Motivated by the identification of numerous novel tetrahydro-β-carboline-carboxylic acids in food samples, we studied the reactions of tetrahydro-β-carbolines in the presence of nitrosating agents. The anticipated formation of nitroso derivatives from unsubstituted tetrahydro-β-carbolines, and from tetrahydro-β-carboline-3-carboxylic acids was indicated by HPLC-MS/MS analysis and validated by the characteristic product ion spectra of the ...