Are We Greenwashing Analytical Chemistry?

• What?
• I have no idea.
• Maybe, because it’s a buzzword these days, right?
• I don’t know enough about the green, never mind the wash.
• Nah, it’s just what the focus is on these days.

These are five responses from colleagues and friends when I recently put this question to them.

I guess the range of response reflects my own knowledge and opinion, until very recently, when I started to think more on the subject.

I’ve held some opinions up to this point. The fact that companies surely could have more impactful sustainability targets than the relatively minor contributions from their analytical department. That really, I’m too busy to properly think about sustainability in a meaningful way. That sustainability appears to be getting more airtime and there are one or two companies who seem to be taking the lead while others seem to be milking it a little.

If this paints a dim picture, at least you know I’m honest.

Perhaps my redemption is that recently, I have started to become much more interested in the greening of analytical chemistry. Why, I cannot say. There was, to my knowledge, no catalytic event, no “road to Damascus” experience. Maybe there was just a point where I had enough time to do a little background research and begin to apply further thinking on how to reduce our environmental impact and play our part in the global green initiative.

There are few people on our planet who are unaware of the importance of reducing waste, cutting energy consumption, and lowering humanity’s carbon footprint. I’m more than aware of the effect we have on our planet and its climate, and that I must dutifully reduce, reuse, and recycle wherever possible. So, what do I need to know to be a good global and corporate citizen in the laboratory?

I started with the 12 Principles of Green Chemistry, developed by Paul Anastas and John Warner in 1998 (1):

• Waste Prevention – prevent waste rather than being smart about dealing with it.
• Atom Economy – reduce waste at a molecular level by ensuring atoms from reagents are included in the final chemical product.
• Less Hazardous Synthesis – chemical reactions and synthesis designed to be as safe as possible.
• Designing Safe Chemicals – minimize toxicity and environmental fate by molecular design.
• Safe Solvents and Auxiliaries – choose the safest solvents available and use the least amount of solvent and other reagents.
• Design for Energy Efficiency – choose the least energy intensive chemical route.
• Use Renewable Feedstocks – use chemicals made from renewable (organic) rather than petrochemical sources.
• Reduce Derivatives – minimise the use of temporary derivatives such as protecting groups, to reduce reaction steps, required resource and waste creation.
• Catalysis – use catalytic rather than stoichiometric reagents.
• Design for Degradation – design for chemicals that degrade and can be more easily discarded without bioaccumulation or environmental persistence.
• Real-time Pollution Prevention – monitor reactions in real time to prevent the formation or release of polluting substances.
• Safer Chemistry for Accident Prevention – develop chemical reactions which are inherently less hazardous and minimize risk.

My initial reaction was that there were one or two “interesting” thoughts here. I can get on board with waste reduction, use of safer solvents, energy efficiency and real time monitoring, because that sounds like analytical chemistry. However, this generally felt like a manifesto for synthetic organic chemists. Nothing wrong with that, but I’m a different type of chemist, with different considerations. I really hope I’m bringing you along on this forthright thought process and that you haven’t disowned me at this point. I just need something more tangible to really spark my thought processes on analytical sustainability.

Next came the 12 principles of Green Analytical Chemistry (GAC) by Agnieszka Gałuszka et. al. from 2013 (2):

1. Direct analytical techniques should be applied to avoid sample treatment.
2. Minimal sample size and minimal number of samples are goals.
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 should be provided.
8. Multianalyte or multiparameter methods are preferred versus methods using one analyte at a time.
9. The use of energy should be minimized.
10. Reagents obtained from renewable sources should be preferred.
11. Toxic reagents should be eliminated or replaced.
12. The safety of the operator should be increased.

Okay, so now, you really have my attention. I’m into process automation and integration. I like saving energy and reducing waste because it saves me money. I don’t like derivatization because the reactions are clumsy and the reagents generally must be handled in fume cupboards. Finally, I like multivariate analysis because I understand it and one-factor-at-a-time (OFATO) method development approaches waste time and are, frankly, less interesting. I also like analyses which can cover all relevant analytes in a single method. Whilst a detailed treatment of each of the principles is outside the scope of this article, an excellent discussion can be found in references 2 and 4.

After further consideration of the GAC principles, I began to think that maybe, even unconsciously, I’d been following a few of these principles and steering a greener course over recent years.

We all know that column geometry has been reducing over time. 150 x 4.6mm were the norm at the turn of the century; now, anecdotally, I’d say that 100 x 2.1mm is the new normal. This has been facilitated by the introduction of smaller particle sizes and superficially porous particles. Of course, reduced column dimensions and particle sizes typically result in lower solvent usage and higher efficiency separations.

