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EC number: 283-042-4 | CAS number: 84539-54-8
Phototransformation in air
Administrative data
Link to relevant study record(s)
Description of key information
Irradiation experiment, 24 h, UV and visible light, different pH values, aerobic and anaerobic conditions: The chelating agent EDDHA is rather stable to photodegradation, only at extreme pH values some photoreactivity was observed. Fe3+-EDDHA is very resistant to photochemical degradation.
Key value for chemical safety assessment
Additional information
The publication reports about experimental investigations of the chelating agent EDDHA as well as the complex Fe3+-EDDHA concerning photodegradation in air (Gómez-Gallego et al., 2005). Irradiations with UV light were done using a 400-W medium-pressure mercury lamp (lambda max.: 254, 313, 365 and 436 nm). Visible light (lambda max. > 313 nm) experiments were performed with a Pyrex filter. The irradiation time was 24 h in all experimental procedures. Under acidic conditions (pH 1) with UV light under aerobic conditions, the experiment with EDDHA leads to the main reaction product o-hydroxyphenyl glycine (44 %) with 51 % unaltered starting material. In visible light, the photodegradation is much slower and only trace amounts of the main product were detected (< 2 %), whereas 93 % EDDHA was recovered unaltered. Using the same conditions, but an alkalic environment, salicylaldehyde imine (11 %) is found as degradation product, accompanied by 73 - 75 % unreacted starting material. Thus, the chelating agent is rather stable to photodegradation and only at extreme pH values (which are rarely found in nature, below pH 2 and above pH 8), some photoreactivity is observed. Furthermore, the process requires UV light. The chelate Fe3+-EDDHA was investigated at pH 2, 6.5 and 11 under aerobic conditions with UV and visible light and was found to be stable in the range of pH 3 - 10. Practically unaltered iron chelate was found in acidic solution. In basic medium, small amounts (6 %) of salicyclic acid and salicylaldehyde were identified. In neutral solution, the chelate was totally inert. Therefore, Fe3+-EDDHA can be considered as very resistant to photochemical degradation in air.
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