# Magnetic Solid-Phase Extraction of Organic Compounds Based on Graphene Oxide Nanocomposites
## 2 Preparation and Applications of GO for the MSPE of Organic Compounds
### Functionalized Nanocomposites of GO with Fe\({}_{3}\)O\({}_{4}\) Nanoparticles
Polythionine was also employed for the functionalization of magnetic graphene oxide through an oxidative polymerization reaction of thionine on the surface of GO/Fe\({}_{3}\)O\({}_{4}\)[84; 85]. This surface modification significantly improved the merits of GO/Fe\({}_{3}\)O\({}_{4}\), providing satisfactory extraction efficiency. The functionalized nanocomposite was used for the MSPE of chlorpheniramine [84] and duloxetine [85] from human plasma prior to their determination by HPLC-UV. In order to enhance the dispersibility of magnetic GO in hydrophobic media, functionalization with phytic acid has been reported. Phytic acid-stabilized GO/Fe\({}_{3}\)O\({}_{4}\) was applied for extraction of PAHs from vegetable oils. Due to the super-amphiphilicity of phytic acid, the dispersibility of the conventional GO/Fe\({}_{3}\)O\({}_{4}\) sorbent increased. [86]. Functionalization of GO/Fe\({}_{3}\)O\({}_{4}\) can also be performed for the enhancement of its selectivity towards the target analytes. In 2015, [PERSON] and [PERSON] synthesized a \(\beta\)-cyclodextrintrin (\(\beta\)-CD) grafted GO/Fe\({}_{3}\)O\({}_{4}\) nano-hybrid and used it for the MSPE of gemfibrozil from human serum and pharmaceutical waste-water samples followed by determination using spectrofluorometry. This chemical compound can selectively bind with various organic, inorganic and biological guest molecules into its cavity to form stable host-guest inclusion complexes by a series of forces such as hydrophobic and van der Waals interactions. Therefore, due to the surface modification of graphene oxide with \(\beta\)-cyclodextrintrin, selective separation of the target analyte from complex sample matrices was achieved [87]. Other examples of chemical molecules that have been used for the functionalization of GO/Fe\({}_{3}\)O\({}_{4}\) are triethylenetetramine [88], silica [89], sporopolenin [90] and phenylethyl amine [91]. The superior adsorption capacity of the functional groups resulted in functionalized magnetic GO nanocomposites with sufficient surface area, excellent extraction efficiency, good stability as well as ease in handling and separation. Table 2 summarizes the application of functionalized GO/Fe\({}_{3}\)O\({}_{4}\) nanocomposites. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Analyte** & **Sample Matrix** & **Functional Group** & **Analytical Technique** & **LODs (ng mL-1)** & **Recovery (\%)** & **Reusability** & **Reference** \\ \hline \multicolumn{7}{c}{_Biological Samples_} \\ \hline Chlorbeniramine & Plasma & Polythionine & HPLC-UV & 0.4 & 87.9-96.4 & At least 6 times & [84] \\ Duloxetine & Plasma & Polythionine & HPLC-UV & 0.5 & 87 & At least 9 times & [85] \\ Gemfbruosil & Serum & g-CD & Spectro filamentometry & \(3\times 10^{-3}\) & 96.0–104.0 & At least 50 times & [87] \\ SSRs & Plasma & PAMAM & HPLC-UV & 0.3–0.9 & 89.1–97.9 & Up to 20 times & [73] \\ \hline \multicolumn{7}{c}{_Environmental Samples_} \\ \hline \multicolumn{7}{c}{_Spinbornamide_} \\ Chlorphenols & Water & Porphyrin & HPLC-DAD & 200 & 83.7-116.7 & At least 8 times & [80] \\ Chlorphenols & Water & Poly & HPLC-MS/MS & 0.6-9.2 & 86.4-99.8 & N.A. & [81] \\ PAHs & Water & Polystyrene & GC-FID & \(3\times 10^{-3}\)-\(10\times 10^{-3}\) & 69.5-88.7 & N.A. & [82] \\ PAHs & Water & Polypyrrole-co-aniline & GC-FID & 0.003-0.01 & 50.4-78.3 & At least 20 times & [83] \\ Estrogens & Water & Triethylenetamine & LC-MS/MS & 0.15-1\(\times 10^{-3}\) & 88.5-105.6 & N.A. & [88] \\ Malachite green & Water & SEP & UV Vis & 0.2 & 96.3 & At least 50 times & [79] \\ \hline \multicolumn{7}{c}{_Food Samples_} \\ \hline \multicolumn{7}{c}{_Organphosphorous_} \\ pesticides & Vegetables & Sporopolenin & GC-ECD & 0.02–0.05 & 81.0–120.0 & N.A.