N-acetyl-(1-amino-2-naphthol-6-sulphonic acid), a common metabolite of sunset yellow FCF, orange GGN and 1-amino-2-naphthol-6-sulphonic acid in rat urine, De Beer, J., Dierickx P.J., and Grimee R.I. , J.Chromatogr., 5/3/1982, Volume 237, Issue 1, Number 125, p.115 - 125, (1982)