Systematics of Mass Bias Correction Models

Thermal ionization mass spectrometry (TIMS) suffers from time-dependent mass bias, referred to as mass fractionation, as a result of the finite amount of sample on the source filament and the more efficient thermal ionization of the lighter isotope. Mass bias correction is more crucial with multi-collector (MC)-ICP-MS as the latter suffers significantly larger bias and, as noted earher, it may not necessarily be constant over extended periods of time. Therefore, rigorous correction methods are required. Over the last few decades, several different mass bias correction methods have been successfully used for the determination of isotope amount ratios, as illustrated by Albarede et al. [16]. 

Over the years, numerous methods have been proposed for calibrating isotope amount ratios [16-19]. At a glance, these methods can be formally classified using two key parameters that differ from method to method - whether or not data for the measurand and calibrant are acquired simultaneously, and whether or not the 

Internal calibration Sr-Sr internal correction Zr-Sr, exponential model 

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