Green Analytical Chemistry—Recent Innovations

Abstract

Green analytical chemistry represents a transformative approach to analytical science, emphasizing sustainability and environmental stewardship while maintaining high standards of accuracy and precision. This review highlights recent innovations in green analytical chemistry, including the use of green solvents, such as water, supercritical carbon dioxide, ionic liquids, and bio-based alternatives, as well as energy-efficient techniques like microwave-assisted, ultrasound-assisted, and photo-induced processes. Advances in green instrumentation, including miniaturized and portable devices, and the integration of automation and chemometric tools, have further enhanced efficiency and reduced the environmental footprint of analytical workflows. Despite these advancements, challenges remain, including the need to balance analytical performance with eco-friendliness and the lack of global standards to measure and promote sustainable practices consistently. However, the future of green analytical chemistry looks promising, with emerging technologies like artificial intelligence and digital tools offering new ways to optimize workflows, minimize waste, and streamline analytical processes. By focusing on these areas, green analytical chemistry is transforming analytical methodologies into tools that not only achieve high performance but also align with global sustainability goals. This review underscores how green analytical chemistry is more than just a scientific discipline, but a pathway for reducing the ecological impact of analytical processes while driving innovation in science and industry. With the continued commitment to research, collaboration, and the adoption of cutting-edge technologies, green analytical chemistry has the potential to shape a greener and more sustainable future for analytical chemistry and its diverse applications.

1. Introduction

Green Analytical Chemistry (GAC) is an evolving discipline that integrates the principles of green chemistry into analytical methodologies, aiming to reduce the environmental and human health impacts traditionally associated with chemical analysis [1]. By minimizing the use of toxic reagents, reducing energy consumption, and preventing the generation of hazardous waste, GAC seeks to align analytical processes with the overarching goals of sustainability. The foundation of GAC lies in the 12 principles of green chemistry, which provide a comprehensive framework for designing and implementing environmentally benign analytical techniques [2]. These principles emphasize waste prevention, the use of renewable feedstocks, energy efficiency, atom economy, and the avoidance of hazardous substances, all of which are central to reimagining the role of analytical chemistry in today’s environmental and industrial landscape.

Although sustainability is a growing priority, the increasing global energy consumption and expanding trade in organic solvents highlight the complexities of achieving a full transition to greener alternatives. Nevertheless, GAC continues to play a pivotal role in advancing cleaner production practices and promoting sustainable scientific research. Analytical chemistry, traditionally reliant on resource-intensive methods and harmful solvents, has faced growing scrutiny for its environmental footprint. GAC addresses these concerns by transforming analytical workflows through the incorporation of green solvents, such as water, ionic liquids, and supercritical fluids, which replace volatile organic compounds (VOCs) and reduce toxicity. Furthermore, GAC embraces energy-efficient techniques, such as microwave-assisted and ultrasound-assisted methodologies, to enhance reaction rates and reduce the energy demands of analytical processes. These innovations not only lower operational costs but also contribute to the broader goals of reducing greenhouse gas emissions and mitigating climate change [3].

The role of GAC extends beyond its immediate environmental benefits, as it fosters a more holistic approach to chemical analysis. By prioritizing the real-time, in-process monitoring of reactions, GAC enables industries to detect and address inefficiencies or hazardous by-products before they escalate, thus preventing pollution at its source. The adoption of chemometric tools further enhances the precision and efficiency of these methods, enabling robust data analysis while minimizing resource use. This shift towards proactive rather than reactive approaches highlights the transformative potential of GAC in redefining traditional paradigms in analytical chemistry [4].

The 12 principles of green chemistry serve as a roadmap for integrating GAC into diverse applications. For instance, the principle of atom economy advocates for the optimization of chemical reactions to ensure maximum incorporation of starting materials into final products, thereby reducing waste. Similarly, the emphasis on safer solvents and auxiliaries has driven the exploration of alternative extraction and separation techniques, such as solid-phase microextraction (SPME) and supercritical fluid chromatography (SFC), which minimize solvent usage and waste generation. Catalysis, another key principle, has found wide application in GAC by replacing stoichiometric reagents with catalytic systems that offer higher selectivity and lower energy requirements. The principle of designing for degradation, which ensures that chemical products break down into harmless substances at the end of their life cycle, is particularly relevant in analytical chemistry, where residues from reagents and solvents can persist in the environment.

GAC also addresses the critical challenge of scalability, ensuring that green analytical methods can be seamlessly integrated into industrial and research-scale operations. The shift from traditional batch processes to continuous-flow systems exemplifies this scalability, enabling more efficient resource utilization and reduced environmental impact. Moreover, the focus on renewable feedstocks, such as bio-based solvents, aligns GAC with the global transition towards a circular economy, where waste is minimized, and materials are continuously reused or recycled [5].

The broader adoption of GAC is not without challenges. Implementing green methodologies often requires significant investment in infrastructure and training, as well as overcoming resistance to change in established practices [6]. However, these challenges are outweighed by the long-term benefits of reducing environmental harm, improving workplace safety, and enhancing the economic viability of analytical techniques. As regulatory frameworks increasingly mandate the use of greener technologies, GAC is poised to become a cornerstone of compliance and innovation in both industrial and academic settings.

GAC represents a fundamental shift in how chemical analysis is conducted, emphasizing environmental stewardship, sustainability, and efficiency. By integrating the 12 principles of green chemistry, GAC not only mitigates the adverse impacts of traditional analytical practices but also positions itself as a driver of innovation in sustainable chemistry. As the global community intensifies its efforts to address emerging contaminants [7], the role of GAC will continue to expand, offering practical solutions to balance industrial progress with ecological preservation. Through ongoing research, collaboration, and the adoption of cutting-edge technologies, GAC will undoubtedly play a pivotal role in shaping the future of analytical chemistry and its contributions to a more sustainable world.

2. Principles and Framework

The 12 principles of green chemistry provide a foundational framework for designing chemical processes and products that prioritize environmental and human health [8]. When applied to analytical techniques, these principles drive the development of methodologies that are safer, more efficient, and environmentally benign. Figure 1 shows the 12 principles of Green Analytical Chemistry (GAC), highlighting key strategies such as waste prevention, atom economy, safer chemicals, energy efficiency, and real-time analysis, which collectively guide the development of sustainable and environmentally conscious analytical techniques. Waste prevention, the first principle, emphasizes designing analytical processes that avoid generating waste rather than managing it after the fact, a critical consideration in high-throughput laboratories [9]. Atom economy, another key principle, ensures that chemical reactions used in analytical processes maximize the incorporation of all starting materials into the final product, reducing by-products and inefficiencies. Less hazardous chemical syntheses and designing safer chemicals focus on minimizing toxicity in reagents and solvents used during analysis, protecting both analysts and the environment. The principle of safer solvents and auxiliaries is particularly relevant to analytical chemistry, as it encourages the use of non-toxic, biodegradable, or less harmful solvents, such as water, ionic liquids, or supercritical carbon dioxide, reducing reliance on hazardous organic solvents [10].

Energy efficiency is another critical aspect, urging the development of techniques that operate under milder conditions, such as room temperature and pressure, to lower energy consumption. This is exemplified in the use of alternative energy sources, such as microwave-assisted or ultrasound-assisted methods, to accelerate processes without excessive energy inputs. The principle of renewable feedstocks encourages the replacement of finite resources with renewable ones, such as bio-based solvents or reagents derived from natural materials. Reducing derivatives, which minimizes the need for temporary chemical modifications like protection or deprotection steps, ensures analytical methods are streamlined and resource-efficient. Catalysis, a cornerstone principle, promotes the use of catalytic reagents over stoichiometric ones in analytical methods, enhancing selectivity and reducing material use while minimizing environmental impacts. The principle of design for degradation ensures that chemicals and materials used in analytical processes decompose into harmless products at the end of their lifecycle, preventing persistent environmental contamination. Real-time analysis for pollution prevention is particularly significant in analytical chemistry, advocating for methodologies that monitor and control processes in real-time to prevent hazardous by-products before they form. Finally, inherently safer chemistry for accident prevention underlines the need to design processes with minimized risk of accidents, explosions, or hazardous releases, ensuring a safer working environment. Together, these principles provide a comprehensive strategy for reimagining analytical chemistry to meet the demands of sustainability, safety, and environmental responsibility. By embedding these principles into the development of analytical techniques, the discipline not only aligns with green chemistry’s ethos but also actively contributes to reducing the ecological footprint of scientific research and industrial processes [11,12].

