Chloroformmethanol

Chloroformmethanol is a widely used binary solvent system consisting of chloroform (trichloromethane) and methanol. Their complete miscibility allows adjustable polarity for various separation techniques, including thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC) with certain silica or reverse-phase columns, and lipid extraction protocols. The relative proportion of the two solvents controls solvent strength: higher methanol increases polarity, affecting retention and elution in chromatographic applications and the partitioning behavior in extraction procedures.

In lipid extraction, the Folch method employs chloroform:methanol in a 2:1 (v/v) ratio, with water added to induce phase separation and yield a chloroform-rich lower phase containing most lipids. The Bligh and Dyer modification uses a 1:2:0.8 ratio of chloroform:methanol:water, also forming two phases that partition lipids into the organic phase. In chromatography, mixtures of chloroform and methanol are used as mobile phases for silica gel TLC to separate lipids, dyes, or other organic compounds; typical ratios range from roughly 9:1 to 4:1 (chloroform:methanol), sometimes with small amounts of water to adjust polarity.

Properties and safety: both components are miscible, and the mixture is flammable. The exact density and polarity depend on composition. Methanol is more polar and highly toxic; chloroform is volatile and may pose health risks. Appropriate laboratory controls, including fume hoods and proper waste handling, are required when using this solvent system.

See also: Folch method, Bligh and Dyer method, TLC solvent systems.