Trisodium 2-(carboxylatomethyl(2-hydroxyethyl)amino)ethyliminodi(acetate)

Phototransformation in water

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

phototransformation in water

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Principles of method if other than guideline:

To investigate the photodegradation pathway of Fe-EDTA, an aqueous solution of the substance was irradiated with a xenon arc lamp.
The reaction mixture was sampled over a period of 4 days.

GLP compliance:

no

Radiolabelling:

yes

Light source:

Xenon lamp

Details on light source:

Wide spectrum 5500-W Xenon lamp

Details on test conditions:

To determine the extent of ferric EDTA removal from the environment by interaction with sunlight - i.e. photodegradation - the behaviour of aqueous solutions of ferric-1-14C-EDTA at pH 4.5, 6.9, and 8.5 under irradiation from a xenon lamp has been studied. 

Initial conc. measured:

0.002 mol/L

Key result

% Degr.:

100

Sampling time:

24 h

Test condition:

Direct photolysis

Carbon dioxide, formaldahyde, N-carboxy-methyl-N,N'-ethylenediglycine  (ED3A), N,N'ethylenediglycine (EDDA-N,N'), iminodiacetic acid (IMDA),  N-carboxymethyl-N-aminoethyleneglycine (EDDA-N,N), N-aminoethyleneglycine  (EDMA), and glycine have been identified as the major photodegradation products. No nitrilotriacetic acid (NTA) was detected during photodegradation.

The rate of photodegradation was pH dependent, being most rapid at pH 4.5. At a light intensity of 4000-ft candles and an initial concentration of 0.0016 M Fe(III)-EDTA removal was complete after 24 h of irradiation at either pH 4.5 or pH 6.9 and after 32 h at pH 8.5.

Reference 2

Endpoint:

phototransformation in water

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Study type:

not specified

Principles of method if other than guideline:

EDTA was dissolved in natural lake water and photodegradation over a period of time was determined.

GLP compliance:

not specified

Radiolabelling:

not specified

Analytical method:

high-performance liquid chromatography

Details on sampling:

Exposure to Sunlight: Sampling volume was 10 mL and samples were taken first at the beginning´, second after two weeks and thereafter samples were taken once a week.

Laboratory conditions: Sampling volume was 7 mL, further data are not available

Buffers:

no data availble

Light source:

Xenon lamp

Light spectrum: wavelength in nm:

315 - 400

Details on light source:

laboratory condition: two black lamps (Sylvania F40W/BL, black light 350), yileding 4.8 mW/cm2 at a distance of 100mm.

direct sunlight: The average intensity of solar radiation at the range 290-385 was 0.9 mW/cm2 in June, 0.92 mW/cm2 in July, 0.55 mW/cm2 in August and 0.30 mW/cm2 in September.

Details on test conditions:

laboratory conditions: Test solutionsin 500 mL glass bowls were placed on magnetic stirrers for mixing. Starting concnetration of EDTA was 0.13 mM in destilled and in lake water. The complexation by FeCl3 reduced pH from 6.5 to 3.1 in both media. Therefore one set was carried out where the pH was adjusted to 6.5 using NaOH

Exposure to sunlight: Four 100 L aquariums were used and each held 64 L of the test solution (destilled water in the dark, destilled water in the sunlight, lake water in the dark, lake water in the sunlight). Concentration of EDTA was 0.13 mM. Experiment lasted from June to September.

Duration:

14 wk

Initial conc. measured:

0.13 mmol/L

Reference substance:

not specified

Dark controls:

yes

Computational methods:

The rate of photodegradation of Fe(III)-EDTA seemed to follow first-order kinetics.

Preliminary study:

no data available

% Degr.:

50

Sampling time:

56.8 d

Test condition:

laboratory (lake water)

% Degr.:

50

Sampling time:

45 d

Test condition:

laboratory (distilled water)

% Degr.:

74

Sampling time:

50 d

Test condition:

Exposure to sunlight

Predicted environmental photolytic half-life:

< 50 d without pH adjustment, exposed to direct sunlight.

Transformation products:

not specified

Validity criteria fulfilled:

not specified

Conclusions:

0.13 mM Na2-EDTA did entirely disappear during 50 days from destilled water, wheras 74 % of NA2-EDTA degraded in lake water during this period of time.

Description of key information

Information on phototransformation in water is not required under REACH.

Additional information

Both HEDTA and its surrogate, EDTA, form complexes with ions. Therefore both exist naturally as a mixture of chelate complexes. Some EDTA species, especially the iron complex, are photolysable (EU Risk Assessment, 2004). Metsärine et al. (2001) have shown that, in natural waters, photodegradation of Na2-EDTA is 74% in 50 days.