Solvents for botanical extraction

Botanical extraction pulls oils, cannabinoids, alkaloids and terpenes out of plant material with a solvent, then removes that solvent until only the extract remains. Ethanol extracts a broad range of compounds and is the base of most large hemp and botanical operations. Hydrocarbons such as heptane and hexane are more selective for non-polar compounds. Ethyl acetate is used in liquid-liquid partitioning and some separations.

Winterization follows: the crude extract is dissolved in ethanol, often 200-proof formula 3C, and chilled well below freezing, commonly -20°C to -40°C or colder. Waxes and lipids precipitate and are filtered off, and the ethanol is recovered by rotary evaporation or falling-film evaporation for reuse.

Every solvent in the process has to satisfy two people: the operator chasing yield and the compliance lead documenting inputs for state testing. Have the SDS and the COA for the lot in hand before the drum is opened. See the extraction collection.

Grade matters most for solvents that stay in contact with the finished product, and least for solvents that are fully recovered or only used to clean equipment.

For extraction and winterization, check three things on the COA. First, the denaturant: formula 3C ethanol uses isopropyl alcohol, while methanol-denatured formulas add a Class 2 solvent that can appear in residual-solvent panels. Second, non-volatile residue, because it concentrates in the extract. Third, for hydrocarbons, the aromatic content: technical hexane can carry trace benzene, a Class 1 solvent. Heptane is often chosen over hexane because its residual limit is far higher.

For cleaning glassware, lines and rotary evaporators, technical acetone or 99% isopropyl alcohol is usually enough. Use ACS reagent grade where a cleaning residue could reach the product.

State cannabis and hemp programs set residual-solvent limits for finished products, and most are modeled on ICH Q3C and USP <467>. Under ICH Q3C, hexane is limited to 290 ppm and methanol to 3,000 ppm, while Class 3 solvents such as ethanol, heptane and acetone are held to 5,000 ppm. Your state's numbers may differ, so check the current rule.

Botanicals sold as dietary supplements fall under FDA's current good manufacturing practice rule, 21 CFR Part 111, which requires specifications and identity checks for incoming components. OSHA's Hazard Communication Standard (29 CFR 1910.1200) requires SDS for every chemical on site. Flammable solvent storage falls under NFPA 30, and many jurisdictions apply the fire code's chapter on processing and extraction facilities to the extraction room itself. Rules change often; consult your compliance team.

• Not checking the denaturant formula. A drum of methanol-denatured ethanol in place of formula 3C can put methanol into a residual-solvent panel. Confirm the formula on the product page and the COA.
• Switching hexane suppliers on price alone. Hexane grades differ in isomer and aromatic content. Compare the new COA, including benzene, before the first batch.
• Cleaning with 70% isopropyl alcohol. The 30% water stays in joints and vessels and dilutes the next ethanol charge. Use 99% isopropyl alcohol or acetone where equipment must be dry.
• Ordering the COA after the batch. Request it when you order so it is on file before the drum is opened.