Detection of carcinogenic amines from dyestuffs or dyed substrates

The second amendment to ‘German Rugulations on Consumer Goods’ states that azo dyestuffs, which can release one or more of the listed 20 carcinogenic amines, should no longer be used in dyeing consumer goods. Many acid and direct dyes which liberate harmful amines such as benzidine, o-tolidine and o-dianisidine after reduction are, however, still use. In this study, it was surprising to find that some dyestuffs or dyed substrates released carcinogenic amines such as 4-amino-diphenyl, 2-naphthylamine, 2,4-toluenediamine and 4,4′-diaminodiphenyl-methane, although such amines had not been employed as intermediates in the manufacture of the dyestuffs. Benzidine was also detected from a dyestuff which was not made from benzidine. The 2-naphthylamine residues were sourced as being due to the use of 1-naphthylamine contaminated with 2-naphthylamine. 4-Aminodiphenyl was formed by dediazoniation and a subsequent coupling reaction between the benzenediazonium ion and aniline. Benzidine was derived from dediazoniation and a subsequent self-coupling reaction of the diazonium ion of 4-nitroaniline. 2,4-Toluenediamine and 4,4′-diaminodiphenylmethane arose from the alkaline hydrolysis of the readily accessible moiety of the corresponding base units in PU foams or PU finishing agents.