Owing to the toxicity of heavy metals, it is increasingly important to test cannabis flowers and other cannabis derivatives so that patient and consumer safety is maintained as the use of cannabis becomes more common. This need has translated into an increasing demand for testing cannabis flowers and other cannabis derivatives for toxins such as the heavy metals cadmium (Cd), lead (Pb), arsenic (As), and mercury (Hg). In this application note, we present data to illustrate the successful validation of the Titan MPS™ Microwave Sample Preparation System and the NexION® ICP-MS for the determination of heavy metals in cannabis flower according to the validation protocols set in USP General Chapter <233>, which are commonly used for evaluation of the levels of elemental impurities in samples.