Modified GAPI (MoGAPI) Tool and Software for the Assessment of Method Greenness: Case Studies and Applications

Abstract

Abstract: The green analytical procedure index (GAPI) has been widely used to assess the greenness of different steps in analytical methodology. In the GAPI index, the different stages of the chemical analysis process are depicted using five pentagrams divided in subsections, labeled green, yellow, or red according to the degree of greenness. This GAPI tool provides a quick overview of the environmental impact and safety of the procedure. However, there is no total score that can be calculated from the GAPI metric to enable comparison between methods. In this work, a modified GAPI tool (MoGAPI) and software have been developed and applied to address the limitations of the current GAPI metric. The presented tool offers a more precise assessment of greenness, while the software simplifies and expedites its application. It also combines the advantages of the analytical Eco-Scale with the merits of the widely used GAPI metric. This tool was successfully applied to calculate the greenness of a few case studies and applications to show the applicability of this modified metric. The software for the MoGAPI tool is also freely available (open source) at bit.ly/MoGAPI to facilitate application and method comparison. The MoGAPI tool and its software represent a significant advancement in greenness assessment, providing researchers with a robust and user-friendly means to evaluate and compare analytical methods.

1. Introduction

Green analytical chemistry (GAC) has emerged as a critical element in promoting sustainable development within quality control and analytical laboratories [1]. The 12 principles of GAC, derived from green chemistry principles, provide a framework for developing environmentally friendly analytical processes [2]. Such efforts typically involve utilizing cleaner, less harmful solvents or eliminating solvents altogether, minimizing reagent consumption, reducing energy utilization, avoiding derivatization, and limiting waste production [3,4,5]. Developing and implementing green metrics is crucial in comparing the sustainability of current and new analytical methods [6,7].

Several tools are currently utilized to estimate the environmental impacts of analytical processes. These metrics include the analytical Eco-Scale [8], green analytical procedure index (GAPI) [9], and AGREE metric [10], which are widely employed besides other tools and modifications such as ComplexGAPI [7] and AGREEprep [11,12], due to their ease of use and applicability to a wide range of analytical techniques, including UV-vis spectrophotometry [13,14], spectrofluorometry [15,16], chromatography [17,18,19], and others. According to the Scopus database, the most commonly cited evaluation tools are the analytical Eco-Scale and GAPI, with 937 and 570 documents, respectively.

The analytical Eco-Scale assigns a score out of 100 based on several factors, including the nature and quantity of solvents and reagents used, energy consumption, occupational hazards, and waste generation and management [15]. However, it does not consider the severity or hazardous nature of pictograms when assigning hazard penalty points to chemicals. Additionally, it is not yet possible to obtain analytical Eco-Scale results using an online tool. It lacks the visual impact of the GAPI and the AGREE metric. Despite these limitations, the analytical Eco-Scale remains a valuable tool for providing quantitative information about the environmental impact of analytical procedures.

The green analytical procedure index (GAPI) evaluates the environmental hazards of the entire analytical methodology using five colored pentagrams for the different steps involved in the analytical methodology. Each pentagram assesses specific aspects of the methodology: sampling, type of method, sample preparation, solvents/reagents used, and energy consumption. The GAPI tool provides a quick and fast overview of the greenness of different steps of the analytical methodology, making it useful for evaluating and optimizing analytical methodologies to reduce environmental effects [3,14,20]. However, the GAPI tool does not provide a total score for each procedure to facilitate comparison between methods. This point is the main drawback related to its use, and it may be a possible element that could further limit the diffusion of this tool.

This work aims to introduce a modified GAPI (MoGAPI) tool and software that merges the advantages of the visual impact of GAPI with the precise total score of the analytical Eco-Scale. The software was applied to calculate the greenness of selected analytical methods.

2. Assessment of the Method Greenness

To evaluate method greenness, the MoGAPI tool and software were developed and applied. The tool not only provides the characteristic red/green/yellow pictograms of the commonly used GAPI tool but also provides an overall assessment of the method greenness by calculating a total score. The score is calculated based on the number of options available in each item. For example, there are three choices in sample collection: in-line, online, or offline. The maximum score is given to in-line collection (3 credits), while the minimum score is attributed to offline collection (1 credit). The total credits are then summed and divided by maximum possible credits to calculate the percentage score. If the question is not applicable, it will be excluded from the total score in order not to affect the percentage. For example, if there is no extraction during sample preparation, then the “not applicable” option should be selected, and the method in this case can still obtain 100% if the other green criteria are fulfilled. The detailed scoring system is detailed in

Table 1. Points system of the proposed MoGAPI (modified with permission from [7]).

