Pereira, Mafalda G.Ribas, Tânia C. F.Mesquita, Raquel B. R.Rangel, António O. S. S.2026-04-142026-04-142026-03-307057e8e7-ab98-416e-b2b1-4ce8770f950dhttp://hdl.handle.net/10400.14/57496Urbanization and industrial processes significantly contribute to the contamination of air, water, and soil. These processes also introduce substantial quantities of metal ions into the environment, which pose health risks to humans as well as other animal species. In water bodies, these metal ions can be present in soluble forms, suspended in sediments, or accumulate in aquatic organisms, therefore, screening and quantifying metal ions is vital. Lead and cadmium are two of the most concerning metals in water, due to their toxicity and their levels in the environment. The maximum limits in industrial effluent discharge are 0.20–2.00 mg/L for Cd (II) and 0.10 mg/L for Pb (II), and for drinking water is 0.005 mg/L for Cd (II) and 0.015 mg/L for Pb (II) [1]. As a result, there is a strong demand for simple and sensitive on-site methods to detect cadmium and lead in water. Flow analysis systems are appropriate for developing these types of methods, as they allow for decreasing instrumentation size and reagent consumption, simplifying manipulation of the water samples and respective analysis. In this work, we propose a flow-based system to determine simultaneously lead and cadmium, using a colourimetric reaction between malachite green and iodide, followed by the formation of a ternary complex between the reagents and the metal cation. This reaction has been previously used for lead [2] and cadmium determination, separately. The developed methodology includes a pre-concentration step in a column packed with Chelex resin, which allows for the simultaneous determination of both metal ions, operating in a sequential injection mode; a flow injection approach is employed for the colourimetric reaction. This methodology will enable a real-time evaluation of water contamination by cadmium and lead.engconference proceedings