Both EELS and FTIR data were collected on commercially available L-methionine and synthesized DL-Tfm (Method A). Stereoisomers, by definition, have the same chemical structure but differ only in the spatial arrangements of atoms. Although there are reports that racemic and enantiomeric compounds can be distinguished in vibrational spectroscopy due to their differences in crystal packing, geometry and hydrogen bonding interaction (7-8), the enantiopurity would not affect the discussion of characteristic C-F stretching mode in this article. An alternative synthetic route leading to L-Tfm would also be provided in Method B, which is more robust and consistent. Further examination into the difference in stereochemistry confirms that both DL-Tfm and L-Tfm exhibit similar spectra data on FT-IR.