Acetone as a recyclable solvent

Acetone has a longstanding use in organic chemistry labs as the solvent of choice for the cleaning of glassware. This application extends to biological labs, where acetone may be used to rinse away organic contaminants, or water following water-based cleaning. Acetone waste from glassware cleaning can be readily recycled by fractional distillation. Its low boiling point (56°C) permits its effective separation from water and other high boiling substances, while small amounts of other volatile organics do not usually interfere with its repeated use in cleaning. Acetone has generally not been the solvent of choice for other applications in organic chemistry including chromatography on silica gel, where ethyl acetate in combination with hexane or other saturated hydrocarbon(s) is typically used as the mobile phase. Despite its limited use, acetone has certain advantages over the commonly used ethyl acetate in chromatography. First, it is typically less expensive. While acetone is generally considered to be UV transparent only above about 300 nm, it actually has a window of low absorbance in the 205 to 220 nm range. In contrast, ethyl acetate absorbs strongly up to about 250 nm. Acetone as solvent along with a non-absorbing saturated hydrocarbon co-solvent permits UV detection of eluent from chromatography at or near 210 nm, a much shorter wavelength that possible with ethyl acetate. This allows UV detection of a wider range of eluents, including simple alkenes. Acetone is generally considered to have a slightly greater eluting power than ethyl acetate in chromatography on silica gel. Acetone is an especially attractive alternative to ethyl acetate for chromatography if one wishes to recover and separate the solvent mixture by distillation, due to its lower boiling point (56°C) vs 77°C for ethyl acetate. Use of acetone in conjunction with heptane is especially practical, as the two solvents can be separated sufficiently for repeated use by fractional distillation using a standard automated commercial distillation instrument. This application of acetone has significant potential for reducing solvent consumption and waste generation in organic chemistry labs.