Reaction mass of Willemite, white and zinc iron chromite brown spinel

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

transformation / dissolution of metals and inorganic metal compounds

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

deviation from the guideline, which do not effect the validity of the 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

Deviations:

yes

Remarks:

The 28-day test with a loading of 1 mg/L was conducted at pH 6 instead of 5.5

GLP compliance:

yes (incl. QA statement)

Remarks:

2011-02-07

Type of method:

flask method

Type of test:

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

Mean dissolved conc.:

0.21 µg/L

Element analysed:

Cr

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

pH 6

Remarks on result:

other: SD: +/- 0.04 µg Cr/L

Key result

Type of test:

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

Mean dissolved conc.:

0.56 µg/L

Element analysed:

Cr

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

pH 6

Remarks on result:

other: SD: +/- 0.10 µg Cr/L

Key result

Type of test:

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

Mean dissolved conc.:

0.74 µg/L

Element analysed:

Cr

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

pH 6

Remarks on result:

other: SD: +/- 0.06 µg Cr/L

Type of test:

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

Mean dissolved conc.:

107 µg/L

Element analysed:

Zn

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

pH 6

Remarks on result:

other: SD: +/- 7.38 µg Zn/L

Key result

Type of test:

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

Mean dissolved conc.:

127 µg/L

Element analysed:

Zn

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

pH 6

Remarks on result:

other: SD: +/- 7.11 µg Zn/L

Key result

Type of test:

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

Mean dissolved conc.:

119 µg/L

Element analysed:

Zn

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

pH 6

Remarks on result:

other: SD: +/- 7.98 µg Zn/L

Type of test:

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

Element analysed:

Fe

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

pH 6

Remarks on result:

other: < LOD

Key result

Type of test:

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

Mean dissolved conc.:

0.76 µg/L

Element analysed:

Fe

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

pH 6

Remarks on result:

other: SD: +/- 0.01 µg Fe/L

Key result

Type of test:

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

Mean dissolved conc.:

1.83 µg/L

Element analysed:

Fe

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

pH 6

Remarks on result:

other: SD: +/- 0.02 µg Fe/L

Type of test:

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

Element analysed:

Al

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

pH 6

Remarks on result:

other: < LOD/LOQ

Key result

Type of test:

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

Element analysed:

Al

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

pH 6

Remarks on result:

other: < method blank concentration

Key result

Type of test:

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

Element analysed:

Al

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

pH 6

Remarks on result:

other: < method blank concentration

Details on results:

Temperature: The mean temperatures were 21.1 ± 0.5 °C for 1 mg/L test.

Solution pH and oxygen levels:
The solution pH remained relatively constant during the 28 days for pH 6 treatment in vessels containing 1 mg/L of the test item and in method blanks, pH was in the range of 5.7 - 6.3. Oxygen levels in all test vessels 1 mg/L loadings were in the range recommended by the OECD Test Guidance 29 during the test: above 70 % of oxygen saturation at 8.5 mg/L (70 % of 8.5 mg/L = 6 mg/L).

Mass balance
After 12 h of digestion with added aqua regia, less insoluble residues were observed in all vessels, indicating an incomplete dissolution/transformation of the test item. Therefore, the pigment could not be dissolved and the recovery is < 100 % for the element zinc in media at pH 6.

Method validation summary (ICP-OES)

