Development of a Sensitive Spectrophotometric Method for Nickel Using Cinnamaldehyde - Thiosemicarbazone Ligand

The present study explores the synthesis, characterization, and spectrophotometric analysis of a Nickel (II) complex with cinnamaldehyde - thiosemicarbazone (Cin - TSC), a Schiff base ligand known for its chelating ability and potential bioactivity. Nickel, a transition metal of significant industrial and biological relevance, often requires selective and sensitive detection methods in various matrices. Traditional reagents for nickel estimation suffer from limitations due to interference by other metal ions. In contrast, thiosemicarbazones offer enhanced selectivity, stability, and analytical utility. In this study, the Ni (II) ?Cin - TSC complex was prepared in ethanol under acidic conditions (pH 3), and its spectrophotometric properties were examined. The complex exhibited a yellow coloration with a maximum absorbance at 360 nm. The molar extinction coefficient at this wavelength was found to be 2.228 ? 10? L mol?? cm??. The stability of the complex was investigated, and it was observed to remain stable for up to 10?12 hours. Beer?s law was obeyed in the concentration range of 8.48 ? 10?? M to 8.48 ? 10?? M of Ni (II). The Sandell?s sensitivity was calculated to be 0.2648 ?g cm??. The stoichiometry of the complex was determined by Job?s method of continuous variation and the mole ratio method, both indicating a 1: 2 metal - to - ligand ratio. The degree of dissociation (?) was found to be 0.0364, and the dissociation constant (K) was calculated as 1.18 ? 10???, indicating the high stability of the complex. The findings support the use of Cin - TSC as a reliable reagent for the spectrophotometric determination of nickel and provide insight into the structural and stability aspects of the complex. Applications: The Ni (II) ?Cin - TSC complex was successfully applied for the quantitative determination of nickel content in commercially available Cadbury chocolate samples. Using the Beer?s law calibration plot, the calculated values of nickel were found to be in close agreement with the experimentally observed values. This confirms the reliability and suitability of the Cin - TSC complex as an effective reagent for analytical applications, especially for nickel determination in food matrices.