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The Precision and Sensitivity of Thermal Ionisation Mass Spectrometry (TIMS): An Overview of the Present Status
Author(s) -
Birck Jean Louis
Publication year - 2001
Publication title -
geostandards newsletter
Language(s) - English
Resource type - Journals
eISSN - 1751-908X
pISSN - 0150-5505
DOI - 10.1111/j.1751-908x.2001.tb00600.x
Subject(s) - meteorite , sensitivity (control systems) , reproducibility , sample (material) , mass spectrometry , sampling (signal processing) , instrumentation (computer programming) , analytical chemistry (journal) , chemistry , environmental science , computational physics , physics , statistics , computer science , mathematics , optics , environmental chemistry , astrobiology , detector , engineering , chromatography , electronic engineering , operating system
This paper illustrates that sample size cannot be reduced below a theoretical limit and still achieve the highest precision obtainable on modern mass spectrometers. Reproducibility at the few ppm level is achievable and is related essentially to ion counting statistics. The number of atoms necessary to carry out such measurements is related directly to the sensitivity of the instrumentation. As most of the elements of interest are not major constituents of natural silicates, a lower limit to the size of the starting sample is assessed. Even for a number of elements for which very high ion per atom yields are attained by TIMS, minimum sample mass is an important limiting factor for precious or rare samples and may reduce the scientific output of experiments or place a major constraint on the sampling strategy itself. For rare meteorites or individual Martian samples expected to be returned in amounts at the gramme scale for rocks or at the microgramme scale for dust, the high sensitivity of TIMS is a requirement. Nevertheless, a compromise has to be found between sample consumption and the minimal desirable precision for a useful isotopic measurement.