# Green Analytical Chemistry--Recent Innovations
## 3 Innovations in Green Analytical Techniques
### Green Separation Techniques
#### 3.1.1 Green Gas Chromatography (GC) and Liquid Chromatography (LC)
It also enhanced sensitivity, achieving low detection limits (0.02-0.63 mg/kg) without pre-concentration, while significantly reducing solvent consumption through a dilution-only sample preparation, aligning with green analytical chemistry principles. In the realm of liquid chromatography, the shift towards greener methodologies has been marked by the reduction in organic solvent usage and the exploration of alternative, less harmful solvents. Liquid chromatography traditionally consumes substantial quantities of organic solvents, contributing to both environmental concerns and operational costs [23; 24]. Techniques such as high-performance liquid chromatography (HPLC) have been adapted to utilize water-rich mobile phases or supercritical fluids, thereby minimizing the reliance on hazardous organic solvents. This approach includes methods like per aqueous liquid chromatography (PALC) and water-only reversed-phase liquid chromatography (WRP-LC), which employ high water content mobile phases to reduce or eliminate the use of organic solvents such as acetonitrile and methanol. PALC leverages silica-based stationary phases, while WRP-LC utilizes polar-embedded or polar-end-capped columns, enabling effective separation with minimal environmental impact [25]. These advancements align with green analytical chemistry principles by improving safety, lowering costs, and reducing hazardous waste generation, making them valuable tools for eco-friendly method development in analytical laboratories. Figure 2: Schematic representation of the portable GC-LIT-MS system used for VOC analysis [20]. Copyright (2024), with permission from Elsevier. The comparison between traditional LC methods, green LC with high water content, and miniaturized capillary LC systems highlights the trade-offs in separation performance, efficiency, and sustainability. While green LC methods reduce the reliance on organic solvents like acetonitrile and methanol, they can lead to increased retention times and minor reductions in sensitivity. However, proper optimization using polar-embedded stationary phases can mitigate these drawbacks, maintaining resolution comparable to traditional LC. A recent review on sustainable solvents in reversed-phase LC highlights the potential of pure water, ionic liquids, and bio-based solvents as green alternatives [26]. While organic modifiers like ethanol and isopropanol maintain similar chromatographic performance to traditional solvents, new-generation solvents, such as Cyrene and deep eutectic solvents (DESs), require further optimization to match the efficiency of acetonitrile-based systems. Studies show that green solvents can achieve comparable peak symmetry and separation efficiency when combined with modified stationary phases or high-temperature LC techniques. However, some solvents, such as dimethyl carbonate, exhibit limited water miscibility, necessitating tailored mobile phase compositions for consistent performance. Table 1 demonstrates that while traditional LC methods provide high separation efficiency and sensitivity, they rely heavily on organic solvents, increasing environmental impact. Green LC methods, in contrast, can achieve comparable resolution and peak symmetry with proper adjustments, though they may require specialized stationary phases and longer retention times. The trade-off between environmental sustainability and analytical performance is evident, reinforcing the need for careful method development when adopting greener approaches. The implementation of miniaturized systems, like nano-LC, has further contributed to solvent reduction and decreased waste generation [27; 28]. Moreover, the integration of green sample preparation methods, including solid-phase microextraction (SPME) [29] and the use of ionic liquids [30] as stationary phases, has enhanced the overall sustainability of LC processes. In a review by [PERSON] et al. [31], ionic liquids as stationary phases in LC processes were highlighted as a sustainable innovation, reducing reliance on volatile organic solvents and minimizing waste.