2}\)S and CH\({}_{4}\)S could not be recovered from any of the three selected sorbent materials. The measurements performed on the 100 nmol/mol gas mixture showed that the COS response relative to C6 decreased with time on Tenax TA. The amount of COS recovered sampling from this sorbent material after D7 was below the detection limit (Figure 8). Instabilities were observed for CS\({}_{2}\) and T-BM on the double bed sorbent material Tenax TA/SulfiCarb. The results for the short-term stability with the 20 nmol/mol gas mixture were comparable to the results obtained with the 100 nmol/mol gas mixture. The uncertainties for the RRF were larger due to higher standard deviations for the measurement at these low concentration levels. The only noticeable difference was that T-BM at 20 nmol/mol could not be detected after D4 on the Carboxen 1003 sorbent material. In summary, Tenax TA was observed to be a good sorbent material for the higher boiling sulphur compounds e.g., THT, CS\({}_{2}\) and T-BM even though some breakthrough occurred for T-BM. The issue could be resolved by lowering the sampling volume. THT and COS can be stored for 2 weeks on the Tenax TA/SulfiCarb sorbent material while CS\({}_{2}\) and T-BM showed decreasing recovery over time. Carboxen 1003 is a suitable sorbent material for COS. The other sulphur compounds showed instability. Tests should be performed to prevent the formation of SO\({}_{2}\) by the reaction of the sulphur compounds with oxygen. The suitability of sorbents for the targeted compounds are summarized in Table 8. Some compounds with low boiling points (COS BP \(-\)50 \({}^{\circ}\)C), propane (BP \(-\)42 \({}^{\circ}\)C), isobutane (BP \(-\)11 \({}^{\circ}\)C), chloromethane (BP \(-\)24 \({}^{\circ}\)C) and vinyl chloride (BP \(-\)14 \({}^{\circ}\)C) were detected with more or less good stability using sorbents such as Carboxen 1003 (COS), Chromosorb 106 or even TCC. Even if recoveries were not always optimal using Tenax TA, most of the compounds exhibited good storage stability for a period of 10-14 days. Figure 6:0 Storage stability of sulphur compounds (\(-\)20 nmol/mol) on Carboxen 1003. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline  & & \multicolumn{3}{c}{**Chromosol 106**} & \multicolumn{3}{c}{**TCC**} & \multicolumn{3}{c}{**Teras TA**} & \multicolumn{3}{c}{**Carbonen 100**} & \multicolumn{3}{c}{**Teras TA/SuitCarb**} \\ \cline{3-14}  & **BP (c)** & \multicolumn{1}{c}{**Resovery**} & \multicolumn{1}{c}{**Storage**} & \multicolumn{1}{c}{**Recovery**} & \multicolumn{1}{c}{**Storage**} & \multicolumn{1}{c}{**Recovery**} & \multicolumn{1}{c}{**Storage**} & \multicolumn{1}{c}{**Recovery**} & \multicolumn{1}{c}{**Storage**} & \multicolumn{1}{c}{**Recovery**} & \multicolumn{1}{c}{**Storage**} & \multicolumn{1}{c}{**Recovery**} & \multicolumn{1}{c}{**Storage**} \\  & & & **Yield** & **Stability** & **Yield** & **Stability** & **Yield** & **Stability** & **Yield** & **Stability** & **Yield** & **Stability** & **Yield** & **Stability** \\ \hline \multirow{2}{*}{ \begin{tabular}{c} Progame \\ Isobutane \\ Butane \\ Ethanol \\ \end{tabular}