Analytical Sciences

Iodometric Amplification Method for the Determinations ofMicrogram Amounts of Manganese(II), Manganese(VII), Chromium(III) andChromium(VI) in Aqueous Solution

Minghao ZHANG* * ,Guoping ZHAN*and Zhanguang CHEN**

*Department of Chemistry, Central South University of Technology,Changsha 410012, P. R. China
**Department of Chemistry and Chemical Engineering, HunanUniversity, Changsha, P. R. China

A simple, rapid and sensitive iodometric amplificationmethod has been developed for the determination of microgram amounts ofMn^II, Mn^VII, Cr^III and Cr^VI.The method is based on the prereductions of Mn^VII andCr^VI with Na₂SO₃, the oxidations of bothMn^II and Cr^III in the absence ofNa₄P₂O₇ and the oxidation of onlyMn^II in its presence with excess periodate in acetate buffer(pH=3.0), removal of the unreacted periodate by masking with molybdate andthe subsequent titration of liberated iodine after adding iodide. Theindividual amounts of Mn^II, Mn^VII, Cr^IIIand Cr^VI in different test solutions were successfullydetermined by this method, which offers 20-fold and 12-fold amplificationfor Mn and Cr, respectively. (Keywords: Iodometric amplification, microtitration,chromium(III), chromium(VI), manganese(II), manganese(VII))

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