Higher efficiency chromatography leads to an increase in the number of analytes which can be separated per injection (peak capacity) and the reduction in column geometry drives lower sample (or at least injection) volumes, both directly in line with the principles of green chemistry.

It's been a very long time since I used normal phase chromatography, whose eluent systems are organic solvents. This is primarily due to the introduction of reversed phase stationary phases with polar functional groups and of hydrophilic interaction chromatography (HILIC), both of which are designed to retain and separate more polar analytes. It’s also very unusual to use THF in reversed phase eluent systems, and the use of primary amines as eluent modifiers to improve peak shape of basic compounds is no longer required due to improvements in bonded phase silica technology. Silica that can be used at more extreme pH values have also led to less usage of ion-pairing reagents.

This reduction in the use of more toxic solvents and additional reagents is directly in line with the principles of green chemistry.

A “waste” feature that I hadn’t previously considered is the use of paper within the laboratory. I think it’s fair to say that we are doing reasonably well in reducing paper usage; consider the use of data systems to produce a result in silico and the use of LIMS and electronic signatures which reduce the requirement to print out methods, data, and results for wet ink signatures as part of our quality compliance.

All this to say, I’m starting to feel a little better about my previously lackadaisical approach to green approaches and have even started using a nice GREEN calculator to characterise the green credentials of each of my analytical methods (3,4). This is a nice tool which produces an easy to interpret graphical output indicating the “weighted score” for each of the 12 GAC principles.

So, what of sample preparation? I feel that to properly consider the green credentials of an analytical method, we need to consider any sample preparation operations, which can obviously involve solvents, reagents, and energy consumption. The AGREE tool excludes these aspects via its first principle, which is to avoid or exclude sample preparation wherever possible. Here is where I found the AGREEprep tool and another set of green principles, termed Green Sample Preparation (GSP) (5,6). Whilst the principles are similar in nature to those of the GAC list, the tool and its accompanying tutorial materials, make it reasonably straightforward to rank various sample preparation techniques and signpost possible improvements in the green credentials of your method.

• Favour in situ sample preparation.
• Use safer solvents and reagents.
• Target sustainable, reusable, and renewable materials.
• Minimize waste.
• Minimize sample, chemical and material amounts.
• Maximize sample throughput.
• Integrate steps and promote automation.
• Minimize energy consumption.
• Choose the greenest possible post-sample preparation configuration for analysis.
• Ensure safe procedures for the operator.

Again, this list appeals to me, as I recognise several areas which have been the focus of development activities in our industry over recent years.

I’ve long been an advocate of automation, especially instrument top automation, which drives miniaturization. The adoption of automation has been facilitated by the reduction in system and column volumes and the ever-increasing sensitivity of detectors, including mass spectral detectors, which are not challenged by the reduced sample volumes typically used by automated systems. Further, the speed and flexibility of instrument top automation favours the Design of Experiments approach to analytical development and multi-variate analysis. Methods can be developed in an unattended fashion with multiplexed screening of columns and analytical variables. The green benefits here are obvious; however, we often overlook Principle 10 of the GSP list, that of reducing the operator’s exposure to harmful chemicals. Most automated sample preparation systems are fully contained, leading to good compliance with Principle 10.

By combining the approaches of GSP and GAC we can get a good relative measure of the “green-ness” of our analytical workflow. Other similar, analytical chemistry relevant measurement tools and methods that I’ve found whilst researching this topic include:

1. AMGS Calculator (ACS Green Chemistry Institute) (7)
2. Analytical Eco-Scale for assessing the greenness of analytical procedures (8)
3. Complementary green analytical procedure index (ComplexGAPI) and software (9, 10)

I‘ve not investigated these other tools in detail, so I won’t comment on their relative merits versus the AGREE tools that I’ve discussed above.

So, given that we have these great tools available and that, without really noticing it, I’ve been following several of these green principles in recent years, can we now answer the titular question in the negative and proclaim that we are indeed where we need to be with sustainability in analytical chemistry? Well, I have some doubts. These may be due to personal ignorance, which I’m sure readers will educate me on. Or it could be that we have a long way to go yet before we can relax and say that we are truly playing our part in the drive towards better chemical sustainability in the analytical lab.

Firstly, I’m not sure just how green the chemicals I use are. Are there “greener” suppliers? How green are the reagents that I use in sample preparation and eluent preparation? Until now, I hadn’t seen a scale or unified approach to “scoring” the green credentials of my solvents and chemicals which makes it possible for me to choose and source solvents and reagents in a more sustainable way. I’ve recently come across the DOZN™ (11) measure from MilliporeSigma, which does seem to be heading in the right direction. I’ll be making use of this tool going forward. If other manufacturers have tools or information which make sustainable choices more obvious, then please let me know, and I’d be happy to promote them in a future blog.

