Forbidden azo dye refers to the azo dye which will decompose into carcinogenic aromatic amines under reduction condition. 118 banned dyes published by German government are only part of azo dyes.

Carcinogenic aromatic amines refer to group mak (III) A1 and A2 aromatic amines. Mak is the maximum concentration allowed.

Mak (LLL) A2 group refers to the substance with carcinogenicity in animals; if the working environment conditions are similar, similar results may occur in humans;

Mak (LLL) A3 group refers to the substance suspected to have obvious carcinogenic potential, which needs further study.

Due to the limitation of detection technology, Germany issued this decree, which stipulated that only when the content of forbidden aromatic amine in the sample was more than 30mg / kg, the forbidden azocouple dye was used in the sample. At present, some large European companies and groups have changed the limit of banned aromatic amines to 20mg / kg, and the standard hjbz30-2000 technical requirements for environmental labeling products ecological textiles issued by the State Environmental Protection Administration of China has set the limit of banned aromatic amines to 20mg / kg. In order to meet the requirements of detection of banned azo dyes, the detection technologies currently used include high performance liquid chromatography (HPLC) and gas chromatography- Mass spectrometry (GC-MS), thin layer chromatography (TCL).