Leveraging Limited Runs for Robust Information: A Resource-Efficient ICP-MS Approach for As, Cd, Pb, and Hg in Cannabis.

Regulatory testing of cannabis and hemp commonly prioritizes As, Cd, Pb, and Hg, yet inductively coupled plasma mass spectrometry (ICP-MS) workflows often require extensive tuning and method setup that can be difficult to implement in resource-limited laboratories. Although general guidance exists, quantitative ranges for critical settings are still sparsely documented for cannabis matrices, and "one-set" conditions may not transfer well across instruments. To address this gap, we developed a resource-efficient, low-run screening strategy intended to reduce trial-and-error, reagent consumption, and instrument time when only a limited number of runs is feasible, using two linked 12-run, resolution-III Plackett-Burman designs generated in R. First, key ICP-MS parameters were screened under QC conditions to define a stable operating region. Second, digestion factors (acid composition/volumes, temperature program, sample mass, and predigestion) were assessed using spiked inflorescence samples. Apparent effects were identified using standard screening diagnostics and supported by two-factor trend visualizations. The screening highlighted three underreported practical contributors-RF power, peristaltic-pump speed, and operation without inrun dilution-as dominant drivers of robustness, together with element-dependent recovery drivers: As was mainly governed by HCl level; Cd and Hg by coupled HCl volume × sample mass trends; and Pb by combined heating-ramp/HNO₃ and temperature/predigestion patterns. Because resolution-III designs alias main effects with specific two-factor interactions, the numerical effects should be interpreted as first-pass screening estimates rather than definitive optima and require higher resolution confirmation. Overall, the study provides a quantitative map of factor relevance for cannabis metal digestion and narrows the experimental space for subsequent optimization and validation.