<b>A Simple and Sensitive Spectrophotometric Method for the Determination of Copper(II) in Aqueous Solutions Using a Novel Schiff Base Reagent</b>

A rapid, accurate, and sensitive spectrophotometric method has been developed for the determination of copper(II) in aqueous solutions. This method utilizes a newly synthesized reagent, 3-hydroxy-4-[(2-hydroxy benzylidene) amino] naphthalene sulphonic acid-1. The reagent reacts with Cu(II) ions in Britton–Robinson buffer at pH 7 and room temperature to form a stable orange complex with a maximum absorbance at λmax = 430 nm. Job's method yielded a 1:2 metal-to-ligand stoichiometry. The method demonstrated a high molar absorptivity of 3.24 × 104 L mol-1 cm-1 and a stability constant (βk) of 0.5749 × 103, with Beer's law being obeyed over the concentration range of 0.3–6 mg L-1. The detection limit was established at 0.0058 mg L⁻¹, and precision studies yielded relative standard deviations (RSD) ranging from 0.25% to 5.26%, with recovery values ranging from 95% to 102.5%. These results demonstrate the proposed method as a simple, cost-effective, and reliable approach for copper determination in aqueous systems, with potential applications in environmental monitoring and water quality assessment.