A simple gas chromatographic-mass spectrometric method for the concurrent determination of novel pentafluoropropionated derivatives of histidine,histamine and their 1-methyl metabolites

Summary Histidine, 1,4-methylhistidine, histamine and 1,4-methyl-histamine were reacted directly for 1.5 hours at 70°C with pentafluoropropionic anhydride (PFPA). No previous esterification of the carboxyl group is needed. The reaction mixture, taken to dryness and redissolved in acetonitrile, can be separated on 3% OV-17 (retention indices: 1736, 1582, 1827 and 1763) and 3% OV-225 (retention indices: 2355, 2015, 2443 and 2147). The derivatives thus obtained are stable for one week at –4°C. The mass spectra of pentafluoropropionated histidine and 1,4-methylhistidine show relatively abundant molecular ions at m/e 403 and m/e 417 respectively, which confirm the incorporation of two PFP groups in both cases. However, both of these m/e values are 44 mass units less than the calculated relative molecular masses, a fact that can be accounted for by an intramolecular decarboxylation during derivatization. Histamine and 1,4-methylhistamine give molecular ions at m/e 257 and m/e 271, corresponding to the calculated values of the monoacylated derivatives.