Integrating Life Cycle Assessment (LCA) into the evaluation of analytical methods is a game-changer for understanding and reducing their environmental impact [13]. LCA provides a big-picture perspective, looking at every stage of a method’s life cycle from sourcing raw materials to disposal of waste. In analytical chemistry, this means examining how much energy is used, how much waste is produced, and the overall footprint of the reagents and instruments involved. For example, take a common method like liquid chromatography. LCA helps us see not just the direct impacts, like solvent use and waste generation, but also the hidden costs, like the energy required to run the equipment or the emissions linked to producing the solvents. This broader view makes it possible to identify areas where we can make smarter, greener choices [14].

LCA is not just about pointing out problems; it is a tool for making better decisions. By comparing methods—say, gas chromatography versus supercritical fluid chromatography—we can see which one is gentler on the environment without sacrificing performance. It also highlights how innovative techniques, like microwave- or ultrasound-assisted methods, can cut down energy use and waste compared to traditional approaches. This kind of insight gives researchers and labs the confidence to adopt greener technologies, knowing they are making a meaningful difference.

Sometimes, though, making a method greener comes with trade-offs. A new approach might use safer chemicals but require more energy, for example. LCA helps balance these pros and cons, ensuring we are making choices that genuinely reduce overall impact. It is also increasingly relevant as regulations and markets push for more sustainable practices. Demonstrating a method’s environmental benefits through LCA can help labs stay ahead of these expectations.

Moreover, Raccary et al. [13] emphasized that LCA provides a systemic view, capturing environmental impacts across the entire life cycle of analytical methods, from raw material extraction to disposal. For instance, it can evaluate whether the benefits of switching to bio-based solvents outweigh the potential environmental burdens from agricultural production, such as eutrophication or land use changes. Additionally, LCA highlights often-overlooked stages, such as the energy demands of instrument manufacturing or the end-of-life treatment of lab equipment. By identifying these environmental hotspots, researchers and industries can prioritize improvements where they matter most, such as optimizing energy efficiency or reducing reliance on rare materials in instrumentation. Incorporating LCA into the development process not only supports eco-design but also provides data-driven evidence to justify green choices to stakeholders and regulatory bodies.

What is exciting about LCA is how it shifts the mindset in the lab. Instead of just focusing on results, it encourages us to think about how we achieve them and the ripple effects our choices have on the planet. It opens the door to rethinking not just individual methods but entire workflows—like swapping out harmful solvents for safer ones or investing in energy-efficient equipment. As LCA tools become more user-friendly and databases grow richer, this approach will become even more powerful, helping analytical chemistry evolve into a discipline that is not only about precision but is also about responsibility.

3. Innovations in Green Analytical Techniques

3.1. Greener Separation Techniques

3.1.1. Green Gas Chromatography (GC) and Liquid Chromatography (LC)

The pursuit of environmentally friendly analytical techniques has led to significant advancements in green gas chromatography (GC) and liquid chromatography (LC). In gas chromatography, efforts to enhance sustainability have focused on reducing or eliminating the use of toxic solvents and gases. For instance, the adoption of hydrogen as a carrier gas, instead of traditional helium, not only mitigates environmental hazards but also addresses the scarcity and high cost associated with helium. Hydrogen offers chromatographic advantages, including faster analysis times and improved resolution due to its higher diffusivity and lower viscosity compared to helium. Studies, such as those by Fernández-Alba et al. [15] demonstrate its successful application in multiresidue pesticide analysis using GC-MS/MS, achieving comparable sensitivity, reproducibility, and linearity to helium-based methods. Hydrogen’s renewable production via water electrolysis and reduced carbon footprint further align with green chemistry goals, making it a sustainable and cost-effective alternative for routine analytical applications [16].

Çetintürk et al. [17] developed a novel GC-MS/MS method using hydrogen as a carrier gas for the analysis of persistent organic pollutants (POPs) like dioxins and PCBs. Their approach reduced analysis time by 2.5 times while maintaining baseline resolution for critical congeners. Although sensitivity was slightly reduced, the method proved to be cost-effective, environmentally friendly, and reliable for long-term environmental analysis. This study highlights hydrogen’s potential as a sustainable alternative to helium in advanced analytical applications. While hydrogen (H₂) offers advantages as a sustainable carrier gas in gas chromatography, its flammability and explosion risk require careful management. Modern GC systems incorporate several safety features to mitigate these risks, including built-in leak detectors, automatic shut-off valves, and controlled flow regulation. Additionally, on-demand electrolytic hydrogen generators reduce the need for high-pressure storage, further enhancing safety [18]. These advancements ensure that H₂ can be used efficiently while minimizing potential hazards, making it a viable alternative to helium in analytical applications.

Additionally, the development of low thermal mass (LTM) technology in GC systems has substantially decreased energy consumption by enabling rapid heating and cooling cycles, thereby improving analytical efficiency [19]. Recently, Junwei et al. [20] demonstrated the application of LTM in a portable GC-LIT-MS system for the analysis of VOCs in water. The LTM column facilitated rapid separation, achieving detection limits below 1.18 µg/L for 55 VOCs within a 4 min runtime, highlighting its potential for high-throughput, energy-efficient, and field-based analytical applications. Figure 2 shows the schematic of the portable GC-LIT system.

Comprehensive two-dimensional gas chromatography (GC × GC) has also emerged as a powerful tool, offering enhanced separation capabilities while maintaining a commitment to green chemistry principles [21]. Arena et al. [22] demonstrated the potential of comprehensive two-dimensional gas chromatography (GC × GC) as a green analytical tool, emphasizing its enhanced separation efficiency and sensitivity for complex matrices. By integrating GC × GC with triple quadrupole mass spectrometry, their method minimized the need for extensive sample preparation and solvent consumption, aligning with green chemistry principles. The GC × GC-QqQMS method provided superior separation, effectively distinguishing co-eluting phthalates like DiNP and DiDP, ensuring accurate quantification in complex vegetable oil matrices. 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.

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. Comparison of chromatographic performance for traditional and green (high-water content) LC methods, highlighting trade-offs between sustainability, efficiency, and analytical performance.

Aspect	Traditional LC	Green LC
Retention Time	Shorter, due to higher elution strength	Longer, especially for hydrophobic analytes
Resolution (Rs)	Typically high (e.g., Rs > 1.5)	Comparable with optimization
Peak Symmetry	Sharp peaks, good symmetry	May broaden, but comparable with polar-embedded phases
Sensitivity (LOD)	Higher (e.g., 0.05 µg/mL)	Slightly lower (e.g., 0.08 µg/mL)
Environmental Impact	High waste, hazardous solvents	Reduced waste, eco-friendly
Optimization Needs	Standard, less complex	Requires specialized columns, temperature adjustments

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 Quintana 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. Their tunable properties, recyclability, and biodegradability enhance separation efficiency while aligning with green chemistry principles for environmentally friendly and sustainable analytical practices.

In line with these sustainable innovations, Chen et al. [32] introduced a novel approach integrating contactless atmospheric pressure ionization (C-API) with capillary-based separation techniques. This method employs a short, tapered capillary that serves as both a separation channel and ionization emitter, enabling highly efficient preconcentration and detection of analytes with minimal solvent consumption. The approach significantly reduces analysis time, eliminates the need for complex interfacing components, and minimizes waste generation [33]. By leveraging the simplicity and cost-effectiveness of this design, Chen et al.’s work represents a promising step toward the miniaturization and sustainability of analytical processes, aligning seamlessly with green chemistry principles while maintaining high sensitivity and performance. A study by Grinias et al. [34] compared various capillary columns (0.2–0.3 mm i.d.) with standard columns, finding that capillary systems offered higher peak capacities and theoretical plates, particularly for standard alkylphenone mixtures. This supports the notion that miniaturization improves separation yields, though it requires optimized instrumentation to handle low flow rates and higher backpressures. Such miniaturized LC techniques have gained attention for their ability to enhance separation efficiency while significantly reducing solvent and sample consumption. These advancements in miniaturized LC not only align with the principles of green analytical chemistry but also demonstrate a commitment to reducing the environmental footprint of analytical practices. By embracing these innovations, laboratories can achieve high-quality analytical performance while promoting environmental sustainability. However, the shift to miniaturized LC comes with trade-offs, including lower sample capacity, potential challenges in method scalability, and the need for specialized instrumentation. Despite these limitations, by adopting miniaturized LC systems, laboratories can achieve high-quality analytical performance while promoting sustainability.

Table 2. Comparison of traditional LC and capillary LC based on efficiency, resolution, solvent use, sample capacity, and sensitivity. Capillary LC enhances efficiency and reduces waste but requires specialized instrumentation and has lower sample capacity.

