Analytical hierarchy processes (AHP) for the selection of solvents in early stages of pharmaceutical process development

The AHP (analytical hierarchy process) mathematical model was implemented into a tool aimed to aid the selection of solvents in the early stages of pharmaceutical process development. The tool assesses environmental implications using the information available in the early stages of development. Solvent properties, characteristics, and their relationship with common operations are exploited. In order to make the approach user-friendly, the tool was incorporated into a VB.NET application. The user obtains a ranked list of potentially good solvents. The result can be used as a starting point in solvent selection. The chemist can explore implications of the solvent selected not only from synthesis perspective, but also from an HSE perspective. A case study is presented for the replacement of benzene, where through a series of steps the chemist inputs ideal solvent characteristics and the importance of each characteristic in the decision. In this case solvent replacement is based in finding a solvent with the same solubility behaviour, but with less toxicity problems and at low cost. The tool considers a wide pool of solvents in a short time and produces ranked choices according to the chemist needs; taking account of both synthesis and HSE perspectives. (C) 2011. The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.