## 7 Sorbents Used in the TFME Technique
### Conductive Polymers  
Conductive polymers (CPs) are among the polymeric materials that exhibit electrical conductivity along their long molecular chains because they contain conjugated \(\pi\)-electron backbones in the macromolecule. With regard to their electrical, mechanical, thermal, and optical properties, CPs find applications in many fields of science and technology. They are often used as electromagnetic screens, corrosion inhibitors, and electroluminescent displays [48]. The large specific surface area and excellent chemical, mechanical, and thermal stability also make CP materials suitable sorbents often applied in microextraction techniques, including TF-SPME [49].  
Polymers showing conductivity are, for example:  
1. Polyacetylene (PA) and polyphenylacetylene (PPA), containing double bonds;
2. Polyfluorene (PF) and polyparaphenylene (PPP), polyaniline (PANI), and polyphenylenevinylene (PPV), containing aromatic rings in the polymer chain;
3. Heterocyclic polymers with a nitrogen atom: polypyrrole (PPy) and polypyridine (PPY);
4. Heterocyclic polymers with a sulfur atom: polythiophene (PTh) and polyethylene dioxythiophene (PEDOT), polyfuran (PFu), as well as polycyanamide (PCN) and polyvinyl ferrocene (pVFc).  
Examples of structural formulas of conductive polymers are shown in Figure 17.  
Conductive polymers, used as a sorption phase in the microextraction process, can interact with analytes through hydrophobic interactions, acid-base interactions, polar functional group interactions, ion exchange, hydrogen bonding, and \(\pi\)-\(\pi\) interactions. Because of their acid-base properties, CPs exhibit diverse extraction selectivity in relation to acidic and basic compounds. They also allow direct extraction of charged particles without derivatization or the application of complex agents [50].  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sorption Phase** & **Analyte** & **Matrix** & **Detection** & **Reference** \\ \hline \multirow{6}{*}{PDMS} & PAHs & water & GC-MS & [34] \\ \cline{2-5}  & polychlorinated biphenyls & fish tissue & LC-MS & [35] \\ \cline{2-5}  & pesticides & water & NCBI-MS & [36] \\ \cline{2-5}  & volatile organic compounds & skin & GC-MS & [37] \\ \cline{2-5}  & insect pheromones & air & GC-MS & [38] \\ \cline{2-5}  & drugs and explosive & standards in & & \\ \cline{2-5}  & substances & different solvents & & \\ \hline \hline \end{tabular}
\end{table}
Table 2: Examples of the use of polymer sorption phases in TF-SPME.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Sorption Phase** & **Preparation** & **Analyte** & **Matrix** & **Detection** & **Reference** \\ \hline DVB/PDMS & bar coating & VOCs/SVOCs & water & GC-TMS & [40] \\ \hline DVB/PDMS & spin coating & N-nitrosamines & water & GC-MS & [22] \\ \hline DVB/PDMS & bar coating & VOCs & water & GC-MS & [24] \\ \hline DVB/PAN & ready for use & \begin{tabular}{c} anti-inflammatory \\ antibacterial drugs \\ \end{tabular} & \begin{tabular}{c} drinking \\ water \\ \end{tabular} & \begin{tabular}{c} LC-ESI- \\ MS/MS \\ \end{tabular} & [41] \\ \hline DVB/PDMS & bar coating & pesticides & water & GC-MS & [42] \\ \hline C18/PAN & \begin{tabular}{c} dip coating \\ spray coating \\ \end{tabular} & benzodiazepines & blood plasma & \
\begin{tabular}{c} LC- \\ MS/MS \\ \end{tabular} & [44] \\ \hline C18/PAN & spray coating & doping agents &
\begin{tabular}{c} urine, blood \\ plasma \\ \end{tabular} & LC-MS & [45,46] \\ \hline C18/PAN & spray coating & estrogens & water & LC-UV & [47] \\ \hline \hline \end{tabular}
\end{table}
Table 3: Examples of the use of polymer sorption phases in TF-SPME.  
Examples of the use of conductive polymers in the TF-SPME technique, reported in scientific publications, are summarized in Table 4.