Aspect	Standard LC Columns (4.6 mm i.d.)	Capillary LC Columns (10–100 µm i.d.)
Column Efficiency (N)	~50,000 plates/m	>100,000 plates/m, due to smaller particles
Resolution (Rs)	Moderate to high (e.g., Rs = 1.8 for enantiomers)	Higher (e.g., Rs = 2.5 for enantiomers)
Solvent Consumption	High (1–1.5 mL/min flow rate)	Low (e.g., 300 nL/min, 100–1000× reduction)
Sample Capacity	High, microgram range	Low, nanogram range, limits preparative use
Sensitivity	Standard, may require larger injection volumes	Enhanced, due to reduced dilution, better with MS
Trade-offs	Lower efficiency, higher waste	Higher efficiency, but lower capacity, higher cost

presents a detailed comparison of chromatographic performance metrics for traditional and capillary columns, including column efficiency (number of theoretical plates), resolution, solvent consumption, sample capacity, and sensitivity. These parameters highlight the practical benefits and limitations of green and miniaturized LC techniques, emphasizing the importance of stationary phase selection, temperature adjustments, and tailored mobile phase compositions for achieving optimal results.

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-CO₂) 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 CO₂. 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]. Pilařová 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 Plachká 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. Plachká 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 π–π interactions, ionic interactions, and hydrogen bonding. These advancements, combined with the introduction of sub-2 μm particles, have improved resolution, efficiency, and peak symmetry, further establishing silica-based columns as indispensable in modern SFC systems [43].

Furthermore, the coupling of SFC with mass spectrometry (MS) has opened new avenues for high-throughput analysis, enabling real-time monitoring and reducing the need for extensive sample preparation [44]. Innovations in instrumentation, including improved pressure control systems and automated solvent recycling units, have further reduced energy consumption and optimized the green credentials of SFC systems. Moreover, the development of advanced interfaces for SFC-MS, such as the “Pre-BPR splitter with sheath pump” and the “BPR and sheath pump with no splitter”, has enhanced compatibility and ionization efficiency. These interfaces prevent solute precipitation and improve desolvation, ensuring stable baselines and higher sensitivity [45]. Additionally, the integration of ultra-high-performance supercritical fluid chromatography (UHPSFC) technology and sub-2 μm particle size columns has significantly improved resolution and reduced analysis times [46]. These advancements have expanded the scope of SFC-MS for the analysis of complex matrices, ranging from food contaminants and nutrients to pharmaceuticals, while maintaining its environmental sustainability

Additionally, the use of supercritical CO₂ contributes to carbon neutrality, as it can be sourced from industrial waste streams, promoting a circular economy. Significant opportunities exist for increased utilization of CO₂ generated from industrial processes. Large-volume sources, such as fossil-fuel power plants, cement production, and ammonia manufacturing, provide a steady supply of CO₂ that can be captured and repurposed for various applications, including its use as a solvent in supercritical fluid processes [47]. As SFC continues to evolve, it not only provides a sustainable alternative to conventional chromatographic techniques but also demonstrates that high analytical performance and environmental consciousness can coexist. These advancements position SFC as a vital tool in the pursuit of greener analytical methodologies across diverse scientific and industrial domains.

3.2. Sustainable Sample Preparation

Solid-phase microextraction (SPME) and liquid-phase microextraction (LPME) have revolutionized sample preparation techniques by aligning with the principles of green chemistry, offering eco-friendly alternatives to traditional extraction methods. These techniques significantly reduce the use of organic solvents, waste generation, and processing times, making them sustainable and efficient for modern analytical applications. SPME, in particular, employs a coated fiber to adsorb analytes directly from a sample matrix, eliminating the need for large volumes of solvent [48]. This solvent-free approach not only minimizes environmental impact but also enhances method sensitivity and reproducibility. Recent advancements in SPME include the development of novel fiber coatings, such as polymeric and carbon-based materials, which improve selectivity and expand its applicability to a wide range of analytes in fields like environmental monitoring, food safety, and pharmaceuticals [49].

Amini et al. [50] highlighted the revolutionary integration of nanostructured materials, such as metal-organic frameworks (MOFs), into the design of SPME fibers. Their work on polyacrylonitrile/nickel-based MOF (PAN/Ni-MOF) composites demonstrated significant improvements in extraction efficiency due to the material’s high porosity, enhanced surface area, and strong interactions with analytes through mechanisms like hydrogen bonding, hydrophobic contacts, and π−π stacking. These innovations not only allow for the efficient detection of trace-level compounds in complex matrices, such as environmental water and food samples, but also improve the thermal and mechanical stability of the fibers, enabling repeated use without performance loss.

LPME, on the other hand, utilizes small volumes of extraction solvents, often in microliter quantities, to isolate analytes [51]. Variants like dispersive liquid–liquid microextraction (DLLME) [52,53] and hollow-fiber liquid-phase microextraction (HF-LPME) [54] have further refined the technique by enhancing efficiency and reducing solvent usage. DLLME, for example, disperses a minimal amount of extraction solvent throughout the sample matrix, achieving rapid equilibration and high enrichment factors. Zhang et al. [55] developed an acid-induced dispersive liquid–liquid microextraction (DLLME) method using in situ hydrophobic deep eutectic solvents (DESs), eliminating the need for toxic dispersive solvents. This green approach, applied to bisphenol A (BPA) and alkylphenols (APs) in environmental and beverage samples, achieved detection limits as low as 0.03 μg L⁻¹ with high recoveries (86.9–105.0%) and enrichment factors (29–32). The method is rapid (<1 min), solvent-free, and highly efficient, demonstrating the potential of switchable solvent systems in sustainable analytical chemistry.

In another recent study, Rageh et al. [56] developed a quasi-hydrophobic deep eutectic solvent (DES)-based DLLME for extracting gliflozins from water samples, enhancing green analytical chemistry. The method, using benzalkonium chloride (BZKCl)-based DES, eliminated toxic solvents and improved extraction efficiency. Coupled with UHPLC/fluorescence detection, it demonstrated high sensitivity, recovery, and sustainability, as confirmed by green assessment metrics.

In a recent review by Faraji [52], advancements in dispersive liquid–liquid microextraction (DLLME) were explored to enhance its compliance with green analytical chemistry principles. The review discusses the shift from conventional toxic solvents to greener alternatives, such as deep eutectic solvents (DESs), ionic liquids (ILs), and supramolecular solvents (SUPRASs). Additionally, innovative dispersion strategies, including magnetic nanoparticles, ultrasound, vortexing, and gas stream flotation, have minimized the need for dispersive solvents, improving efficiency and sustainability. Faraji also highlights alternative phase separation techniques, such as salting-out and gas-assisted flotation, which eliminate the need for centrifugation, thus facilitating automation and high-throughput analysis. Furthermore, automation in DLLME, incorporating flow-based, batch, and in-syringe systems, has been a key focus, ensuring greater reproducibility and reduced solvent consumption. These innovations position DLLME as a sustainable and efficient method in modern green analytical sample preparation [52].

Lorenzo-Parodi et al. [57] explored innovative approaches in liquid-phase microextraction (LPME) for aromatic amines, emphasizing the potential of hollow fiber liquid-phase microextraction (HF-LPME) and parallel artificial liquid membrane extraction (PALME). Their findings revealed that PALME offers significantly higher recoveries compared to HF-LPME, while also being less labor-intensive and greener, as it requires much smaller volumes of organic solvents. They highlighted PALME’s suitability for complex biological matrices, such as urine, due to its ability to reduce matrix interferences and achieve low limits of detection in the nanogram per liter range. These advancements demonstrate how miniaturized and efficient sample preparation techniques can address analytical challenges in environmental and biomedical studies. As illustrated in Figure 3, both HF-LPME and PALME share similar fundamental extraction principles but differ in their membrane configurations, solvent choices, and processing efficiency. The choice of membrane material plays a critical role in analyte selectivity, stability, and recovery efficiency. HF-LPME, with its hollow fiber structure, allows for precise control over extraction conditions but requires manual handling, making it less practical for high-throughput applications. PALME, in contrast, offers a more automated, scalable, and reproducible alternative, making it an attractive choice for laboratories requiring batch processing of multiple samples. The experimental results further demonstrated that PALME exhibited higher extraction recoveries for most aromatic amines, attributed to the increased surface area and enhanced mass transfer kinetics enabled by its membrane structure. The shorter extraction time and automation potential of PALME present a significant advantage over HF-LPME, particularly for applications in environmental and pharmaceutical analysis. However, HF-LPME remains a viable option for selective, small-scale extractions where high enrichment factors are required. Both SPME and LPME have seen integration with advanced analytical instruments, such as gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS), for comprehensive and highly sensitive analyses. These techniques are increasingly employed in trace analysis of environmental contaminants, VOCs, and bioactive compounds, demonstrating their versatility and relevance in addressing contemporary analytical challenges. As research continues, innovations such as the incorporation of ionic liquids and deep eutectic solvents in microextraction systems further bolster the green credentials of these methods. By reducing resource consumption and improving analytical performance, SPME and LPME exemplify the synergy between technological innovation and sustainability in modern analytical chemistry.

