Expanded uncertainty modeling of the uranium isotope dilution standards

Journal of Analytical Science and Technology

Table 4 Calculated ratios of the spike and sample mixtures with duplicates

Spike + sample	SP1 + SA1	SP1 + SA1	SP2+ SA2	SP2 + SA2	SP3 + SA3	SP3 + SA3	SP4 + SA4	SP4+ SA4
Spike/sample portion	1:4	1:2	1:2	1:2	1:3	1:3	1:2	1:2
Mixture no.	SP1-1	SP1-2	SP2-1	SP2-2	SP3-1	SP3-2	SP4-1	SP4-2
235 U spike	6.6608E-05	9.34141E-05	1.31114E-05	1.31414E-05	8.05092E-06	8.059E-06	1.93253E-06	1.93642E-06
235 U sample	0.0397475	0.0262613	0.0198501	0.0198647	0.0297869	0.0298043	0.0198615	0.0198527
238 U spike	0.00918	0.01288	0.00181	0.00181	0.00111	0.00111	0.00027	0.00027
238 U sample	0.00227	0.00150	0.00113	0.00114	0.00170	0.00170	0.00114	0.00113
235 U mix sum	0.03981	0.02635	0.01986	0.01988	0.02979	0.02981	0.01986	0.01985
238 U mix sum	0.01145	0.01438	0.00294	0.00295	0.00281	0.00281	0.00140	0.00140
R(235U/238U)mix	3.47622	1.83302	6.75211	6.74569	10.59544	10.59368	14.17368	14.16706

All mixtures simulated with duplicates. Ratio of U²³⁵/U²³⁸ mixture is not corrected for the mass fractionation. It will be taken into account for the extended uncertainty estimations
²³⁵U(spike/sample) = Spike/Sample Conc (g/g) × Spike/Sample (g) × ²³⁵U Frac. sample/spike
²³⁸U(spike/sample) = Spike/Sample Conc (g/g) × Spike/Sample (g) × ²³⁸U Frac. sample/spike
R(²³⁵U/²³⁸U)mix = ²³⁵Uspike+sample(mix sum)/²³⁸Uspike+sample(mix sum)
See Certified Reference Material (CRM) certificates issued by NBL for regarded atomic fractions. All concentration values are listed in Tables 2 and 3 for the diluted spike solutions (SP1, SP2, SP3, SP4) and sample (CRM 149). For the abbreviations, see Table 1