Figure ) are ubiquitous components of vegetable oils and animal fats and are incorporated in many foodstuffs. TAG distributions can be complex owing to differences in the structure of the fatty acids (FAs) and their site of attachment to the glycerol (sn-1, sn-2 or sn-3). Methyl transesterification is the most usual procedure for liberating the individual free fatty acids (FFAs) from the TAG mixture as their fatty acid methyl esters (FAMEs) in order to undertake routine analysis for quality, source and authenticity assurance . Gas chromatography (GC) where the oven is cycled up to around 300°C enables efficient separation of individual FAMEs using a suitable chromatographic column. When coupled with flame ionisation detection (FID) this approach can be used for quantitative analysis where response factors for individual FAMEs are approximately equivalent. Coupling of GC with mass spectrometry (GC-MS) allows the molecular characterisation of the separated FAMEs using their 'fingerprint' mass spectra and relative retention times . Liquid chromatographic (LC) techniques with ultraviolet detection and MS have also been used to identify and quantify FAMEs (e.g. . Similarly, LC coupled with refractive index detection or MS (electrospray ionisation, atmospheric pressure chemical ionisation, atmospheric pressure photoionisation or matrix assisted laser desorption ionisation; ESI, APCI, APPI or MALDI) have been used for intact TAGS, as recently reviewed by Tena et al 2019. In addition to quantitative analysis and molecular identification, measurement of the stable isotopes of constituent carbon, hydrogen and oxygen atoms can provide a profile of the biological, chemical and physical processes that each molecule has undergone . Stable isotopic values of individual FAMEs (compound specific) are usually obtained when GC is coupled with a stable isotope ratio mass spectrometer (GC-IRMS; . Methyl esterification has been reported to have a modest effect on the  13 C and  2 H values of FAMEs . Although LC has been coupled with IRMS it is less well established due to difficulties removing organic solvent necessary to effect some chromatographic separations. When GC is coupled to the IRMS via a catalytic combustion reactor operated at around 1000°C (GC-C-IRMS) the FAMEs are converted to CO2 and the   C of the CO2 measured relative to a reference gas.