SPME is a well-established technique in analytical chemistry due to its solvent-free nature, minimal sample preparation, and high sensitivity, making it an attractive tool for environmentally friendly analysis. While its adoption in routine industrial workflows is not yet widespread due to scalability challenges, advancements in automated SPME systems and fiber durability are expanding its applicability, particularly in quality control and high-throughput screening. Its benefits in reducing solvent consumption and waste align well with green chemistry principles, though for large-scale industrial processes, alternative green extraction methods, such as supercritical fluid extraction (SFE), may offer better scalability. Despite these challenges, SPME remains a valuable technique in sectors like food safety, environmental monitoring, and pharmaceutical analysis, where precise and low-volume extractions are required.

Ionic Liquids and Eutectic Solvents

The use of ionic liquids (ILs) and eutectic solvents (ESs) in analytical chemistry has gained significant attention due to their alignment with the principles of green chemistry. These solvents serve as innovative and sustainable alternatives to traditional organic solvents, offering unique physicochemical properties, such as low volatility, high thermal stability, and tunable solubility. Ionic liquids, composed entirely of ions, can be designed with specific cation–anion combinations to tailor their properties for various analytical applications. Their negligible vapor pressure reduces environmental emissions, while their high solvating power enhances the extraction efficiency of polar and non-polar analytes. Recent advancements in ILs include the development of task-specific ionic liquids (TSILs), engineered for targeted analytical purposes, such as the selective extraction of heavy metals, pharmaceuticals, or bioactive compounds from complex matrices. Do-Thanh et al. [58] emphasized the unique advantages of task-specific ionic liquids (TSILs) in separation processes, particularly for rare earth elements (REEs). Their work highlighted that TSILs, tailored with functional groups such as carbamoylmethylphosphine oxide (CMPO) or diglycolamide (DGA), offer exceptional selectivity and efficiency by combining ion-exchange and coordination mechanisms. These TSILs not only enhance extraction performance but also reduce the environmental impact by minimizing solvent loss and enabling recycling. For instance, CMPO-based TSILs demonstrated superior performance in separating actinides and lanthanides under acidic conditions, reinforcing the potential of TSILs as green alternatives in advanced separation technologies. Lu et al. [59] developed a novel residue analysis method for task-specific ionic liquids (TSILs) in environmental matrices such as water, soil, and plants. By employing high-performance liquid chromatography–tandem mass spectrometry (HPLC-MS/MS) combined with accelerated solvent extraction (ASE), they achieved detection limits as low as 10⁻¹⁵ g for compounds like 1-aminoethy l-3-methylimidazolium tetrafuoroborate ([C₂NH₂MIm]BF₄) and 1-hydroxyethyl-3-methylimidazolium tetrafuoroborate ([HOEMIm]BF₄). Their study highlighted the high recovery rates of TSILs in water and soil, demonstrating the effectiveness of optimized extraction solvents, such as water–methanol mixtures, for complex matrices. This approach offers a sensitive and reliable framework for monitoring TSIL residues and assessing their environmental impact. Traditional solvent extraction methods, such as CMPO dissolved in TBP with xylene, benefit from the thermal stability of TBP, which minimizes evaporation losses and enhances extraction efficiency. However, task-specific ionic liquids (TSILs) provide distinct advantages over conventional liquid–liquid extraction methods. Unlike TBP-based extractions that require organic solvents, TSILs are non-volatile, recyclable, and offer improved selectivity for specific target analytes. Additionally, TSILs facilitate phase separation without the need for large solvent volumes, reducing environmental impact and making them a more sustainable alternative in green sample preparation techniques.

Eutectic solvents, particularly natural deep eutectic solvents (NADES), have emerged as a greener alternative to ILs. Formed by mixing inexpensive and biodegradable components, such as sugars, amino acids, and organic acids, ESs exhibit low toxicity and high biodegradability. These solvents are increasingly used in sample preparation techniques like liquid–liquid extraction, solid-phase extraction, and microextraction due to their ability to replace hazardous solvents while maintaining or improving extraction efficiency. Additionally, their biocompatibility makes them ideal for applications in food analysis, pharmaceutical quality control, and environmental monitoring. Furthermore, Volpatto and Vitali demonstrated the effectiveness of using hydrophobic natural deep eutectic solvents (NADES), such as those formed by thymol and butyric acid, in dispersive liquid–liquid microextraction (DLLME) for the analysis of multiclass emerging contaminants in surface water. Their study optimized parameters such as pH, temperature, and solvent volume, achieving recoveries between 70% and 120%, with relative standard deviations below 20%. This innovative approach not only replaces traditional toxic chlorinated solvents but also ensures environmentally sustainable and efficient extraction of contaminants across diverse water matrices [60].

The integration of ILs and ESs into analytical workflows has also enhanced the sensitivity and selectivity of various analytical methods, such as gas chromatography (GC), liquid chromatography (LC), and mass spectrometry (MS). For example, ILs have been successfully used as stationary phases in GC [61] and as additives in LC mobile phases [62], improving separation performance. Similarly, ESs have been employed in the preconcentration of trace analytes, reducing matrix interference and improving detection limits.

Despite their numerous advantages, challenges remain, such as the high cost of some ILs and the need for a deeper understanding of their long-term environmental impact. However, ongoing research continues to address these issues, with efforts focusing on synthesizing low-cost, biodegradable ILs and exploring new combinations of ES components. The adoption of these green solvents represents a significant step toward more sustainable analytical chemistry practices, offering a balance between performance and environmental responsibility. As innovations in ILs and ESs advance, their role in analytical chemistry is set to expand, driving the transition toward safer and more eco-friendly methodologies.

3.3. Real-Time and In-Process Monitoring

3.3.1. Advances in Spectroscopic Methods for Real-Time Analysis

Advances in spectroscopic methods for real-time analysis have revolutionized the field of analytical chemistry, providing sustainable, efficient, and highly sensitive tools for monitoring chemical processes and detecting analytes. These innovations align with the principles of green chemistry by reducing the need for extensive sample preparation, minimizing waste generation, and enhancing energy efficiency. Real-time spectroscopic techniques, such as Raman spectroscopy [63], Fourier-transform infrared (FTIR) spectroscopy [64], and ultraviolet-visible (UV-Vis) spectroscopy [65], have become indispensable in applications ranging from industrial process control to environmental monitoring and medical diagnostics.

Raman spectroscopy, in particular, has seen significant advancements with the development of portable and miniaturized instruments, enabling real-time, in situ monitoring of chemical reactions and analytes in complex matrices. Techniques like Surface-Enhanced Raman Spectroscopy (SERS) [66] have further increased sensitivity, allowing for trace-level detection of pollutants, biomolecules, and pharmaceutical compounds. Similarly, FTIR spectroscopy has evolved to include real-time monitoring capabilities for gaseous, liquid, and solid samples. Modern FTIR systems equipped with quantum cascade lasers (QCL) offer improved resolution and rapid scanning, making them ideal for real-time monitoring of VOCs and industrial emissions.

The integration of UV-Vis spectroscopy with flow-through cells and fiber-optic probes has enhanced its application in process analytical technology (PAT) [67], enabling continuous monitoring of reaction progress and product quality in pharmaceutical manufacturing. Advances in chemometric algorithms have further augmented these techniques, enabling real-time data processing, multivariate analysis, and predictive modeling for complex datasets.

Emerging spectroscopic methods, such as near-infrared (NIR) and mid-infrared (MIR) spectroscopy [68], have also gained traction due to their non-destructive nature and ability to analyze complex biological and environmental samples. NIR spectroscopy, in particular, has found widespread use in agricultural and food quality analysis, allowing for rapid and eco-friendly assessment of moisture content, protein levels, and contaminants [69,70].

Coupling spectroscopic techniques with other analytical tools, such as mass spectrometry (MS) and chromatography, has expanded their scope and sensitivity. For instance, laser-induced breakdown spectroscopy (LIBS) and its combination with MS offer unparalleled capabilities for elemental analysis in real time [71]. Portable spectroscopic devices, powered by advancements in photonics and computational technology, have democratized access to real-time analysis, enabling on-site measurements in remote or field settings [72].

These advances underscore the role of real-time spectroscopic methods as a cornerstone of modern green analytical chemistry. By reducing reliance on consumables, shortening analysis times, and providing immediate feedback, these techniques not only improve efficiency but also contribute to the sustainability and environmental responsibility of analytical workflows. As research continues, the integration of artificial intelligence (AI) and machine learning (ML) with spectroscopic data is expected to further enhance real-time analysis, paving the way for smarter, more adaptive analytical solutions.

