The Green Component: Assessing the Environmental Impact of Analytical Methods

Green analytical chemistry (GAC) has emerged as a critical discipline focused on minimizing the environmental footprint of analytical methods. This article traces the evolution of GAC through the development of its key greenness assessment metrics. Beginning with foundational tools like the National Environmental Methods Index (NEMI), the field has progressed toward more holistic and user-friendly assessments. The introduction of Green Analytical Procedure Indexes (GAPI) and Analytical Greenness (AGREE) metrics established comprehensive frameworks, offering visual and quantitative evaluations of the entire analytical workflow. Recent advancements, including AGREEprep, Modified GAPI (MoGAPI), Carbon Footprint Reduction Index (CaFRI), and Analytical Green Star Analysis (AGSA), have further refined these assessments by addressing specific stages like sample preparation and incorporating lifecycle and climate impact considerations. A case study evaluating a sugaring-out liquid-liquid microextraction (SULLME) method using MoGAPI, AGREE, AGSA, and CaFRI illustrates how these complementary tools provide a multidimensional view of a method's sustainability, highlighting both its strengths in miniaturization and its weaknesses in waste management and reagent safety. This progression of metrics highlights the growing importance of integrating environmental responsibility into analytical science, enabling chemists to design, select, and implement methods that are both scientifically robust and ecologically sustainable.

Green analytical chemistry (GAC) emerged as an extension of green chemistry in 2000. GAC was specifically applied to analytical chemistry techniques and procedures to decrease or eliminate dangerous solvents, reagents, and other materials, while also providing rapid and energy-saving methodologies that maintain the validation parameters. GAC motivates analytical chemists to address health, safety, and environmental issues during analysis (1). This represents a shift in how analytical difficulties are approached while striving for environmental benignity.

The assessment of method’s greenness is crucial to ensure adherence to sustainability goals and environmental precautions. Traditional green chemistry metrics like E-Factor (2) or Atom Economy (3) are inadequate for assessing the greenness of analytical chemistry. To address this need, numerous greenness metrics have been established to contribute to the appraisal of analytical methods. These tools help chemists to evaluate whether an analytical procedure can be considered “green”. This article provides a comprehensive overview of the history of GAC and thoroughly investigates, conveys, and implements existing greenness assessment metric tools. Figure 1 summarizes the milestones in the development of greenness metrics for methods’ evaluation.

Metrics for Assessing the Greenness of Analytical Methods

Green chemistry was the first “color” introduced in the triadic model of evaluating analytical methods. This model later evolved into the broader framework of white analytical chemistry (WAC) (4), which integrates three color-coded dimensions: the green component focuses on environmental sustainability, the blue assesses methodological practicality, and the red evaluates analytical performance and functionality. Among these, the green component served as the cornerstone for the sustainable transformation of analytical science, stimulating the development of numerous tools and metrics to assess and compare the environmental impact of analytical procedures.

A foundational milestone in this evolution was the establishment of the National Environmental Methods Index (NEMI) which introduced a user-friendly pictogram indicating whether a method complied with four basic environmental criteria related to toxicity, waste, and safety. While it was widely appreciated for its simplicity and accessibility, NEMI’s binary structure limited its utility as it lacked the accuracy to distinguish degrees of greenness or assess the full analytical workflow (5-7).

To address the need for more quantitative evaluation, the Analytical Method Volume Intensity (AMVI) was introduced (8). AMVI focused solely on the total volume of solvents and reagents consumed per analytical run in high-performance liquid chromatography (HPLC) methods, providing a straightforward measure of material usage. While this approach contributed to minimizing chemical consumption, its narrow scope excluding considerations such as toxicity, energy usage, or waste management limited its comprehensiveness. As such, AMVI is best employed in combination with more holistic assessment tools. A broader, semi-quantitative approach appeared with the introduction of the Analytical Eco-Scale (AES) (9). This metric applies penalty points to non-green attributes, such as hazardous reagent use or high energy demand, which are subtracted from a base score of 100. The resulting score facilitates direct comparison between methods and encourages transparent evaluation. However, the method still relies on expert judgment in assigning penalty points and lacks a visual component, which may reduce its accessibility especially in educational contexts or for non-specialist users.

