11
Table 3: Averaged observed volume % values for each NTGA in oxygenate-free gasoline at spikes of 1%, 3%, 5%, and 10% v/v. With the exception of gamma-valerolactone, all compounds demonstrated a high degree of linearity. *Because gamma-valerolactone was not soluble at 10% v/v in oxygenate-free gasoline, it was re-analysed in E10 gasoline, whose ethanol content allowed it to dissolve.
Compound Acetone
Dimethoxymethane Methyl acetate 2-Butanone
2-Methylfuran
Dimethyl carbonate Ethyl acetate
2-Methyltetrahydrofuran 2-Pentanone 2-Pentanol
2,5-Dimethylfuran
4-Methyl-2-Pentanone 2-Methyl-1-butanol sec-Butyl acetate Cyclopentanone Isobutyl acetate 3-Hexanone
Diethyl carbonate
2,4-Dimethyl-3-pentanone Ethyl butanoate n-Butyl acetate
Methyl pentanoate Ethyl pentanoate Anisole
Isobutyl isobutyrate
Gamma-valerolactone (in Oxygenate-Free Gasoline)
Gamma-valerolactone (in E10 Gasoline)* Aniline
Methyl levulinate Ethyl levulinate N-Methylaniline
Retention Time (min) 2.65 2.83 2.85 3.33 3.55 3.61 3.63 4.61 4.83 5.39 5.69 6.62 6.97 7.83 8.33 8.60 8.87 8.95 9.66
10.35 11.16 11.70 15.33 15.55 15.99
16.01 16.01
17.39 17.59 19.79 20.01
10% Spike
10.9 10.4 10.4 10.4 10.2 10.5 10.3 10.2 10.6 10.2 10.2 10.3 10.3 10.5 10.1 10.5 10.0 10.5 10.1 10.0 10.2 10.1 10.3 10.1 10.0
6.71 10.3
10.3 10.2 10.2 10.3
Individual solutions of each NTGA were prepared by dissolving each compound in oxygenate-free gasoline at concentrations of 10%, 5%, 3%, and 1% v/v and analysed in triplicate. One compound, gamma- valerolactone, was not soluble at 10% in oxygenate-free gasoline, so it was dissolved in E10 gasoline at concentrations of 10%, 5%, 3%, and 1% v/v and analysed in triplicate. Additionally, individual solutions of three compounds - dimethoxymethane, 2,5-dimethylfuran, and N-methylaniline - were prepared with concentrations of 20%, 10%, 5%, 2%, 1%, 0.5%, 0.2%, 0.1%, and 0.05% v/v in E10 gasoline and again analysed in triplicate.
All data was processed using retention indices (RI) relative to methane and spectral matching. Quantification was achieved by comparing each compound’s response to benzene and calculating a relative response factor (RRF). Procedures for determining RI and RRF values are listed in ASTM D8071 [21]. The RI and RRF values used in this experiment can be found in Table 2.
5% Spike
4.96 5.12 5.20 5.12 5.24 5.21 5.65 5.13 5.32 5.19 5.18 5.30 5.38 5.43 5.18 5.40 5.25 5.36 5.15 5.22 5.27 5.17 5.37 5.16 5.12
5.02 5.51
5.23 5.13 5.20 5.32
3% Spike
3.00 3.13 3.14 3.09 3.17 3.09 3.66 3.13 3.18 3.32 3.18 3.19 3.21 3.25 3.14 3.20 3.25 3.18 3.18 3.19 3.16 3.13 3.31 3.03 3.13
3.08 3.26
3.19 3.19 3.16 3.28
3. Results and Discussion:
The quantification results for each NTGA can be found in Table 3. Each compound of interest was quantified in gasoline over a range of 1% - 10% v/v.
While most NTGAs would likely fall between 1% and 10% v/v, this concentration range can be expanded. Three additives were chosen to be analysed over a range of 0.05% - 20% v/v and were analysed in triplicate. Those results can be found in Table 4.
Unlike methods such as DHA which rely on chromatographic separation to identify compounds through retention time, GC- VUV takes advantage of spectral deconvolution to compress the chromatography, giving a shorter run time of 34 minutes. While NTGAs may coelute with other compounds in gasoline, spectral deconvolution allows them to be identified and quantified without issue. For example, although acetone coelutes with isopentane under
1% Spike
0.956 1.08 1.06 1.11 1.05 1.05 1.25 1.04 1.01 1.15 1.03 1.06 1.08 1.08 1.00 1.04 1.09
0.954 1.08 1.06 1.06 1.03 1.18 1.04 1.04
1.00 1.05
1.07 1.10 1.06 1.08
R2 0.998
>0.999 >0.999 >0.999 >0.999 >0.999 0.997
>0.999 >0.999 >0.999 >0.999 >0.999 0.999
>0.999 >0.999 >0.999 >0.999 >0.999 >0.999 0.999
>0.999 >0.999 >0.999 >0.999 >0.999
0.917 0.998
>0.999 >0.999 >0.999 >0.999
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