## 3 Selected Applications of GBMs in Key Miniaturized Techniques
### Microextraction by Packed Sorbent  
MEPS stands as another pivotal analytical technique within the realm of solid-based microextraction methods. It was pioneered in 2004 by [PERSON], drawing upon conventional SPE principles [92]. In MEPS, a packed sorbent (\(\pm\)2 mg) is housed within a syringe, either as a plug or as a cartridge between the barrel and the needle [93; 94]. Moreover, the system's format primarily comprises two key components: the MEPS syringe and the MEPS cartridge, also referred to as the barrel insert and needle (BIN). The packed sorbent within the BIN section is pivotal in interacting with the target, significantly influencing the method's analytical performance [95]. This analytical approach offers significant ad vantages by integrating sample extraction, pre-concentration, and clean-up into a single methodology. Therefore, this consolidation enhances the sample throughput for large-scale analyses, streamlining the analytical process and improving efficiency [93; 96]. Since the analytical performance of the method is intricately linked to the sorbent phase, the evolution of GMBs has greatly enhanced MEPS applications, ushering in new horizons for this miniaturized approach. [PERSON] and [PERSON] [54] reported the synthesis of an ionic liquid supported on silica, functionalized with graphene oxide (ILz/Si@GO) as a sorbent phase for MEPS extraction of pesticides in coffee samples, followed by gas-chromatography-tandem mass spectrometry (GC-MS/MS). The authors demonstrated the application of the covalent bonding method, employing N, N\({}^{\prime}\)-dicyclohexylcarbodiimide (DCC) as the coupling agent to anchor the IL onto the modified silica. Characterization assays of the synthesized material revealed irregularly shaped particles of uniform size, affirming the successful deposition of IL particles onto GO leaves. Moreover, adsorption experiments indicated a rise in adsorption at 100 ug mL\({}^{-1}\), reaching saturation at 200 ug mL\({}^{-1}\). Additionally, the authors stated a substantial enhancement in the adsorption properties of the final sorbent with the application of the IL in the ILz/Si@GO composite. The final application of the sorbent in the MEPS procedure achieved recoveries ranging from 35 to 97%. Although the pesticides aldrin and endosulfan sulfate weren't detected at quantifiable levels, their identification through the proposed method underscores their persistence in the environment. Such a finding highlights the significance of the developed MEPS sorbent featuring the ILz/Si@GO sorbent phase as a valuable analytical tool for pesticide environmental monitoring. The rGO sorbent phase was reported by [PERSON] et al. [97] for the MEPS extraction of local anesthetics in plasma and saliva samples with later LC-MS/MS analysis. The study highlighted the exceptional performance of the rGO phase in mitigating matrix effects, eliminating interference peaks at the retention times of target analytes. Notably, the reported method achieved recovery values ranging from 97.26% to 106.83% in plasma and 95.21% to 105.83% in saliva, with LOQ values within the nanomolar range (nmol L\({}^{-1}\)). An outstanding feature of the reported rGO sorbent was its reusability in MEPS extraction. The material demonstrated remarkable durability, enduring over 100 extractions without compromising the analytical performance of the method. [PERSON] et al. [98] detailed the synthesis and application of a polyacrylamide/graphene oxide (PAN/GO) sorbent for microextraction by MEPS, followed by LC-MS/MS analysis of anesthetic drugs (lidocaine, prilocaine) and their metabolites (2,6-xylidine, o-toluidine). The optimization of MEPS revealed that pH significantly influences the interaction of target analytes with the sorbent phase. A basic pH enhances the distribution of the analytes in the sorbent phase, as the target compounds contain amino groups attached to aromatic rings, which are more interactive under alkaline conditions.