## 3 Selected Applications of GBMs in Key Miniaturized Techniques
### Pipette-Tip Solid-Phase Extraction and Disposable Pipette Extraction
Automated or semi-automated PT-SPEstrategies like this hold promise in pursuing greener sample preparation methods, as they promote more sustainable laboratory practices while improving operational efficiency and analyst safety, reducing exposure to toxic substances and the risks associated with manual procedures. Another approach that uses sorbents in pipette tips is DPX, which emerged in 2003. This method employs an extraction device similar to PT-SPE but with a crucial difference: in DPX, the sorbent is not fixed between two filters (frits). Instead, the sorbent remains free inside the pipette tip, allowing more efficient interaction with the sample and analytes. Only a bottom filter, made of polyethylene or glass wool, retains the sorbent phase within the tip. This configuration facilitates handling and enhances the extraction process efficiency, which follows principles similar to those of dispersive solid-phase extraction (DSPE), based on extraction driven by the contact surface of the sorbent with the sample, achieving a partition equilibrium of analytes between phases. The extraction/desorption steps are the same as those used in PT-SPE, with the washing step not mandatory [105]. Once again, as it is a non-exhaustive technique, the affinity of the sorbent for analytes will play a crucial role in the performance of DPX methods. When it comes to graphene compounds, [PERSON] and [PERSON] [14] recently anchored GO nanosheets onto silica, which was subsequently functionalized with octadecyl silane endcapped to produce SiGOC18 end sorbent employed in DPX for the extraction of eleven multi-class herbicides in sugar cane-derived food and beverage samples, followed by determination by LC-MS/MS. The anchoring of GO onto aminopropyl silica was performed to minimize aggregation issues of GO sheets when dispersed in the sample matrix, and the functionalization of this material with C18 was carried out to enhance the analytes' surface area and adsorption capacity. The end-capping procedure was conducted to replace surface hydroxyl groups with trimethylsilane groups, rendering the sorbent more apolar and capable of providing hydrophobic interactions with the analytes. Using SiGOC18 end in this technique could offer LOQs in the 1-25 ng g\({}^{-1}\) range for the analytes among the investigated samples and satisfactory linearity (r\({}^{2}\) > 0.99) for all matrices. The extraction was completed in six minutes, using 0.68 mL of organic solvents, 0.8 mL of sample, and 10 mg of extraction phase. Until today (May 2024), no further records involving graphene derivatives in DPX methods have been found. One contributing factor may be attributed to the two-dimensional structure of its nanosheets, which could potentially interfere with the dispersive adsorption/desorption process within the pipette tip. However, the advantages of this technique, when combined with the possibility of anchoring and functionalizing these phases with various materials (such as silica derivatives, ILs, and DESs), offer significant potential. These combinations can improve the material structure, address device clogging and particle aggregation issues, and improve selectivity. Consequently, they present many opportunities for future research, providing more efficient and sustainable methods for sample preparation.