validation parameter	results	Comment
Selectivity	similar data with different element wavelengths for ICP-OES method	no interferences observed
Linearity	applied calibration functions were linear	correlation coefficient at least 0.9987
Limit of detection	Al: 1.39 – 1.89 µg/L Zn: 0.35 – 5.07 µg/L
Limit of quantification	Al: 4.17 – 5.67 µg/L Zn: 1.06 – 16.9 µg/L
Accuracy Al	mean recovery for CRM TMDA-70 (dilution factor 10): Al: 107 ± 4.3 (n = 10)	mid concentration range (Al: 415 µg/L; diluted 41.5 µg/L)
Accuracy Al	mean recovery for CRM TM15.2: Al: 111 ± 2.4 (n = 10)	low concentration range (Al: 33.9 µg/L)
Accuracy Zn	mean recovery for CRM TMDA-70 (dilution factor 10): Zn: 103 ± 4.7 (n = 2)	low concentration range (Zn: 477 µg/L; diluted 47.7 µg/L)
Accuracy Zn	mean recovery for CRM TMDA-70 (dilution factor 2): Zn: 107 ± 0.6 (n = 3)	high concentration range (Zn: 477 µg/L; diluted 239 µg/L)
Trueness Al	mean recovery for recalibration standard: Al: 106 ± 3.8 % (n = 10)	high concentration range (50 µg/L)
Trueness Zn	mean recovery for quality control standard (Merck IV): Zn: 94.1 ± 2.3 % (n = 5)	low concentration range (50 µg/L)
Trueness Zn	mean recovery for recalibration standard: Zn: 98.0 ± 0.5 % (n = 5)	mid concentration range (100 µg/L)
Reproducibility Al	mean recovery for CRM TMDA-70 (dilution factor 10): Al: 107 ± 4.3 (n = 10)	mid concentration range (Al: 415 µg/L; diluted 41.5 µg/L)
Reproducibility Al	mean recovery for CRM TM15.2: Al: 111 ± 2.4 (n = 10)	low concentration range (Al: 33.9 µg/L)
Reproducibility Zn	mean recovery for CRM TMDA-70 (dilution factor 10): Zn: 103 ± 4.7 (n = 2)	low concentration range (Zn: 477 µg/L; diluted 47.7 µg/L)
Reproducibility Zn	mean recovery for CRM TMDA-70 (dilution factor 2): Zn: 107 ± 0.6 (n = 3)	high concentration range (Zn: 477 µg/L; diluted 239 µg/L)

Method validation summary (ICP-MS)

validation parameter	results	Comment
Selectivity	similar data with at least two different isotopes for ICP-MS method or with similar isotope in different gas mode	measurements with best recoveries of reference material were used for calculation
Linearity ICP-MS	applied calibration functions were linear	correlation factor at least 0.9991
Limit of detection	Cr: 0.003 – 0.01 µg/L Fe: 0.02 – 0.10 µg/L Zn: 0.02 – 0.24 µg/L
Limit of quantification	Cr: 0.01 – 0.03 µg/L Fe: 0.05 – 0.30 µg/L Zn: 0.06 – 0.72 µg/L
Method blanks Cr	Mainly method blanks below LOD/LOQ, few above LOQ	method blanks >LOQ are below the sample concentration (>factor 9.00 – 46.2)
Method blanks Fe	Method blanks mainly above LOQ and mainly same concentration as in samples at least 2.62 (504 h), 2.86 (168 h) and 3.36 (672 h) fold lower than concentrations in samples	method blanks for sampling point 168h, 504h and 672h >LOQ are below the sample concentration (>2.86 factor, 2.62 factor and 3.36 factor)
Method blanks Zn	Method blanks above LOQ	Method blanks >LOQ are below the sample concentration (>factor 42.5 – 77.2)
Accuracy	mean recovery for CRM TMDA-70 (dilution factor 20): Cr: 102 ± 5.2 % (n = 15) Fe: 108 ± 6.1 % (n = 14) Zn: 104 ± 6.7 % (n = 10; samples 336 h, 504 h and 672 h and method blanks) Zn: 100 ± 4.4 % (n = 6; samples 2 h, 6 h, 24 h, 96 h and 168 h)	high concentration range of samples (389 µg Cr/L – diluted 19.45 µg Cr/L; 368 µg Fe/L – diluted 18.4 µg Fe/L; 477 µg Zn/L – diluted 47.7 µg Zn/L)
Accuracy	mean recovery for CRM TM15.2 (dilution factor 10): Cr: 101 ± 6.1 % (n = 15) Fe: 111 ± 11 % (n = 14) Zn: 107 ± 12 % (n = 10; samples 336 h, 504 h and 672 h and method blanks) Zn: 101 ± 9.2 % (n = 6; samples 2 h, 6 h, 24 h, 96 h and 168 h)	low concentration range of samples (16.4 µg Cr/L – diluted 1.64 µg Cr/L; 25.8 µg Fe/L – diluted 2.58 µg Fe/L; 35.4 µg Zn/L – diluted 3.54 µg Zn/L)
Trueness	mean recovery for quality control standard CPI standard (5 µg/L): Cr: 98.0 ± 1.7 % (n = 5) Fe: 100 ± 4.4 % (n = 8) Zn: 97.7 ± 9.4 % (n = 9; samples 336 h, 504 h and 672 h and method blanks)	Mid concentration range
Trueness	mean recovery for quality control standard CPI standard (1 µg/L): Cr: 98.5 ± 2.1 % (n = 5) Fe: 98.5 ± 8.0 % (n = 7) Zn: 101 ± 18 % (n = 6; samples 336 h, 504 h and 672 h and method blanks)	Low concentration range
Trueness	mean recovery for quality control standard CPI standard (10 µg/L): Zn: 100 ± 13 % (n = 6; samples 2 h, 6 h, 24 h, 96 h and 168 h)	Low concentration range
Trueness	mean recovery for recalibration standard (5 µg/L): Cr: 105 ± 2.0 % (n = 4) Fe: 115 ± 5.3 % (n = 4)	Mid concentration range
Trueness	mean recovery for recalibration standard (1 µg/L): Cr: 94.9 ± 2.7 % (n = 4)	Low concentration range
Trueness	Fortification of samples in the range of 90.8% - 97.8%	See tableTable15
Trueness	Fortification of samples Zn remeasurement in the range of 88.6 % - 108 %	See tableTable16
Reproducibility	mean recovery for CRM TMDA-70 (dilution factor 20): Cr: 102 ± 5.2 % (n = 15) Fe: 108 ± 6.1 % (n = 14) Zn: 104 ± 6.7 % (n = 10; samples 336 h, 504 h and 672 h) Zn: 100 ± 4.4 % (n = 6; samples 2 h, 6 h, 24 h, 96 h and 168 h)	high concentration range of samples (389 µg Cr/L – diluted 19.45 µg Cr/L; 368 µg Fe/L – diluted 18.4 µg Fe/L; 477 µg Zn/L – diluted 47.7 µg Zn/L)
Reproducibility	mean recovery for CRM TM15.2 (dilution factor 10): Cr: 101 ± 6.1 % (n = 15) Fe: 111 ± 11 % (n = 14) Zn: 107 ± 12 % (n = 10; samples 336 h, 504 h and 672 h) Zn: 101 ± 9.2 % (n = 6; samples 2 h, 6 h, 24 h, 96 h and 168h)	low concentration range of samples (16.4 µg Cr/L – diluted 1.64 µg Cr/L; 25.8 µg Fe/L – diluted 2.58 µg Fe/L; 35.4 µg Zn/L – diluted 3.54 µg Zn/L)

