Trends in Analytical chemistry 50 (2013) 78–84

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Trends in Analytical chemistry

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Review

The 12 principles of green analytical chemistry and the SIGNIFICANCE mnemonicof green analytical practices

Agnieszka Gałuszka a, Zdzisław Migaszewski a, Jacek Namiesnik b,⇑a Geochemistry and the Environment Div., Institute of Chemistry, Jan Kochanowski University, 15G Swietokrzyska St., 25-406 Kielce, Polandb Department of Analytical Chemistry, Chemical Faculty, Gdansk University of Technology (GUT), 11/12 G. Narutowicz St., 80-233 Gdansk, Poland

a r t i c l e i n f o a b s t r a c t

Keywords:Energy reductionGreen analytical chemistry (GAC)Green chemistry principlesMiniaturized methodsMinimization of analytical wasteNatural reagentRisk reductionSafe reagentWaste reduction12 principles of green analytical chemistry(GAC)

0165-9936/$ - see front matter � 2013 Elsevier Ltd. Ahttp://dx.doi.org/10.1016/j.trac.2013.04.010

⇑ Corresponding author. Tel.: +48 58 347 10 10; FaE-mail address: chemanal@pg.gda.pl (J. Namiesnik

The current rapid development of green analytical chemistry (GAC) requires clear, concise guidelines inthe form of GAC principles that will be helpful in greening laboratory practices. The existing principles ofgreen chemistry and green engineering need revision for their use in GAC because they do not fully meetthe needs of analytical chemistry.

In this article we propose a set of 12 principles consisting of known concepts (i.e. reduction in the use ofreagents and energy, and elimination of waste, risk and hazard) together with some new ideas (i.e. theuse of natural reagents), which will be important for the future of GAC.

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Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 782. The 12 principles of GAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 793. The key components of green analysis – a backbone of GAC principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

3.1. Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 793.2. Methods and instruments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 803.3. Reagents and safety of the operator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 823.4. Analytical wastes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

4. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

1. Introduction

The idea of green chemistry has its roots in sustainabledevelopment. The first activities undertaken by chemists for sus-tainability were focused mostly on industrial-scale processes andproducts, as clearly postulated in the most widely known defini-tion of green chemistry proposed by Anastas [1]. The beginningsof green chemistry were dominated by the subject of green organicsynthesis in different branches of the chemical industry, especiallythe pharmaceutical industry.

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x: +48 58 347 26 94.).

Green analytical chemistry (GAC) emerged from green chemis-try in 2000 [2]. This relatively new area of activity within greenchemistry concerns the role of analytical chemists in making labo-ratory practices more environmentally friendly, and it has gained agreat deal of interest among chemists [3–5]. Aside from thedevelopment in instrumentation and methodologies, which arenecessary for improvements in the quality of chemical analyses, ef-forts are being made to reduce the negative impact of chemicalanalyses on the environment and to enable implementation of sus-tainable development principles to analytical laboratories. In thiscontext, GAC should be recognized as a stimulant to the progressof analytical chemistry. The most important challenge to the futureof this discipline is to reach a compromise between the increasingquality of the results and the improving environmental friendliness

A. Gałuszka et al. / Trends in Analytical chemistry 50 (2013) 78–84 79

of analytical methods. Guidelines that provide the framework forGAC are needed to meet this challenge.

In 1998 Anastas and Warner [6] formulated the 12 principles ofgreen chemistry. Designed to meet the needs of synthetic chemis-try, only some of these principles can directly be applied to analyt-ical chemistry. The principles that find such application for bothsynthetic and analytical purposes are:

(i) prevention of waste (principle number 1);(ii) safer solvents and auxiliaries (principle number 5);

(iii) design for energy efficiency (principle number 6); and,(iv) reduction of derivatization (principle number 8).

Efforts were also made to find analytical consequences of the 12principles of green chemistry [7], but at least one of the 12 princi-ples – the maximization of atom economy (principle number 2) –is inadequate for analytical chemistry. There are also importantconcepts in GAC that have not been included in the 12 principlesproposed by Anastas and Warner [6]. Considering this, we suggestthat the 12 principles of green chemistry should be revised to findfull application in analytical chemistry. In our proposal, we usedfour of the principles provided by Anastas and Warner [6] and sup-plemented them with eight new principles that find their impor-tant application to GAC.

