Determination of aromatic amines in FD&C yellow no. 5 by diazotization and coupling followed by reversed-phase HPLC

Benzidine, aniline, 4-aminobiphenyl (4-ABP) and 4-aminoazobenzene are determined at trace levels in the colour additive FD&C Yellow No. 5 by diazotization and coupling with disodium 3-hydroxy-2,7-naphthalenedisulphonate (R-salt). The products are separated and determined by reversed-phase HPLC. All four amines were found in a survey of commercial colours. 4-ABP is determined with 4,5-dihydro-5-oxo-1-(4-sulphophenyl)-1H-pyrazole-3-carboxylic acid as the coupling agent. Calibration is done by spiking a reference commercial colour at several levels.