Reaction products of sodium glucoheptonate with copper sulfate and ammonium hydroxide

Endpoint summary

Description of key information

No biodegradation screening test for copper glucoheptonate was available. Therefore, read-across was performed using the source substance sodium gluconate. This approach is justified since biodegradation is not applicable to dissociating metals in aqueous environement. Therefore, only the organic part of copper glucoheptonate, the glucoheptonate moiety undergoes biodegradation. Glucoheptonates and gluconates differ only in one carbon segment (HCOH): glucoheptonate is longer (C7) than gluconate (C6). Thus, biodegradation is expected to be similar for both substances.

Biodegradation of sodium gluconate (CAS 527-07-1) was investigated according to EU Method C.4-E (Closed bottle test) in compliance with GLP (OECD SIDS, 2004).

Based on the ThOD, 61.13% degradation were reported after 3 days, followed by 74.35% after 7 days, 66.09% after 14 days, 71.94% after 21 days and 88.88% after 28 days.

Additional information

According to the data requirements outlined in EU Regulation No. 1907/2006, only screening tests in water are mandatory for this tonnage band.

Referring to biodegradation, two experimental study reports are cited in the OECD SIDS Report (2004) on Gluconic Acid and its Derivatives. Both studies refer to the read-across substance sodium gluconate (CAS 527 -07 -01). Actual data on the target substance is not available for this endpoint. Nevertheless, conclusions drawn on the read-across substance are assignable for the target substance as well.

Referring to the key information, the biodegradation of sodium gluconate (CAS 527-07-1) was investigated according to EU Method C.4-E (Closed bottle test) in compliance with GLP (OECD SIDS, 2004).

All in all, 16 test bottles with a test item concentration of 3 mg/L with 4 mL/L inoculum (secondary effluent of a municipal sewage plant) were filled bubble-free and incubated in the dark at 20°C for 28 days. On days 3, 7, 10, 14, 21 and 28, at least duplicate bottles were removed for determination of dissolved oxygen and pH. At the end of the test, dissolved oxygen concentration in all remaining bottles was measured. Reference item bottles containing sodium acetate stock solution (concentration= 4 mg/L) with 0.4 mL/L inoculum were also filled and incubated in the dark at 20°C. A blank was also prepared without any stock solution.

Referring to the test substance and based on the ThOD, 61.13% degradation were reported after 3 days, followed by 74.35% after 7 days, 66.09% after 14 days, 71.94% after 21 days and 88.88% after 28 days. With regard to the reference substance, 67.15% degradation were measured after 3 days and 80.93% after 28 days – both based on the ThOD.

With regard to the supporting information, the biodegradation of sodium gluconate (CAS 527-07-1) was investigated according to DIN EN ISO 11734 in compliance with GLP (OECD SIDS, 2004).

Washed digested sludge containing very low amounts of inorganic carbon (IC) was diluted to 1-3 g/L total solids concentration and incubated in the absence of oxygen at 35 +/-2°C in sealed vessels with the test item (303 mg/L) at a concentration of 20-200 mg/L total organic carbon (TOC) for 35 days. As reference substance, sodium benzoate (0.069 g/400 mL) has been used. The percentage biodegradation is calculated from the total carbon transformed to biogas and DIC and the measured or calculated amount of carbon added as test item.

Referring to the test substance, 8% degradation has been determined after 1 day, followed by 51% after 8 days, 57% after 15 days, 61% after 22 days and 100% after 35 days. With regard to the reference substance, 6% degradation was determined after 8 days and 100% after 35 days.