To minimize tailing of the curium at the higher solvent concentration, the nitric acid concentration in the eluent has been increased from 0.2 to 0.3M. Recoveries of the z44Cm and z W f under the conditions described are typically >99 %. Any Am(II1) present in the oxidized solution elutes with the Cm(II1). Persulfate ion in the americium fraction corrodes stainless steel plates, thereby decreasing the resolution of alpha particle measurements. To avoid this problem, one may use tantalum or platinum plates, because they provide excellent sources for ordinary process control measurements. Also the need for an additional electrodeposition step is eliminated, but for more elegant studies, electrodeposition is still recommended. A plausible explanation for the experimental results is the following: persulfate oxidizes Am(II1) to Am(V1). In the absence of a holding oxidant, like silver ion, or a strong complexing anion, like fluoride ion (2),Am(V1) readily reduces to Am(V). Further reduction is more difficult because of the necessity to break oxygen bonds. Am(V) disproportionates to form Am(II1,VI) slowly-an observation which is successfully exploited in this new method. Inasmuch as the large Am02+ ion exhibits negligible tendency to complex with HDEHP and sorb on the column, it elutes rapidly. Under the conditions used, the AmOz+ ion is relatively stable for some time, even in the presence of a large excess of hydrogen peroxide. For instance, in the first exploratory experiments, it was thought that a mild reductant, like hydrogen peroxide would be required to provide high yields of Am(V) by reduction of Am(V1). Interestingly, the yields of Am(V) were essentially equal, whether excess hydrogen peroxide (as high as 5M) was present or not. In a brief study, after the persulfate oxidation in the standard method, the solution was adjusted to 1.8M hydrogen peroxide and allowed to sit for various periods of time at room temperature (-23 “C) prior to sorption on the column. Recoveries of Am(V) were 87% after 5 minutes, 7 4 z after 1 hour, and
