2-[4-[[2-(cyanoimino)hexahydro-4,6-dioxo-5-pyrimidyl]azo]phenyl]-6-methylbenzothiazole-7-sulphonic acid, compound with 2,2',2''-nitrilotris[ethanol] (1:1)

Toxicity to aquatic plants other than algae

Description of key information

The toxicity of the test substance to Lemna gibba was determined in a study (Institute of Industrial Organic Chemistry, 2017) according to the principles of OECD 221 (2006). After 7 days, the ErC50 based on frond number and the ErC50 based on dry weight were determined to be greater than 1000 mg/L.

Additional information

The toxicity of the test substance to Lemna gibba was determined in a study (Institute of Industrial Organic Chemistry, 2017) according to the principles of OECD 221 (2006). The growth of Lemna gibba exposed to the test item was investigated in a 7 day semi-static test with two renewals each 48 hours. The definitive test was performed using five test item concentrations: 1000, 333, 111, 37 and 12.3 mg/L plus the control. The test item concentrations were evaluated using three replicates and for the control six replicates were used. The appropriate amount of the test item was weighed in a glass crystallizer and quantitatively transferred into a flask by multiple washing with the 20X AAP medium and filled up to appropriate volume. The test item concentration of 1000 mg/L was visually homogeneous. Lower test item concentrations were prepared by sequential dilutions with the 20X AAP medium in a ratio 1:2 (v/v). The control was 20X AAP medium (1000 mL). From each test item concentration and the control 50 mL were taken as a sample for chemical determinations at exposure initiation. The content of the main ingredient in the test item concentrations was determined with a validated spectrophotometric method. Samples of all fresh test item concentrations and the control at exposure initiation and all old test item concentrations and the control at the first renewal were chemically analyzed. Moreover, samples of fresh test item concentrations of 1000 and 12.3 mg/L and the control at all further renewals as well as old test item concentrations of 1000 and 12.3 mg/L and the control at all further renewals and at exposure termination were chemically analyzed. In the fresh samples collected at exposure initiation and at all renewals the determined content of the main ingredient was in the range of 91.9 – 96.3 % of nominal concentration. Therefore, the results confirm correct preparation of the test item concentrations. In the old samples collected at all renewals and at exposure termination the determined content of the main ingredient was in the range of 83.3 – 92.1 % of nominal concentration. Therefore, the test item concentrations were stable under test conditions during renewals. The mean concentrations measured in the fresh test solution were determined to be 8.06, 24.07, 72.24, 225.33 and 672.87 mg/L. After two days the mean concentrations measured in the old test solution were determined to be 7.72, 22.34, 65.00, 215.50 and 619.88 mg/L. After renewal (2 days) the mean concentrations measured in the fresh test solution were determined to be 8.036 and 659.40 mg/L. After four days the mean concentrations measured in the old test solution were determined to be 7.24 and 604.76 mg/L. After four days (renewal) the mean concentrations measured in the fresh test solution were determined to be 7.95 and 677.18 mg/L and after seven days the mean concentrations measured in the old test solution were determined to be 7.70 and 630.40 mg/L. A blank control with the test solution without test material and a reference control with the reference substance 3,5-dichlorophenol were performed. After 7 days the ErC50 of the reference substance 3,5-dichlorophenol was determined to be 9.94 mg/L. The validity criteria were fulfilled. After 7 days, the ErC50 and the EyC50 based on frond number were determined to be greater than 1000 mg/L. In addition the ErC50 and the EyC50 based on dry weight were determined also to be greater than 1000 mg/L.