2. The 12 principles of GAC

In our approach, the 12 principles of GAC are as follows:

1. Direct analytical techniques should be applied to avoidsample treatment.

2. Minimal sample size and minimal number of samples aregoals.

3. In situ measurements should be performed.4. Integration of analytical processes and operations saves

energy and reduces the use of reagents.5. Automated and miniaturized methods should be selected.6. Derivatization should be avoided.7. Generation of a large volume of analytical waste should be

avoided and proper management of analytical waste shouldbe provided.

8. Multi-analyte or multi-parameter methods are preferredversus methods using one analyte at a time.

9. The use of energy should be minimized.10. Reagents obtained from renewable source should be preferred.11. Toxic reagents should be eliminated or replaced.12. The safety of the operator should be increased.

We also propose the mnemonic SIGNIFICANCE (Fig. 1) followingthe idea of the mnemonic of the condensed 24 principles of green

Fig. 1. The principles of green analytical chemistry expressed as the mnemonicSIGNIFICANCE.

chemistry and green engineering ‘‘IMPROVEMENTS PRODUC-TIVELY’’ [8,9].

3. The key components of green analysis – a backbone of GACprinciples

Modern analytical chemistry offers many techniques andinstruments for determination of a given analyte in different sam-ples. The key goals to be achieved in greening analytical methodsare:

(1) elimination or reduction of the use of chemical substances(solvents, reagents, preservatives, additives for pH adjust-ment and others);

(2) minimization of energy consumption;(3) proper management of analytical waste; and,(4) increased safety for the operator.

Most of these issues require reductions (e.g., sample number,reagents, energy, waste, risk and hazard) [10].

One of the drawbacks of greening laboratory practices is theneed for compromise between the performance parameters andGAC requirements. Most of the guidelines for analytical chemistsproposed in our 12 principles may cause the decrease of perfor-mance parameters such as accuracy, precision, sensitivity (Table 1).The reliability of analytical methods may easily be questioned inminimizing sample size, applying direct methods and miniaturiz-ing instruments. However, rapid technological development andknowledge about existing problems will lead to improvements ingreen analytical methods. Sometimes, these problems can besolved in simple ways (e.g., modifying in-situ measurements to im-prove calibration by running standards between samples) [11].

Chemical analysis is a complex process consisting of severalsteps, for which green alternatives can be employed. It is importantto evaluate each of the processes and the operations that are com-ponents of analytical methodology for their agreement with theprinciples of green chemistry. In our recent paper [12], weintroduced such a green analytical evaluation tool – an analyticalEco-Scale – which will be helpful for finding and improving theweakest link in the method.

Despite the diversities of analytical methods and analytesdetermined, a sample and an operator take part in every analysis.Most of the methods also require the use of at least one reagentand produce analytical waste. Although chemical analysis is a pro-cess comprising several steps influencing each other, we find six is-sues critical for GAC principles (Fig. 2). Table 2 compares less greentechniques used for determination of the same analyte in the samematrix with their greener alternatives. This comparison, based ondifferent analytical applications (environmental, food, pharmaceu-tical, industrial and biomedical) has some practical implications forthe use of green techniques. Most of recently introduced greenanalytical procedures [14,16,22,26,30] are characterized by notonly environmental friendliness, but also relatively high sensitiv-ity, low cost of analysis, lower energy consumption, simplicityand efficiency in using time. Thus, it is very likely that some tradi-tional methods will soon be replaced by these new greentechniques.

3.1. Sampling

Except for the use of direct analytical techniques, every analysisbegins with sampling. According to the second principle of GAC,the number and the size of samples should be minimal. This prin-ciple has special importance in environmental sample analysis be-cause the sampling strategy can easily be modified. Twoapproaches may be used to reduce the number of samples. The first

Table 1Practical consequences of GAC principles for selected parameters of analytical process.

STEPS IN ANALYSIS PARAMETERS OF THE ANALYTICAL PROCESS

Representativeness Accuracy Precision Selectivity Sensitivity Detectability

SamplingMinimal sample sizeMinimal sample number 0 0 0 0 0Sample treatmentWithout derivatization 0Minimal use of energy 0Reagents from renewable source 0Without toxic reagents 0Safety for operator 0MeasurementDirectIn-situ *

Integrated operations and processes 0 0 0Automation 0Miniaturized instrumentsMulti-analyte and multi-parameter 0 0 0 0 0 0Minimal use of energy 0

NOTE: – decrease; – increase; 0 – neutral effect.* method dependent

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involves the use of non-invasive methods, such as different geo-physical techniques (e.g., remote sensing, seismic and magneticsurveys), [35], or instruments (e.g., portable XRF) [36,37] for fieldscreening, and selection of sampling sites for a detailed chemicalstudy. The second is to use statistics for selection of sampling sitesto obtain maximum data for reliable interpretation of the resultswith a minimal sample number. A barbell cluster ANOVA designmay be given as an example [38].

