## 3 Results
### Extracted Ion Data for Carpet Substrates
#### 3.2.1 Carpet #1 Stain Master Pet Protect (Nylon 6,6)  
Potential Interference with Identification of Gasoline  
Comparison of the total ion chromatograms obtained for carpet #1 sample burned without ILs with that of unburnt neat gasoline, suggests the presence of interfering compounds and it can be suspected that gasoline is present in the sample (Figure 3). The following interfering compounds were identified in carpet burned without ILs: toluene (RT = 3.30 min, RSI = 900), ethylbenzene (RT = 5.61 min, RSI = 948), m- p- xylene (RT = 5.86 min, RSI = 892), n-propylbenzene (RT = 8.37 min, RSI = 908), and naphthalene (RT = 15.38 min, RSI = 912). However, the extracted ion profiles of carpet burned without ILs and unburned neat gasoline present distinguishable differences. In other words, although the extracted ion profiles of the two samples have common peaks (e.g., extracted alkylbenzene profile), the peak abundance ratios are not similar, indicating that gasoline is not present in the sample. However, since the carpet was burned and the neat gasoline was unburned, it might be argued that the difference is due to the evaporation, degradation, or combustion of the potentially present gasoline in the sample. To clear this ambiguity, the TIC and the extracted ion profiles of the carpet #1 burned with gasoline were obtained and compared to those of neat gasoline and carpet #1 burned without ILs. Figure 2: GC-MS extracted ion data related to neat kerosene. (**a**) Total ion chromatogram; (**b**) extracted alkane profile; (**c**) extracted cycloalkanes and alkenes profile; (**d**) aromatics (alkylbenzenes) profile; (**e**) extracted polynuclear aromatics profile; (**f**) extracted indane profile. A comparison of the TIC and extracted ion profiles of carpet #1 burned with gasoline and neat gasoline (Figure 3b,c) shows clear similarities. All target compounds of gasoline were identified in the carpet burned with gasoline and with the same proportions as found in neat gasoline. The comparison of the extracted ion profile for alkylbenzene compounds in neat gasoline with that of carpet #1 burned without ILs clearly shows that even though some of the characteristic alkylbenzene compounds of gasoline are present in carpet #1 burned without gasoline (Figure 4a), the abundance and peak ratios are different from that of neat gasoline (Figure 4c). The abundance and peak ratios of alkylbenzene compounds in the carpet burned with gasoline (Figure 4b), however, are comparable with those of neat gasoline (Figure 4c), making it easy to distinguish between the presence and absence of gasoline in the fire debris. Figure 4: _Cont._  
Figure 3: Total ion chromatograms (_m/z_ 50–500) of (a) carpet #1, burned without ILs; (b) carpet #1 burned with gasoline; and (c) neat gasoline. To further investigate the presence of interfering compounds in carpet #1, the extracted polynuclear aromatics profiles were compared (Figure 5), and naphthalene (RT = 15.38 min, RSI = 943) was identified in carpet #1 burned without ILs, which is also present in carpet burned with gasoline (RT = 15.37 min, RSI = 925), and neat gasoline (RT = 15.38 min, RSI = 925). Therefore, based on the extracted polynuclear aromatics profiles, the carpet burned without ILs cannot be distinguished from the carpet burned with gasoline, and naphthalene is an interfering compound in the analysis of gasoline. Figure 4: Extracted aromatic (alkylbenzenes) profiles of (**a**) carpet #1 burned without ILs; (**b**) carpet#1 burned with gasoline; and (**c**) neat gasoline. Figure 5: _Cont._  
A comparison of the indane profiles shows that the pattern and intensities of peaks in chromatograms obtained from carpet #1 without ILs (Figure 6a) are different from that of neat gasoline (Figure 6c). Identification of peaks showed indane was present in neat gasoline (RT = 10.92 min, RSI = 919) and carpet #1 burned with gasoline (RT = 10.84 min, RSI = 904; however, this compound was not identified in the chromatogram of carpet burned without ILs (Figure 6a).