Diiron magnesium tetraoxide

Hydrolysis

Administrative data

Endpoint:

hydrolysis

Data waiving:

study technically not feasible

Justification for data waiving:

the study does not need to be conducted because the substance is highly insoluble in water

Cross-reference

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Endpoint:

transformation / dissolution of metals and inorganic metal compounds

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2015-05-06 to 2015-06-15

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Series on Testing and Assessment No. 29 (23-Jul-2001): Guidance document on transformation/dissolution of metals and metal compounds in aqueous media

Version / remarks:

2001

GLP compliance:

yes (incl. QA statement)

Type of method:

other: transformation/ dissolution

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.904 µg/L

Element analysed:

Fe

Loading of aqueous phase:

1 mg/L

Incubation duration:

672 h

Test conditions:

pH 6, agitation at 100 rpm, 21.5 ± 1.5 °C

Remarks on result:

other: at least

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.301 µg/L

Element analysed:

Fe

Loading of aqueous phase:

1 mg/L

Incubation duration:

168 h

Test conditions:

pH 6, agitation at 100 rpm, 21.5 ± 1.5 °C

Remarks on result:

other:

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.301 µg/L

Element analysed:

Fe

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

pH 6, agitation at 100 rpm, 21.5 ± 1.5 °C

Remarks on result:

other:

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.185 µg/L

Element analysed:

Fe

Loading of aqueous phase:

1 mg/L

Incubation duration:

672 h

Test conditions:

pH 8, agitation at 100 rpm, 21.5 ± 1.5 °C

Remarks on result:

other:

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.185 µg/L

Element analysed:

Fe

Loading of aqueous phase:

1 mg/L

Incubation duration:

168 h

Test conditions:

pH 8, agitation at 100 rpm, 21.5 ± 1.5 °C

Remarks on result:

other:

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.555 µg/L

Element analysed:

Fe

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

pH 8, agitation at 100 rpm, 21.5 ± 1.5 °C

Remarks on result:

other: at least

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.445 µg/L

Element analysed:

Zn

Loading of aqueous phase:

1 mg/L

Incubation duration:

672 h

Test conditions:

pH 6, agitation at 100 rpm, 21.5 ± 1.5 °C

Remarks on result:

other: at least < LOQ (<0.4446)

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

2.746 µg/L

Element analysed:

Zn

Loading of aqueous phase:

1 mg/L

Incubation duration:

168 h

Test conditions:

pH 6, agitation at 100 rpm, 21.5 ± 1.5 °C

Remarks on result:

other: SD: ± 0.241 µg/L

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

1.537 µg/L

Element analysed:

Zn

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

pH 6, agitation at 100 rpm, 21.5 ± 1.5 °C

Remarks on result:

other: SD: ± 1.448 µg/L

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.041 µg/L

Element analysed:

Zn

Loading of aqueous phase:

1 mg/L

Incubation duration:

672 h

Test conditions:

pH 8, agitation at 100 rpm, 21.5 ± 1.5 °C

Remarks on result:

other: < LOD (<0.0411)

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.041 µg/L

Element analysed:

Zn

Loading of aqueous phase:

1 mg/L

Incubation duration:

168 h

Test conditions:

pH 8, agitation at 100 rpm, 21.5 ± 1.5 °C

Remarks on result:

other: < LOD (<0.0411)

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

0.209 µg/L

Element analysed:

Zn

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

pH 8, agitation at 100 rpm, 21.5 ± 1.5 °C

Details on results:

Temperature
The temperature of the thermostatically controlled room was recorded with a Testo 175-T2 data logger. The mean temperature was 20.3 ± 0.3 °C during the test with 1 mg/L loading at pH 6 and 20.4 ± 0.2 °C during the test at pH 8. Therefore, the mean temperature is in agreement with the OECD guidance document 29.

Solution pH and oxygen concentrations
In solutions containing 1 mg/L of the test item at pH 6 and pH 8 as well as in method blanks (BW), the pHs were in the range of 5.8 – 6.6 and 7.4 – 8.1, respectively

Mass balance
The measured iron concentrations in samples with test item were mostly below respective LODs/LOQs or slightly above. Therefore, these amounts of iron were not considered for calculation of mass balance. The recovery was 21.4 % - 61.0 % for pH 6 and 42.0 – 51.4 % for pH 8., indicating that aqua regia is not sufficient for a complete dissolution of the test item. This is expected for inorganic pigments.

Within-vessel variation and between-vessel variation
According to the guidance, “[…]it is reasonable to anticipate that for a constant loading of a substance, tested in a narrow particle size (e.g. 37 - 44 μm) and total surface area range, the within-vessel variation in transformation data should be less than 10 % and the between-vessel variation should be less than 20 %”.
The particle size distribution of each loading replicate may differ and thus resulting in different overall total surface areas per vessel. Since the exposed surface area is affecting the rate of transformation and dissolution of sparingly soluble metal compounds, increases in vessel variations may be observed in tests of materials with wider particle size distributions.
For the measured iron and zinc concentrations these variations are mostly not within the limits
Background concentrations for zinc at pH 6 and pH 8 were measured to be in the range of test item loaded samples. Therefore, the measured concentrations from test item loaded vessels at pH 6 and 8 were background (means) corrected. The background concentration of iron was below the LOD.

