Table 2.

Th Mass spectrometry analysis information.

Laboratory	LANL	LLNL	IPGP-CEA
Instrument	ThermoFisher Neptune MC-ICP-MS	Nu-Plasma HR MC-ICP-MS	ThermoFisher Neptune MC-ICP-MS (at IPGP)
Collectors	9 Faraday, 7 Channeltron, 1 SEM w/ RPQ	5 Faraday, 3 SEMs (2 w/ RPQ)	9 Faraday, 1 SEM w/RPQ
Introduction System	Stable Signal Spray Chamber	Cetac Aridus II	APEX HF (ESI)
Nebulizer	PFA-FTST Element Scientific	Cetac PFA Nebulizer	PFA Micro-flow Nebulizer
Nebulizer Gas Flow	0.9 L/min	0.94 L/min	Not Reported
Solution Uptake	250 µL/min	120 µL/min	50 µL/min
Mass Bias CRM	CRM U010 (NBL, 2008a)	CRM U010 (NBL, 2008a)	CRM U500 (NBL, 2008b)
Quality Control CRM	IRMM-035 (IRMM, 1997) CRM 112A (NBL, 2010)	CRM U005A (NBL, 2008c)	CRM U100 (NBL, 2008d)
Corrections Applied	Detector Baseline Instrument Background Peak Tailing Detector Gains Mass Bias Hydride Correction	Detector Baseline Instrument Background Peak Tailing Detector Gains Mass Bias	Detector Baseline Instrument Background Peak Tailing Detector Gains Mass Bias Hydride Correction

Summary of instrumental parameters and analysis conditions for thorium isotopic ratio measurements. MC-ICP-MS is Multi-Collector Inductively Coupled Plasma Mass Spectrometry.