Aquatic toxicity evaluation of new direct dyes to the Daphnia magna

The aquatic toxicity of a series of new direct dyes based on benzidine congeners, 2,2′-dimethyl-5,5′-dipropoxybenzidine and 5,5′-dipropoxybenzidine, and a commercial dye (C.I. Direct Blue 218) were evaluated in acute toxicity studies using Daphnia magna. The purpose of the research described in this paper was to use bioassays with daphnids to determine the aquatic toxicity of new direct dyes synthesized. The results clearly show that C.I. Direct Blue 218 examined was highly toxic to daphnids and more toxic than unmetallized new direct dyes as expected. The study also suggested that the assay with D. magna was an excellent method for evaluation of dyes for aquatic toxicity.