As of this past May, Canada and 36 U.S. states have legalized medical or recreational marijuana.

Predictably, as more countries are becoming open to legalizing cannabis, regulations are slowly following suit to ensure adequate product safety and quality.

Why is Cannabis Different?

Cannabis products are somewhat atypical since they span the healthcare, pharma, consumer goods, and agricultural markets.

These other sectors have had regulatory frameworks and product standards in place for a long time, and most of those standards are consistent from one jurisdiction to another. The same cannot be said for the cannabis industry, where there is a lack of standardization among countries and even within the same country.

The cannabis market has two parallel segments growing in tandem: medical/recreational cannabis, and cannabidiol (CBD, the non-psychoactive substance extracted from cannabis). Both the medical/recreational and CBD market segments are experiencing rapid growth.

Purification of the CBD Extract

CBD is extracted via supercritical fluid extraction (SFE) or using ethanol.

Following the extraction, several steps remain to purify the CBD. These steps involve the removal of chlorophyll as well as any other contaminants that might be in the extract.

The purity of the CBD extract will dictate its use in different applications as well as its value.

Cannabis Contaminant Analysis

Ensuring quality is a key critical step for both CBD and cannabis producers. Regulators increasingly want to see CBD purification strategies reliant on strong analytical chemistry and contaminant analysis to ensure products fall within established specifications. As mentioned above, this can be complicated by the desired end-use, whether for pharmaceuticals, consumer goods (topical and ingestible) or agricultural applications.

As Leghissa, et al. stated in a 2018 Journal of Separation Science article, "Despite a growing number of laboratories focused on cannabis analysis, the separation science literature pertaining to the determination of cannabis natural products is still in its infancy." A more current review of the literature reveals that studies detailing methodologies tailored to cannabis natural product contaminant analysis remain quite sparse. Much of it remains protected by trade secret – a common practice in emergent markets.

Typical Cannabis Contaminants

With agricultural products such as cannabis, there are numerous potential sources of contaminants due to cultivation practices, water quality, soil quality or manufacturing procedures. Common among them: herbicides, insecticides, pesticides, residual solvents, microbial contamination (e.g., fungal spores or salmonella) and heavy metal impurities.

The risk of these contaminants is complicated by the different routes of administration, namely ingestion (oral route) versus inhalation (smoking). With supplements and edible products, contaminants such as lead are easily absorbed into the bloodstream. When smoked, the heat generated can burn volatile pesticide compounds which are inhaled into the lungs. Regardless of the administration route, serious health risks of contaminant exposure remain.

  • Metal Contaminants

    Heavy metal impurities in particular can be an issue with cannabis, since the plant is considered a 'hyperaccumulator' – meaning it efficiently takes up compounds from the soil into roots and leaves. The most common heavy metals found in cannabis production are arsenic (As), cadmium (Cd), mercury (Hg) and lead (Pb).

    Any ideal solution to heavy metal contamination should offer rapid adsorption kinetics at flow rates and processing capacities suitable for laboratory, pilot and commercial operations.

    For example, SiliCycle SiliaMetS E-PAK® Radial Fixed Bed Flow-Through Cartridges provide high adsorption capacity and flow rates, safer handling, clean-up and disposal, and large adsorbent capacity in a small footprint. (To learn more, read the application note on the use of E-PAK to remove chlorophyll in a cannabis sample).

    Active AdsorbentFor removal and/or recovery of:
    SiliaMetS ThiolBest scavenger for: Pd, Ag, Hg, Os & Ru
    Good scavenger for: Cu, Ir, Pb, Rh, Se & Sn
    SiliaMetS DMTBest scavenger for: Pd, As, Ir, Ni, Os, Pt, Rh, Ru & Se
    Good scavenger for: Cd, Co, Cu, Fe, Sc & Zn
    SiliaMetS ImidazoleBest scavenger for: Cd, Co, Cu, Fe, Ir, Li, Mg, Ni, Os, W & Zn
    Good scavenger for: Cr, Pd & Rh
    SiliaMetS AmineBest scavenger for: Pd, Cr, Pt, W & Zn
    Good scavenger for: Cd, Co, Cu, Fe, Hg, Ni, Pb, Ru, Sc & Se
    SiliaMetS Diamine
    SiliaMetS Triamine
    SiliaFlash Bare SilicaVery vast range of organic impurities, metals, pigments, etc.
    Activated CarbonsPrecious metal catalysts, pigments and reaction contaminants

  • Solvent Contaminants

    A variety of solvents are used in the manufacture of cannabis extracts and concentrates to remove cannabinoids from the plant material. Extraction is commonly performed using supercritical fluid extraction (SFE), in which the plant material is introduced to a vessel with a solvent at high pressure or with ethanol at low temperature. Removal of these solvents, which generally pose a health risk, can be critical.

    As the emerging cannabis industry has no established residual solvent threshold limits, established pharmaceutical procedures can provide a reasonable guideline for cannabis and CBD manufacturers. In particular, the US Pharmacopeia's National Formulary (chapter 467) provides guidance for the use of solvents in the manufacturing of pharmaceutical products. For example, in Oregon, limits for solvents in cannabis products are based on the International Conference on Harmonized (ICH) Tripartite Guideline for Residual Solvents (ICH Q3C).

Process Chemistry and Purification

While analytical determination of contaminants and potency is a critical aspect of cannabis separation science, so – too – is the removal of solvents and heavy metals in the production setting. In this white paper, Testing and Analysis of Cannabis Products for Safety & Potency, we discuss both of these potential sources of contaminants.

While solvents and metal contaminants are worrisome, the good news is that residual solvents and heavy metals can be easily removed in a commercial scale processing environment, often in just a single pass.


Using high quality silica gel stationary phase packing materials and metal scavengers. If you are interested in producing higher quality cannabinoid products, this next section will be particularly interesting.

SiliCycle and the Cannabis Industry

We've developed a broad selection of analytical and purification solutions for contaminants including mycotoxins, heavy metals, pesticides, and residual solvents. Our products are widely used in the cannabis industry for sample prep, detection & separation, and purification. All of our products are already in use by the highly regulated food, healthcare, pharmaceutical and biopharmaceutical industries.

Aside from our extensive collection of products for cannabis production and analysis (more below), SiliCycle offers confidential extraction and purification services to assist companies with their product development or purification projects. Popular services include the development of extraction processes from different biomasses, refinement & purification of natural & essential oils to ultra-high purity, production of health ingredients such as Omega-3, Polyphenols and Probiotics and scale-up services from the laboratory bench to industrial production.

SiliCycle products are useful across the entire span of cannabis/CBD product development, analysis and manufacturing. From the removal of chlorophyll while maintaining CBD concentrations at 96% using the E-PAK SiliaCarb HA (Application Note: Using E-PAK technology to remove chlorophyll in a biomass sample) to a case study with Florisil showing the removal of 98% of pesticides in a contaminated cannabis extract, to our extensive work with the food & pharmaceutical industries in removing metal contaminants, SiliCycle's robust product portfolio is applicable to the cannabis industry.



How will SiliaMetS and SiliaBond scavengers trap impurities in your samples