The concentration of both L and D amino acid isomers was determined by HPLC (High-performance liquid chromatography) for multiple amino acids. 30 samples of proboscidean enamel were taken from the collections at BGS. Samples of enamel (~30 mg) was removed from the teeth of proboscideans using a small electric drill. All of the samples were from UK sites dating to the Quaternary. These samples were used to build a regional geochronology based on the extent of racemisation of amino acids from the intra-crystalline fraction (Dickinson, 2018). Thesis http://etheses.whiterose.ac.uk/22261. A published paper 'A new method for enamel amino acid racemization dating: A closed system approach' is also available; https://doi.org/10.1016/j.quageo.2018.11.005