Schiff base aminoquinoline derivative for spectrophotometric determination of micro amounts of the mercury (II) Ion: thermodynamic evaluation and analytical applications

This study involves the use of a reagent prepared via the Schiff base reaction method between 8-aminoquinoline and 4,4'-dimethoxybenzil to produce 1,2-bis(4-methoxyphenyl)-2(quinolone-8-ylimino)ethan-1-one (BMPQYE1). The reagent was characterized by various spectrophotometric techniques such as FTIR, UV–visible spectrophotometry, 1H NMR, 13C NMR, and mass spectrometry. All analyses approved the formation of a new ligand. The impact of pH, time, temperature, volume of reagent, sequence addition, and interferences have been investigated to determine the optimal conditions for the reaction. The calibration curve was found to obey Beer's law in the range of 1 − 12 µg mL⁻¹ with a linearity coefficient of R² = 0.9998 at λ_max = 554 nm. The molar absorptivity (ε) was 9.403 × 103 L mol⁻¹ cm⁻¹, the M:L ratio was found to be 1:2, and the thermodynamic functions such as enthalpy, entropy, and Gibbs free energy indicated that the reaction was endothermic with a stability constant of 3.749 × 10⁸.The analytical method was accurate and precise, as demonstrated by relative standard deviations (RSD%) ranging from 0.598 to 1.567% and recovery percentages from 98.490 to 101.190% for five different concentrations, while the limit of detection and limit of quantification were found to be 0.449 µg mL⁻¹ and 1.481 µg mL⁻¹, respectively. The proposed method demonstrated high accuracy and sensitivity in the determination of trace amounts of mercury (II) ions in tap and river water.