ISO 17234-2:2011 is supplementary to ISO 17234-1 and describes a special procedure to detect the use of certain azo colorants in commodities, which can release 4-aminoazobenzene. The procedure also detects 4-aminoazobenzene (Solvent Yellow 1) which is already available as free amine in commodities without reducing pretreatment. Azo colorants that are able to form 4-aminoazobenzene generate, under the conditions of ISO 17234-1, the amines aniline and 1,4-phenylenediamine. The presence of these 4-aminoazobenzene colorants cannot be reliably ascertained without additional information (e.g. the chemical structure of the colorant used) or without a special procedure.