Method validation summary

Validation parameter	Results	Comment
selectivity	selective wavelength and isotopes for detection and evaluation of Fe and Zn
linearity	applied calibration functions were linear	correlation factor at least 0.999961
limit of detection	Fe: 0.1216 – 0.7443 µg/L Zn: 0.0149 – 0.1482 µg/L
limit of quantification	Fe: 0.3647 – 2.2298 µg/L Zn: 0.0448 – 0.4446 µg/L
accuracy and precision	Mean recovery for TM-25.4 1st series: Fe (259.940 nm): 94.6 ± 1.6 % (n = 10) Zn (213.857 nm): 103.1 ± 1.8 % (n = 10) 2nd series: Fe (240.489 nm): 92.2 ± 2.7 % (n = 4) 3rd series: Fe (259.940 nm): 113.9 ± 39.8 % (n = 11) Zn (202.548 nm): 98.9 ± 3.4 % (n = 11) 4th series: Fe (239.563 nm): 108.2 ± 23.5 % (n = 4) 5th series: Fe (259.940 nm): 103.1 ± 21.7 % (n = 7) Zn (202.548 nm): 99.6 ± 2.7 % (n = 7)	Diluted (5 fold) to 6.2 μg Fe/L, 8.9 μg Zn/L Due to ubiquitous Fe a slight contamination cannot be excluded for two samples from 3rd series, one sample from 4th series and one sample from 5th series. These are not within 100 ± 15 % resulting in these standard deviations. Not critical > 60% of all QA/QC samples are within these limits.
accuracy and precision	Mean recovery for TMDA-53.3 2nd series: Fe (240.489 nm): 100.8 ± 1.9 % (n = 4) 3rd series: Fe (259.940 nm): 110.1 ± 39.7 % (n = 11) Zn (202.548 nm): 96.3 ± 1.1 % (n = 11) 4th series: Fe (239.563 nm): 103.6 ± 7.1 % (n = 4) 5th series: Fe (259.940 nm): 99.6 ± 5.1 % (n = 7) Zn (202.548 nm): 102.5 ± 11.1 % (n = 7)	Diluted (10 fold) to 32.5 μg Fe/L, 38.5 μg Zn/L The increased standard deviation in the 3rd series for Fe might be due to a contamination with ubiquitious Fe; one sample is not within 100 ± 15 %. Not critical > 60% of all QA/QC samples are within these limits.
accuracy and precision	Mean recovery for TMDA-53.3 1st series: Fe (259.940 nm): 97.9 ± 1.1 % (n = 10) Zn (213.857 nm): 102.4 ± 1.0 % (n = 10)	Diluted (5 fold) to 65 μg Fe/L, 77.2 μg Zn/L
accuracy and precision	Mean recovery for quality control standard QC 1st series: Fe (259.940 nm): 95.5 ± 1.8 % (n = 10) Zn (213.857 nm): 92.4 ± 2.1 % (n = 10) 2nd series: Fe (240.489 nm): 98.5 ± 2.0 % (n = 4)	Diluted to 10 μg Fe/L, 10 μg Zn/L
accuracy and precision	Mean recovery for quality control standard QC1 3rd series: Fe (259.940 nm): 96.6 ± 0.9 % (n = 8); Zn (202.548 nm): 95.4 ± 1.6 % (n = 8) 4th series: Fe (239.563 nm): 97.3 ± 2.1 % (n = 4) 5th series: Fe (259.940 nm): 95.8 ± 2.1 % (n = 7); Zn (202.548 nm): 92.4 ± 2.4 % (n = 7)	Diluted to 10 μg Fe/L, 10 μg Zn/L
accuracy and precision	Mean recovery for quality control standard QC1 3rd series: Fe (259.940 nm): 97.2 ± 0.6 % (n = 2) Zn (202.548 nm): 95.1 ± 0.3 % (n = 3)	Diluted to 100 μg Fe/L, 100 μg Zn/L In the 3rd series one sample with a recovery of 428 % regarding Fe is rejected because this can assigned to a Fe contamination. Not critical > 60% of all QA/QC samples are within these limits.
accuracy and precision	Mean recovery for recalibration standard 1st series: Fe (259.940 nm): 94.7 ± 10.6 % (n = 10) Zn (213.857 nm): 104.0 ± 44.4 % (n = 10) 2nd series: Fe (240.489 nm): 91.2 ± 3.9 % (n = 4) 3rd series: Fe (259.940 nm): 101.8 ± 6.0 % (n = 8) Zn (202.548 nm): 85.7 ± 1.0 % (n = 8) 4th series: Fe (239.563 nm): 95.9 ± 2.0 % (n = 4) 5th series: Fe (259.940 nm): 99.7 ± 2.6 % (n = 7) Zn (202.548 nm): 104.2 ± 10.9 % (n = 7)	Diluted to 5 μg Fe/L, 5 μg Zn/L The increased standard deviation in the 5th series for Zn might be due to a contamination with ubiquitous Zn; one sample is not within 100 ± 15 %. Not critical > 60% of all QA/QC samples are within these limits.
accuracy and precision	Mean recovery for recalibration standard 3rd series: Fe (259.940 nm): 97.7 ± 0.6 % (n = 3) Zn (202.548 nm): 94.3 ± 0.3 % (n = 3)	Diluted to 50 μg Fe/L 50 μg Zn/L
trueness	Mean recoveries of fortified samples: Fe: 81.8 – 109.6 % Zn: 84.0 – 164.9 %	In sample fortification from the 1st and the 5th measurement series there was obviously a mistake in sample preparation because the recoveries are not all within 100 ± 15 %. This is not critical, the series are valid because > 60 % of all QA/QC samples are within these limits. This approach is according to internal SOPs for GLP and accreditation according to ISO 17025

