Mono- and Binuclear Complexes in a Centrifuge-Less Cloud-Point Extraction System for the Spectrophotometric Determination of Zinc(II)
The hydrophobic reagent 6-hexyl-4-(2-thiazolylazo)resorcinol (HTAR) was investigated as part of a cloud-point extraction (CPE) system for the spectrophotometric determination of Zn(II). In the system, complexes with different stoichiometries, including 1:1 and 2:2 (Zn:HTAR), are formed. Their ground...
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| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2024-09-01
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| Series: | Molecules |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1420-3049/29/18/4511 |
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| Summary: | The hydrophobic reagent 6-hexyl-4-(2-thiazolylazo)resorcinol (HTAR) was investigated as part of a cloud-point extraction (CPE) system for the spectrophotometric determination of Zn(II). In the system, complexes with different stoichiometries, including 1:1 and 2:2 (Zn:HTAR), are formed. Their ground-state equilibrium geometries were optimized at the B3LYP/6-31G level of theory. The obtained structures were then used to calculate vertical excitation energies in order to generate theoretical UV/Vis absorption spectra. The comparison between theoretical and experimental spectra demonstrated that, under optimal conditions, a binuclear complex containing oxygen-bridging atoms is the dominant species. The absorbance was found to be linearly dependent on the concentration of Zn(II) within the range of 15.7 to 209 ng mL<sup>−1</sup> (<i>R</i><sup>2</sup> = 0.9996). The fraction extracted (%<i>E</i>), logarithm of the conditional extraction constant (log <i>K</i><sub>ex</sub>), and molar absorption coefficient (<i>ε</i>) at <i>λ</i><sub>max</sub> = 553 nm were calculated to be 98.3%, 15.9, and 4.47 × 10<sup>5</sup> L mol<sup>−1</sup> cm<sup>−1</sup>, respectively. The method developed is characterized by simplicity, convenience, profitability, sensitivity, and ecological friendliness. It has been successfully applied to the analysis of pharmaceutical and industrial samples. |
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| ISSN: | 1420-3049 |