Table 4.

²²⁹Th Reference Material Attribute Uncertainty Budgets.

Components	Comment	Type	ui%
n (230Th)/n (229Th) Isotope Amount Ratio
Measured n(230Th)/n   (229Th)	Standard uncertainty of measurement data	A	2.4
Calibration CRM(s)	Standard uncertainty of calibration CRMs for MC-ICP-MS measurements	B	0.041
Detector Yield   Calibration	Uncertainty for SEM-Faraday collector inter-calibration	B	0.50
Th Blank Correction	Reagent and instrument blank uncertainty	B	0.085
229Th Hydride   Correction	229ThH+ correction uncertainty	B	0.097
	Relative combined standard uncertainty (uc)		2.5
n(230Th)/n(229Th)	Expanded Uncertainty (k = 2)
5.18 × 10−5	0.26 × 10−5 (Relative: 5.0%)
n(232Th)/n(229Th) Isotope Amount Ratio
Measured n(232Th)/n   (229Th)	Standard uncertainty of measurement data	A	1.1
Calibration CRM(s)	Standard uncertainty of calibration CRMs for MC-ICP-MS measurements	B	0.041
Detector Yield   Calibration	Uncertainty for SEM-Faraday collector inter-calibration	B	0.50
Th Blank Correction	Reagent and instrument blank uncertainty	B	0.12
	Relative combined standard uncertainty (uc)		1.2
n(232Th)/n(229Th)	Expanded Uncertainty (k = 2)
3.815 × 10−4	0.092 × 10−4 (Relative: 2.4%)
229Th Molality
Measured 229Th   Molality	Standard uncertainty of measurement data	A	0.043
Molality 232Th Spikes	Standard uncertainties of IDMS spikes	B	0.015
Calibration CRM(s)	Standard uncertainties of calibration CRMs for MC-ICP-MS measurements	B	0.042
Mass Bias Correction	Uncertainty for use of uranium CRM for thorium mass bias correction	B	0.025
Aliquot Weighing	Uncertainty for potential evaporation during sample weighing.	B	0.015
	Relative combined standard uncertainty (uc)		0.068
229Th Molality (mol g−1)	Expanded Uncertainty (k = 2)
1.1498 × 10−10	0.0016 × 10−10 (Relative: 0.14%)

Uncertainty budgets for the ²²⁹Th reference material attributes. Values are shown for a reference date of 15 September 2012. Only the most significant uncertainty components are shown.