3.3.2. Electrochemical Methods

Electrochemical techniques play a crucial role in real-time and in-process monitoring, offering high sensitivity, rapid response times, and minimal environmental impact. These methods are widely used in industrial process control, environmental monitoring, and biomedical diagnostics, aligning with green analytical chemistry by reducing reagent consumption, minimizing waste, and enabling on-site analysis.

Among these, electrochemical aptamer-based (EAB) sensors offer a unique capability for continuous, in vivo molecular monitoring. EAB sensors function independently of the chemical reactivity of their targets, enabling real-time detection of small molecules, drugs, and metabolites in complex biological environments [73]. These sensors have demonstrated high-frequency, seconds-resolved measurements of various analytes in live animal models, including therapeutic drugs and metabolic biomarkers, highlighting their potential in biomedical and environmental applications. The key advantage of EAB sensors lies in their modular design, which allows the selection of aptamers specific to a wide range of targets. This adaptability, combined with their ability to function in undiluted biological fluids, makes them a powerful tool for real-time monitoring in clinical and pharmaceutical settings. Recent advancements have focused on improving sensor stability and extending measurement duration, ensuring that these sensors remain functional for long-term in vivo applications.

Antonacci et al. [74] highlighted the significance of paper-based electrochemical analytical devices (ePADs) for real-time and in-process monitoring in pharmaceutical applications. These low-cost, sustainable sensors enable rapid detection of active pharmaceutical ingredients (APIs), excipients, and contaminants, ensuring efficient quality control. Advancements in screen-printed electrodes (SPEs) and carbon-based nanomaterials have improved ePAD sensitivity and selectivity while maintaining eco-friendly workflows. Multiplexing ePAD platforms further enhance simultaneous analyte detection, reinforcing green analytical chemistry principles.

Li and co-workers [75] developed a wireless, transient electrochemical sensor for real-time nitric oxide (NO) detection, demonstrating high selectivity and a low detection limit (3.97 nM). This innovative sensor successfully monitored NO levels in cultured cells, organ tissues, and live mammals, highlighting its potential for biomedical diagnostics, environmental monitoring, and process control applications. A key advancement of this technology is its biodegradable sensor components, which minimize medical waste and eliminate the need for surgical removal in implanted applications. Additionally, its wireless data transmission capability enhances real-time monitoring without bulky instrumentation. These innovations reinforce the role of electrochemical sensors in sustainable, real-time analytical applications, aligning with green analytical chemistry principles.

Electrochemical sensors have gained significant attention in green analytical chemistry due to their ability to provide rapid, cost-effective, and environmentally friendly detection of various analytes. These sensors are widely implemented across multiple industries, demonstrating their practical application in sustainable practices, as summarized in

Table 3. Industrial applications of electrochemical sensors in green analytical chemistry, highlighting key sectors, specific applications, example companies, and their contributions to sustainability.

Industry	Application	Example Companies	Green Alignment
Environmental Monitoring	Detect heavy metals, greenhouse gases, air quality	Sensorix, Figaro USA Inc., Cambridge Sensotec	Reduces pollution, real-time monitoring
Agriculture	Soil moisture, nutrient levels, plant health	Multi Nano Sense Technologies	Optimizes resource use, reduces waste
Medical/Pharmaceutical	Sweat chloride, drug degradation kinetics	Sensirion AG, Cambridge Sensotec	Supports sustainable healthcare, low waste
Food Industry	Detect contaminants like dyes, monitor storage conditions	Figaro USA Inc., Sensirion AG	Enhances food safety, reduces chemical use

. In environmental monitoring, electrochemical sensors are used to detect heavy metals, greenhouse gases, and air quality parameters. Companies such as Sensorix (Bonn, Germany), Figaro USA Inc. (Rolling Meadows, IL, USA), and Cambridge Sensotec (St Ives, UK) have developed advanced sensor-based technologies that facilitate real-time pollution control, reducing environmental impact. Similarly, in agriculture, Multi Nano Sense Technologies (Nagpur, India) has integrated electrochemical sensors to monitor soil moisture, nutrient levels, and plant health, optimizing resource use and minimizing agricultural waste.

In the medical and pharmaceutical industry, electrochemical sensors have been employed for applications such as sweat chloride analysis and drug degradation kinetics. Companies like Sensirion AG (Stäfa, Switzerland) and Cambridge Sensotec(UK) are leveraging these sensors to support low-waste, sustainable healthcare solutions. Furthermore, in the food industry, electrochemical sensors are utilized to detect contaminants like dyes and monitor storage conditions, ensuring food safety while reducing the need for excessive chemical testing, as seen in the technologies developed by Figaro USA Inc. and Sensirion AG. These real-world applications exemplify the role of electrochemical sensors in advancing green analytical chemistry by reducing reagent use, minimizing waste, and enabling real-time monitoring. Their widespread industrial adoption underscores their effectiveness in supporting sustainable practices while maintaining analytical accuracy and efficiency.

4. Application of Green Solvents

Use of Water, Supercritical Carbon Dioxide, Ionic Liquids, and Bio-Based Solvents in Analytical Processes

The use of water, supercritical carbon dioxide (SC-CO₂), ionic liquids (ILs), and bio-based solvents in analytical processes reflects a meaningful step toward more sustainable and environmentally friendly practices [76,77]. Water, often called the universal solvent, has become a cornerstone of green analytical chemistry. Its non-toxic, abundant, and cost-effective nature makes it an excellent alternative to hazardous organic solvents. Techniques like water-based extractions and aqueous chromatographic systems have shown that water is not just eco-friendly, it is also highly effective in separating biomolecules, pharmaceuticals, and environmental pollutants. Hafez et al. [78] developed a solvent-free micellar HPLC method for antidiabetic drug analysis, replacing hazardous organic solvents with water as the primary solvent. Using Brij-35 and SDS, the method forms a micellar environment that enhances separation efficiency while minimizing VOC emissions and solvent waste. Its GAPI and AGREE assessments confirm superior sustainability compared to conventional reversed-phase HPLC. This study highlights the potential of water-based solvent systems in advancing green chromatography. In another work by Tomikj et al. [79], a sustainable HPLC method was developed using a water-based mobile phase consisting of ethanol (63%) and an aqueous phosphate buffer (37%), adjusted to pH 3.0. This method eliminates the need for hazardous organic solvents like acetonitrile and methanol, making it an environmentally friendly alternative for pharmaceutical analysis. With a short analysis time of 5 min, reduced solvent consumption, and improved Eco-scale and AGREE scores, this approach demonstrates the effectiveness of water-based solvent systems in advancing green analytical chemistry while maintaining high analytical performance.

Similarly, supercritical carbon dioxide has also gained recognition for its unique properties. Acting as both a solvent and a mobile phase, SC-CO₂ offers exceptional separation capabilities without the harmful environmental impacts associated with traditional solvents. It is widely used in the extraction of natural products like essential oils and pharmaceuticals, and its recyclability makes it even more appealing. For industries and researchers looking to minimize their ecological footprint, SC-CO₂ provides a practical and scalable solution. Nováková et al. [80] developed an ultra-high-performance supercritical fluid chromatography (UHPSFC) method utilizing supercritical carbon dioxide (SC-CO₂) as a green mobile phase for the analysis of complex plant extracts. This approach enabled the efficient separation of volatile terpenes, flavonoids, and phenolic acids within a single chromatographic system, eliminating the need for traditional gas and liquid chromatography. By replacing hazardous organic solvents with SC-CO₂ and minimal organic modifiers, the method significantly reduces solvent waste and aligns with green chemistry principles. Additionally, the recyclability of SC-CO₂ enhances its sustainability, making it an attractive alternative for environmentally friendly analytical applications. The study highlights the potential of supercritical fluids in green chromatography, offering a high-throughput and scalable solution for complex sample analysis.

