Determination of Ultra Trace Amounts of Selenium(IV) by Means of a New Reaction System —Methyl Yellow and Hydrogen Peroxide

Abstract

A spectrophotometric method for the determination of selenium is described, based on the selenium(IV)-catalyzed oxidation of methyl yellow with hydrogen peroxide in a nitric acid medium. As the redox reaction proceeds, the red color of methyl yellow is decolorized. The values of logA0/A show a good linear relationship with the amounts of selenium (A0: absorbance of uncatalyzed reaction solution; A: absorbance of catalyzed reaction solution.). The new method is extremely sensitive, as little as 2 × 10⁻¹⁰ g ml⁻¹ can be easily measured. The detection range is from 5 × 10⁻⁷ to 2 × 10⁻¹⁰ g ml⁻¹. In addition, the system possesses extremely high selectivity, most of ions including copper and tellurium can be tolerated during the determination of selenium. The method has been used to determine selenium in egg and wheat, and satisfactory results were obtained.

Key Words:

• Selenium
• methyl yellow
• hydrogen peroxide
• spectrophotometry
• catalytic method