Highly Efficient Spectrophotometric Determination of Cu²⁺ ion in Aqueous Medium Using a thiosemicarbazone-derivative...

A new simple spectrophotometric method for the determination of Cu²⁺ ion was developed using an thiosemicarbazone compound, 2-{4-[Bis(2-chloroethyl)amino]benzylidene}-N-[(4-methylthio)phenyl]hydrazinecarbothioamide (TSC). A simultaneous color change was observed (from colorless to bright yellow) by the addition of Cu²⁺ ion to the TSC ligand solution. The maximum absorbance of the TSC ligand measured at 366 nm was decreased by the presence of Cu²⁺ ion. The graphs of absorbance obtained by means of the Job's method and the molar-ratio method proposed a complex formation with a 1:2 Cu²⁺-TSC ligand stoichiometry. The molar-ratio method with emission measurements also confirmed the stoichiometry. The complex stability constant of TSC-Cu²⁺ complex (K) was evaluated to be 1.76 × 10⁵. The proposed spectrophotometric method was associated with the change in absorbance at 366 nm owing to the interaction between the TSC ligand and Cu²⁺ ion. From the spectrophotometric titration data, it was pointed out that TSC ligand (1.5 × 10^- 5 mol L^-1) selectively reacted with Cu²⁺ ion in DMSO/water (1:1, v/v, citrate buffer at pH = 6.0). The calibration curve for Cu²⁺ ion was obtained with a good linearity in the range of 0.0191-0.3241 mg L^-1. The detection limit for Cu²⁺ ion was 0.0063 mg L^-1. The proposed method was achievemently implemented in real water samples (drink water, tap water and, distilled water). Satisfactory recoveries were confirmed at three different concentrations. The method presented a relative standard deviation (RSD%) of less than 3.08%.