Ethyl Maltol as a New Ligand for Spectrophotometric Determination of Iron

In this study a new simple selective and sensitive spectrophotometric procedure for determination of Fe(III) is described. It is based on the formation of a colored complex between ferric iron and ethyl maltol, a strong and highly selective ligand for Fe(III). After mixing sample and reagent, and incubating at the room temperature, Fe(III)-ethyl maltol complex was extracted with different solvents and the absorbance was measured at 395 nm. The effect of analytical variables, i.e. amount and type of the reagents, pH, ratio of Fe(III)/ethyl maltol, presence of other ions, etc., in the determination of iron were studied. Our findings showed that the optimum wavelength for the measurement was 395 nm. The optimum condition for complex formation and determination of Fe(III) were: molar ratio of ethyl maltol/Fe(III) = 6-10; pH = 5. The best solvent for extraction was chloroform. Under the recommended conditions, formation of the complex is completed in less than 2.5 h. Limit of detection was found to be 2.5×10-6 M of Fe(III). Linear regression (r2=0.9998) was observed over the range of 2.5×10-6 to 5×10-4 M of the Fe(III) with respect to the complex nominal concentration. Ions commonly associated with iron did not interfere in the present method. This is a simple, reproducible, and sensitive method for determination of Fe(III) in μmolar levels.