Rapid synergistic cloud point extraction of copper in environmental samples with greenness and toxicity evaluation using a triazole based Schiff base

Abstract

Herein, a novel copper-triazole derivative Schiff base nanocomplex (HIT-Cu²⁺) was obtained via the reaction of the 3-(2-(4-amino-5-mercapto-4 H-1,2,4-triazol-3-yl)hydrazineylidene)indolin-2-one (HIT) Schiff base with CuCl₂.6H₂O. The non-ionic surfactant Triton X-114 (TX-114) was used as the extractant. The HIT, HIT-Cu²⁺, and HIT-Cu²⁺ in the organic layer were characterized by several techniques, including CHNS elemental analysis, ultraviolet-visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FT-IR), and transmission electron microscopy (TEM). The TEM results revealed the formation of the HIT-Cu²⁺ nanocomplex, with a particle size ranging from 13 to 25 nm. Moreover, an improved preconcentration method, named rapidly synergistic cloud point extraction (RS-CPE), was established for Cu²⁺ preconcentration and determination to overcome the issues investigated in CPE. Decanol acted as a cloud point revulsant and synergistic reagent, lowering the cloud point temperature (CPT) of TX-114, so that CPE could be done at room temperature without heating. Compared with traditional CPE (about 30 min for heating, incubation and cooling), RS-CPE was accomplished in 1 min with considerably high extraction efficiency. The improved extraction technique, RS-CPE, was combined with ICP-OES to improve the analytical performance and expand the application of ICP-OES determination. Various parameters that influence the Cu²⁺ removal efficiency (R, %) utilizing HIT Schiff base were investigated, including the solution's pH and volume, the concentration of HIT and Cu²⁺, type of surfactant, TX-114 concentration, equilibrium temperature and time, interfering ions, and centrifugation time and rate. At optimum conditions, the Cu²⁺ linear range, the correlation coefficient, the limit of detection (LOD), and the limit of quantification (LOQ) were 0.5-5 µg.mL^{- 1}, 0.9999, 0.018, and 0.054 µg/L, respectively. The investigated RS-CPE/ICP-OES approach was applied to real water and pharmaceutical samples, achieving recoveries higher than 97% with a preconcentration factor of 125. The HIT-Cu²⁺ CPE mechanism in the organic layer of TX-114 is elucidated. The greenness of the methods was evaluated using two recent methods: the Analytical Greenness (AGREE) calculator and the Blue Applicability Green Index (BAGI), which produced results in the ranges of 0.64-0.71 and 60-67.5, respectively. These results are strongly aligned with both green ideals and environmentally friendly practices. The predicted toxicity of HIT and HIT-Cu²⁺ nanocomplex was evaluated using PROTOX 3 software.