The Determination of potentially toxic elements (Arsenic, Cadmium, Mercury, and Lead) in Hemp (Cannabis sativa L.) from using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP OES)

BACKGROUND: Hemp (Cannabis sativa L.) readily accumulates potentially toxic elements (PTEs) from soil. PTE exposure is linked to cancer, nephrotoxicity, and neurotoxicity. Non-intoxicating hemp products in New Jersey are not subject to mandatory PTE testing, posing a consumer safety risk. OBJECTIVE: This study presents a single-laboratory validation of an ICP OES method for the determination of As, Cd, Pb, and Hg in hemp, evaluated against AOAC SMPR 2020.001 performance criteria. METHODS: Ground hemp (0.125 g) was digested using HNO3/HCl/H2O2 (190 °C, 20 min) and diluted to 50 mL. Samples were analyzed on an Agilent 5800 ICP OES with a seven-point calibration (1-100 μg/L), Au/Sc internal standards, and KHP carbon for matrix matching. RESULTS: Spike recoveries for Cd (92.7%) and Pb (96.2%) met AOAC SMPR 2020.001 criteria (80-115%). Mercury recovery (47%) fell below acceptance limits due to matrix suppression and volatility losses. The As LOD (0.807 μg/g) exceeded sample concentrations in most specimens. LOQ values for all four elements exceeded the SMPR 2020.001 threshold of 10 µg/kg (0.01 µg/g). Calibration linearity was confirmed for all analytes (r ≥ 0.995). CONCLUSION: Partial validation was achieved: Cd and Pb demonstrated acceptable accuracy and repeatability, but LOQ criteria were not met for any analyte. ICP OES is not suitable for Hg or As at regulatory trace levels; ICP MS is recommended for these elements. This method offers a cost-effective screening tool for Cd and Pb in hemp. HIGHLIGHTS: This study presents the first single-laboratory ICP OES validation for PTEs in hemp under AOAC SMPR 2020.001. Cd and Pb met accuracy and repeatability criteria; As and Hg did not meet sensitivity requirements. ICP MS is recommended for regulatory As and Hg testing in hemp.