Sodium [[α,α'-(ethylenediimino)bis[2-hydroxybenzene-1-acetato]](4-)]ferrate(1-)

Phototransformation in air

Link to relevant study record(s)

Reference

Endpoint:

phototransformation in air

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reason / purpose for cross-reference:

read-across source

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
- Name of test material (as cited in study report): ethylenediamine N,N`bis-(2-hydroxy)phenylacetic acid (EDDHA)

Estimation method (if used):

Not applicable.

Light source:

other: UV lamp (400-W medium-pressure mercury lamp) and visible light

Light spectrum: wavelength in nm:

254 - 436

Details on light source:

- UV lamp: 400-W medium-pressure mercury lamp (254, 313, 365 and 436 nm)
- Visible light: 313 nm (Pyrex filter)

Details on test conditions:

- Preparations: Analytically pure o,o-EDDHA was prepared following the synthetic method. The complex FeIII–EDDHA was obtained as a sodium salt from the pure ligand o,o-EDDHA and ferric chloride in basic medium. Reactions requiring an inert atmosphere were conducted under argon and the glassware was flame-dried under vacuum (<0.2 mmHg). Tetrahydrofuran was distilled from sodium and benzophenone immediately prior to use. 1H NMR and 13C NMR spectra were recorded at 22 °C on Bruker Avance 300 (300.1 and 75.4 MHz) or Bruker 200-AC (200.1 and 50 MHz) spectrometers. Chemical shifts are given in ppm relative to TMS (1H, 0.0 ppm), CDCl3 (13C, 77.0 ppm), C3D6O (1H, 2.0 ppm), C3D6O (13C, 206.0 ppm), D2O/NaCO3 (1H, 4.78 ppm), D2O/NaCO3 (13C, 165.7 ppm). ESI-MS spectra were carried out in methanol using an ESQUIRE-LC (Bruker Daltonic, Bremen, Germany) ion trap spectrometer by using the negative-ion mode.The stainless-steel capillary was held at a potential of 5.0 kV. Nitrogen was used as nebulizer gas at a flow-rate of 3.98 L/min (nebulizer pressure 11 psi) at 150 °C.
- Photochemical procedures: All photochemical reactions were carried out in distilled water at 22 °C in a magnetically stirred Pyrex vessel using a 400-W medium-pressure mercury lamp (lambda max 254, 313, 365, 436 nm) placed in a water-cooled quartz immersion well. For the visible-light experiments (lambda max. 313 nm) a Pyrex filter was used. The pH of the different experiments was adjusted with HCl 2m or NaOH 3m solutions in distilled water. The samples were irradiated either in the presence or in the absence of O2. In the experiments with O2, air was bubbled through the solutions during the irradiation. In the deoxygenated experiments the samples were purged with argon for at least 20 min prior to the irradiation and then irradiated in sealed tubes.

Duration:

24 h

Temp.:

22 °C

Reference substance:

no

Remarks:

Not applicable.

Preliminary study:

No preliminary study performed.

Test performance:

Not applicable.

% Degr.:

49

Sampling time:

24 h

Test condition:

EDDHA, pH 1, UV light, aerob

% Degr.:

25

Sampling time:

24 h

Test condition:

EDDHA, pH 12, UV light, aerob

% Degr.:

2 - <= 6

Sampling time:

24 h

Test condition:

Fe3+-EDDHA, pH 2, 6.5, 11, UV light, visible light, aerob, anaerob

Transformation products:

yes

No.:

#1

No.:

#2

Results with reference substance:

Not applicable.

Validity criteria fulfilled:

yes

Remarks:

Basic scientific principles were met.

Conclusions:

An experimental report about a valid scientific study is present. The chelating agent EDDHA is rather stable to photodegradation, Fe3+-EDDHA is found to be very resistent for this environmental process. The same result is expected for the target substance because the core chemical structures of EDDHA-moiety-containing constituents are the same in the source and in the target substance. Thus the same phototransformation rates are expected.

Executive summary:

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 producte 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.

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. 

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.