The isotopes the KAr system relies on are Potassium (K) and Argon (Ar).Potassium, an alkali metal, the Earth's eighth most abundant element is common in many rocks and rock-forming minerals.
Because this (primary) standard ultimately cannot be determined by Ar, it must be first determined by another isotopic dating method.
Argon loss occurs when radiogenic K by a fast neutron reaction) can be used as a proxy for potassium.
Therefore, unlike the conventional K/Ar technique, absolute abundances need not be measured.
The monitoring of the interfering reactions is performed through the use of laboratory salts and glasses.
For example, to determine the amount of reactor produced Ar ratio of the glass is then measured in the mass spectrometer to determine the correction factor that must be applied to the rest of the samples in that irradiation.
Instead, the ratios of the different argon isotopes are measured, yielding more precise and accurate results.