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Water solubility

Administrative data

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2013-03-07 to 2013-05-07

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2013

Materials and methods

Test guideline

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:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

signed, 2011-02-07

Type of method:

flask method

Remarks:

analysis by ICP-MS

Test material

Test material information

Constituent 1

Test material form:

other: solid

Details on test material:

- Name of test material (as cited in study report): optical glass
- Chemical name: Inorganic glass
- Physical state: colourless, transparent solid, odourless
- Storage condition of test material: Store in dry environment. Avoid high humidity.

Results and discussion

Water solubility

Water solubility 1

Water solubility:

60.1 µg/L

Temp.:

21.1 °C

pH:

>= 4.6 - <= 5.8

Remarks on result:

other: dissolved lead, SD: 17.2 µg/L, at 1 mg/L loading, after 28 days, with blank subtraction

Water solubility 2

Water solubility:

18.7 µg/L

Temp.:

21.1 °C

pH:

>= 5.7 - <= 6.1

Remarks on result:

other: dissolved lead, SD: 2.08 µg/L, at 1 mg/L loading, after 7 days, with blank subtraction

Water solubility 3

Water solubility:

46.3 µg/L

Temp.:

21.1 °C

pH:

>= 6.4 - <= 6.6

Remarks on result:

other: dissolved lead, SD: 5.83 µg/L, at 1 mg/L loading, after 28 days, with blank subtraction

Water solubility 4

Water solubility:

17.7 µg/L

Temp.:

21.1 °C

pH:

>= 6.7 - <= 6.9

Remarks on result:

other: dissolved lead, SD: 1.36 µg/L, at 1 mg/L loading, after 7 days, with blank subtraction

Water solubility 5

Water solubility:

37.8 µg/L

Temp.:

21.1 °C

pH:

>= 7.4 - <= 7.5

Remarks on result:

other: dissolved lead, SD: 3.64 µg/L, at 1 mg/L loading, after 28 days, with blank subtraction

Water solubility 6

Water solubility:

17 µg/L

Temp.:

21.1 °C

pH:

>= 7.5 - <= 7.6

Remarks on result:

other: dissolved lead, SD: 1.99 µg/L, at 1 mg/L loading, after 28 days, with blank subtraction

Details on results:

Temperature
The temperature of the thermostatically controlled room was recorded with a data logger. The mean temperatures were 21.1 ± 0.4 °C. Therefore the mean temperature is in agreement with the OECD guidance document 29.

Solution pH values and oxygen levels
According to the guidance, the solution pH can be expected to remain constant (± 0.2 units) during most tests.
The solution pH remained relatively constant for the pH 6 treatment till sampling day 7 (168h). After day 7 the pH in vessel 3 (sample and blank vessels) decreases till day 28. In vessel 2 (sample and blank vessels) after day 14 (336h) the pH decreases till day 28. In test item vessels pH was in the range of 4.6 – 6.2 and in method blank vessels pH was in the range of 4.3 – 6.2. Therefore, an effect of the test substance can be excluded.
Oxygen levels in all test vessels pH 6 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).
The solution pH remained relatively constant for the pH 7 treatment at the pH which was measured at the sampling time 2h. After day 4 the pH in vessel 1 and 2 (sample vessels) increases till day 14 and afterwards the pH decreases till day 28. In test item vessels pH was in the range of 6.4 – 6.9 and in method blank vessels pH was in the range of 6.1 – 6.9. Therefore, an effect of the test substance can be excluded
Oxygen levels in all test vessels pH 7 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).
The solution pH remained relatively constant for the pH 8 treatment at the pH which was measured at the sampling time 2h. In the test item vessels pH was in the range of 7.3 – 7.6 and in method blank vessels pH was in the range of 7.3 – 7.8.
Oxygen levels in all test vessels pH 8 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).
The discrepancy in the pH for the setting for pH 6 could result on the usage of polycarbonate vessels instead of glass vessels. The decrease of the pH in test vessels and in method blank vessels can be explained by a possible leaching effect of the polycarbonate vessels. The vessels were washed prior to the test with HNO3 and H+ ions could be absorbed onto the polycarbonate walls and released after a period of time. This could influence the pH of the media and in the case of the pH 6 test just a less amount of H+ ions could have a greater effect to the pH than in the pH 7 and 8 test.

