Spectrophotometric Assay of Phenylephrine Hydrochloride Using 4-Aminoantipyrine and Copper (II). Pakistan Journal of Analytical & Environmental Chemistry, Pakistan, v. 11, n. 1, p. 01–07, 2010. DOI: 10.21743/. Disponível em: https://pjaec.pk/index.php/pjaec/article/view/421. Acesso em: 5 nov. 2025.