Measurement and Traceability Issues in Isotope Amount Ratio Determination of Stable Isotopes

Accurate and precise measurement of isotopic ratio of stable isotopes for establishing the traceability is essential for its wide applications such as geological survey, food authentication, geographical origin and environment. Now a days, it has been extensively used due to development of sophisticated instrument with improved technologies and established methods/procedures. According to the International Committee for Weights and Measures (CIPM) in 2015, the isotope ratio or delta value could be achieved by an internationally inter comparison following an established method/procedure. And the isotope ratio or delta value assignment can be realized by comparing with a certified value of an Isotopic Reference Materials (IRMs) so as to get the comparable as well as traceable isotope amount ratio value. The major lacuna faced during the isotopic ratio measurement is due to the instrumental mass fractionation and mass discrimination, which affect to the ultimate result of the isotopic ratio. Various artifact standards and IRMs are used to rectify these mass discrimination and mass fractionation. Though, several IRMs have been developed by the National Metrology Institutes (NMIs) which are used to establish traceability linkage to the SI unit for the measurement of isotope amount ratio; however, availability of IRMs to develop traceability for the routine measurement of isotopic ratio is still a major issue. The present paper is focused mainly on the measurement and traceability issues in the isotope amount ratio determination and the availability of various isotopic reference materials.