Table 3.

Impurity fractions determined by HPGe spectrometry. The HPGe-determined ²²⁸Th activities were decay-corrected to the separation time, t_sep, and expressed relative to the corresponding (decay-corrected) ²²⁴Ra activities. See text for assay details.

Solution	f Th-228
E2	3.3(4) × 10−6
E3	5.0(16) × 10−6
E4	4.2(6) × 10−6
S3	1.11(11) × 10−5