## 2 Hybrid Graphene-Based Materials (Hybrid GBMs)
### Deep Eutetic Solvents  
Since the discovery of the adsorptive properties of GBMs and their utilization in sample preparation techniques, various materials with unique properties have been reported as functionalizers aimed at enhancing the extraction capacity of these sorbents, as discussed in the sections of this topic. However, some of these materials have a significant drawback: the use of toxic organic reagents or solvents in their preparation and an additional purification step. Therefore, the quest for more sustainable materials has brought DESs into the spotlight for modifying GBMs [21]. DESs, such as ILs, are designer solvents, meaning their physicochemical properties can be tailored according to their compounds, which are formed from eutectic mixtures of two or more components, one acting as a hydrogen bond donor (HBD) and the other as a hydrogen bond acceptor (HBA) through non-covalent interactions, resulting in compounds with melting points < 100 \({}^{\circ}\)C. Additionally, their preparation is carried out in just one step and does not require a purification step [79; 80]. Their properties include thermal stability, low vapor pressure, low flammability, low volatility, adjustable composition, high solvation capacity, and higher biodegradability rates. Additionally, they are easy to obtain and synthesize, low-cost, and highly reusable, and their constituents are derived from renewable sources such as alcohols, amines, carboxylic acids, sugars, glycols, phenols, quaternary ammonium salts, and phosphonium salts. These qualities make DESs a greener and safer alternative than ILs [79; 81]. Various applications have been reported in modifying GBMs, with investigations in diverse areas such as food, beverages, environmental, and biological samples [22; 44; 45; 82]. [PERSON] et al. [22] developed a sorbent based on GO nanoparticles modified with a DES consisting of phosphocholine chloride/1-naphth for pesticide residue extraction in zucchini using an approach combining d-\(\mu\)-SPE combined with dispersive liquid-liquid microextraction (DLLME). The authors reported that GO was modified by simple ultrasonication, and its adsorption capacity was enhanced due to the presence of DES compared to unmodified GO, with recovery values above 70% for the eight pesticides investigated. In the field of hydrophobic DESs, [PERSON] et al. [44] modified GO with allyltriethylammonium bromide/ethylene glycol to extract toluene and xylene exposure biomarkers in urine samples by PT-SPE. The selectivity of the prepared sorbent, deep eutectic solvent functionalized graphene oxide (DFG), proved superior to some evaluated commercial phases and even pure GO for extracting the same analytes. This fact was attributed to functional groups in the DES, which promote multiple adsorption mechanisms with the biomarkers,including hydrophobic interactions. Additionally, 2 mg of the sorbent in the extraction device recovered percentages above 90% of the analytes. [PERSON] et al. (2018) developed a magnetic graphene oxide based on Fe\({}_{3}\)O\({}_{4}\) modified with choline chloride/citric acid, resulting in a hybrid material (MGO@DES) used in magnetic solid phase extraction (MSPE) for the extraction of three estrogens in milk samples (Figure 4). In addition to the \(\pi\)-\(\pi\) and hydrogen interactions already promoted by GO, the hydrophobicity of the sorbent was enhanced by the addition of DES, which showed excellent selectivity for more non-polar analytes through the increase in hydrophobic interactions, as well as electrostatic interactions promoted by the opposite charges of the analyte and the sorbent in the extraction medium. The method showed recovery rates above 90% for the investigated estrogens using only 3 mg of sorbent and the possibility of reuse for seven cycles without considerable loss in extraction efficiency. Therefore, as observed in this topic, DESs can be tailored according to the desired interaction mechanism. When coupled with GBMs, they can extract various types of analytes, even in complex samples.