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Redefining solvent selection

Posted on 07 August 2018

A solvent selection guide developed in collaboration with researchers from York’s Green Chemistry Centre of Excellence has been adopted by the ACS Green Chemistry Institute, a world leader in green chemistry education, as their recommended method of selecting more environmentally friendly solvents.

The guide was developed as part of the CHEM21 project by scientists from Sanofi, GlaxoSmithKline, Pfizer, the Green Chemistry Centre of Excellence and Charnwood Technical Consulting Ltd. The CHEM21 project was a European consortium of academics, organisations and enterprises collaborating to develop sustainable manufacturing technologies.

Greener solvents

Solvents make up the bulk of materials used to produce pharmaceutical ingredients, so selecting a greener solvent is an efficient way of reducing the environmental impact of a pharmaceutical product.

The freely available guide, designed to encourage chemists to seek out greener solvents, ranks solvents against safety, health and environmental criteria to give a clear assessment of how environmentally-friendly many traditional and more modern solvents are.

Bio-derived solvents

A key feature of the guide is that it examines bio-derived solvents, which have generally not been included in previous guides. Because many traditional solvents are derived from finite resources such as petroleum, bio-derived solvents - which are renewable - are being used more frequently. But not all bio-derived solvents are green and it is important to assess these solvents on a level playing field alongside classical solvents.

New methodology

To develop the guide, the research team initially surveyed the in-house solvent selection guides of GlaxoSmithKline, the ACS GCI Pharmaceutical Roundtable, Pfizer and Sanofi and looked for overlaps and differences in how the guides classified 51 solvents. By combining data from these guides, each solvent was categorised as recommended, problematic, hazardous or highly hazardous. However, disagreement between the guides meant 17 solvents could not be ranked using this method.

To deal with these discrepancies, the researchers created a new methodology for rating solvents which would unify the four selection guides. A series of well understood solvent and chemical criteria were grouped into one or more measures - Safety, Health and Environment - which each solvent was scored and ranked against. These rankings were cross-referenced with the rankings from the survey; 81% of rankings were found to be in line.

The guide is accompanied by an interactive tool, which allows users to add new solvents to the guide and rank them as they are developed, through the same process.

Dr Rob McElroy, paper co-author, said “This transparent and relatively simple ranking system as compared to current pharmaceutical tools offers scientists (and anyone with an interest in solvents) an easy to use, automated solvent ranking system that shows excellent correlation to existing guides.

“It also has the ability to be further populated by novel compounds and/or non-classical solvents dependent on the user preferences using information that is easily accessible and freely available.  Adoption by the ACS GCI vindicates the benefits of the new methodology and will significantly increase its impact".

ACS Green Chemistry

Founded in 1876 and chartered by the U.S. Congress,  American Chemical Society (ACS) is the world’s largest scientific society. Its mission is to advance the broader chemistry enterprise and its practitioners for the benefit of Earth and its people.

The ACS Green Chemistry Institute seeks to be the premier change agent that has the knowledge, expertise, and capabilities to catalyse the movement of the chemical enterprise toward sustainability through the application of green chemistry principles. ACS GCI supports research, works to integrate green chemistry into all levels of chemical education, aids companies with industrial implementation, hosts conferences, and coordinates efforts with an international network of green chemistry advocates.


The CHEM21 solvent selection guide was created as part of the IMI funded CHEM21 project (Chemical Manufacturing Methods for the 21st Century Pharmaceutical Industries). CHEM21 has received funding from the Innovative Medicines Initiative Joint Undertaking under grant agreement n°115360, resources of which are composed of financial contribution from the European Union’s Seventh Framework Programme (FP7/2007-2013) and EFPIA companies’ in kind contribution.

Further information 

ACS Green Chemistry: Tools for Green Chemistry & Engineering

CHEM21: The CHEM21 solvent selection guide