Radiometric Polarography of Manganese with Displacement by ⁶⁵Zn

Abstract

Radiopolarography is an analytical method of which use can be made for determining low concentration radioactive element without any nuisance of residual current. Radioactivity of the element deposited on mercury drop is measured and plotted against potential to get a curve similar to polarographic current-potential curve.
Recently, A.A. Katsanos, et al, reported that radiopolarography can be extended to nonradioactive element in the presence of a radioactive element due to oxidation-reduction replacement. For example, using radioactive ⁶⁵Zn and natural Mn²⁺ radiopolarographic waves are obtained at the corresponding half-wave potentials of -1.00 and -1.51 V vs. S.C.E., respectively.
The depositd manganese is oxidized and replaced by radioactive zinc and gives rise to the second plateau;
(Hg, Mn) +Zn²⁺= (Hg, Zn) +Mn²⁺
The height of the first plateau is proportional to the concentration of Zn²⁺ and the difference between those two plateaux is proportional to the concentration of Mn²⁺ and independent of that of Zn²⁺, thus allowing the quantitative determination of Mn²⁺.
In the present experiment, the authors report a new type cell which is made of two separated cells (Fig. 1) : in the first cell, there is a solution of non-radioactive element (Mn²⁺), and in the second cell, there is a solution of radioactive element (⁶⁵Zn²⁺) .
Mercury drops with electrodeposited manganese in the first cell fall into the second cell, in which it is oxidized and replaced by ⁶⁵Zn²⁺.
So, the labeled mercury drops give a polarographic plateau the height of which is quantitatively proportional to the concentration of manganese.