Determination of the Formation Constant of the Copper Chelate of β-Cyclodextrin by Spectrophotometric Titration with Ethylenediaminetetraacetic Acid Using Window Factor Analysis
| Autor: | Mike Darj, Edmund R. Malinowski |
|---|---|
| Rok vydání: | 2002 |
| Předmět: |
Aqueous solution
010401 analytical chemistry Inorganic chemistry chemistry.chemical_element Ethylenediaminetetraacetic acid Solubility equilibrium 01 natural sciences Copper Complexometric titration 0104 chemical sciences 010309 optics chemistry.chemical_compound chemistry Stability constants of complexes 0103 physical sciences Titration Chelation Instrumentation Spectroscopy |
| Zdroj: | Applied Spectroscopy. 56:257-265 |
| ISSN: | 1943-3530 0003-7028 |
| Popis: | Copper(II) is known to form a 2:1 complex with β-cyclodextrin in alkaline solution (pH ≥ 12), but its formation constant has not been determined. The present investigation involves the determination of the formation constant of the complex by spectrophotometric titration with ethylenediaminetetraacetic acid (EDTA) using window factor analysis (WFA). WFA is a self-modeling chemometric technique that extracts the concentration profiles of individual species from evolutionary processes such as complexometric titration. The visible absorption spectra of eleven aqueous solutions, at pH 12, containing fixed amounts of copper and cyclodextrin and different amounts of EDTA, were recorded. Principal factor analysis (PFA) of the absorbances gave evidence that three components were responsible for the spectral data. The concentration profiles of the components formed were extracted by WFA. Applying stoichiometric balance to the concentration profiles, the titration complex was determined to be (Cu2HO2CD·EDTA)−7, and the logarithm of its formation constant was calculated to be 8.51 ± 0.21. Using this information and the solubility product constant of Cu(OH)2 as well as the formation constant of (CuOH·EDTA)−3, the logarithm of formation constant of (Cu2HO2CD)−3 was detemined to be 35.78 ± 0.38. |
| Databáze: | OpenAIRE |
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