Fast and High-resolution Method for Determining Cations in Environmental Samples using Ion Chromatography

Determining cation levels in aqueous matrices is fundamental for controlling water quality and safety, ensuring compliance with legal standards for potability and environmental use, and contributing to the sustainable management of water resources and the protection of public health. In this context, this study proposed an ion chromatography method for the simultaneous determination of Li⁺, Na⁺, NH₄⁺, K⁺, Mg²⁺, and Ca²⁺ in different aqueous matrices, including tap water, mineral water, carbonated water, well water, drinking fountain water, and wastewater. The chromatographic conditions were optimized using a 2² full factorial design with a central point, resulting in a total analysis time of 11 minutes. The method employed an 11-mM H₂SO₄ mobile phase, a Dionex IonPac CS12A column, a 2-mm CSRS conductivity suppressor, a flow rate of 0.38 mL min⁻¹, and an injection volume of 5 µL. In the method validation, linearity, limits of detection and quantification, selectivity, precision, and accuracy were evaluated. The results for tap water showed Na⁺ and NH₄⁺ concentrations below the legal limits, confirming potability. One sample of well water showed an NH₄⁺ concentration approximately 25 times higher than the limit established by the Brazilian Ministry of Health. Despite the low agreement in mineral water, between labeled and experimentally determined values, the concentrations met potability standards. Thus, the method proved selective for monitoring water and wastewater quality and for regulatory control of mineral water labels.