# 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 Magnetic GO with MOPs  
Microporous organic polymers (MOPs) represent a class of amorphous porous materials, composed of fully covalently bound organic building blocks. MOPs have lately gained much research interest, due to the combined superiority of porous materials and functional polymers [108; 109; 110]. MOPs exhibit well-defined porosity as well as high surface area. Because of their tunable surface chemistry, MOPs can be easily functionalized [108]. Depending on the choice of monomers, functionality and polymerization method, MOPs can be prepared both as solution processable or as insoluble networked materials [109]. Therefore, MOPs have various applications including gas storage [111], environmental remediation [112], catalysis [113], energy storage [114] etc. In analytical chemistry, MOPs have been used as sorbents for the extraction of different organic compounds including hydroxylated PAHs [115] and 5-nitroimidazoles [116]. By combining MOPs and magnetic GO it is possible to develop nanocomposites that combine the extraordinary properties of both MOPs and GO. [PERSON] et al. synthesized a triazine-based polymeric network modified magnetic nanoparticles/GO nanocomposite and used it for the MSPE of basic and acidic pesticides from food (e.g., cucumber, tomato) and water samples by HPLC-UV. For the fabrication of the material, Fe\({}_{3}\)O\({}_{4}\) nanoparticles were modified by triazine-based polymeric prepared from melamine and terephthalaldehyde. Subsequently, the functionalized Fe\({}_{3}\)O\({}_{4}\) nanoparticles were mixed with GO in THF and the mixture was sonicated. The novel sorbent showed well-defined porosity, high surface area, good chemical stability and tunable surface chemistry. Due to the different functional groups of the nanocomposite (i.e., amine and carboxylic groups), simultaneous extraction of basic and acidic pesticides was achieved [108]. Applications of Magnetic GO Nanocomposites Modified with Ionic Liquids (ILs) and Deep Eutectic Solvents (DESs)  
Ionic liquids (ILs) and deep eutectic solvents (DESs) are an alternative to environmentally harmful ordinary organic solvents. ILs are generally composed of bulky, non-symmetrical organic cations (i.e., imidazolium, ammonium pyrrolidinium, pyridinium etc.) and different inorganic or organic anions [117; 118; 119]. DESs are systems formed from a eutectic mixture of Lewis or Bronsted acids and bases that contain a variety of anionic and/or cationic species [120; 121]. ILs and DESs have  
Figure 5: SEM images of Cu-MOFs (**a**) and Fe\({}_{3}\)O\({}_{4}\)@SiO\({}_{2}\)-GO-MOFs (**b**) and TEM images of Cu-MOFs (**c**) and Fe\({}_{3}\)O\({}_{4}\)@SiO\({}_{2}\)-GO-MOFs (**d**). Reproduced with permission from [107]. Copyright Elsevier, 2018.  
a tunable nature and their properties can be optimized through the choice of their cationic and anionic constituents [118; 119]. Although DESs and ILs have similar physical properties, their chemical properties differ resulting in different potential applications [122; 123]. By combining ionic liquids and deep eutectic sorbents with magnetic graphene oxide it is possible to design and develop new extraction sorbents with extraordinary properties [117; 123]. In 2016, [PERSON] et al. synthesized a planar graphene oxide-based magnetic ionic liquid nanomaterial for extraction of chlorophenols from environmental water samples coupled with HPLC-MS/MS [123]. For this purpose, Fe\({}_{3}\)O\({}_{4}\)@SiO\({}_{2}\) magnetite microspheres functionalized with amino-groups (Fe\({}_{3}\)O\({}_{4}\) @SiO\({}_{2}\)-NH\({}_{2}\)) and 1-carboxymethyl-3-methylimidazolium chloride were used to functionalize graphene oxide. The novel sorbent exhibited great adsorption capacity and was successfully used to extract both polar and non-polar chlorophenols from tap, river and well water. The sorbent was found to be reusable for at least six times. [PERSON] et al.