# Green Analytical Chemistry--Recent Innovations
## 3 Innovations in Green Analytical Techniques
### Green Separation Techniques
#### 3.1.2 Supercritical Fluid Chromatography (SFC)  
Supercritical Fluid Chromatography (SFC) [35] has emerged as a prominent green analytical technique, aligning with the principles of sustainability and environmental responsibility. The technique utilizes supercritical carbon dioxide (SC-CO\({}_{2}\)) as the primary mobile phase, which is an environmentally benign alternative to the organic solvents commonly used in traditional liquid chromatography. This significant reduction in solvent consumption not only decreases chemical waste but also lowers operational costs and minimizes potential environmental hazards. Moreover, SFC offers remarkable versatility and efficiency, enabling rapid separations with high resolution due to the low viscosity and high diffusivity of supercritical CO\({}_{2}\). The use of modifiers, such as methanol or ethanol, further enhances its applicability by improving the solubility of polar analytes, thereby broadening the range of compounds that can be effectively analyzed [36]. [PERSON] et al. [37] demonstrated that Supercritical Fluid Chromatography (SFC) is particularly advantageous for analyzing thermally labile compounds, such as cannabinoids, due to its ability to avoid the thermal degradation commonly associated with gas chromatography. In their study, they highlighted the use of low-temperature conditions and optimized backpressure to ensure the stability of cannabinoids throughout the analysis process. Furthermore, the ability to optimize parameters such as pressure, temperature, and co-solvent composition ensures precise control over separation conditions, making SFC a highly adaptable technique for complex matrices and diverse applications [38]. Recent advancements in SFC have focused on improving its versatility and efficiency, allowing for the separation of a broader range of analytes [39], including polar and non-polar compounds [40; 41], with high precision. Developments in stationary phase technology, such as the introduction of advanced silica-based columns and hybrid materials, have enhanced the selectivity and resolution of SFC, making it suitable for complex separations in pharmaceutical, food, and environmental analyses. Hybrid materials, such as bridged ethylene hybrid (BEH) silica-based columns, have been successfully implemented in supercritical fluid chromatography (SFC). These columns offer enhanced mechanical stability, improved peak shape, and reduced silanol activity, making them suitable for high-throughput applications. For instance, BEH columns have been used in ultra-high-performance SFC-MS (UHPSFC/MS) for rapid lipid analysis, enabling the efficient separation of multiple lipid classes within minutes [42]. Their robustness and efficiency make them valuable for expanding the capabilities of SFC in various analytical applications. Silica-based columns, as highlighted by [PERSON] et al. [43], have become a cornerstone in Supercritical Fluid Chromatography (SFC) due to their versatility and adaptability through various chemical modifications. Traditional silica columns are extensively utilized for their polar surface, which supports hydrogen bonding and dipole-dipole interactions, making them ideal for separating moderately polar and non-polar compounds. However, issues like interactions with free silanols have driven advancements in stationary phase design. [PERSON] et al. discuss the development of hybrid silica-based columns, incorporating polar-embedded groups or end-capping techniques, which reduce silanol activity and enhance stability under high-pressure SFC conditions. Additionally, innovations in bonded ligand chemistries, such as diol, cyano, amine, and alkyl groups, have significantly broadened their applicability, allowing precise control over selectivity through \(\pi\)-\(\pi\) interactions, ionic interactions, and hydrogen bonding.