 

Measured dissolved aluminium concentrations for loading 1 mg/L pH 6 after 7 d and 28 d (with mean blank subtraction)

sample	LOD [µg/L]	LOQ [µg/L]	Mean Al conc. per vessel ± SD [µg/L]	Mean Al conc. all vessels ± SD [µg/L]
1 168h	1.39	4.17	Below method blank concentration	Below method blank concentration
2 168h	1.39	4.17	Below method blank concentration
3 168h	1.39	4.17	Below method blank concentration
1 672h	1.39	4.17	Below method blank concentration	Below method blank concentration
2 672h	1.39	4.17	Below method blank concentration
3 672h	1.39	4.17	Below method blank concentration

Measured dissolved chromium concentrations for loading 1 mg/L pH 6 after 7 d and 28 d (with mean blank subtraction)

sample	LOD [µg/L]	LOQ [µg/L]	Mean Cr conc. per vessel ± SD [µg/L]	Mean Cr conc. all vessels ± SD [µg/L]
1 168h	0.01	0.03	0.48 ± 0.03	0.56 ± 0.10
2 168h	0.01	0.03	0.68 ± <0.01
3 168h	0.01	0.03	0.51 ± 0.03
1 672h	0.01	0.03	0.70 ± 0.01	0.74 ± 0.06
2 672h	0.01	0.03	0.81 ± 0.04
3 672h	0.01	0.03	0.70 ± <0.01

Measured dissolved iron concentrations for loading 1 mg/L pH 6 after 7 d and 28 d (with mean blank subtraction)

sample	LOD [µg/L]	LOQ [µg/L]	Mean Fe conc. per vessel ± SD [µg/L]	Mean Fe conc. all vessels ± SD [µg/L]
1 168h	0.02	0.05	<LOD	0.76 ± 0,01
2 168h	0.02	0.05	0.76 ± 0,01
3 168h	0.02	0.05	<LOD
1 672h	0.10	0.29	<LOD/LOQ	1.83 ± 0,02
2 672h	0.10	0.29	1.83 ± 0,02
3 672h	0.10	0.29	<LOD / Below method blank concentration

