Residual Solvent Testing

SC Labs has developed a Residual Solvent Test (RST) to identify the presence of harmful solvents, impurities, and/or other added odorants and chemicals present in super-concentrated forms of Cannabis. Increasingly, more patients are seeking out super-concentrated forms of Cannabis (i.e wax, hash oil, RSO, hemp oil, shatter, amber glass, crumble, budder, etc.) These types of concentrates are produced by using a solvent (such as butane, CO2, ethanol, propane, etc.) to extract cannabinoids and terpenoids from plant-material. Finally, heat, vacuum, and/or other methods are applied to purge out any remaining solvent from the concentrate.

To ensure that the highest quality of concentrates are being produced and made available to patients, SC Labs offers collectives and concentrate manufacturers a Residual Solvent Test (RST). By testing for Residual Solvents, we are able to ensure that the producer’s concentrate process is sound, not only verifying that the producer has used a high-quality solvent, free of impurities and toxic odorants, but has also followed a proper purging process (i.e. vacuum, desiccation, etc.) Utilizing a combination of Gas Chromatography/FID, Head-space analysis, and Mass Spectrometry, SCL is able to identify all of the most commonly used solvents and trace residues of chemicals in the process of extracting cannabinoids, including:

• Acetone
• Butane
• Propane
• Pentane
• Hexane
• Heptane
• Ethanol
• Isopropanol (iso-alcohol)

As the rise of the "dab" continues to gain popularity amongst the Cannabis community, the need to ensure the highest levels of product purity and patient safety becomes paramount. There is no denying the efficiency (?) of vaporizing a concentrate, as a method for ingesting a concentrated dose of cannabinoids with very little to no carcinogenic plant-material. Many municipalities and other states that have authorized medical Cannabis for medicinal use are growing concerned with the rising trend of super-concentrates, In many cases, due to the strength in potency of these products and the negative connotations that various production methods may present, a Collective may find itself at risk of legal issues if chemical-solvent extracted concentrates are offered.

More importantly, chemical residues can have a significant impact on the health of a patient, especially over time and with repeated exposure. Our community must self-regulate to ensure that patients are receiving the highest of quality, solvent-free concentrates possible.

Acceptable Limits for Residual Solvents

There has not yet been a universal standard set for limits on residual solvents in cannabis concentrates. The United States Pharmacopeia (USP) has set guidelines for daily exposure limits for individual solvents. Solvents are broken into three “classes” based on their risk assessment.

Residual Solvent Class Assessment
Class 1 Solvents to be Avoided

Known human carcinogens
Strongly suspected human carcinogens
Environmental hazards

Class 2 Solvents To Be Limited

Nongenotoxic animal carcinogens or possible causative agents of other irreversible toxicity, such as neurotoxicity or teratogenicity.
Solvents suspected of other significant but reversible toxicities.

Class 3 Solvents With Low Toxic Potential

Solvents with low toxic potential to humans; no health-based exposure limit is needed. [*NOTE—Class 3 residual solvents have PDEs. Source of 50 mg or more per day.]
* Class III solvents include Ethanol, Isopropanol, Propanes, Butanes, and Pentanes.


SC Laboratories currently serves the cannabis industries in both Washington and California, two markets with differing regulatory requirements with respect to residual solvents in inhaled cannabis concentrates. For Washington, under the WAC Chapter 314-55-104, the PPM (parts per million) for one gram of finished extract cannot exceed 500 PPM of residual solvent or gas. Although a statewide standard has not been established for California, the City of Berkeley has set a limit of 400 PPM for residual solvents or gas in one gram of finished extract.

“Tested/Detected” instead of “Pass/Fail”

All samples on which a residual solvent test has been requested are designated as “Tested” and highlighted in green. Samples where residual solvents are detected in amounts greater than 400 PPM are designated as “Detected” and highlighted in yellow. The 400 PPM limit is the lowest tolerance established by a regulatory body in a market where SC Labs test data is used for verification. “Detected” does not equate to “Fail”.

Due to the lack of a universal standard for tolerance limits, residual solvent data is displayed in PPM format without a pass/fail determination. Individual processors, patients or consumers must make the decision for what is “safe” for themselves.



Why Test?

Cannabis testing provides consumers with important information about the quality of their medicine. As is the case with all pharmaceutical companies, cannabis providers should be subject to third party certification. Why? The answer is obvious: credibility.

All Tests Are Not Equal

At SC Labs, all methods are consistent with FDA, ELAP, and EPA guidelines. It’s not enough to know that your medicine has been tested; you should also have access to the science behind it. For analytical testing to be reliable, established methods must be used and available for scientific scrutiny. For this reason, we provide detailed accounts of all our testing procedures upon request.