Reduction of sample size can be obtained through the applicationof miniaturized analytical methods [39] or alternative sample-introduction systems (e.g., laser ablation of solid samples by LA-ICP-MS). Reductions in sample number and volume should be donecarefully with awareness of the possibility of losing sample repre-sentativeness, especially in sampling heterogeneous materials.

Fig. 2. Important components of analytical procedures in the aspect of GAC.

3.2. Methods and instruments

Selection of the greenest method from all the methods meetingthe needs of the user (e.g., detection limits, and accuracy), whichare available for a given analyte, is critical for GAC. This is why fiveof the 12 GAC principles refer to the method. Ideally, direct, auto-mated, miniaturized analytical techniques are the greenest option(principles number 1, 3 and 5). Important also is integration ofanalytical processes and operations (principle number 4) becausesuch an approach makes it possible to obtain all information froma single analysis. Integration of analytical systems is best exempli-fied by microdevices, in which different steps of chemical analysis(e.g., mixing, reaction and separation) are performed. A goodexample of this approach is a successful application of integratedmicrochip capillary electrophoresis-electrochemical detection forsimultaneous determination of trace amounts of metals (e.g., Pb,Cd and Cu) in vegetable juices [40]. It was shown that this simple,quick technique has high resolution and sensitivity, requires smallamounts of sample and reagents, and is competitive with tradi-tional analytical techniques.

Moreover, in many cases, it is necessary to determine more thanone analyte or parameter in one sample. In this case, multi-analyteor multi-parameter methods should be preferred (principle num-ber 8). These methods are of special importance in environmentalmonitoring, when more than one analyte should be determined,for instance in determination of potentially toxic trace elements.Instead of time-consuming and reagent-consuming techniques(e.g., atomic absorption spectrometry), a multi-element technique(e.g., inductively coupled plasma mass spectrometry) will be moresuitable. It is preferable to avoid derivatization and other addi-tional steps in analysis (principle number 6) because they consumereagents and generate waste. If derivatization cannot be avoided, itmay be integrated with other processes (e.g., filtration, and extrac-tion) in a single system [41]. The use of remote sensing, portableinstruments and miniaturized systems are often considered thegreenest methodologies [42–44]. Their advantages in the light ofGAC principles are summarized in Fig. 3.

Each analytical methodology is characterized by its own specificrequirements and problems. Thus, it is important to evaluate andto improve the greenness of an analytical method or techniqueand to focus on its least green aspect. In GAC literature, there aregood examples of reviews on green spectroscopy [45,46], greenelectrochemistry [44] and green chromatography [47–50]. Some

Table 2Examples of green alternatives to conventional methods in different fields of analytical chemistry.

Less green alternative Greener alternative Refs.

Determination of lead in waterGF-AAS Stripping voltammetry [13,14]Advantages Disadvantages Advantages DisadvantagesSelective, sensitive,

accurateRequires preconcentration, consumesreagents, produces wastes, time- andcost-consuming

Low detection limits, sensitive, simple,rapid, reliable, inexpensive, possible touse in-situ

Possible interferences with other metals,needs monitoring of electrode stability

Determination of nitrate in tap waterHPLC Microchip electrophoresis [15,16]Advantages Disadvantages Advantages DisadvantagesRapid, small sample

volume, low cost, highsensitivity, accuracyand selectivity

Poor repeatability, consumes reagents Small sample volume, reduced reagentand energy use, automated, rapid

Often poor reproducibility and sensitivity

Determination of atrazine in waterSpectrophotometry Electrochemical biosensor [17,18]Advantages Disadvantages Advantages DisadvantagesSimple, rapid,

inexpensiveConsumes reagents, produces wastes,poor sensitivity and selectivity

Rapid, high sensitivity, inexpensive andsimplified procedures

Poor stability and short life-time ofenzymes, time-consuming preparation ofimmuno-reagents

