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Environmental fate & pathways

Phototransformation in water

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Description of key information

The indirect photolysis of Mequinol in water, with Lumichrome as sensitizer, is very rapid in the conditions of the test.

Key value for chemical safety assessment

Additional information

Tatsumi et al. (1992, reliability 2) described the photooxidation of some phenols sensitized by lumichrome which is one of the photobreakdown products of riboflavin. The degradation was followed by HPLC analysis and TOC measurement.

Based on the rate constants reported for direct photolysis, it was possible to assess the DT50 as follows:

DT50 = Ln 2 / rate constant (equation of EU TGD, 2003)

DT50 = 0.4h at pH 7 and 8

DT50 = 0.5 h at pH 9

These half-life values indicate that the indirect photolysis of the substance in water, with Lumichrome as sensitizer, is very rapid. This conclusion is consistent with the measurement of the disappearance of 100% of the substance, when irradiated during 4 hours and concentrations of 300µM and 20µM of test substance and Lumichrome respectively.