Investigation of Low-Toxicity Azoic Direct Dyes Synthesized from 4,4′-Diaminobenzanilide

In this paper, a toxicological investigation was carried out on a series of azoic direct dyes generally with an affinity for cellulosic fibers, presenting symmetrical and asymmetrical structures having as a central component a non-carcinogenic, mutagenic, or teratogenic and accessible precursor potential substitute for benzidine, namely 4,4′-diaminobenzanilide, and, as coupling components, 2-hydroxybenzoic acid, 2-hydroxy-3,6-naphthalenesulfonic acid, 2-amino-8-hydroxynaphthalene-6-sulfonic acid, 1-amino-8-hydroxynaphthalene-3,6-disulfonic acid, 1-(4′-sulfophenyl)-3-methyl-5-pyrazolone, and 2-hydroxy-6-naphthalenesulfonic acid, respectively. For the purpose of their safe use, this study shows the results regarding the toxicity of the above-mentioned dyes, obtained through biological tests on colonies of Hydractinia echinata (H. echinata). The toxicity tests were performed on heterotrophic bacteria cultures obtained from the Bega River. The minimum toxic concentration was monitored using the dilutions 0.6 g/L, 24 g/L, and 48 g/L, obtained by dilution of a stock solution of 60 g/L. The symmetric dye with the coupling component 2-hydroxybenzoic acid presents the highest degree of toxicity, the lowest being shown by dyes with symmetric and asymmetric structures with the following coupling components: 2-amino-8-hydroxynaphthalene-6-sulfonic acid, 1-amino-8-hydroxynaphthalene-3,6-disulfonic acid, 1-(4′-sulfophenyl)-3-methyl-5-pyrazolone, and 2-hydroxy-6-naphthalenesulfonic acid.