Measured dissolved zinc concentrations for loading 1 mg/L pH 6 after 7 d and 28 d (with mean blank subtraction)

sample	LOD [µg/L]	LOQ [µg/L]	Mean Zn conc. per vessel ± SD [µg/L]	Mean Zn conc. all vessels ± SD [µg/L]
1 168h	0.02	0.06	123 ± 0.20	127 ± 7.11
2 168h	0.02	0.06	136 ± 1.24
3 168h	0.02	0.06	121 ± 0.08
1 672h	0.12	0.37	124 ± 0.81	119 ± 7.93
2 672h	0.12	0.37	125 ± 0.30
3 672h	0.12	0.37	109 ± 0.54

FORTIFICATION

Selected samples were analysed by ICP-MS after fortification with a known amount of chromium, iron and zinc (by standard addition of a commercial multi element standard; Merck VIII Multi element standard 1000 mg/L lot no. HC957274, Darmstadt, Germany) and recoveries were determined Recoveries of fortified test samples (Cr, Fe and Zn) were in the range of 90.8 – 97.8 %.

 

Recovery of fortified samples 1 mg/L loading

sample	measured concentration [µg/L]	calculated level after addition [µg/L] #	recovery [µg/L] / [%] #
loading 1 mg/L	Cr	Cr	Cr
sample b vessel 3 672h	0.71	6.88	6.25 / 90.8
loading 1 mg/L	Fe	Fe	Fe
sample b vessel 2 672h	2.33	22.1	20.9 / 94.4
loading 1 mg/L	Zn	Zn	Zn
sample a vessel 1 672h	128	135	132 / 97.8

# values were rounded. Calculations were performed with more digits.

Furthermore selected samples were analysed by ICP-MS after fortification with a known amount of zinc (by standard addition of a commercial multi element standard; Merck VIII Multi element standard 1000 mg/L lot no. HC957274, Darmstadt, Germany) and recoveries were determined. Recoveries of fortified test samples were in the range of 88.6 – 108 %.

Recovery of fortified samples 1 mg/L loading

sample	measured concentration [µg/L]	calculated level after addition [µg/L] #	recovery [µg/L] / [%] #
loading 1 mg/L	Zn	Zn	Zn
sample a vessel 1 2h	89.1	124	110 / 88.6
sample a vessel 1 6h	71.9	110	118 / 108
sample a vessel 1 24h	101	134	139 / 104
sample a vessel 1 96h	114	145	149 / 103
sample a vessel 1 168h	126	155	158 / 102

# values were rounded.

Conclusions:

The transformation/dissolution of the pigment reaction mass of willemite, white and zinc iron chromite brown spinel was measured according to the method OECD test series No. 29 (Guidance document on transformation/dissolution of metals and metal compounds in aqueous media). The transformation/dissolution of the pigment resulted in the following dissolved concentrations:

Full test, 1 mg/L loading, 24 h at pH 6:
- chromium: 0.21 ± 0.04 µg/L
- aluminium: < LOD/LOQ
- zinc: 107 ± 7.38 µg/L
- iron: < LOD

Full test, 1 mg/L loading, 7 days at pH 6:
- chromium: 0.56 ± 0.10 µg/L
- aluminium: below method blank concentration
- zinc: 127 ± 7.11 µg/L
- iron: 0.76 ± 0.01 µg/L

Full test, 1 mg/L loading after 28 days at pH 6:
- chromium: 0.74 ± 0.06 µg/L,
- aluminium: below method blank concentration
- zinc: 119 ± 7.93 µg/L;
- iron: 1.83 ± 0.02 µg/L

The dissolved Cr, Al, Zn and Fe concentrations were below 130 µg/L at a loading of 1 mg/L after 7 and 28 days, respectively, referring to a solubility of <=13 wt%.

Description of key information

The solubility of reaction mass of willemite, white and zinc iron chromite brown spinel is < =13 wt% at a 1mg/L loading. A GLP-conform transformation/dissolution test with a loading of 1 mg/L at pH6 resulted in dissolved chromium, aluminium, iron and zinc concentrations 0.56 µg Cr/L, < 1 µg Al/L (LOD), 127 µg Zn/L and 0.76 µg Fe/L after 7 days. The dissolved chromium, aluminium, iron and zinc concentrations at pH6 were 0.74 µg Cr/L, < 1 µg Al/L (LOD), 119 µg Zn/L and 1.83 µg Fe/L after 28 days, respectively (Knopf, 2013).