Similarly, ionic liquids (ILs) have emerged as promising green solvents due to their versatility and customizable properties. These designer solvents can be tailored for specific tasks, such as extracting metals, purifying pharmaceuticals, or analyzing environmental pollutants. Their stability and effectiveness in challenging conditions make them an attractive alternative to conventional solvents. Axente et al. [81] demonstrated the effectiveness of ionic liquids (ILs) as mobile phase additives in HPLC analysis. By incorporating 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM[BF4]) and 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM[PF6]) into a water:acetonitrile mobile phase, the study achieved enhanced separation of nicotine and cotinine in biological samples. ILs improved peak shape, minimized interactions with silanol groups, and reduced the need for toxic organic modifiers. Their low volatility and recyclability further highlight their potential as green alternatives in liquid chromatography. As green analytical chemistry advances, the use of task-specific ionic liquids (TSILs) continues to offer tailored, efficient, and environmentally conscious solutions. In recent years, task-specific ionic liquids (TSILs) have pushed the boundaries even further, allowing for solutions that are both efficient and environmentally conscious. A novel approach utilizing task-specific ionic liquids (TSILs) nanoconfined in nitrogen-doped porous carbon (ILs@PC) was developed recently to improve the detection and adsorption of sulfonamide antibiotics (SAs) in environmental and food samples [82]. This method eliminates the need for hazardous organic solvents by leveraging functionalized ILs tailored for selective solid-phase extraction (DSPE). When combined with high-performance liquid chromatography (HPLC-UV), the system achieved low detection limits (0.75–1.88 µg L⁻¹) and high recoveries (86.0–111.9%). To further enhance practicality, a portable syringe-based device was introduced for on-site rapid testing, demonstrating the scalability of IL-based methods in green analytical chemistry. This study highlights the growing role of TSILs as effective, environmentally friendly alternatives to conventional extraction solvents.

Bio-based solvents, derived from renewable resources like plants and sugars, are another exciting development. Not only are they biodegradable and less toxic than their petroleum-based counterparts, but they also perform exceptionally well in applications like liquid–liquid extraction and chromatography. A notable example is glycerol, a natural and renewable trihydric alcohol derived from plant and animal sources, which has been successfully applied as a mobile phase modifier in reversed-phase HPLC. Habib et al. [83] demonstrated that a glycerol-phosphate buffer (7:93 v/v) mobile phase effectively separated four antiviral drugs while minimizing the need for hazardous organic solvents. The study found that glycerol enhanced chromatographic efficiency, controlled retention factors, and improved resolution compared to traditional organic modifiers like acetonitrile. Additionally, its biodegradability, low toxicity, and stability make it an excellent choice for green analytical chemistry. As sustainable alternatives become more essential, bio-based solvents such as glycerol offer a promising and environmentally friendly direction for chromatography. Deep eutectic solvents (DESs), a newer class of bio-based solvents, stand out for their simplicity, cost-effectiveness, and green credentials, making them perfect for a variety of analytical uses. Azadeh et al. [84] demonstrated the potential of deep eutectic solvents (DESs) as sustainable alternatives to conventional organic solvents in gas chromatography (GC). By synthesizing a DES-based stationary phase using oleic acid and tetrabutylammonium bromide, the study successfully separated alkanes, alcohols, and aromatic compounds while reducing reliance on toxic organic solvents. The method showed moderate polarity (McReynolds constant: 1420) and enabled efficient separation of BTEX (Benzene, Toluene, Ethylbenzene, Xylene) and VOCs. Additionally, the high thermal stability, biodegradability, and recyclability of DESs reinforce their role as green solvents in analytical chemistry. This study highlights DESs as promising, eco-friendly alternatives for chromatographic applications, further expanding the scope of green analytical chemistry.

The shift to these greener solvents is more than just a technological advancement. It is a cultural shift in how we approach analytical chemistry. By replacing traditional solvents with water, SC-CO₂, ionic liquids, and bio-based options, we are reducing chemical waste, improving safety, and making strides toward a cleaner, more sustainable future. These innovations prove that analytical chemistry can maintain its high standards of performance while actively contributing to the global effort to protect our environment.

5. Application of Green Materials

The development and application of sustainable materials in analytical chemistry have gained significant attention as part of the broader effort to minimize environmental impact. These green analytical materials contribute to eco-friendly practices by reducing waste, enhancing biodegradability, and replacing hazardous components in analytical workflows.

5.1. Sustainable Materials in Sample Preparation

In sample preparation, biodegradable sorbents and natural polymer-based adsorbents have emerged as effective alternatives to traditional materials. Cellulose, chitosan, and biochar-based sorbents have been successfully employed in solid-phase extraction (SPE) and dispersive solid-phase extraction (d-SPE) due to their high adsorption capacities, reusability, and biodegradability. Additionally, magnetic nanoparticles coated with eco-friendly polymers offer selective and efficient analyte extraction, reducing the need for organic solvents.

Rana et al. [85] have provided a comprehensive review on the role of cellulose-based materials in the removal of pesticides from contaminated water, highlighting their effectiveness as green adsorbents in environmental remediation and sample preparation. The review discusses pristine and functionalized cellulose sorbents, biochar, and cellulose nanocomposites, emphasizing their adsorption efficiency, sustainability, and recyclability. These materials not only reduce the dependence on hazardous synthetic sorbents but also contribute to green analytical chemistry by minimizing solvent use and promoting waste reduction. Recent advancements have explored hybrid bio-based sorbents that integrate natural and synthetic materials for enhanced extraction efficiency. Jiang and co-workers [86] developed an MIL-68(Al)/Chitosan-coated melamine sponge for vortex-assisted solid-phase extraction (V-SPE) of parabens in water samples, offering a solvent-free, biodegradable alternative to conventional extraction methods. This approach eliminates organic solvents in the preparation process while utilizing chitosan, a renewable biopolymer, as an adsorbent and adhesive, further reinforcing sustainability.

Ge et al. [87] developed a magnetic biochar-based imprinted polymer (FeNi@Mct-MIPs) for solid-phase extraction (SPE) of monocrotaline (Mct) from herbal medicine samples, utilizing shrimp shell-derived biochar functionalized with iron-nickel oxide. The sorbent demonstrated high selectivity and sensitivity, with recovery rates of 85.17–97.81% and a limit of detection (LOD) of 0.60 µg/mL. Compared to conventional C18 and resin adsorbents, it offered greater efficiency, better selectivity, and lower solvent consumption, making it a more sustainable alternative.

This biochar-based sorbent exemplifies the integration of renewable and eco-friendly materials in sample preparation, aligning with green analytical chemistry principles by minimizing waste and enhancing extraction efficiency.

5.2. Green Chromatographic Columns

Traditional chromatographic columns rely on silica-based stationary phases, which often require environmentally hazardous modification processes. Recent advancements have led to the development of hybrid organic-inorganic phases, bio-based silica alternatives, and polymer-based stationary phases, which reduce energy-intensive synthesis steps while maintaining high separation efficiency. Additionally, water-compatible stationary phases have facilitated the transition toward aqueous-based mobile phases, further supporting green chromatography principles.

Sultan et al. [88] demonstrated the potential of limonene, a bio-based pore expander, as a sustainable alternative to fossil-based trimethylbenzene (TMB) for micellar templated mesoporous silica synthesis. Their study found that limonene effectively expands silica pores while reducing environmental impact, as confirmed by a comparative life cycle assessment (LCA). This innovation aligns with green chromatography principles, offering a renewable, waste-derived alternative for eco-friendly column material production. By adopting bio-based silica synthesis approaches, chromatographic methods can move towards more sustainable practices, reducing reliance on fossil-based reagents while ensuring optimal separation performance.

Polymeric stationary phases have emerged as sustainable alternatives in green chromatography due to their high thermal stability and solvent-free compatibility. Dembek and Bocian [89] reviewed polystyrene divinylbenzene (PS–DVB) and PRP-1 crosslinked polymer phases, commonly used in superheated water chromatography (SHWC), demonstrating their ability to withstand prolonged operation at temperatures above 200 °C. Additionally, novel amino acid-modified polymeric phases exhibit stability in heated water conditions, extending column lifespan and reducing solvent dependency. While polymeric phases offer enhanced durability, they may exhibit lower efficiency compared to silica-based phases, requiring optimization for specific applications. Their chemical robustness and compatibility with water-based mobile phases, however, make them an essential advancement in green chromatography, promoting reduced solvent consumption and improved sustainability.

5.3. Eco-Friendly Materials in Sensor Fabrication

The integration of sustainable materials in sensor fabrication is essential for reducing the environmental footprint of analytical devices while maintaining high performance. Recent advancements have focused on the development of biodegradable, recyclable, and natural materials for electrochemical and optical sensors, replacing conventional synthetic components that contribute to electronic waste.

