Recycling of Analytical Grade Solvents on a Lab Scale with a Purpose-Built Temperature-Controlled Distillation Unit

Solvents constitute a major portion of a chemical laboratory’s waste and cause immediate costs for proper disposal and reordering. Next to reducing solvent usage, the recycling of used solvents by distillation is an obvious measure. In practice, commercially available equipment for distillation often offers insufficient separation and is inappropriately sized, overly costly, or simply not solvent-resistant. We constructed and put into service two distillation units for 6 L batches to recover analytical grade solvents–ethyl acetate and toluene for preparative chromatography and <i>N</i>,<i>N</i>-dimethylacetamide for analytical size exclusion chromatography. The systems separate fractions automatically at freely programmable vapor temperatures with high accuracy (0.1 K). The recovered solvents are therefore highly pure and are reused for analytical applications without any problems. Common laboratory glassware and standard electric components were used for construction. All wetted parts of the distillation systems are solvent-resistant and have withstood the distillation of corrosive, high-boiling solvents on a daily basis. Even high-boiling <i>N,N</i>-dimethylacetamide (164 °C) was conveniently recovered from waste GPC eluent. To verify the recovered solvents’ purity, a GC-MS method was developed, which encompassed both possible target solvents and impurities. UV/vis spectroscopy, Karl Fischer titration, and the chromatographic performance of the solvents were used as critical quality parameters. Typically, the recycled solvents were of higher purity than commercial ones. Additionally, several safety features were included in the distillation setup to prevent uncontrolled escape of solvent vapors with possibly catastrophic consequences. Both the construction of the distillation unit and its everyday operation are described in detail, offering an affordable, easily accessible, and reliable facility for greener solvent usage in common student and research laboratories