Table 4.

IDMS sample data and measurement results for the molality of ²³¹Pa in the RM solution

Sample ID	231Pa RM solution aliquots (g)	233Pa spike aliquots (g)	Measured isotope ratio* n(233Pa)/n(231Pa)	Molality of 231Pa (pmol g−1)
231Pa 1	0.6318 ± 0.0010	3.0843 ± 0.0010	0.016894 ± 0.000046	27.56 ± 0.13
231Pa 2	1.0531 ± 0.0010	3.5580 ± 0.0010	0.011701 ± 0.000048	27.54 ± 0.11
231Pa 3	0.7848 ± 0.0010	3.4152 ± 0.0010	0.015067 ± 0.000047	27.55 ± 0.14
231Pa 4	0.5688 ± 0.0010	3.4580 ± 0.0010	0.021023 ± 0.000044	27.58 ± 0.12
231Pa 5	0.8931 ± 0.0010	3.1462 ± 0.0010	0.012203 ± 0.000055	27.53 ± 0.16

For IDMS calculations, the molality of ²³³Pa in the S solution was decay corrected to the time of final purification for the protactinium IDMS mixes, 14 July 2017 18:20 UTC. Uncertainties are expanded uncertainties (U=ku_c) with a coverage factor (k) of 2. All mass values are corrected for air buoyancy

^*A correction factor (0.99936 ± 0.00059) was applied to measured n(²³³Pa)/n(²³¹Pa) ratios to account for mass spectrometer efficiency differences between ²³³Pa and ²³³U. The correction factor was calculated based on the relative proportion of ²³³U that grew in over the interval between purification and the mass spectrometer measurements and an observed transmission efficiency difference between uranium and protactinium (8.7%). This transmission difference was empirically determined based on the bias between the measured n(²³³Pa)/n(²³¹Pa) ratio of a mixed solution and the n(²³³U)/n(²³¹Pa) ratio of the same solution after the decay of ²³³Pa