Isotope dilution analysis (IDA) or isotope dilution
mass spectrometry (ID-MS) is a well-known analytical
technique based on the measurement of isotope
ratios in samples where the isotopic composition has
been altered by the addition of a known amount of
an isotopically enriched element. It is an absolute
quantitative method (traceable to the primary isotopic
standard) and is commonly used for applications
where high accuracy and certainty is required, for
example in National Metrology Institutes. Also, since
the quantification solely depends on the measurement
of the isotope ratio in the sample itself and does
not involve the use of external calibration, IDA is
significantly less prone to matrix effects. IDA offers
the possibility to determine major to ultra-trace
concentrations of elements in virtually any matrix, with
superior accuracy and precision compared to external
calibration and is often used as a reference method for
certified reference material characterisation.