Category	Color (Points)
	Green (3)	Yellow (2)	Red (1)
Sample preparation
Collection (1)	In-line	Online or at-line	Offline
Preservation (2)	None	Chemical or physical	Physicochemical
Transport (3)	None	Required	—
Storage (4)	None	Under normal conditions	Under special conditions
Type of method: direct or indirect (5)	No sample preparation	Simple procedures, e.g., filtration and decantation	Extraction required
Scale of extraction (6)	Nanoextraction	Microextraction	Macroextraction
Solvents/reagents used (7)	Solvent-free methods	Green solvents/reagents used	Non-green solvents/reagents used
Additional treatments (8)	None	Simple treatments (extract clean up, solvent removal, etc.)	Advanced treatments (derivatization, mineralization, etc.)
Reagents and solvents
Amount (9)	<10 mL (<10 g)	10–100 mL (10–100 g)	>100 mL (>100 g)
Health hazard (10)	Slightly toxic, slightly irritant; NFPA health hazard score is 0 or 1	Moderately toxic; could cause temporary incapacitation; NFPA = 2 or 3	Serious injury on short-term exposure; known or suspected small animal carcinogen; NFPA = 4
Safety hazard (11)	Highest NFPA flammability, instability score of 0 or 1. No special hazards.	Highest NFPA flammability or instability score is 2 or 3, or a special hazard is used.	Highest NFPA flammability or instability score is 4
Instrumentation
Energy (12)	≤0.1 kW h per sample	≤1.5 kW h per sample	>1.5 kW h per sample
Occupational hazard (13)	Hermetization of the analytical process	—	Emission of vapors to the atmosphere
Waste (14)	<1 mL (<1 g)	1–10 mL (1–10 g)	>10 mL (<10 g)
Waste treatment (15)	Recycling	Degradation, passivation	No treatment
ADDITIONAL MARK: QUANTIFICATION
Oval in the middle of GAPI: Procedure for qualification and quantification (5)		No oval in the middle of GAPI: Procedure only for qualification (1)

.

This pictogram evolution enables the GAPI tool to give an overall assessment of the greenness of analytical methods, instead of just evaluating each step separately. It also allows for more accurate and objective comparison between methods. Figure 1 shows four different methods assessed using the presented MoGAPI tool. The four methods exhibited a total score of 70, although each method has different green characteristics. Comparing these methods without a total score assigned to each method, depending on the entire analytical process, is not easy. For example, Method I has moderate greenness, as indicated by the multiple yellow sections. However, it is hard to compare Method I with Method II, which has more green sections, but at the same time, it has more red sections. This problem is more pronounced with Method III and Method IV. The proposed and developed evolution in the currently used GAPI scale not only allows comparison between these methods but also helps classify methods into excellent green (≥75), acceptable green (50–74), and inadequately green (<50), similar to the score used in the analytical Eco-Scale. The total score in this MoGAPI assessment appears on the chart, and the color of the scale around the pentagrams indicates the overall evaluation of the method. The software used to calculate the score and to generate the MoGAPI assessment is freely available (open source) at bit.ly/MoGAPI. It should be noted that a similar modification has been recently applied to ComplexGAPI to assign a total score, and an overall evaluation of analytical methods with pre-analytical procedures [21].

3. Case Studies

In the first application, a mixture of chloroform and dodecanol (30:70, v:v) was used for the dispersive liquid–liquid microextraction of four antiviral agents in environmental water, before analysis by HPLC-UV [22]. The stationary phase was a typical Hypersil ODS C18 column and the mobile phase consisted of ACN:phosphate buffer (50 mM, pH 6) (50:50, v:v). The samples were collected offline, with no preservation nor transportation required, stored under normal conditions, and microextracted using non-green solvent, without any additional treatment, with less than 10 mL of toxic solvent. The energy required for the instrument is ≤1.5 kWh per sample, with hermetic sealing and 1–10 mL waste per sample. As shown in Figure 2a, the total score is 70, which renders the method intermediate in greenness. The score was compared with the calculated greenness of the same method using the AGREE metric. As shown in Figure 2b, comparable results were obtained. It is worth mentioning that the two metrics do not have to give the same exact scores, but they should lead to the same conclusions.