Rahmani et al. [90] reviewed advancements in sustainable sensor manufacturing, emphasizing the role of biodegradable substrates, recyclable electronics, and low-impact conductive materials in next-generation IoT-based analytical devices. The study highlights the use of bioplastics, cellulose-based materials, and conductive bio-polymers, which not only minimize toxic waste but also enhance sensor flexibility and adaptability. Additionally, the integration of self-powered sensors and energy-harvesting technologies reduces reliance on external power sources, further supporting green analytical chemistry principles. Advancements in carbon-based nanomaterials derived from biomass, along with biopolymer-based sensor platforms, are making sensor fabrication more sustainable. These materials offer high conductivity, mechanical stability, and environmental compatibility, making them ideal for applications in environmental monitoring, biomedical diagnostics, and industrial sensing. Another comprehensive review highlighted the use of biopolymeric materials, such as cellulose acetate (CA), methyl cellulose (MC), polyvinyl alcohol (PVA), chitosan (QT), and polylactic acid (PLA), as promising alternatives to traditional synthetic substrates [91]. These materials offer mechanical flexibility, environmental degradability, and low toxicity, making them ideal for wearable biosensors, single-use diagnostic tools, and disposable environmental sensors. The transition from petrochemical-based components to renewable, bio-derived materials has been a key focus in the field, reinforcing the need for green innovation in analytical technology. In addition to biodegradable substrates, carbon-based nanomaterials derived from biomass, such as graphene and carbon nanotubes (CNTs), have been incorporated into sensor platforms to enhance conductivity while maintaining sustainability. Conductive bio-polymers, including polyaniline, polypyrrole, and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), are also being explored as alternatives to metal-based electrodes, offering tunable electrical properties, flexibility, and recyclability. These materials enable the fabrication of low-energy, high-performance sensors while reducing reliance on hazardous substances. Further advancements in self-powered sensors and energy-harvesting technologies have expanded the possibilities for fully sustainable sensor platforms, allowing devices to function without external power sources, thereby minimizing resource consumption. The combination of eco-friendly materials, biodegradable electronics, and self-sustaining energy systems is paving the way for next-generation sustainable sensors, aligning with green analytical chemistry principles and promoting environmentally responsible analytical methodologies.

6. Alternative Energy in Green Chemistry

6.1. Role of Microwave-Assisted and Ultrasound-Assisted Techniques in Reducing Energy Requirements

Microwave-assisted and ultrasound-assisted techniques have emerged as transformative tools in analytical chemistry, playing a crucial role in promoting greener, more sustainable practices. These energy-efficient methods offer significant advantages over traditional techniques by reducing reaction times, minimizing energy consumption, and enhancing reaction efficiency. Microwave-assisted techniques leverage the ability of microwaves to generate heat rapidly and uniformly within the sample, leading to faster reaction kinetics and improved yields. This approach has been widely adopted in sample preparation, such as digestion and extraction processes, where it significantly reduces the need for harsh reagents and long processing times. For example, microwave-assisted extraction (MAE) [92] has proven highly effective in isolating bioactive compounds from plant materials, offering both enhanced efficiency and reduced solvent usage [93]. Figure 4 from Tran et al.’s [94] study presents a comparative schematic of two different pectin extraction techniques: conventional heating reflux extraction (HRE) and microwave-assisted extraction (MAE). The figure illustrates the key differences between the two methods, highlighting the processing parameters, such as extraction temperature, duration, and solvent interactions. HRE, a widely used method, involves prolonged heating with solvents, which can lead to thermal degradation of pectin and lower extraction efficiency. In contrast, MAE utilizes microwave energy to accelerate the extraction process, significantly reducing time while maintaining high extraction yields. As depicted in the figure, the structural characterization of the extracted pectin is performed using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and rheological analysis to evaluate its chemical composition, morphology, and functional properties. This comparison underscores the advantages of MAE as a more sustainable and efficient alternative to conventional extraction techniques.

Microwave-assisted extraction (MAE) and digestion techniques have also significantly contributed to green analytical chemistry by reducing solvent consumption, enhancing efficiency, and minimizing waste. Recent advancements, such as the Ethos X Advanced Microwave Extraction System (Milestone Srl, Milan, Italy), have been successfully applied in environmental analysis, demonstrating their ability to efficiently process complex matrices while minimizing reagent use (Biale et al.) [95]. Additionally, the ultraWAVE system from Milestone utilizes high-pressure digestion chambers sealed with nitrogen, allowing for a reduction in acid volumes while maintaining uniform pressure and temperature conditions. These innovations align with green analytical chemistry principles by improving digestion efficiency, reducing reagent consumption, and minimizing environmental impact.

Similarly, ultrasound-assisted techniques, which employ high-frequency sound waves to create localized high-energy environments through cavitation, have found extensive applications in analytical processes. These techniques enhance mass transfer, accelerate reaction rates, and enable the use of milder conditions, aligning perfectly with the principles of green chemistry. Ultrasound-assisted extraction (UAE) [96] is particularly valued for its ability to extract compounds efficiently from complex matrices with minimal solvent and energy input. It has been successfully applied in the food industry for extracting natural flavors and in environmental science for isolating pollutants from soil or water samples.

Both techniques are increasingly integrated into modern workflows, often in combination with other advanced analytical methods like chromatography and mass spectrometry. Their versatility extends to fields such as nanomaterial synthesis, pharmaceutical analysis, and environmental monitoring, where they contribute to precision and sustainability. Additionally, their non-invasive and scalable nature makes them suitable for industrial applications, bridging the gap between laboratory research and real-world processes [92].

The role of microwave- and ultrasound-assisted methods extends beyond their practical benefits. They embody the spirit of green analytical chemistry by reducing reliance on hazardous chemicals, lowering energy demands, and minimizing waste generation. By enabling faster, cleaner, and more efficient analytical processes, these techniques not only enhance productivity but also underscore the potential of innovation to drive sustainability in the field of analytical chemistry. As research continues, further optimization and integration of these methods are expected, cementing their role as essential tools in the transition to greener analytical practices.

6.2. Application of Photo-Induced Processes in Analysis

Photo-induced processes have become increasingly important in analytical chemistry, offering innovative and sustainable solutions for various applications. These processes utilize light energy, often in the form of ultraviolet (UV), visible, or near-infrared (NIR) radiation, to drive chemical reactions or enhance analytical techniques. Their environmentally friendly nature, which often eliminates the need for hazardous reagents and reduces waste, aligns closely with the principles of green chemistry [97].

One prominent application of photo-induced processes is in photocatalysis, where light activates a catalyst to drive a chemical reaction. Photocatalytic methods have been effectively employed for the detection and quantification of pollutants, such as heavy metals and organic contaminants, in environmental samples. Titanium dioxide (TiO₂), a widely used photocatalyst, has shown remarkable efficiency in degrading complex pollutants under UV light, enabling both qualitative and quantitative analysis of environmental matrices [98]. Building on this, Chen et al. [99] developed a novel Al–TiO₂-ZIF-8-Ag composite sheet, which integrates the photocatalytic properties of TiO₂ with the enhanced adsorption capabilities of ZIF-8 and the SERS activity of Ag nanoparticles. This multifunctional material not only enables the sensitive detection of 4-aminothiophenol (4-ATP) at concentrations as low as 1 × 10⁻⁹ M but also achieves efficient photocatalytic degradation of the pollutant under UV light. The synergistic interaction among the components improves charge separation and electron transfer, enhancing both detection sensitivity and catalytic efficiency, making it a promising platform for real-time environmental monitoring and remediation.

Fluorescence spectroscopy [100] is another powerful example of a photo-induced process in analysis. Light-induced fluorescence has been extensively used for the detection of trace amounts of analytes, including biomolecules, pharmaceuticals, and toxins. Advances in fluorometric techniques, such as time-resolved fluorescence [101] and confocal fluorescence microscopy [102], have significantly enhanced sensitivity and selectivity, enabling detailed analysis of complex samples with minimal sample preparation.

Photo-induced reactions also play a crucial role in chromatography, where photochemical derivatization enhances the detectability of certain compounds. For instance, UV-induced derivatization can convert non-fluorescent analytes into fluorescent derivatives, improving their detection in high-performance liquid chromatography (HPLC) or gas chromatography (GC) systems. This approach minimizes the need for chemical reagents, reducing both cost and environmental impact [103].

Additionally, photo-electrochemical methods, which combine light and electrochemical processes, have emerged as a promising tool for real-time analysis. These methods utilize photoelectrodes to enhance the sensitivity of detection systems, particularly in applications such as biosensors and food quality analysis. They have proven highly effective for detecting trace analytes, such as glucose, pesticides, and pathogens, with excellent precision.

The application of photo-induced processes extends to cutting-edge fields like nanomaterial synthesis and photothermal imaging, where light energy enables precise manipulation of materials and detection of minute signals. These advancements not only improve analytical capabilities but also reduce the environmental footprint of analytical workflows by replacing energy-intensive and reagent-heavy methods.

Overall, photo-induced processes exemplify the convergence of innovation and sustainability in analytical chemistry. By harnessing the power of light, these methods enhance analytical efficiency, reduce environmental impact, and open new possibilities for complex analyses, making them indispensable in the pursuit of greener and more advanced analytical practices. As technology evolves, photo-induced processes are expected to play an even greater role in shaping the future of analytical chemistry.

