Taking advantage of the close proximity of customers and suppliers at the Informex trade show this month, the ACS Green Chemistry Institute’s Pharmaceutical Roundtable introduced its Process Mass Intensity (PMI) calculator to active pharmaceutical ingredient (API) makers. Roundtable members include 12 pharmaceutical and three custom chemical firms.
Available in spreadsheet form, the PMI tool assesses the efficiency of a synthetic process by calculating the amount of raw materials, including solvents, used to make each kilogram of product. That amount, called the PMI value, is a simple metric that is “transparent and equitable” and that allows comparisons across companies and processes, said David L. Hughes, a process chemist at Merck & Co., in a presentation about the PMI tool.
Such measurements are needed to encourage more sustainable and greener manufacturing processes, Hughes explained. In 2006, roundtable members began benchmarking their own processes. The results show that PMI values drop during process development and by the final commercial stage average about 200 kg of materials per kilogram of API. Solvents and water make up about 86%.
Today, as they outsource more, pharma companies that were focused on their internal processes want to “capture the chemistry that is done externally,” Hughes added. “Going forward, we are going to be requesting that our suppliers calculate PMI data for all APIs and API intermediates they provide, at all stages of development.”
This initiative is expected to give greater and more consistent insight into processes used. Although touted as a measure of “greenness,” the simple PMI metric doesn’t account for what actual materials are used, Hughes pointed out. To this end, the roundtable has developed a solvent selection tool. Further ahead, the group intends to explore more complex analyses that touch on the nature of materials and wastes.