Mass balance calculation
Samples were taken from vessels at least 12 hours after adding aqua regia to dissolve the residues. Dissolved lead concentration was measured by ICP-MS and the mass balance was calculated considering the replacement of sampling solution after each sampling by adding blank test media (120 mL after 24h and 40 mL after each subsequent sampling). The filters used for sampling were extensively rinsed with an exact amount of aqua regia and the lead concentration in the filtrate was determined and considered in the mass balance calculation.
The nominal amount of lead was calculated by:
Added test item (mg) * 35.65[§] (percentage of Pb in test item).

[§] according to the SDS/MSDS 38.4% Pb as leadoxides (considered as PbO) in the raw material for production of glass=> 92.8321 % lead in PbO=> (38.4 % * 92.8321 %)/100 % = 35.65% Pb in test item

Recovery of lead in one mass balance sample (vessel and filter/syringes) for each pH.
Vessel Measured Added test Volume Calculated amount Pb in filters Amount of Pb Lead recovery in
Pb conc item of lead in in final column relation to Zn in
final volume plus Pb in filter added test item
[µg/L] [mg] [L] [mg] [mg] [mg] [%]
1 pH 6 301 1.253 1.743 0.524 0.003 0.527 118
1 pH 7 316 1.115 1.605 0.508 0.003 0.511 128
3 pH 8 287 1.325 1.840 0.529 0.002 0.531 112

It has to be considered that for the optical glass only a product information is given in which lead concentration in the raw material as leadoxides (considered as PbO) is given. Possible impurities in the other raw materials which were used for production are not specified in detail. Furthermore no lead concentration in the final product is defined. Therefore the recovery of lead in the mass balance differ and result in a higher recovery as calculated by the loading of the test item into the test vessels.

Any other information on results incl. tables

Fortification of test samples.

sample	measured concentration [µg/L]	calculated level after addition [µg/L]	recovery [µg/L] / [%]
Vessel 1 sample a 14d (336h) pH6	28.2	42.5	41.1 / 96.5
Vessel 1 sample b 14d (336h) pH6	27.7	42.1	41.7 / 98.9
Vessel 2 sample a 14d (336h) pH7	31.7	45.3	44.6 / 98.3
Vessel 2 sample b 14d (336h) pH7	31.7	45.3	42.8 / 94.5
Vessel 3 sample a 14d (336h) pH8	22.6	38.0	36.8 / 96.7
Vessel 3 sample b 14d (336h) pH8	21.1	36.9	36.4 / 98.7

 

The certified reference materials TM-15.2 (certified with 11.6 µg/L lead, diluted to 1.16 µg/L dilution factor 10) and TMDA70 (certified with 444 µg/L lead, diluted to 44.4 µg/L dilution factor 10) as well as the recalibration standard (5 µg Pb/L and 1 µg Pb/L) were analyzed as quality assurance samples along with the mass balance samples (vessels and filters). To meet quality assurance requirements recovery needs to be in the range of ± 15 % of the respective certified value.

For the measurement series of the mass balance, the mean accuracy and precision were 103 ± 4.4 % (n = 7) for TM-15.2 (dilution factor 10) and 102 ± 4.1 % (n = 5) for TMDA70 (dilution factor 10). The average recovery for the recalibration standard 5 µg Pb/L was 95.7 ± 0.7 % (n = 3) and for 1 µg Pb/L 101 ± 0.9 % (n = 2).

As further quality assurance measurement, routine analyses of method blank samples were performed. Elevated concentrations of Pb in method blanks origin from applied chemicals for preparation of different media. Although all used chemicals are at least of pro Analysis quality, low metal amounts cannot be excluded.

 

Lead concentration in method blanks.

Media
pH 6	Method blanks mainly above LOD/LOQ except for method blanks 2h (three blanks <LOD, two <LOQ, one >LOQ --> 0.04 µg/L --> 7.90 fold lower than concentration in samples) and 6h (five blanks <LOQ, one >LOQ --> 0.09 µg/L --> 11.0 fold lower than concentration in samples); method blanks of further sampling points above LOQ but at least 177 -494 fold lower than concentration in samples
pH 7	Method blanks mainly above LOD/LOQ except for method blanks 2h (three blanks <LOQ, three >LOQ --> 0.02 µg/L --> 16.5 fold lower than concentration in samples) and 6h (four blanks <LOQ, two >LOQ --> 0.03 – 0.04 µg/L --> 25.7 fold lower than concentration in samples); method blanks of further sampling points above LOQ but at least 141 - 601 fold lower than concentration in samples
pH 8	Method blanks mainly above LOD/LOQ except for method blanks 6h (two blanks <LOQ, four >LOQ --> 0.03 – 0.04 µg/L --> 27.2 fold lower than concentration in samples); method blanks of further sampling points above LOQ but at least 11.1 - 441 fold lower than concentration in samples

