Free metal ion concentrations of amalgamating elements such as Zn, Cd, In, or Pb can be determined with absence of gradients and Nernstian equilibrium stripping(AGNES) in a variety of matrices, ranging from seawater to wine or dissolving nanoparticles. In this hands-on paper, we review the fundamental concepts and provide the practical steps to implement AGNES, including ready-to-run files for the software controlling the potentiostat, computation spreadsheets, step-bystep laboratory protocols, etc. Two case studies with a free Zn concentration determination are discussed: (i) a synthetic solution with the ligand oxalate and (ii) a natural sample of the Segre river (Catalonia, Spain). Suggestions for the extension of AGNES to other systems are indicated.This research received funding from the Spanish Ministry of Science and Innovation MCIN/AEI/10.13039/501100011033 (projects PID2019-107033GB-C21 and PID2020-117910GB-C21) and from the European Union’s H2020 research and innovation programme under Marie Sklodowska- Curie grant agreement No 801586.