Determination of 17b-estradiol in waterGC-MS Electrochemical sensor [19,20]Advantages Disadvantages Advantages DisadvantagesSelective, sensitive,

accurate, lowdetection limit

Requires the use of toxic reagents,produces wastes, needs heavylaboratory workload, time-consuming

Simple and fast, low detection limit,highly sensitive, portable, rapid, lowenergy consumption

Time-consuming preparation of immuno-reagents

Determination of bisphenol A in urban wastewaterGC-MS Electrochemical sensor [21,22]Advantages Disadvantages Advantages DisadvantagesHigh selectivity and

sensitivity, accurate,low detection limit

Multi-stage sample treatment, usestoxic reagents and produces wastes,sometimes low reproducibility, requiresderivatization

High sensitivity, and accuracy, goodselectivity, in-situ measurement, rapid,low energy consumption, low cost

Sometimes poor reproducibility, in case oftraditional sensors determination ofbisphenol a is problematic because of thepoor response

Determination of Hg in soilsSpectrophotometry Solid sampling GF-AAS [23,24]Advantages Disadvantages Advantages DisadvantagesSimple, rapid,

inexpensiveConsumes reagents, produces wastes,poor sensitivity and selectivity

Direct determination, cost-effective,fast, reliable results for the purpose ofscreening

Possible loss of analyte due tovolatilization

Determination of total petroleum hydrocarbons in soilsGC-FID Hand-held FTIR [25,26]Advantages Disadvantages Advantages DisadvantagesLow detection limits,

high-sensitivity toabroad range ofhydrocarbons,economic

Matrix effect, low resolution, time-consuming, use of toxic reagents,production of toxic wastes, destructivetechnique,

In-situ measurements, no reagentsconsumed, fast, no need for sampletreatment, simple and cost-effective,non-destructive

High detection limit, mostly for screeningpurposes

Determination of trace metals in alloysF-AAS LA-ICP-MS [27,28]Advantages Disadvantages Advantages DisadvantagesSimple, economic,

accurate, selective,and sensitive

Needs preconcentration, time-consuming sample treatment, consumesreagents, produces toxic and corrosivewastes

Non-destructive, small sample size, noneed of sample treatment

Expensive, needs professional experience,suffers from interferences

Determination of folic acid in pharmaceuticalsSpectrophotometry Electrochemical biosensor [29,30]Advantages Disadvantages Advantages DisadvantagesSimple, rapid,

inexpensiveHigh detection limit, instability of thecolored product formed, consumesreagents and produces wastes

Simple and inexpensive, requires smallamount of sample

Poor sensitivity, time-consumingpreparation of immuno-reagents

Determination of blood glucoseSpectrophotometry Biosensor [31,32]Advantages Disadvantages Advantages DisadvantagesSimple and rapid,

economicUses toxic and corrosive reagents,produces wastes, high detection limit

Real-time analysis, small samplevolume, economic

Poor accuracy, possible interferences,possible errors from incorrect use

(continued on next page)

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Fig. 3. Advantages of portable instruments, remote sensing and miniaturizedsystems in the context of GAC principles.

Table 2 (continued)

Less green alternative Greener alternative Refs.

Determination of mercury in wineET-AAS Atomic fluorescence spectrometry [33,34]Advantages Disadvantages Advantages DisadvantagesAccurate, simple and

preciseTime-consuming sample treatment,consumes reagents, produces wastes

High sensitivity, simplicity, rapidness,cost-effectiveness, uses sample matrixas a reductant, no sample treatment

Relatively high detection limit

NOTE: AAS, Atomic absorption spectrometry (GF, Graphite furnace, F, Flame, ET, Electrothermal); HPLC, High-performance liquid chromatography; GC-MS, Gas chroma-tography with mass spectrometry; GC-FID, Gas chromatography with flame-ionization detector; FTIR, Fourier-transform infrared spectroscopy; LA-ICP-MS, Laser-ablationinductively coupled plasma mass spectrometry.

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of the published GAC reviews are devoted to a specific step of ana-lytical procedure (e.g., sample treatment) [51].

