Evaluation and comparison in caffeine extraction under green conditions: Solvent selection and ultrasound-assisted process

This study compared the green solvents ethyl acetate and water for caffeine extraction from coffee pills against four traditional solvents (ethanol, methanol, acetone, and acetonitrile). Each solvent's green degree (GD) was calculated using seven environmental and technical performance parameters. The environmental parameters were obtained from the Glaxo Smith Kline guide. Fick's law of effective diffusion was used as the technical parameter. Water was selected as the preferred solvent (among the six evaluated in this study), and its ultrasound-assisted extraction (UAE) conditions were optimized. The optimal conditions were estimated by ridge analysis. It was found that caffeine extraction was approximately 4.3 times higher in UAE than in conventional solid-liquid processes, and the extraction time was reduced by 96%. Moreover, this process improved caffeine extraction with water. Therefore, the use of UAE over conventional solid extraction and water as an inexpensive, easily accessible, manageable, and environmentally friendly solvent provides extraction alternatives for caffeine in different matrices. Additionally, a methodology is proposed to evaluate the GD for each solvent in the green chemistry framework to achieve sustainable development goals.