## 2 Results and Discussion  
### Headspace-Solid Phase Microextraction (HS-SPME) Analysis  
In all cases, sensitivity was seen to decrease with increased ethanol content. A very stark decrease was seen immediately with the addition of ethanol (0-0.5%) on Carboxen-PDMS (Figure 1) for smaller compounds, except H2S. Ethanol had less influence on the absorption of DMTS, DEDS, and DIDS on DVB/Car/PDMS fiber, and no influence on Car/PDMS fiber. It was postulated that the ethanol competed with adsorption of small VSCs on the active Carboxen site, such that the addition of ethanol could dramatically decrease the absorption of small VSCs on the fiber. On the other hand, H2S had a stronger affinity on the Carboxen, so it was not influenced by ethanol content. Similarly, large VSCs including DMTS, DEDS, and DIDS compete more favorably on the Carboxen fiber, so ethanol had no influence on their absorption. Similar trends were observed for DVB-Carboxen-PDMS fibers, except ethanol, which decreased the absorption of DMTS and DEDS (Figure 2). The results from the DVB-PDMS fiber are shown in Figure 3. DMS, DMDS, MeSOAc, EtSOAc (Figures 1B, 2B and 3B), as well as the internal standards EMS, DES, MIS, and EIS (Figures 1A, 2A and 3A), all exhibited similar curve shapes. DEDS, DMTS, and DIDS (Figures 1C, 2C and 3C) shared a different shape, with more gradual decreases with respect to concentration. Methanethiol showed a decrease, but with a more gradual curve, like those of larger species. Hydrogen sulfide exhibits very little influence from ethanol concentration, possibly suggesting the ability to enter very small pores on the Carboxen fiber phase and avoid competition (Figures 1D, 2D and 3D).  
Figure 1: Effects of ethanol on the adsorption of the Carboxen-PDMS solid-phase microextraction (SPME) fiber of: (**A**) ethyl methyl sulfide (EMS), methyl isopropyl sulfide (MIS), diethyl sulfide (DES), and ethyl isopropyl sulfide (EIS); (**B**) dimethyl sulfide (DMS), methyl thioacetate (MeSOAc), dimethyl disulfide (DMDS), and ethyl thioacetate (EtSOAc); (**C**) dimethyl trisulfide (DMTs), diethyl disulfide (DEDS), and diisopropyl disulfide (DIDS); (**D**) methanethiol (MeSH) and H\({}_{2}\)S.  
Figure 2: _Cont._  
Figure 3: Effects of ethanol on the adsorption of DVB-PDMS SPME fiber of: (**A**) Internals standards EMS, MIS, DES, and EIS; (**B**) DMS, MeSOAc, DMDS, and EtSOAc; (**C**) large compounds DMTS, DEDS, and DIDS (IS); (**D**) highly-volatile compounds MeSH and H\({}_{2}\)S.  
Figure 2: Effects of ethanol on the adsorption of DVB-Carboxen-PDMS SPME fiber of: (**A**) Internal standards EMS, MIS, DES, and EIS; (**B**) DMS, MeSOAc, DMDS, and EtSOAc; (**C**) large compounds DMTS, DEDS, and DIDS (IS); (**D**) highly-volatile compounds MeSH and H\({}_{2}\)S.  
The DVB-PDMS fiber showed less sensitivity toward all compounds, but also less dependence on ethanol concentration (Figure 3), as has been previously noted [14]. The smaller compounds and internal standards (such as DIDS) show a less-sudden decrease with ethanol, almost linearly (Figure 3A,B). Larger compounds like DEDS show a gradual decrease, while DMTS and DIDS can be seen to be barely affected (Figure 3C). Hydrogen sulfide and methanethiol show no signs of significant change above 0.5% ethanol (Figure 3D). These phenomena may be an indication of a more adsorptive mechanism, while the Carboxen allows a more absorptive mechanism [9]. This is due to the uniform structure of solid microspheres within the DVB phase, compared to the non-uniform porosity of activated charcoal.