Quality Control in Isotope Ratio Applications

In the early days of mass spectrometry, research was focused on gas source isotope ratio mass spectrometry (IRMS) or thermal ionization mass spectrometry (TIMS), with as the main aim the determination of the isotopic composition and molar masses of the elements. Since the 1940s, isotope ratio measurements have also been used for the determination of isotope ratios involving a radiogenic nuclide and for quantitative element determination via isotope dilution (see also Chapter 8). The age of the solar system and the Earth were also of particular interest within isotope ratio science. With the establishment and improvement of TIMS instrumentation, the awareness of the importance of precision and accuracy and the need to be able to reproduce a result in another laboratory grew, while 

First Edition. Edited by Frank Vanhaecke and Patrick Degryse. 

The definition of the measurand (the quantity that is being determined by measurement) is the heart of a result [3]. A correct measurand is needed to answer (fundamental) questions. However, this goal is dependent on the fitness-for-purpose of the currently available methods. Consider the following measurands relating to a 500 mg laboratory sample from one particular meteorite (the basic idea was taken from [3])  

the amount concentration of tungsten in a meteorite class (e.g., carbonaceous chondrites) 

the isotope amount ratios (or, shorter, isotope ratios) of tungsten expressed as epsilon values (see also Chapter 1) in a 100 mg test portion 

---

I 7 Quality Control in Isotope Ratio Applications Repeatability condition of measurement... 

H.-L. Schmidt, A. RoBmann, R.A. Werner (1998) Stable isotope ratio analysis in quality control of flavourings. In E. Ziegler, H. Ziegler (eds.) Flavourings - Production, Composition, Applications, Regulations. Wiley-VCH, Weinheim, New York, Chichester, pp. 539-594... 

---