Disodium 2-(3-oxo-6-oxidoxanthen-9-yl)benzoate

Biodegradation in water: screening tests

Description of key information

A combination of two biodegradation tests (Closed Bottle test and Manometric Respiratory test, OECDs 301 D, F) was carried out to investigate the biodegradability of the Uranine.  Closed Bottle Test was performed according to the guidelines of the Organization for Economic Co-operation and Development OECD 301D. This test is characterized by low bacteria density (102–105 colony forming units (CFUs)/mL), low nutrient content, and constant temperature (20 ± 1 °C) and it was kept in the dark. The average percentage biodegradation value of test substance Uranine after 28 days by oxygen concentration was found to be 7.6%. Based on the results obtained, Uranine is expected to be not readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

A number of studies for the test compoundSodium fluorescein (CAS no 518-47-8) were reviewed for the biodegradation end point which are summarized as below:

 

A combination of two biodegradation tests (Closed Bottle test and Manometric Respiratory test, OECDs 301 D, F) was carried out to investigate the biodegradability of the Uranine (Lukasz Gutowski et. al; 2015).Closed Bottle test was performed according to the guidelines of the Organization for Economic Co-operation and Development OECD 301D. This test is characterized by low bacteria density (10²–10⁵colony forming units (CFUs)/mL), low nutrient content, and constant temperature (20 ± 1 °C) and it was kept in the dark. The average biodegradation value after 28 days for Uranine monitored by measurement of the oxygen concentration was found to be 7.6%.

The Manometric Respiratory tests works with higher bacterial density (5–10×10⁶CFUs/mL) and diversity as the Closed Bottle test thus increasing the probability for biodegradation. This test was also performed according to the OECD guidelines in the dark at room temperature (20 ± 1 °C) under gentle stirring. CO2 production as the parameter of the endpoint biodegradation was measured indirectly by the OxiTop OC110-system. The concentration of standard solution for uranine was 16.7 mg/L, corresponding to the theoretical oxygen demand ThOD of 30 mg/L. Inoculum was derived from the municipal sewage treatment plant (Lüneburg, Germany).Aliquots (measuring) of 80ml of inoculum were added to 1 L of mineral medium. The test consisted of four different series: (i) a blank series (containing only the mineral medium and inoculum), (ii) quality control (containing readily biodegradable sodium acetate as the only relevant carbon source apart from the inoculum), (iii) a test series (containing the target compound) and (iv) toxicity control (containing target compound and sodium acetate as carbon source). The amount of sodium acetate for each series corresponded to ThOD of 5 mg/L. Samples from the beginning (day 0) and the end of the test (day 28) were collected and stored at−20 °C until analysis with HPLC-FLD and LC–M/MS. No toxic effects on bacteria were observed in the toxicity control as well as no degradation was observed in the sterile control. The measurements with HPLC-FLD confirmed that no elimination of uranine occurred during the Manometric Respiratory Test. Only 0.1% degradation of test substance Uranine was observed. Based on the results obtained in Closed Bottle test and Manometric Respiratory test method, Uranine is expected to be not readily biodegradable.

 

Aerobic biodegradation study (U. Pagga and O. Brown, 1986) of fluorescein sodium was studied by a modification of the OECD Guideline 302B used as the static test method.In the test experiment, test chemical was exposed with concentration of 100 mg/l in an activated sludge of 0.5g/l dry material upto 42 days. Feeding of the inoculums carried out each week at 100 mg/l yeast extract.The parameter followed for biodegradation was DOC elimination. Based on study results of test substance sodium fluorescein i.e, only 11% degradation by DOC removal after 42 days and thus the substance cannot be considered as inherently biodegradable.

Biodegradation screening test (J-CHECK, 2016) was conducted for 28 days (4 weeks) for evaluating the percentage biodegradability of the test substance. The purity of test substance by HPLC was found to be 92.1% and water solubility value is ≥ 300 g/l at 20ᵒC (Flask method). GLP compliance is followed for biodegradation study. By analytical methods, the recovery ratio was found to be-

(Water + test substance) system: 98.4 %

(Activated sludge + test substance) system: 99.0 %

Concentration of inoculum i.e, sludge is 30 mg/l and initial test substance conc. used in the study is 100 mg/l. The percentage degradation of test substance is found to be 0% by O2 consumption and by TOC removal whereas only 1% degradation was observed by HPLC. Thus, the substance Fluorescein sodium isexpected to benot readily biodegradable.

 

 

On the basis of above results of various studies for target substance, it can be concluded that the substance can be considered as non-biodegradable in nature.