The negative ion mass spectra of (M – H) – ions from phenylthiohydantoin derivatives of amino acids

The mass spectra of (M – H)− ions of phenylthiohydantoin (PTH) amino acids show characteristic fragmentations through the side chain (the α-side chain of the original amino acid) which may be used to identify each of the common amino acids. Some of these fragmentations are Leu (C3H8), Ile (CH4, C2H6), Phe (PhH), Tyr (CH2=C6H4=O), Trp (CH2=C8H5N), Ser (CH2O), Thr (MeCHO) and Met (MeSH). The formulae in parentheses represent the neutrals lost.