Rapid determination of magnesium and calcium ions in saline and seawater

Abstract

Access to fresh water from seawater treatment is crucial for sustaining human life. Furthermore, Ca and Mg in seawater represent valuable resources for agricultural and industrial purposes, warranting thorough analysis and recovery efforts. This study introduces the use of ortho-cresolphthalein complex one (o-CPC) for the rapid determination of Ca and Mg concentrations in saline and seawater samples. This approach utilizes a basic complexation reaction and follows the concept of a swift, point-of-care testing kit used to analyze samples, specifically biological specimens. The methodology was meticulously examined and optimized, encompassing key parameters such as reagent concentration, employment of masking agents, determination of optimal wavelengths, and assessments of accuracy and precision. The resulting standard curve exhibited high linearity (R2 > 0.995) across 0.5–5 mg. L−1 for Ca and 0.5–10 mg. L−1 for Mg. Notably, the method demonstrated good repeatability (% RSD < 5%) and achieved high recovery rates (95%–105%) when tested on spiked samples within real sample matrices. A comparative analysis between the o-CPC method and the F-AAS method (in accordance with the SMEWW 3111B:2017 standard) was conducted using three seawater samples, revealing no significant discrepancies in the analysis of Mg and Ca with a confidence level of 95%.