Current regulations for nanomedicines overlook the effects of the different forms of the same element, such as ions, nanoparticles, and aggregates. In a recent study, researchers developed a new analytical method combining an asymmetric flow field-flow fractionation system and mass spectrometry to separately quantify these forms. This technique allows for better quality control and safety evaluation of metal-based nanomedicines, promoting their development and clinical use, with applications also extending to food, cosmetics, and the environment.