Validation of an analytical method with modified acid purity and iron matrices to measure heavy metals (Cd, Pb, Cr and As) in fertilizers. UNED Res. J. [Internet]. 2022 May 11 [cited 2026 Jul. 30];14(1):e3485. Available from: https://revistas.uned.ac.cr/index.php/cuadernos/article/view/3485