# Carbonyl Composition and Electrophilicity in Vaping Emissions of Flavored and Unflavored E-Liquids
## 3 Results and Discussions
Using the NIST mass spectral library search (NIST MS Search 2.0), Table 1 displays 14 carbonyls identified using their signature ions (e.g., \(m/z\) 181 and the molecular ion of carbonyl-PFBHA oxime derivatives). The derivatization reaction between each identified carbonyl and PFBHA, and their oxime derivatives are shown in Scheme S1. The identified carbonyls are formaldehyde, acetaldehyde, acetone, propionaldehyde, acrolein, butyraldehyde, glyoxal, methylglyoxal, dimethylglyoxal, _trans_-2-hexenal, benzaldehyde, _trans_-2-methyl-butenal, 3-methyl-2-butenal, and 2-methyl-2-pentenal. At least one of the identified carbonyls was present in vaping emissions of one e-liquid. Figure 1: Extracted ion chromatographs (EICs) of \(m/z\) 181 for carbonyl-PFBHA oxime derivatives. EICs of (**A**) _trans_-2-hexenol, (**B**) benzyl alcohol, (**C**) l-(-)-menthol, and (**D**) linalool emissions samples were compared with PG-VG (dashed black chromatograms). \begin{table}
\begin{tabular}{l l l l l l l l l l l l} \hline \hline \multicolumn{1}{c}{\#} & \multicolumn{1}{c}{**Enited Carbonly**} & \multicolumn{1}{c}{**CAS \#**} & \multicolumn{1}{c}{**Formula**} & \multicolumn{1}{c}{**Signature Ions (m/z)**} & \multicolumn{1}{c}{**Retention Time \({}^{\textbf{A}}\) (min)**} & \multicolumn{1}{c}{**PG-VG**} & \multicolumn{1}{c}{**trans-2-Hexenol**} & \multicolumn{1}{c}{**Benzyl Alcohol**} & \multicolumn{1}{c}{**1-d-Menthol**} & \multicolumn{1}{c}{**Linaloid**} \\ \hline
1 & formaldehyde & 50-00-0 & CH\({}_{0}\) & 181, 195, 225 & 4.79 & + & + & + & + & + & + \\
2 & acetaldehyde & 75-00-0 & CH\({}_{0}\) & 181, 209, 239 & 6.74, 657 & + & + & + & + & + & + \\
3 & acetone & 67-64-1 & CH\({}_{0}\) & 181, 223, 326, 253 & 8.27 & + & + & + & + & + & + \\
4 & propionaldehyde & 123-36-6 & CH\({}_{0}\) & 181, 236, 253 & 9.00, 924 & + & + & + & bd & bd & + \\
5 & ardenden & 107-02-8 & CH\({}_{0}\) & 181, 231, 250, 251 & 913, 93, 97 & + & + & bd & bd & + \\
6 & butylaldehyde & 123-72-8 & CH\({}_{0}\)H & 181, 239, 267 & 11.84, 12.02 & bd & + & bd & bd & bd & bd \\
7 & _trans_-2-hexenol & 6728-26-3 & CH\({}_{0}\)H & 181, 239, 164, 16.52 & bd & + & bd & + & + & + \\
8 & benzaldehyde & 105-27 & CH\({}_{0}\) & 181, 301 & 182, 185, 183 & bd & bd & + & bd & bd & bd \\
9 & _trans_-2-methyl-2-buchant & 497-03-0 & CH\({}_{0}\) & 181, 279 & 18.50 & bd & + & bd & bd & bd \\
10 & -methyl-2-buchant & 107-68-8 & CH\({}_{0}\)H & 181, 279 & 19.97, 20.26 & bd & bd & bd & bd & bd & + \\
11 & methyl glyoxal & 78-98-8 & CH\({}_{0}\)H & 181, 462 & 20.67, 214, 21.29, 21.51 & + & + & + & + & + \\
12 & glyoxal & 107-22-2 & CH\({}_{0}\)H & 181, 448 & 21.09, 21.16, 21.23 & + & + & + & + & + \\
13 & dimethylglyoxal & 431-03-8 & CH\({}_{0}\)H & 181, 476 & 21.70 & + & + & bd & + & + \\
14 & 2-methyl-2-pental & 623-69 & CH\({}_{0}\)H & 181, 293 & 22.12 & bd & + & bd & bd & bd & bd \\ \hline \multicolumn{1}{c}{\# Number \({}^{\textbf{A}}\): Retention times of carbonyl-FPBIA online stereoisomers (f and f) 2 \(\prime\) applicable, \(\star\) Carbonly detected (S/N \(>\) 3), bd, below detection limit (S/N \(<\) 3).} \\ \end{tabular}
\end{table} 
Table 1: Emitted carbonyls identified in varying emissions of FG-VG and four flavored e-liquids. The signature ions (m/z) of carbonyl-FPBIA cosine derivatives were used to characterize carbonyl identities in Figure 1.  
Table 1 shows that low molecular weight carbonyls, such as formaldehyde, acetaldehyde, acetone, glyoxal, and methylglyoxal, were detected in vaping emissions of PG-VG and four flavored e-liquids. Propionaldehyde and acrolein were detected in emission samples of PG-VG, _trans_-2-hexenol-flavored, and linalool-flavored e-liquids. Benzaldehyde and 3-methyl-2-butenal were present in vaping emissions of benzyl alcohol- and linalool-flavored e-liquids, respectively. _trans_-2-Hexenal was detected in emissions of e-liquids flavored with _trans_-2-hexenol, l-(-)-menthol, or linalool. Additionally, butylraldehyde and 2-methyl-2-pentenal were detected in emissions of the _trans_-2-hexenol-flavored e-liquid.