Recoveries of fortified samples Iron (values were rounded, internal calculations were performed with more digits)

	measured Fe [μg/L]	calculated Fe after addition [μg/L]	Recovery [μg Fe/L]	Recovery [%]
1st series 1 mL of sample + 4 mL of 5 μg Fe/L
vessel 4, sample a after 2h	<LOD	4.000	4.148	103.7
vessel 4, sample a after 6h	<LOD	4.000	4.255	106.4
vessel 4, sample a after 1d	<LOD	4.000	4.305	107.6
vessel 4, sample a after 4d	<LOQ	4.000	4.214	105.3
vessel 4, sample a after 7d	<LOD	4.000	4.127	103.2
vessel 4, sample a after 14d	0.914	4.183	4.583	109.6
vessel 4, sample a after 21d	<LOQ	4.000	4.266	106.7
vessel 4, sample a after 28d	<LOD	4.000	4.182	104.6
2nd series 2 mL of sample + 3 mL of 75 μg Fe/L
vessel 4	95.64	83.254	84.302	101.3
4th series 2 mL of sample + 3 mL of 75 μg Fe/L
vessel 1	201.213	60.243	61.925	102.8
5th series 1 mL of sample + 4 mL of 50 μg Fe/L
vessel 1, sample a after 2h	1.595	40.319	34.124	84.6
vessel 1 sample a after 6h	<LOD	40.000	33.185	83.0
vessel 1, sample a after 1d	<LOQ	40.000	32.902	82.3
vessel 1, sample a after 4d	<LOQ	40.000	32.991	82.5
vessel 1, sample a after 7d	22.402	44.480	36.867	82.9
vessel 1, sample a after 14d	<LOD	40.000	32.735	81.8
vessel 1, sample a after 21d	<LOD	40.000	32.923	82.3
vessel 1, sample a after 28d	<LOD	40.000	32.895	82.2

Recoveries of fortified samples Zinc (values were rounded, internal calculations were performed with more digits)

	measured Zn [μg/L]	calculated Zn after addition [μg/L]	Recovery [μg Zn/L]	Recovery [%]
1st series 1 mL of sample + 4 mL of 5 μg Zn/L
vessel 4, sample a after 2h	1.217	4.243	6.706	158.0
vessel 4, sample a after 6h	1.539	4.308	6.921	160.7
vessel 4, sample a after 1d	1.881	4.376	7.012	160.2
vessel 4, sample a after 4d	1.449	4.290	6.860	159.9
vessel 4, sample a after 7d	1.564	4.313	6.884	159.6
vessel 4, sample a after 14d	2.386	4.477	7.381	164.9
vessel 4, sample a after 21d	2.911	4.582	6.984	152.4
vessel 4, sample a after 28d	2.716	4.543	7.245	159.5
5th series 1 mL of sample + 4 mL of 50 μg Zn/L
vessel 1, sample a after 2h	2.110	40.422	34.249	84.7
vessel 1 sample a after 6h	1.360	40.272	34.518	85.7
vessel 1, sample a after 1d	0.696	40.139	34.015	84.7
vessel 1, sample a after 4d	1.244	40.249	34.118	84.8
vessel 1, sample a after 7d	2.573	40.515	34.258	84.6
vessel 1, sample a after 14d	1.752	40.350	33.981	84.2
vessel 1, sample a after 21d	10.927	42.185	34.295	81.3
vessel 1, sample a after 28d	1.767	40.353	34.261	84.9

Conclusions:

The transformation/dissolution test (OECD Series on Testing and Assessment Number 29, 2001) of "Magnesium ferrite " at a loading of 1 mg/L at pH 6 and 8, performed for 28d, resulted in Fe concentrations below the LOD/LOQ and maximum Zn concentrations of 2.75 µg/L (pH = 6, 7d). Thus, the extent to which "Magnesium ferrite " can produce soluble available ionic and other metal-bearing species in aqueous media is limited.