In response to these limitations, the Green Analytical Procedure Index (GAPI) was developed (10), offering a more comprehensive and visually intuitive approach. GAPI assesses the entire analytical process from sample collection through preparation to final detection using a five-part, color-coded pictogram. This allowed users to visually identify high-impact stages within a method. Despite its advantages, GAPI lacks an overall greenness score, and its color assignments can still be somewhat subjective.

The field advanced significantly with the emergence of Analytical Greenness (AGREE) (11), a tool based on in the 12 principles of GAC. AGREE provides both a unified circular pictogram and a numerical score between 0 and 1, enhancing interpretability and facilitating direct comparisons between methods. Its strength lies in its comprehensive coverage and user-friendly interface. However, it does not sufficiently account for pre-analytical processes, such as the synthesis of reagents or preparation of probes, and still involves subjective weighting of its evaluation criteria. To extend greenness evaluation into these pre-analytical phases, ComplexGAPI was introduced (12). This tool explicitly incorporates preliminary steps, making it especially relevant for material-based testing, where procedures before chemical analysis can be a significant source of environmental impact. While ComplexGAPI broadened the assessment scope, it added complexity to the pictogram and did not offer a cumulative score, limiting ease of comparison between methods. Efforts to overcome the limitations of previous tools led to the development of Modified GAPI (MoGAPI) (13) and ComplexMoGAPI (12). These modified versions retained the pictographic approach while introducing cumulative scoring systems to improve comparability and clarity.

In a different context, AGREEprep (14) was introduced as the first tool dedicated exclusively to evaluating the environmental impact of sample preparation. As this step often involves substantial solvent use, energy consumption, or hazardous reagents, AGREEprep addresses a crucial but often overlooked part of the analytical workflow. It provides both visual and quantitative outputs, enhancing usability; however, it must be used alongside broader tools for full method evaluation, as it focuses solely on sample preparation.

By 2025, rising global awareness of climate change influenced the development of the Carbon Footprint Reduction Index (CaFRI) (15), which estimates and encourages reduction of carbon emissions associated with analytical procedures. This tool aligns the goals of analytical chemistry with broader environmental targets. CaFRI considers the different stages in analytical methods can either directly or indirectly increase the carbon footprints. In the same year, AGSA was introduced as a novel metric that combines intuitive visualization with an integrated scoring system (16). AGSA uses a star-shaped diagram to represent performance across multiple green criteria including reagent toxicity, waste generation, energy use, and solvent consumption. The total area of the star offers a direct and visually compelling method comparison.

Case Study

In this case study, the environmental profile of the sugaring-out-induced homogeneous liquid–liquid microextraction (SULLME) method, developed for the determination of antiviral compounds (17), was systematically evaluated using a selection of widely recognized and recently developed GAC metrics. These include MoGAPI, AGREE, AGSA, and CaFRI, each offering a distinct perspective on the method’s sustainability and environmental footprint.

The MoGAPI score of 60 suggests a moderate level of greenness (Figure 2a). Several aspects contributed positively to this score, notably the use of green solvents and reagents, and the application of microextraction, which limits solvent consumption to less than 10 mL per sample. Additionally, the method does not require further sample treatment, minimizing environmental impact. However, the greenness is offset by certain drawbacks, such as the need for specific storage conditions, the use of moderately toxic substances, and the emission of vapors factors that raise concerns regarding operator safety and atmospheric release. Furthermore, the generation of more than 10 mL of waste per sample without any accompanying waste treatment strategy significantly detracts from its overall environmental sustainability.

