## 2 Sample Preparation Methods
### Solid-Phase Extraction
#### 2.1.2 Magnetic Solid-Phase Extraction  
Briefly, the magnetic nanoparticles (MNPs) coated or hybridized with other materials (magnetic sorbent) is added to the sample, vortexed and then separated from the solution under magnetic conditions. After separation, the material (containing the analytes) was dissolved in low amount of a suitable organic solvent to form the extract to be analysed [72; 75; 88; 112]. MNPs have attracted a great deal of interest in the separation of different organic environmental contaminants due to their unique paramagnetic properties, high surface areas, customized surface modifications, and good dispersion in solution, which can affect the sensitivity and selectivity of the method [114]. Additionally, magnetic adsorbents can be readily recycled, which is economical and eco-friendly. The current trends are the development of new magnetic adsorbents with high adsorption capacity and selectivity [112; 115]. Several materials have been used for preparation of the surface coatings of MNPs, such as silica, carbon nanomaterials, polymers, surfactants, and ionic liquids [113; 116; 117; 118]. A tremendous increment in progress of MSPE is also associated with the use of carbon nanomaterials. Carbon exists in several allotropic forms, such as fullerenes, carbon nano tubes (CNTs), including single-walled CNTs (SWCNTs) and multi-wall CNTs (MWCNTs), carbon nanohorns, carbon nanocones, carbon nanodisks, carbon nanofibers, nanotube rings, graphene oxide (GO) and graphene (G), and diamonds. However, to date, from the analytical point of view, the applications have mainly been focused on the use of fullerenes, CNTs, and GO/G [119; 120; 121]. The magnetite (Fe\({}_{3}\)O\({}_{4}\)) nanoparticles coated with different materials have been used to extract different classes of pharmaceuticals in surface water. These MNPs were used to extract macrolide antibiotics in surface waters by MSPE [122]. Graphene was easily immobilized on silica-coated magnetite (designated Fe\({}_{3}\)O\({}_{4}\)@SiO\({}_{2}\)/graphene) and it was used as an adsorbent to extract six sulfonamide antibiotics (sulfapyridine, sulfararazine, sulfarameter, sulfachloropyridazine, and sulfadoxine) from surface water and wastewater samples [123]. A novel magnetic polyethyleneimine modified reduced graphene oxide (Fe\({}_{3}\)O\({}_{4}\)@PEI-RGO) was used as adsorbents for the extraction of polar non-steroidal anti- drugs (NSAIDs) from tap water, groundwater, and river water. When compared with Fe\({}_{3}\)O\({}_{4}\)@PEI and Fe\({}_{5}\)O\({}_{4}\)@PEI-GO, the Fe\({}_{3}\)O\({}_{4}\)@PEI-RGO showed a higher extraction efficiency for polar NSAIDs [114]. Gemfibrozil was extracted by MSPE using \(\beta\)-cyclodextrintrin-grafted graphene oxide (GO)/magnetic (Fe\({}_{3}\)O\({}_{4}\)) nano-hybrid [124]. [PERSON] & [PERSON] evaluated the use of MNPs composite Fe\({}_{3}\)O\({}_{4}\)@(Fe-benzene-1,3,5-tricarboxylic acid) as a sorbent for a higher group of lipid regulators (bezafibrate, clofibric acid, clofibric, gemfibrozil, and fenofibric) in water matrices [125]. Ethylenediamine-functionalized magnetic carbon nanotubes (EDA@Mag-CNTs) that were used as sorbent showed a high extraction capacity of the steroid hormone by MSPE procedure [126]. Several other coatings were evaluated as sorbent in MSPE for the extraction of PhACs that belong to different therapeutic classes [127; 128]. The metal organic frameworks (MOFs) are another type of sorbents used in the extraction of organic compounds in water matrices. They show several advantageous properties, such as high porosity, tunable structures, ultra-high surface areas, outer-surface functionalization, and high thermal stability. Based on metal ion geometry and bridging ligands, MOFs can show different topologies and dimensionalities: one-dimensional, two-dimension or three-dimension MOFs (1D MOFs, 2D MOFs, and 3D MOFs). The 3D MOFs are highly porous and stable, since coordination bonds spread in three directions [78; 112; 129].