7. Advances in Green Instrumentation

Green instrumentation has undergone significant advancements, focusing on sustainability, efficiency, and reduced environmental impact. Among these, the development of miniaturized and portable instruments has been a major milestone. These compact devices are designed to use fewer resources, generate less waste, and operate with minimal power consumption, making them ideal for field applications and laboratories alike. Portable spectrometers, chromatographs, and electrochemical analyzers allow on-site analysis of environmental samples, reducing the need for sample transportation and preservation, which often involve energy-intensive processes and additional waste. Furthermore, these instruments often require smaller sample volumes and reduced reagent use, aligning with the principles of green chemistry.

Trimpin et al. [104,105] pioneered Matrix-Assisted Ionization (MAI), a groundbreaking mass spectrometry technique that achieves ionization by exposing the matrix:analyte sample to sub-atmospheric pressure, without requiring lasers, high voltages, or heat. MAI offers exceptional sensitivity and selectivity, enabling the analysis of both volatile and non-volatile compounds while minimizing issues like sodium adduction and chemical background [106]. Its simplicity and robustness make it a valuable tool for complex biological and environmental analyses. This technique eliminates the need for high-energy inputs such as lasers, high voltages, or desolvation gases, offering enhanced sensitivity, robustness, and simplicity. Its applications span clinical diagnostics and pharmaceutical analyses, showcasing its potential to make mass spectrometry more sustainable and accessible [107]. Complementing this, Karki et al. [108] developed an automated, multi-ionization mass spectrometry platform that integrates matrix-assisted ionization (MAI), solvent-assisted ionization (SAI), and electrospray ionization (ESI). This innovative system supports high-throughput analyses while minimizing sample consumption and carryover, making it particularly effective for complex mixtures and pharmaceutical applications. Together, these advancements highlight a transformative shift toward greener, more efficient analytical methodologies in mass spectrometry [109,110,111].

Automation and chemometric approaches have also transformed green instrumentation, enabling higher efficiency and precision in analytical workflows. Automated systems streamline complex processes, such as sample preparation, data acquisition, and analysis, minimizing human intervention and errors [112]. These systems are often integrated with advanced software that optimizes reagent consumption and energy use. Additionally, chemometric tools, which involve multivariate statistical methods, enhance the analysis and interpretation of complex datasets, allowing for real-time monitoring and decision-making [113]. This not only improves the accuracy and reliability of results but also reduces the need for repetitive analyses, saving resources and time.

The integration of green instrumentation with emerging technologies, such as the Internet of Things (IoT) [114] and artificial intelligence (AI) [115], has further elevated the potential for sustainable practices. IoT-enabled devices can monitor and control instrument usage remotely, reducing unnecessary power consumption and enabling predictive maintenance to extend equipment lifespans. Similarly, AI algorithms can optimize analytical methods, such as selecting the most efficient solvent or energy settings, to reduce the environmental footprint of analyses.

However, it is also important to acknowledge that AI implementation often relies on high-performance computing infrastructure, which may have associated energy demands. While the benefits of AI in analytical chemistry, including improved efficiency and data-driven decision-making, are well documented [116], future developments should focus on balancing these advantages with energy-efficient computational models to ensure AI-driven solutions remain truly sustainable. It is important to distinguish between different types of AI, such as generative AI, predictive AI, and neural networks, as they vary in resource consumption and efficiency. Generative AI, while powerful, often requires extensive computational resources and energy for model training. In contrast, predictive AI and locally programmed neural networks are more efficient, consuming fewer resources while optimizing analytical workflows, shortening processing times, and improving data interpretation. These aspects make predictive AI and neural networks particularly suitable for green chemistry by optimizing workflows, reducing reagent use, and improving data analysis, thereby enhancing efficiency and sustainability”

These advancements reflect a growing commitment to sustainability in analytical chemistry. By reducing the physical and environmental footprint of instrumentation while enhancing performance, green instrumentation not only meets current analytical needs but also sets a new standard for environmentally conscious scientific practices. As these technologies continue to evolve, they are expected to play a central role in shaping a more sustainable future for analytical chemistry and beyond.

8. Discussion

As green analytical chemistry keeps evolving, there are still quite a few challenges to tackle to ensure it is adopted more widely and delivers long-lasting impact. One of the biggest hurdles is finding the right balance between analytical performance and environmental friendliness. While green methods aim to cut down on waste, energy usage, and toxic chemicals, they still need to meet the high expectations of precision and accuracy that modern applications demand. For example, switching to greener solvents like water or bio-based options can sometimes reduce analyte solubility or make separation less effective, which means there is still work to do to optimize these methods without giving up performance.

Another challenge is the lack of global collaboration and standardization in green analytical chemistry. While tools like NEMI, GAPI, and AGREE provide frameworks for assessing the “greenness” of analytical methods, they are fragmented and lack consistent benchmarks or universal guidelines [117]. This inconsistency makes it difficult for researchers, industries, and regulatory bodies to confidently compare and adopt these techniques. One of the biggest challenges in assessing the greenness of an analytical method is the lack of a universal way to weigh different environmental factors. Solvent toxicity, energy use, waste production, and hazard potential all contribute to a method’s overall impact but deciding which of these is most important or how much weight each should carry is not straightforward. For example, a method that eliminates toxic solvents may still require a large amount of energy, creating a trade-off that is hard to measure with a single score. Adding to the complexity, different assessment tools approach greenness evaluation in their own ways, often leading to inconsistent results. NEMI simplifies things with a yes-or-no classification for hazardous components, which is easy to interpret but does not capture varying levels of sustainability. GAPI expands on this with a scoring system across multiple categories, though it still requires some subjective judgment when assigning values. AGREE takes a more visual and algorithmic approach, trying to offer a balanced evaluation, but it can still struggle when applying a one-size-fits-all model to different types of analyses. Another challenge is that greenness assessments often focus on lab-scale experiments, making it hard to predict how these methods will perform in real-world industrial settings. Factors like instrument availability, regulatory requirements, and economic feasibility can affect whether a greener method is practical outside of a research lab. Life cycle assessment (LCA), which looks at a method’s long-term environmental footprint, could help fill this gap, but it is not yet widely used in routine greenness assessments.

Moving forward, researchers should work toward a more integrated approach—one that blends multiple assessment tools to provide a more complete picture of sustainability. A potential solution could be a hybrid framework that combines quantitative LCA data with qualitative green chemistry principles, making evaluations more accurate and meaningful. By recognizing these trade-offs and challenges, we can take steps toward a standardized, widely accepted system for greenness assessment, one that helps researchers and industries truly measure the environmental impact of their analytical methods. Harmonized global standards would provide an objective way to assess methods and promote sustainable practices more effectively. Additionally, increased collaboration between countries and sectors could accelerate progress by pooling resources, sharing ideas, and working towards common sustainability goals. Establishing global networks for green chemistry or creating platforms to share and refine green methods could play a pivotal role in addressing these gaps.

Then there is the potential of emerging technologies, like AI and digital tools, which offer exciting possibilities for making green analytical chemistry even better. Artificial intelligence and machine learning can help optimize workflows by figuring out the most efficient processes, reducing reagent use, or even predicting environmental impacts before experiments are performed. Digital tools, like IoT-connected devices or cloud-based systems, can improve real-time monitoring and remote management of instruments, cutting down on waste and resource consumption. There is even the idea of using digital twins, which is basically virtual models of systems to test how different processes impact the environment before they are tried in real life.

Looking forward, the future of green analytical chemistry really depends on how well it can adapt to new challenges, like climate change, resource shortages, and stricter regulations. By encouraging teamwork between different fields, investing in new technologies, and spreading awareness, the field can keep leading the way in creating solutions that are both effective and eco-friendly. These efforts are crucial for making sure green analytical chemistry stays at the heart of sustainable science and industry for the future.

9. Conclusions

GAC is paving the way for a more sustainable future in science, blending innovation with environmental responsibility. By incorporating the principles of green chemistry, such as reducing waste, using safer chemicals, and improving energy efficiency, GAC is transforming how we approach analytical methods. It is no longer just about achieving precise results—it is about doing so in a way that minimizes harm to the planet. From green solvents like water and bio-based alternatives to energy-saving techniques like microwave- and ultrasound-assisted processes, these advancements show that analytical chemistry can be both effective and eco-friendly.

While there has been incredible progress, challenges remain. Finding the right balance between performance and sustainability can be tricky, and there is still a need for global standards to guide the adoption of greener practices. But the future looks bright, thanks to emerging technologies like artificial intelligence and digital tools that are making it easier to optimize workflows, reduce waste, and streamline processes. As more industries and researchers embrace these approaches, GAC will continue to grow, helping us meet the demands of modern science without compromising the environment. With collaboration, innovation, and a shared commitment to sustainability, GAC has the potential to leave a lasting positive impact on both science and the world.