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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

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Diss Factsheets

Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

L-Cystine is readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

L-Cystine has been tested by Japanese authorities in an OECD 301A guideline study. The publication is written in Japanese with only the results available in English: L-Cystine is readily biodegradable. The read-across substance L-Cysteine has been tested in an OECD 301A guideline study and was also found to be readily biodegradable. The read-across is based on an oxidation study of L-Cysteine in water. It is known that aqueous solutions of L-Cysteine oxidize readily in air to give L-Cystine at neutral or basic pH (data from Biochemical Research, 3rd ed., Dawson,R. M. C., et al., Oxford University Press (New York, NY: 1986), pp. 12-13). Within this analysis it could also be demonstrated that the initial concentrations of two similar samples of the same batch taken on January 11, 2013 show L-Cysteine levels of 94.69 and 97.60 area % when dissolved in the mobile phase. L-Cystine was present at a range of 0.238 to 0.277 area percent at this starting point. Taken together it can be stated that after 4 h of stirring at room temperature the L-Cysteine has been oxidized nearly completely to L-Cystine.