I’m also still slightly concerned about operator exposure to eluent systems, chemicals, and reagents. We recently moved to install safer caps and filters for our eluent bottles and a system which reduces exposure risk when disposing eluent waste, but I do see plenty of labs which have not taken such steps yet. I also believe that automation of sample preparation activities involving larger volumes of solvents could be taken more seriously in terms of reducing operator exposure. I know I’m behind the curve in this respect and feel that many others may be in the same position. Exposure of operators also means environmental exposure to potentially damaging chemicals.

Think of the amount of plastic and glass that we use in the laboratory. Pipette tips, pipette tip racks, plastic Pasteur pipettes, vials, solvent Winchester bottles, gloves, volumetric glassware, plastic solvent dispenser bottles, etc. Do you recycle those in your laboratory? Do you know of a supplier who offers to recycle these in a financially reasonable way? Should the cost even be worth consideration if we are serious about becoming more sustainable? What about the amount of “blue roll” that is used? Could we source more sustainable laboratory paper-roll?

Many of the calculators that I’ve mentioned above rely on calculating the energy consumption of various instruments, and in a particular set of power units. I really struggle to find these figures from manufacturers, and it would be much more helpful if we could standardise a power consumption unit while the manufacturers provide these figures upon purchase or through a readily accessible section of their website.

I could go on. I’m sure there will be readers who have done more and considered other aspects of sustainability that I haven’t thought about yet, and please get in touch if this is the case. What I can promise is that I have personally committed to undertake more research, implement further sustainability measures and work hard to find suppliers who are more advanced on their sustainability journey.

Are we greenwashing analytical chemistry? I’ve been greener by accident, by following industry trends which are inherently more sustainable. Yet I realise that I, and perhaps we all, have a long way to go before we can be comfortable. Let’s say for now that the lid is off the tin of greenwash, and that we need to guard against complacency and marketing our green credentials before we’ve taken a good long look at what that really means.

References

[1] Anastas, P. T.; Warner, J. C. Green Chemistry: Theory and Practice, Oxford University Press: New York, 1998, 30

[2] Gałuszka, A.; Migaszewski, Z.; Namieśnik, J. The 12 principles of green analytical chemistry and the SIGNIFICANCE mnemonic of green analytical practices, Trends Analyt Chem, 2013, 50, 78-84

[3] Pena-Pereira, F.; Wojnowski, W; Tobiszewski, M. AGREE Analytical GREENness Metric Approach and Software, Anal. Chem. 2020, 92, 10076−10082

[4] Wojnowski, W. AGREE: Analytical Greenness Calculator. https://mostwiedzy.pl/en/wojciech-wojnowski,174235-1/AGREE (accessed 2023-02-01)

[5] Pena-Pereira, F.; Tobiszewski, M.; Wojnowski, W.; Psillakis, E. A Tutorial on AGREEprep and Analytical Greenness Metric for Sample Preparation, Advances in Sample Preparation 3, 2022, 100025

[6] Wojnowski, W. AGREEprep: Analytical Greenness Metric for Sample Preparation. https://mostwiedzy.pl/en/wojciech-wojnowski,174235-1/agreeprep (accessed 2023-02-14)

[7] ACS Green Chemistry Institute. About the AMGS Calculator. https://www.acsgcipr.org/tools-for-innovation-in-chemistry/about-the-analytical-method-greenness-score-amgs-calculator/ (accessed 2023-04-07)

[8] Gałuszka, A.; Migaszewski, Z.; Konieczka, P.; Namieśnik, J. Analytical Eco-Scale for assessing the greenness of analytical procedures, Trends Analyt Chem 37, 61–72

[9] Płotka-Wasylka, J.; Wojnowski, W. Complementary green analytical procedure index (ComplexGAPI) and software, Green Chem.,2021, 23, 8657-8665

[10] Płotka-Wasylka, J. ComplexGAPI: Complementary Green Analytical Procedure Index. https://mostwiedzy.pl/en/justyna-plotka-wasylka,647762-1/complexgapi (accessed 2023-04-07)

[11] MilliporeSigma. DOZN™ Quantitative Green Chemistry Evaluator. https://www.sigmaaldrich.com/GB/en/services/software-and-digital-platforms/dozn-tool?utm_source=redirect&utm_medium=promotional&utm_campaign=dozn (accessed 2023-03-24)