The AGREE score of 56 reflects a reasonably balanced green profile (Figure 2b). The method aligns with several GAC principles, benefiting from miniaturization, semiautomation, and the absence of derivatization steps. The small sample volume (1 mL) and reduced procedural steps contribute to its operational efficiency. Although the inclusion of some biobased reagents is commendable, the continued use of toxic and flammable solvents presents both environmental and safety risks. Additionally, the method’s relatively low throughput processing only two samples per hour and moderate waste generation slightly reduces its overall green performance.

The AGSA tool, which integrates a star-shaped visual framework to assess factors such as automation, reagent safety, and process integration, assigned the method a score of 58.33 (Figure 2c). Strengths included the method’s semi-miniaturization and avoidance of derivatization. However, limitations were evident in the manual handling of samples, pretreatment steps, and the absence of integrated processes. The presence of six or more hazard pictograms, along with the combined use of renewable and non-renewable reagents, indicates potential for improvement in chemical selection. Moreover, the lack of any reported waste management practices highlights a continuing oversight in addressing the end-of-life stage of the analytical process.

The CaFRI score of 60 reflects a comprehensive life-cycle assessment of the method’s environmental footprint (Figure 2d). On the positive side, the analytical energy consumption remains within a relatively low range (0.1–1.5 kWh per sample), and no energy-intensive equipment is employed. However, the absence of clean or renewable energy sources and the lack of CO₂ emissions tracking limit the method’s alignment with climate-focused sustainability goals. Other environmental burdens include transportation over long distances using non-ecofriendly vehicles and the absence of a defined waste disposal procedure. Additionally, the use of over 10 mL of organic solvents per sample further undermines the overall sustainability of the procedure.

These metrics provide a multidimensional evaluation of the SULLME method, demonstrating both its strengths such as reduced solvent use and avoidance of derivatization and its limitations, particularly in waste management, reagent safety, and energy sourcing. The application of diverse greenness tools indicating the importance of using complementary metrics to achieve a comprehensive and realistic assessment of sustainability in analytical practice.

Conclusion

The evolution of greenness metrics in analytical chemistry reflects a growing global commitment to sustainable scientific practices. From early binary tools like the NEMI to the advanced, multidimensional models such as AGREE, MoGAPI, and AGSA, the field has significantly matured, enabling more nuanced and actionable evaluations of environmental impact. These tools empower analysts to go beyond method performance and consider chemical toxicity, energy consumption, waste generation, and broader lifecycle effects. The application of these metrics to the SULLME method for antivirals determination highlights their practical value: while the method demonstrates commendable green attributes such as low solvent volume, partial automation, and green reagent use, it also reveals critical areas for improvement, notably in vapor emissions, transportation logistics, and waste disposal. Ultimately, the integration of greenness assessment into routine method development is no longer optional. By embracing these tools, analysts can align with global sustainability goals, reduce laboratory footprints, and contribute to a greener future for analytical science.

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Fotouh R. Mansour is with the Pharmaceutical Analytical Chemistry Department of the Faculty of Pharmacy at Tanta University, in Tanta, Egypt, and the Medicinal Chemistry Department of the Faculty of Pharmacy at King Salman International University (KSIU), in South Sinai, Egypt. Alaa Bedair is with the Department of Analytical Chemistry of the Faculty of Pharmacy at the University of Sadat City, in Sadat City, Egypt. Mahmoud Hamed is with the Pharmaceutical Chemistry Department of the Faculty of Pharmacy at Misr International University in Cairo, Egypt, and the MIU Chemistry Society (MIU-CS) of the Faculty of Pharmacy at Misr International University, in Cairo, Egypt. Adrián Fuente-Ballesteros, José Bernal, and Ana M. Ares are with I. U. CINQUIMA, in the Analytical Chemistry Group (TESEA) of the Faculty of Sciences at University of Valladolid, in Valladolid, Spain. Direct correspondence to fotouhrashed@gmail.com and adrian.fuente.ballesteros@uva.es