Nelson et al. 2022 - AOAC cannabis heavy-metals method validation

Nelson et al. (2022) report AOAC Official Method 2021.03 for total arsenic, cadmium, total mercury, and lead in cannabis and cannabis-derived products after microwave-assisted acid digestion and ICP-MS. The paper is primarily a single-laboratory method-validation study, but Table 5 includes native concentration values for four validation matrices: flower, hemp butter, pain relief cream, and CBD crude extract. These values are limited occurrence context and should not be treated as a market-prevalence survey.

Key numbers

Table 5 reports native levels in ppb, µg/kg for four cannabis/cannabis-derived matrices. The table labels arsenic, cadmium, mercury, and lead as As, Cd, Hg, and Pb; arsenic and mercury are not speciated, so this page records them as tAs and tHg.

Table 2021.03H gives method LOQs, also in ppb, µg/kg, as As 9.171, Cd 6.247, Hg 2.155, and Pb 7.849. The paper reports that spike recoveries for As, Cd, Hg, and Pb met AOAC SMPR 2020.001 recovery criteria across the four cannabis matrices at low, medium, and high spike levels.

The broader sample list in Table 2021.03G includes hemp flower, CBD vape oil, hemp isolate extract, full spectrum softgel capsules, full spectrum tincture, isolate tincture, CBD coffee grounds, hemp butter, hemp seed oil, CBD beef jerky, CBD hard candy, CBD pineapple drink, CBD balm, CBD topical oil, hemp biomass, spent hemp biomass, CBD crude extract, CBD distillate, and CBD isolate, but the paper says those data are available upon request rather than publishing all native concentration rows.

Methods (brief)

Samples were homogenized where needed, digested by closed-vessel microwave digestion using a typical 0.5 g sample portion with 9 mL HNO3 and 1 mL HCl, diluted to 50 g, and analyzed by single-quadrupole ICP-MS. The method used helium collision mode/kinetic energy discrimination, ultra-high matrix introduction aerosol dilution, internal standards, calibration verification, continuing calibration blanks, and plant-based NIST SRMs. The paper validates total As, Cd, Hg, and Pb for dried plant materials, concentrates, oils, extracts, tinctures, and other cannabis-related products.

Implications

The native values in Table 5 provide bounded occurrence context for cannabis-derived oral, inhaled, topical, and manufacturing matrices, while the main contribution of the paper is analytical: AOAC First Action validation of microwave digestion plus ICP-MS for cannabis heavy-metals testing. Product routing should preserve the matrix split. Hemp butter, flower, topical cream, and CBD crude extract should not be pooled as one finished-product distribution.

Wiki pages this source may touch

• herbal-botanicals
• supplements-botanicals-herbs
• dietary-supplements
• body-hand-leave-on-skin-care
• arsenic-total
• cadmium
• mercury
• lead

Verification notes

• Identity checks before writing found no existing DOI, raw-handle, or cite-key page for 10.1093/jaoacint/qsab173, MFK_determination-of-heavy-metals-in-a-variety-of-cann, or nelson2022-cannabis-heavy-metals-method.
• Source scope: method-validation study, not a market survey. Table 5 native-level values are the only published occurrence numbers for actual cannabis/cannabis-derived matrices; broader sample data are explicitly described as “available upon request.”
• Speciation: As and Hg are total/unspecified in the paper; no iAs or MeHg values were inferred.
• Units preserved: native values and LOQs remain in ppb, µg/kg; no conversions were performed.
• Jurisdictions record the method-regulatory scope the paper states: U.S. state cannabis testing programs and Canadian cannabis laws. The paper does not report purchase or production jurisdictions for the validation samples, so these codes should not be read as sample-provenance claims.
• Missing slug note: the taxonomy snapshot has no hemp, cannabis, CBD, or cannabis-derived-products ingredient/product slug. Frontmatter uses the existing broad [[ingredients/herbal-botanicals]], [[products/supplements-botanicals-herbs]], [[products/dietary-supplements]], and [[products/body-hand-leave-on-skin-care]] slugs instead of inventing cannabis-specific pages.
• Brand firewall: sample labels are generic matrix descriptors. Instrument/vendor names in Methods are scientific reproducibility details, not product-brand contamination claims.

Page history

The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.