Ferrate(1-), [[N,N'-1,2-ethanediylbis[N-[[2-(hydroxy-.kappa.O)phenyl]methyl]glycinato-.kappa.N,.kappa.O]](4-)]-, sodium (1:1), (OC-6-13)-

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2009

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: No standardized experimental procedure, scientific principles are met.

Principles of method if other than guideline:

Chelate stability test. Interaction experiment of iron chelates at different pH values and with presence of Ca2+, which may compete with Fe3+ in calcareous soils.

GLP compliance:

not specified

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
No surrogate or analogue material was used.

Radiolabelling:

not specified

Analytical monitoring:

no

Details on sampling:

No details available.

Buffers:

pH 5 - 6: MES
pH 7-8: HEPES
pH 9: AMPSO
pH 10 - 13: CAPS

Estimation method (if used):

Not applicable.

Details on test conditions:

- Used chelates: HJB/Fe3+, HBED/Fe3+, o,o-EDDHA/Fe3+ and o,p-EDDHA/Fe3+
- Preparation of iron chelate solutions: Fe was added asFe(NO3)3 x 9H2O (5 % in excess respect to the chelating agent), followed by slow addition to a chelating agent solution, maintaining the pH between 6.0 and 8.0 by adding NaOH or HCl. The solution was left overnight and filtered through 0.45μm membranes.
- Test procedures: 1 mL of each solution, 4 mL of 0,125 M CaCl2, and 4 mL of a biological buffer were added to a 50-mL beaker. Then, 30 mL of water were added and the pH adjusted to: 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 10.5,11.0, 11.5, 12.0, 12.5 and 13.0, either with HCl or NaOH solutions as it was needed. Each sample was transferred to a 50 mL volumetric flask, diluted to the mark with water and transferred to a plastic vessel. Solutions were shaken at 25 ºC for 3 days in darkness. At the end of this period pH values and total soluble iron were assessed by AAs.

Number of replicates:

None.

Positive controls:

not specified

Remarks:

Not applicable.

Negative controls:

not specified

Remarks:

Not applicable.

Statistical methods:

No details available.

Preliminary study:

No preliminary study performed.

Test performance:

Neither unusual observations nor deviations from test procedure which will affect the obtained results are reported.

Transformation products:

not specified

Details on hydrolysis and appearance of transformation product(s):

Not applicable.

Remarks on result:

not measured/tested

Other kinetic parameters:

No other kinetic parameters are reported.

Details on results:

HJB/Fe3+ led to iron complexes more stable than o,p-EDDHA/Fe3+ but not as stable as those formed from o,o-EDDHA. HBED/Fe3+ formed extremely stable complexes. In all cases almost the total amount of soluble iron was recovered between pH 2 and 8, but above this point, the stability of the iron complexes was considerably reduced in o,p-EDDHA. Although HJB/Fe3+ showed slightly less stability than o,o-EDDHA iron chelates, the percentage of Fe in solution was 85 % at pH 11.

Validity criteria fulfilled:

yes

Remarks:

Basic scientific principles were met.

Conclusions:

The study report describes an chelate interaction experiment of iron chelates at different pH values. The test substance formed extremely stable complexes.

Executive summary:

Different iron chelates, beside HBED/Fe3+ also HJB/Fe3+, o,o-EDDHA/Fe3+ and o,p-EDDHA/Fe3+ were used in an interaction experiment at different pH values (Lucena et al., 2009). Fe was added as Fe(NO3)3 x 9H2O (5 % in excess respect to the chelating agent), followed by slow addition to a chelating agent solution, maintaining the pH between 6.0 and 8.0 by adding NaOH or HCl. The solution was left overnight and filtered through 0.45μm membranes. 1 mL of each solution, 4 mL of 0,125 M CaCl2, and 4 mL of a biological buffer were added to a 50-mL beaker. Then, 30 mL of water were added and the pH adjusted to: 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 10.5,11.0, 11.5, 12.0, 12.5 and 13.0, either with HCl or NaOH solutions as it was needed. Each sample was transferred to a 50 mL volumetric flask, diluted to the mark with water and transferred to a plastic vessel. Solutions were shaken at 25 ºC for 3 days in darkness. At the end of this period pH values and total soluble iron were assessed by AAs. The following results were obtained, which are in agreement with theoretical modelization: HJB/Fe3+ led to iron complexes more stable than o,p-EDDHA/Fe3+ but not as stable as those formed from o,o-EDDHA. HBED/Fe3+ formed extremely stable complexes. In all cases almost the total amount of soluble iron was recovered between pH 2 and 8, but above this point, the stability of the iron complexes was considerably reduced in o,p-EDDHA. Although HJB/Fe3+ showed slightly less stability than o,o-EDDHA iron chelates, the percentage of Fe in solution was 85 % at pH 11.

Description of key information

Iron chelate interaction experiment: The test substance formed extremely stable complexes.

Additional information

Different iron chelates, beside HBED/Fe3+ also i.e. HJB/Fe3+, o,o-EDDHA/Fe3+ and o,p-EDDHA/Fe3+ were used in an interaction experiment at different pH values (Lucena et al., 2009). Fe was added as Fe(NO3)3 x 9H2O (5 % in excess respect to the chelating agent), followed by slow addition to a chelating agent solution, maintaining the pH between 6.0 and 8.0 by adding NaOH or HCl. The solution was left overnight and filtered through 0.45μm membranes. 1 mL of each solution, 4 mL of 0,125 M CaCl2, and 4 mL of a biological buffer were added to a 50-mL beaker. Then, 30 mL of water were added and the pH adjusted to: 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 10.5,11.0, 11.5, 12.0, 12.5 and 13.0, either with HCl or NaOH solutions as it was needed. Each sample was transferred to a 50 mL volumetric flask, diluted to the mark with water and transferred to a plastic vessel. Solutions were shaken at 25 ºC for 3 days in darkness. At the end of this period pH values and total soluble iron were assessed by AAs. The following results were obtained, which are in agreement with theoretical modellling: HJB/Fe3+ led to iron complexes more stable than o,p-EDDHA/Fe3+ but not as stable as those formed from o,o-EDDHA. HBED/Fe3+ formed extremely stable complexes. In all cases almost the total amount of soluble iron was recovered between pH 2 and 8, but above this point, the stability of the iron complexes was considerably reduced in o,p-EDDHA. Although HJB/Fe3+ showed slightly less stability than o,o-EDDHA iron chelates, the percentage of Fe in solution was 85 % at pH 11.