Analytical Sciences

Kinetic Spectrophotometric Determination of Traces of Molybdenum(VI) by Its Inhibitory Effect on the Oxidation of 4-Hydroxycoumarine by Potassium Permanganate

Ruzica J. MICIC, Ranko M. SIMONOVIC, and Branka B. PETKOVIC

Faculty of Natural Sciences and Mathematics, University of Priština, 38220 Kosovska Mitrovica, Serbia and Montenegro

The present paper describes a simple, selective and sensitive kinetic method for the determination of trace amounts of molybdenum(VI) based on its inhibitory effect on the reaction oxidation of 4-hydroxycoumarine by KMnO₄ in the presence of hydrochloric acid, at pH 1.75 at 25°C. The rate of the indicator reaction was followed spectrophotometrically by measuring the decrease in the absorbance of KMnO₄ at 525 nm. The development method includes optimization of the reagent concentration and temperature. The calibration graph was linear in the range of concentrations from 20 to 200 ng/cm³ of molybdenum(VI). The probable relative error was in the interval 3.10 - 10.52% for the concentration range of 200 - 20 ng/cm³ molybdenum(VI), respectively. The interference effects of the foreign ions were determined to assess the selectivity of the method. The developed method was found to have relatively good selectivity, sensitivity, simplicity and rapidity. The proposed method was applied to the determination of molybdenum(VI) in a particular type of steel and alloy (hastelloy).

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