## 3 Results and Discussion
### Effects of Derivatization Time and Displacement of 2-Furfural
\begin{table}
\begin{tabular}{l c c c c c c c c c} \hline \multirow{3}{*}{**Chemical**} & **Henry’s** & \multicolumn{3}{c}{**Extraction-time**} & \multicolumn{3}{c}{**Average Uptake of**} & \multirow{3}{*}{**Average RSD (\%)**} \\  & **Law** & & & **Linearity (R\({}^{2}\))** & & **Carbonyls/mg** & & \\ \cline{3-10}  & **Constant/** & & **2–60** & & **2–20 s** & & **60 min** & **5 s** & **2–60** & \\  & **(M/atm)** & & & **min** & & & & **min** & \\ \hline
**Ethanal** & 15 \({}^{\text{a}}\) & 86,600 & 0.932 & 0.932 & 6.49 \(\pm\) 1.82 & 1.14 \(\pm\) 0.16 \({}^{\text{f}}\) & 12.7 & 10.2 & 14.4 \\ \hline
**Propanal** & 13 \({}^{\text{a}}\) & 60,200 & 0.942 & ND & 14.01 \(\pm\) 3.10 & ND & 13.7 & ND & ND \\ \hline
**Butanal** & 8.7 \({}^{\text{a}}\) & 342,000 & 0.930 & 0.969 & 5.93 \(\pm\) 1.02 & 0.05 \(\pm\) 0.01 & 11.1 & 8.94 & 10.4 \\ \hline
**Pentanal** & 6.8 \({}^{\text{a}}\) & 73.40 & 0.973 & ND & 7.39 \(\pm\) 2.27 & ND & 24.6 & ND & ND \\ \hline
**Hexanal** & 4.7 \({}^{\text{a}}\) & 64,200 & 0.973 & 0.957 & 4.50 \(\pm\) 0.74 & 0.24 \(\pm\) 0.02 & 12.3 & 15.9 & 7.90 \\ \hline
**Octanal** & 1.9 \({}^{\text{a}}\) & 31,400 & 0.941 & 0.930 & 5.87 \(\pm\) 1.15 & 0.34 \(\pm\) 0.06 & 10.5 & 24.4 & 17.7 \\ \hline
**Acetone** & 25 \({}^{\text{a}}\) & 112,000 & 0.968 & 0.562 & 5.29 \(\pm\) 1.29 & 1.11 \(\pm\) 0.05 & 8.64 & 8.43 & 4.19 \\ \hline
**2-Heptanone** & 7.0 \({}^{\text{a}}\) & 125,300 & 0.988 & 0.825 & 1.56 \(\pm\) 0.18 & 0.04 \(\pm\) 0.01 & 10.8 & 25.0 & 17.3 \\ \hline
**2-Furfural** & 263.2 \({}^{\text{b}}\) & 100,800 & 0.874 & 0.963 \({}^{\text{d}}\) & 0.51 \(\pm\) 0.05 & 0.08 \(\pm\) 0.00 & 29.1 & 14.3 & 1.61 \\ \hline
**Benzaldehyde** & 42 \({}^{\text{c}}\) & 130,900 & 0.776 & 0.999 \({}^{\text{d}}\) & 3.32 \(\pm\) 1.94 & 0.17 \(\pm\) 0.02 & 17.1 & 14.4 & 9.34 \\ \hline \end{tabular} Note: PFBHA dopant concentration was at 17 mg/mL. Response factor (RF) = peak area count/carbonyl injection mass (ng). ND: not detected. \({}^{\text{a}}\) [PERSON] _et al._, 1969 [36]. [PERSON]’s law constants at \(T\)= 298.15 K were measured in the lab. \({}^{\text{b}}\) SRC, 2006 [37]. [PERSON]’s law constant at \(T\)= 298.15 K was estimated. \({}^{\text{c}}\) Zhou and Mopper, 1990 [38]. [PERSON]’s law constant at \(T\)= 298.15 K was measured in the lab. \({}^{\text{d}}\) Linearity was calculated for the 2 to 10 s of extraction times. \({}^{\text{e}}\) Concentration of each carbonyl was \(\sim\)5 \(\mu\)g/L. \({}^{\text{f}}\) Concentration of ethanol in this series was \(\sim\)2 \(\mu\)g/mL.  
\end{table} 
Table 3: Comparison of on-fiber derivatization at different derivatization time ranges. oxime. That is to say, desorption kinetic of 2-furfurral oxime is significant compared with the low reaction kinetics of 2-furfurral derivatization in a lengthy on-fiber derivatization procedure. Thus, much shorter 2 s to 20 s on-fiber derivatization time was tested to optimize derivatization of 2-furfurral and to prevent this apparent competitive, non-linear reaction. This had to be accomplished simultaneously with derivatization of other target compounds. The concentration of ethanal was \(\sim\)2 \(\mu\)g/mL, while each of the other chemicals was at \(\sim\)5 \(\mu\)g/L to simulate carbonyl content in ozonated FL solution/suspension. Despite a significant drop in uptake rate after 5 s of extraction, the derivatization efficiency of 2-furfurral became higher than propanal, butanal, pentanal, and 2-heptanone (Table 3 and Figure 5). The apparent displacement effect associated with derivatization of 2-furfurral was minimized with very short, 5 s derivatization. The calibration RSDs with 2-furfurral for 2-20 s derivatization were reduced to 14.3% (Table 3). Subsequently, 5 s on-fiber derivatization were tested and the calibration RSD improved to 1.61%. Carbonyl recovery decreased with a shorter derivatization time (Figures 1 and 5), while the accuracies on 2-furfurral and benzaldehyde were enhanced. Thus, the 5 s extractions/derivtizations were selected for simultaneous sampling of all target aldehydes in this study.