# Mussel Inspired Polydopamine as Silica Fibers Coating for Solid-Phase Microextraction
## 4 Discussion  
In this paper, a novel SPME fiber bearing a silica core and a cheap, fully organic polymer as coating active layers was proposed. Silica fiber is a robust, smooth, functionalizable matrix which can undergo further functionalization processes assisted by different manufacture techniques. Here, the active layer was polydopamine (PDA), a mussel inspired soft polymer produced by cheap, simple air-assisted self-polymerization of dopamine in aqueous medium at ecological and mild conditions. Scanning electron microscopy (SEM) and FT-ATR spectroscopy were used here for the surface characterization of the systems, demonstrating the different morphologies exhibited passing from low to high dopamine concentration in the reaction vessels, and the presence of PDA functional groups on silica \begin{table}
\begin{tabular}{l l l l l l l} \hline
**PA** & & & & & & \\ \hline Analyte & \(\delta\)-max (nm) & Equation & R\({}^{2}\) & LOD (ng/mL) & LOQ (ng/mL) & RSD \% \\ \hline naphthalene & 275 & y = 4 \(\times\) 10\({}^{6}\)x + 16,672 & 0.9998 & 2.2 & 7.3 & 10 \\ \hline biphenyl & 247 & y = 4 \(\times\) 10\({}^{6}\)x - 14,358 & 0.9993 & 2.0 & 6.7 & 9 \\ \hline acenaphthene & 226 & y = 7 \(\times\) 10\({}^{6}\)x - 22,425 & 0.9985 & 1.5 & 5.0 & 11 \\ \hline anthracene & 251 & y = 2 \(\times\) 10\({}^{6}\)x + 1865 & 0.9999 & 3.5 & 11.6 & 10 \\ \hline pyrene & 239 & y = 8 \(\times\) 10\({}^{5}\)x + 873 & 0.9990 & 4.7 & 15.6 & 9 \\ \hline chrysene & 267 & y = 2 \(\times\) 10\({}^{5}\)x + 3008 & 0.9084 & 29.7 & 98.9 & 12 \\ \hline benzo(k)fluoranthene & 306 & y = 2 \(\times\) 10\({}^{5}\)x + 3741 & 0.9285 & 44.2 & 147.3 & 12 \\ \hline benzo(a)pyrene & 295 & y = 2 \(\times\) 10\({}^{5}\)x + 4030 & 0.9186 & 69.2 & 230.4 & 12 \\ \hline benzo(ghi)perylene & 298 & y = 4 \(\times\) 10\({}^{4}\)x + 6214 & 0.9083 & 24.7 & 82.2 & 13 \\ \hline
**PDA** & & & & & & \\ \hline Analyte & \(\delta\)-max (nm) & Equation & R\({}^{2}\) & LOD (ng/mL) & LOQ (ng/mL) & RSD \% \\ \hline naphthalene & 275 & y = 9 \(\times\) 10\({}^{5}\) - 8229 & 0.9913 & 9.2 & 30.6 & 12 \\ \hline biphenyl & 247 & y = 1 \(\times\) 10\({}^{5}\)x - 21,299 & 0.9911 & 8.2 & 27.3 & 10 \\ \hline acenaphthene & 226 & y = 2 \(\times\) 10\({}^{6}\) - 52,369 & 0.9986 & 5.2 & 17.3 & 12 \\ \hline anthracene & 251 & y = 2 \(\times\) 10\({}^{6}\) - 39,062 & 0.9987 & 3.6 & 12.0 & 13 \\ \hline pyrene & 239 & y = 9 \(\times\) 10\({}^{5}\) - 28,916 & 0.9994 & 4.6 & 15.3 & 10 \\ \hline chrysene & 267 & y = 6 \(\times\) 10\({}^{5}\) - 11,471 & 0.9991 & 9.8 & 32.6 & 9 \\ \hline benzo(k)fluoranthene & 306 & y = 7 \(\times\) 10\({}^{5}\) - 11,663 & 0.9992 & 14.6 & 48.6 & 10 \\ \hline benzo(a)pyrene & 295 & y = 7 \(\times\) 10\({}^{5}\) - 12,287 & 0.9990 & 18.7 & 62.2 & 11 \\ \hline benzo(ghi)perylene & 298 & y = 5 \(\times\) 10\({}^{4}\) - 9957 & 0.9991 & 22.2 & 73.9 & 10 \\ \hline \end{tabular}
\end{table} 
Table 2: Validation parameters obtained with PA and PDA fibers, respectively, for the analysis of PAHs in soot samples. \begin{table}
\begin{tabular}{l l l} \hline
**Analyte** & **ng/mL** & **\(\mu\)g/g** \\ \hline naphthalene & 61.2 \(\pm\) 7.5 & 24.5 \(\pm\) 3.0 \\ \hline biphenyl & 30.3 \(\pm\) 4.7 & 12.1 \(\pm\) 1.9 \\ \hline acenaphthene & 46.8 \(\pm\) 4.8 & 18.7 \(\pm\) 1.9 \\ \hline anthracene & 12.9 \(\pm\) 2.2 & 5.2 \(\pm\) 0.9 \\ \hline pyrene & 52.1 \(\pm\) 5.2 & 20.8 \(\pm\) 2.1 \\ \hline chrysene & 35.5 \(\pm\) 3.5 & 14.2 \(\pm\) 1.4 \\ \hline benzo(ghi)perylene & LOD & 9.5 \(\pm\) 2.1 \\ \hline \end{tabular}
\end{table} 
Table 3: Estimated concentration of PAHs found in soot using the PDA fiber (n = 3). surfaces, respectively (Figures 1 and 2). Thanks to steady-state UV-visible assays, an absence of the leakage of monomer or oligomer species from PDA coatings was demonstrated using different solvent mixtures (Figure 3). Then, these new SPME hybrid fibers were tested for the extraction of polycyclic aromatic hydrocarbons (PAHs) in combination with LC-UV-DAD using a commercial SPME-LC interface.