CHEM21 Solvent Selection Guide
Solvents constitute the bulk of the materials used in the production of fine chemical and pharmaceutical products. Therefore, to limit the environmental impact of these products, solvent selection is paramount in reaction and process design; many large pharmaceutical companies have developed their own solvent selection guides which they use in-house as a manual for solvent selection.
Researchers within the CHEM21 consortium surveyed the solvent selection guides of GlaxoSmithKline, the ACS GCI Pharmaceutical Roundtable, Pfizer and Sanofi to interrogate them for areas of overlap as well as divergence. Of the 51 classical solvents investigated, a good correlation was found between all four solvent guides for 34 of the solvents, which were assigned to one of four categories: recommended, problematic, hazardous and highly hazardous, and are given in Table 1. The remaining solvents where good correlation between the guides could not be found were initially assigned into either “recommended or problematic” and “problematic or hazardous”.
CHEM21 Researchers then went on to develop a CHEM21 solvent selection guide to unify the surveyed solvent selection guides, as well as come to a clear assignment for those solvents that did not correlate well across the four guides.The guide ranked solvents according to how well they performed across three categories: safety, health and environment. For each category a solvent was assigned a score from 1-10, where:
- a score of 1-3 denoted a recommended attribute
- a score of 4-6 denoted a problematic attribute
- a score of 7-10 denoted a hazardous property
The safety score is based mainly on the solvent flash point, with increments introduced subject to the auto-ignition temperature, resistivity or ability to form peroxides, which would give diethyl ether a safety score of 10. In the circumstance that such data is unavailable for a given solvent, the score is automatically assigned as 5. The combination of the scores for all three categories provides the final solvent ranking according to Table 2.The ranking obtained from the CHEM21 solvent guide was in line for 81% of the solvents ranked in the previously published guides, it also went further and for the first time ranked a number of bioderived solvents, to give a clearer picture of how well they performed when scrutinised in the same manner as classical solvents. The publication is available as an open access article at: http://pubs.rsc.org/en/content/articlelanding/gc/2016/c5gc01008j#!divAbstract. In addition, there is an associated Excel spreadsheet (in the supplementary data) that will enable the user to rank a solvent not included in the list according to the guidelines outlined in the publication.
Reference: D. Prat, A. Wells, J. Hayler, H. Sneddon, C. R. McElroy, S. Abou-Shehada, et al., Green Chem., 2016, 18, 288