What is a Residual Solvent Analysis?

Residual Solvents Testing

During the manufacturing process of cannabis concentrates, solvents are used to extract the active ingredients (cannabinoids & terpenes) from the raw plant material. Common solvents for such extractions include carbon dioxide, ethanol, propane, butane, hexane and many others.

Commercially available solvents have varying degrees of purity - for instance, commercial butane is actually a mixture of many different isomers of butane, pentane and sometimes also propane and hexane. In the United States, alcoholic beverages - including ethanol - are heavily taxed for revenue and public health policy purposes. For this reason, denatured ethanol is sometimes used in the extraction process to avoid paying the alcohol tax. Common denaturing additives include heptane, isopropyl alcohol, and acetone to form a foul-tasting (and often toxic) solution to discourage recreational consumption.

After the extraction process, techniques that use heat and vacuum are commonly used to ensure the removal of residual solvents. However, the experience level of a manufacturer can greatly impact the efficiency of the purging process. Being nearly impossible to remove all residual solvents from an extract, these compounds are often found in many cannabis products.

At Green Scientific Lab, we use Headspace - Gas Chromatography Flame Ionization Detection (HS-GC-FID) to identify the presence of harmful solvent impurities, which are then confirmed and quantified using HS-GC-MS. A full list of residual solvents that we quantify include:

Propane, Butane, Methanol, Pentane, Ethanol, Ethyl ether, Acetone, Isopropyl Alcohol, Acetonitrile, Dichloromethane n-Hexane, Ethyl Acetate, Chloroform, Benzene, Dichloroethane n-Heptane, Trichloroethene, Toluene, Xylenes, Ethylene, Oxide.