Determination of Heavy Metals in a Variety of Cannabis and Cannabis-Derived Products, First Action 2021.03

Overview

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 arsenic (As), cadmium (Cd), mercury (Hg), and lead (Pb); arsenic and mercury are not speciated, so this page records them as total arsenic (tAs) and total mercury (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.

Related evidence

• Herbal botanicals
• Ingredient class — botanicals/herbs/traditional formulas
• Dietary Supplements
• Body/hand leave-on skin care
• Arsenic, Total
• Cadmium
• Mercury
• Lead

Update history

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