## Results  
### Selection of the Optimal SPME Fiber  
Selection of the optimal SPME fiber for quantification of multiple analytes having different physicochemical properties is a difficult process. In most cases, the fibers are chosen based on an experimental or theoretical basis. Experimental fiber selection is straightforward only when one fiber provides greater responses for all analytes. In other cases, a theoretical approach can be involved based on known selectivity of the coatings to compounds having different molecular weights and polarities (Stein  
\begin{table}
\begin{tabular}{l c c c c} \hline \hline \multirow{2}{*}{**Analyte**} & \multicolumn{4}{c}{**Relative Standard Deviation of a Slope (\%)**} \\ \cline{2-5}  & **Car/PDMS** & **PDMS** & **DVB/Car/PDMS** & **PDMS/DVB** \\ \hline
2,2,4-Trimethylpentane & 0.50 & 2.7 & 1.7 & 2.7 \\ \(n\)-Heptane & 44 & 11 & 4.5 & 5.2 \\ Methyl ethyl ketone & 42 & 14 & 7.8 & 25 \\ Methylene chloride & 95 & 200 & 5.3 & 4.2 \\ Benzene & 4.4 & 9.4 & 3.2 & 1.1 \\ \(n\)-Decane & 3.5 & 5.6 & 0.50 & 5.9 \\
1,1,2,2-Tetrachlororetiylene & 2.6 & 1.2 & 0.40 & 3.1 \\ Toluene & 18 & 3.4 & 5.8 & 6.4 \\
1,2-Dichloroethane & 2.1 & 9.0 & 10 & 20 \\ \(n\)-Undecane & 5.9 & 5.7 & 1.8 & 4.7 \\ Ethylbenzene & 0.50 & 2.7 & 4.8 & 4.4 \\ \(m\)-Xylene & 3.8 & 1.7 & 9.6 & 4.6 \\ \(p\)-Xylene & 1.2 & 6.8 & 7.5 & 15 \\ Propylbenzene & 4.0 & 2.4 & 9.6 & 2.2 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Relative standard deviations of calibration slopes obtained using different SPME fibers.  
\begin{table}
\begin{tabular}{l c c c c} \hline \hline \multirow{2}{*}{**Analyte**} & \multicolumn{4}{c}{**Limit of Detection (\(\mu\)g m\({}^{-3}\))**} \\ \cline{2-5}  & **Car/PDMS** & **PDMS** & **DVB/Car/PDMS** & **PDMS/DVB** \\ \hline
2,2,4-Trimethylpentane & 3 & 8 & 0.7 & 1.8 \\ \(n\)-Heptane & 50 & 9 & 8 & 7 \\ Methyl ethyl ketone & 15 & 7 & 0.8 & 1.9 \\ Methylene chloride & 1.8 & 9 & 1.1 & 0.6 \\ Benzene & 0.6 & 6 & 0.5 & 1.2 \\ \(n\)-Decane & 3 & 3 & 1.2 & 1.5 \\
1,1,2,2-Tetrachlororetiylene & 0.04 & 0.2 & 0.04 & 0.04 \\ Toluene & 0.5 & 4 & 1.6 & 1.2 \\
1,2-Dichloroethane & 0.2 & 1.2 & 0.8 & 1.7 \\ \(n\)-Undecane & 2 & 1.0 & 0.8 & 1.0 \\ Ethylbenzene & 0.010 & 0.10 & 0.2 & 0.03 \\ \(m\)-Xylene & 0.2 & 0.2 & 0.6 & 0.2 \\ \(p\)-Xylene & 0.10 & 0.2 & 0.2 & 0.2 \\ Propylbenzene & 0.3 & 0.3 & 0.2 & 0.10 \\ \(o\)-Xylene & 0.04 & 0.10 & 0.10 & 0.04 \\ Chlorobenzene & 0.04 & 0.10 & 0.05 & 0.04 \\
1,3,5-Trimethylbenzene & 0.3 & 0.10 & 0.10 & 0.10 \\
1,2,4-Trimethylbenzene & 0.2 & 0.04 & 0.04 & 0.10 \\
3-Picoline & 0.5 & 0.2 & 0.10 & 0.010 \\ Benzaldehyde & 0.10 & 0.10 & 0.4 & 0.10 \\ \(n\)-Hexadecane & - & 5 & 10 & 5 \\ Naphthalene & 0.2 & 0.10 & 0.10 & 0.04 \\ Phenol & 0.8 & 0.10 & 0.10 & 0.10 \\ Acenaphthene & 0.3 & 0.10 & 0.2 & 0.10 \\ Fluorene & 5 & 0.10 & 0.6 & 0.10 \\ \hline \hline \end{tabular}
\begin{tabular}{l c c c} \hline \hline \multirow{2}{*}{**Analyte**} & \multicolumn{4}{c}{**Relative Standard Deviation of a Slope (\%)**} \\ \cline{2-5}  & **Car/PDMS** & **PDMS** & **DVB/Car/PDMS** & **PDMS/DVB** \\ \hline
2,2,4-Trimethylpentane & 0.50 & 2.7 & 1.7 & 2.7 \\ \(n\)-Heptane & 44 & 11 & 4.5 & 5.2 \\ Methyl ethyl ketone & 42 & 14 & 7.8 & 25 \\ Methylene chloride & 95 & 200 & 5.3 & 4.2 \\ Benzene & 4.4 & 9.4 & 3.2 & 1.1 \\ \(n\)-Decane & 3.5 & 5.6 & 0.50 & 5.9 \\
1,1,2,2-Tetrachlororetiylene & 2.6 & 1.2 & 0.40 & 3.1 \\ Toluene & 18 & 3.4 & 5.8 & 6.4 \\
1,2-Dichloroethane & 2.1 & 9.0 & 10 & 20 \\ \(n\)-Undecane & 5.9 & 5.7 & 1.8 & 4.7 \\ Ethylbenzene & 0.50 & 2.7 & 4.8 & 4.4 \\ \(m\)-Xylene & 3.8 & 1.7 & 9.6 & 4.6 \\ \(p\)-Xylene & 1.2 & 6.8 & 7.5 & 15 \\ Propylbenzene & 4.0 & 2.4 & 9.6 & 2.2 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Limits of detection obtained using different SPME fibers.