The instrument is directly linked to the method. In general, for thepurpose of GAC, instrumental methods are preferred, but there mayalso be some classical, wet chemistry methods that are as green asthe instrumental ones (e.g., procedures for determination of Cu ina brass sample by titration, electrogravimetry and AAS – Tables 3–5 in [12]). The problem that still needs discussion in GAC is the largeecological footprint of the production and the maintenance of ana-lytical instruments, which can be fully understood and amelioratedthrough assessing the life-cycle of analytical instruments. Auto-mated and miniaturized instruments reduce the amounts of re-agents consumed and waste generated (GAC principle number 7),increase the safety of the operator (GAC principle number 12) and fa-vor proper waste treatment (GAC principle number 7) [52].

The best example of miniaturization and integration of pro-cesses and operations (GAC principle numbers 4 and 5) is providedby miniaturized total analysis systems (lTAS), in which sampletreatment and measurement are located extremely close to eachother. First introduced in 1990 [53], these systems quickly becamevery popular and found their applications mostly in clinical/bioan-alytical and environmental laboratories [54]. Another clear advan-tage of lTAS is the minimal sample and reagent volumes (betweenpL and nL), which is favored for GAC (GAC principle number 2).

3.3. Reagents and safety of the operator

Elimination or replacement of toxic, persistent reagents show-ing bioaccumulative properties with their more environmentally

friendly equivalents is an important trend in GAC (GAC principlenumber 11). The majority of reagents to be replaced in analyticalprocedures are organic solvents [55]. Ionic liquids and supercriticalfluids are considered as alternative (green) solvents. Different ionicliquids, mostly based on quaternary nitrogen cations, have foundwide application in chromatographic and electromigration tech-niques, electrochemistry and spectroscopy [56–58]. Except forserving as alternative solvents for extractions [59], ionic liquidscan be used as stationary phases in gas chromatography [60].

Green alternatives for extraction with traditional solvents aresupercritical fluid extraction (SFE) and a subcritical water extrac-tion (SWE). Advantages of supercritical CO2 as an alternative sol-vent made SFE one of the most popular sample-preparationtechniques in chromatography [61]. Application of supercriticalfluids in chromatography resulted in the introduction of capillarycolumn supercritical fluid chromatography (SFC) and packed col-umn SFC [62].

One of the recent trends in GAC is the use of reagents obtainedfrom renewable sources in analysis (GAC principle number 10).Plants, animals, microorganisms and their extracts may be usedas the pH and redox indicators, reagents for spectrophotometry,fluorimetry or applied in biosensors [63]. Despite their limitationsin quantitative analysis, the green natural reagents may be used inteaching analytical chemistry [64]. One of the priorities in sustain-able development is to reduce the use of non-renewable resourcesin favor of renewables. This should stimulate the progress of ana-lytical methods utilizing natural reagents.

Safer (less toxic, natural) reagents contribute to increase thesafety of the operator (GAC principle number 12). However, reduc-ing the risk for the operator is also ensured through the use ofautomated instrumental methods, miniaturized systems, and on-line decontamination of analytical waste [3].

3.4. Analytical wastes

Analytical methods differ in the volume of waste produced.Greenest are methods that generate no waste or generate only asmall volume of waste (i.e. <50 mL(g)) [65]. In general, the moresteps in an analytical procedure and the more reagents consumed,the higher the volume of analytical waste. Thus, reduction in theuse of reagents by the methods discussed above contributes tominimizing the production of waste.

Another important issue is ensuring the proper treatment ofanalytical waste (GAC principle number 7). The toxicity of wastemay be reduced through recycling, degradation and passivationof waste, preferably performed on-line [66].

4. Conclusion

Most analytical methods cannot be considered green and theyneed certain improvements through eliminating toxic reagents,reducing the use of reagents and energy, and increasing operatorsafety. Changes are needed in the whole analytical process, begin-

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ning with sampling and ending with treatment of analytical waste.These changes may be made with the help of different strategies,including:

(1) use of chemometrics and statistics for the reduction of thenumber of samples;

(2) use of integrated analytical systems for improvement of ana-lytical efficiency;

(3) reduction of reagent use;(4) application of less toxic, preferably natural reagents; and,(5) miniaturization of methods to decrease the risk to the oper-

ator and environmental hazard.

The GAC principles will provide essential guidelines for makinganalytical laboratories greener. Considering the diversity of analyt-ical methods and their demands, it is impossible to formulate prin-ciples that would be universal for all possible applications. Ourproposal may be considered as rather a general approach that willbe necessary for future quantitative assessment of specific analyt-ical processes and operations.

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