In the second application, an ultrasound-assisted dispersive liquid–liquid microextraction was applied for the preconcentration of three gliflozins in deproteinized human plasma [23]. The extract was then determined using HPLC-DAD employing a C18 column and a mobile phase consisting of ACN:0.1% TFA pH 2.5, (40:60, v:v). The maximum enrichment was attained using dodecanol as an extractant. The samples were collected offline, with no preservation nor transportation required, stored under normal conditions, and microextracted using a green solvent, without any additional treatment, with less than 10 mL toxic solvent with no special hazards. The energy required for the instrument is ≤1.5 kWh per sample, with hermetic sealing and waste in the range 1 to 10 mL. As depicted in Figure 3a, the method has a total score of 80, which makes it overall green. A similar score was obtained when the method was assessed using AGREE (Figure 3b).

In the third application, a C18 column was dynamically modified using sodium dodecyl sulfate to introduce anionic functional groups on the surface of the column, thus enabling size exclusion of negatively charged analytes such as short-chain carboxylic acids in fruit juice and soft drink [24]. The analytes were separated using 1.84 mM sulfuric acid at pH 2.43 in less than 4 min. The samples were collected offline and stored under normal conditions, with no need for preservation or transportation. No microextraction or additional treatment was required. Less than 10 mL of low-toxicity solvents, with no special hazards, were used. The instrument required ≤1.5 kWh of energy per sample, and the process generated 1 to 10 mL of waste, all contained with hermetic sealing. The total score shown in Figure 4a was 79, which indicates the method’s greenness. The AGREE assessment gave a total score of 80, which leads to the same conclusion (Figure 4b).

The fourth application used a paper-based test strip designed for point-of-use quality testing of ethanol-based hand sanitizers [25]. The visual detection was dependent on complex formation between Fe³⁺ and methyl paraben in the presence of ethanol, where the latter is essential to dissolve methyl paraben. The samples were collected online, with no preservation, transportation, storage, or sample treatment required. Less than 10 mL of toxic solvents were employed with no special hazards. The energy required for the instrument is ≤1 kWh per sample, with hermetic sealing and waste less than 1 mL. The method had excellent greenness with a total score of 94 and 0.91 on MoGAPI and AGREE, respectively, as illustrated in Figure 5.

The reproducibility and reliability of the proposed score was assessed by evaluating the case studies by two independent experts and by comparing the scores obtained from MoGAPI with the scores obtained using AGREE. Statistical analysis was performed using Student’s t-test and F test. As indicated in

Table 2. Statistical comparisons between the proposed MOGAI metric and AGREE using Student’s t-test and F test.

Case Study	MoGAPI Score (%)	AGREE
Antivirals [22]	0.70	0.69
Antidiabetics [23]	0.80	0.79
Carboxylic acids [24]	0.79	0.80
Ethanol [25]	0.94	0.91
Student’s t-test	0.308
F test	0.877

, no significant differences between the metrics were observed, as indicated by the high p-values in both statistical tests at 95% significance levels.

4. Conclusions

A MoGAPI tool has been developed and successfully applied to assess the greenness of four reported methods. This modification of GAPI enables us to provide a visual overview of the environmental impact and safety of the method, while assigning a total score to each method. The case studies presented in this work demonstrate the practical utility and effectiveness of the MoGAPI tool in various analytical applications. The consistent results obtained using MoGAPI compared to other metrics like AGREE highlight its reliability and robustness in greenness assessment. In comparison to the analytical Eco-Scale, the MoGAPI offers a visual representation that provides insights into each step of the analysis process. Additionally, it can facilitate better comparisons between methods based on their total scores, particularly when the steps differ significantly. Moreover, the software facilitates faster and easier application of the MoGAPI. This MoGAPI tool provides a holistic assessment of method greenness, while the accompanying software makes application faster and easier. In future, the MoGAPI tool, supported by its user-friendly software, will undoubtedly serve as a valuable resource for researchers and practitioners aiming to develop and implement greener analytical methods. The continuous application and refinement of this tool will contribute to the broader goals of sustainability and environmental protection in analytical sciences. Applying this new metric to different analytical methods and techniques will be the focus of our future work.