Determination of cadmium, lead and mercury in cannabis flowers by microwave plasma atomic emission spectrometry.

Pereira M.; Machado I.; Tissot F. · Journal of AOAC International · 2026

**Background & Methods** This analytical methodology review evaluates microwave plasma atomic emission spectrometry (MP AES) as a cost-effective alternative to conventional argon plasma techniques for detecting cadmium (Cd), lead (Pb), and mercury (Hg) in cannabis flowers. The study employed microwave-assisted acid digestion using nitric acid, with sequential MP AES analysis for Cd and Pb, and cold vapor generation coupled to MP AES (CV-MP AES) for Hg quantification, validated according to Eurachem guidelines and applied to 30 commercial cannabis flower samples. **Key Findings** • The proposed MP AES and CV-MP AES methodologies demonstrated adequate analytical performance with limits of quantification of 0.40 µg/g for Cd, 0.18 µg/g for Pb, and 0.015 µg/g for Hg, with excellent linearity (R² > 0.999). • Among 30 commercial cannabis samples analyzed, cadmium and mercury were not detected above quantification limits; lead was quantified at 2.12 ± 0.13 µg/g, indicating potential contamination from environmental or cultivation sources. • Method validation showed acceptable accuracy with recoveries of 95-101% for reference materials and 81-90% for spiked samples, with relative standard deviations below 15%, supporting the reliability of the analytical approach. **Dosage & Administration** Not reported. **Safety & Adverse Effects** Not reported. This study focused on analytical methodology for detecting toxic metal contaminants in cannabis products rather than clinical safety outcomes or adverse effects in users. **Evidence Quality** This is a methodological validation study rather than a clinical trial, representing a limited level of evidence specific to analytical chemistry. Strengths include rigorous adherence to Eurachem validation guidelines, good analytical performance metrics, and practical application to commercial samples. Limitations include the relatively small sample size (n=30) for cannabis products, lack of comparison between MP AES and conventional argon plasma methods, and absence of correlation with regulatory limits or health-based exposure thresholds. The study demonstrates technical feasibility but does not assess potential health impacts of detected contaminant levels or provide epidemiological evidence regarding cannabis product safety.

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