Analysis of the pentafluorobenzoyl derivative of phenylethylamine utilizing negative ion chemical ionization and gas chromatography/mass spectrometry

A negative ion chemical ionization (NICI) mass spectrometric procedure has been developed to measure phenylethylamine in human urine as the pentafluorobenzoyl derivative. The aromatic amine was isolated from alkaline urine by hexane and ethyl acetate extraction followed by a back‐extraction into diluted acid. The acid extract was lyophilized and the residue derivatized with (2,3,4,5,6)‐pentafluorobenzoyl chloride. Quantification was achieved by comparing the peak areas of the [M  HF]⁻ ion to a ratio of internal and external standards. The phenylethylamine levels excreted by normal subjects and patients with phenylketonuria were found to be consistent with previous reports.