Where nC represents the molar quantity of carbon in the parent TAG and constituent glycerol backbone and fatty acid moieties and F is the fractional isotopic abundance (Eq 1). Bulk isotope analysis of an individual TAG can be used to represent the left hand side of Eq 5 (where FTAG = 1) and CSIRMS used to determine the (derivative adjusted) value for FA1, FA2 and FA3. In this way the isotopic contribution due to the glycerol moiety can be estimated by solving the equation. Alternatively the isotopic value of glycerol can be measured directly when recovered from the saponification liquor . However, where more than one TAG is present the isotopic value measured for the bulk TAGs then represents an average value. Cleavage of glycerol during saponification or transesterification of FAMEs from TAGs means that the intact structure and isotopic value of the TAG is lost, and the distribution and isotopic composition of cleaved FAs and glycerol are averaged. In complex TAG mixtures the parent TAG isotopic data cannot be calculated using this approach and potentially useful isotopic information of individual TAGs is lost. For natural samples such as olive oil, bulk isotope measurements are dominated by the contribution from TAGs but also reflect the presence of other organic compounds e.g. FFAs, sterols, glycerol, pigments and flavour compounds .