Different behaviour of 3-nitrotyrosine and tyrosine toward perfluorinated reagents suitable for the one-step preparation of volatile derivatives

With the view of developing a gas-chromatographic (GC) determination of the 3-nitrotyrosine (NY)/tyrosine (Y) ratio as a marker of nitro-oxidative stress, different reagents were tested with the objective of obtaining a single volatile fluorinated product for each amino acid in a one-step derivatisation procedure. The heptafluorobutyric anhydride (HFBA)/heptafluorobutanol (HFBOH) mixture proved unsuccessful for the simultaneous analysis of NY and Y. The reaction with different chloroformates, isobutyl chlorofomate (iBuCF) and ethyl chloroformate (EtCF) in the presence of different perfluorinated alcohols, such as trifluoroethanol (TFEOH) and HFBOH, was investigated. A combination EtCF/fluorinated alcohols yielded derivatives of NY and Y as single peaks suitable for the GC determination of the NY/Y ratio. The different behaviours of the two amino acids in the employed reaction mixtures and the parameters influencing the results are discussed.