where \(\delta_{\text{raw}\left(\text{sample}\right)}\) is the
measured isotope composition (Rmeasured ) of the
sample relative to the working gas (wg ) and\(\delta_{\text{true}\left(\text{wg}\right)}\) is the actual isotope
composition of the working gas specified by the operator. Per
convention, the relative difference of isotope ratios (δ ) for N
and C are expressed in parts per thousand (‰)26.
Although it is possible to quantify\(\delta_{\text{true}\left(\text{wg}\right)}\) and thus calculate the
true isotope composition of the sample\((\delta_{\text{true}\left(\text{sample}\right)})\) via a one-point
anchoring using the working gas alone, identical treatment principle
dictates replacing Eq. 2 with replicate analyses of combusted reference
material according to the following equation: