The acute toxicity of gluconic acid, β-alaninediacetic acid, diethylenetriaminepentakismethylenephosphonic acid, and nitrilotriacetic acid determined by Daphnia magna, Raphidocelis subcapitata, and Photobacterium phosphoreum

Acute toxicity of four relatively new chelating agents and their equimolar manganese and cadmium complexes was studied. The chelating agents studied were gluconic acid (GA), β-alaninediacetic acid (ADA), diethylenetriaminepentakis- methylenephosphonic acid (DTPMP), and nitrilotriacefic acid (NTA). Three common bioassays, namely Daphnia magna, Raphidocelis subcapitata, and Photobacterium phosphoreum (Microtox™ bioassay) were applied. R. subcapitata proved the most sensitive to these compounds. With D. magna bioassay the LC₅₀ values were 600-900 mg/L with all other studied chelates and their Mn complexes, except Mn-GA, which yielded LC₅₀ value of 240 mg/L. The Cd-chelate complexes proved highly more toxic compared to Mn-chelate complexes or uncomplexed chelates exhibiting LC₅₀ values of 130-200 μg/L. However, Cd-DTPMP was an exception exhibiting LC₅₀ value of 2170 μg/L. That is to say, DTPMP proved the strongest chelating agent to reduce the Cd toxicity in the present study. The results from these bioassays were well in agreement to each other as well as with the results published elsewhere.