Sensitive endpoint detection for coulometric titration of microgram amounts of plutonium. Part I: Use of polarized indicator electrodes for the endpoint detection

The determination of plutonium by coulometric titration based on the preliminary oxidation of plutonium to PuO22+ followed by titration with electro-generated Fe2+ using zero current potentiometry as the indicating system is reported earlier. The lowest amount of plutonium titrated is of the order of 25 micrograms with a precision of about 1%. At still lower amounts, the results are found to be less precise because of the slow attainment of the equilibrium. Since in polarized indicator electrodes the continuous flow of current accelerates the attainment of equilibrium, this indicating system was tried in the coulometric titration of plutonium; and the results show that plutonium as low as a microgram can be titrated with a precision of about 6%. The precision at 10 micrograms level is found to be about 1%. Earlier Carson et al reported the coulometric determination of plutonium using similar indicating system; however their method involved elaborate sample pretreatment procedures. The present method, because of simple sample treatment will find application for routine use. The paper give substantial information regarding the sensitivity and the reproducibility of the indicating system. (author)