 

Method validation summary.

validation parameter	results	Comment
Selectivity	similar data with two different gas modes	No interference observed
Linearity	applied calibration functions were linear	correlation coefficient at least 0.9953
Limit of detection	0.001 – 0.01 µg/L
Limit of quantification	0.004 – 0.03 µg/L
Method blanks	Summary seeTable11	Elevated concentrations of Pb in method blanks origin from the applied chemicals for preparation of different media
Accuracy measurement test samples and method blanks	Mean recovery for CRM TM15.2 (dilution factor 5): Pb 102 ± 5.4% (n = 41)	Low concentration range (11.6 µg Pb/L – diluted 2.32 µg Pb/L)
Accuracy measurement test samples and method blanks	Mean recovery for CRM TMDA70 (dilution factor 10): Pb: 98.6 ± 9.3% (n = 41)	High concentration range (444 µg Pb/L – diluted 44.4 µg Pb/L)
Accuracy mass balance	Mean recovery for CRM TM15.2 (dilution factor 10): Pb 103 ± 4.4% (n = 7)	Low concentration range (11.6 µg Pb/L – diluted 1.16 µg Pb/L)
Accuracy mass balance	Mean recovery for CRM TMDA70 (dilution factor 10): Pb: 102 ± 4.1% (n = 5)	High concentration range (444 µg Pb/L – diluted 44.4 µg Pb/L)
Trueness measurement test samples and method blanks	mean recovery for recalibration standard: Pb: 97.9 ± 4.6% (n = 16)	Mid concentration range (10 µg/L)
Trueness mass balance	mean recovery for recalibration standard: Pb: 95.7 ± 079% (n = 3)	Mid low concentration range (5 µg/L)
Trueness mass balance	mean recovery for recalibration standard: Pb: 101 ± 0.9% (n = 2)	Low concentration range (1 µg/L)
Trueness measurement test samples and method blanks	Fortification of samples: 94.5 – 98.9%
Reproducibility measurement test samples and method blanks	Mean recovery for CRM TM15.2 (dilution factor 5): Pb 102 ± 5.4% (n = 41)	Low concentration range (11.6 µg Pb/L – diluted 2.32 µg Pb/L)
Reproducibility measurement test samples and method blanks	Mean recovery for CRM TMDA70 (dilution factor 10): Pb: 98.6 ± 9.3% (n = 41)	High concentration range (444 µg Pb/L – diluted 44.4 µg Pb/L)
Reproducibility mass balance	Mean recovery for CRM TM15.2 (dilution factor 10): Pb 103 ± 4.4% (n = 7)	Low concentration range (11.6 µg Pb/L – diluted 1.16 µg Pb/L)
Reproducibility mass balance	Mean recovery for CRM TMDA70 (dilution factor 10): Pb: 102 ± 4.1% (n = 5)	High concentration range (444 µg Pb/L – diluted 44.4 µg Pb/L)

Results

Under the described conditions of this test with inorganic glass (KZFSN5 optical glass), the following dissolved concentrations were measured at the respective loading, exposure and solution pH:

 

1 mg/L loading after 28 days pH 6 without blank subtraction:

-      Lead: 60.5 ± 17.2 µg/L

 

1 mg/L loading after 28 days pH6 with blank subtraction:

-      Lead: 60.1 ± 17.2 µg/L

 

1 mg/L loading after 28 days pH 7 without blank subtraction:

-      Lead: 46.4 ± 5.83 µg/L

 

1 mg/L loading after 28 days pH 7 with blank subtraction:

-      Lead: 46.3 ± 5.83 µg/L

  

1 mg/L loading after 28 days pH 8 without blank subtraction:

-      Lead: 37.9 ± 3.64 µg/L

 

1 mg/L loading after 28 days pH 8 with blank subtraction:

-      Lead: 37.8 ± 3.64 µg/L

 

The OECD Series 29 requires a limit of 20 % and 10 % for the between-vessel and within vessel variation, respectively.

 

Loading 1 mg/L pH 6 without blank subtraction:

Lead: The observed variations within the test flasks were in compliance with the guidance except for the within-vessel variations of vessel 1 (20.0 %) after 2 h and vessel 2 (11.8 %) after 504 h. The observed variations between the test flasks over the experimental period were in the range of 11.1 – 28.5 %.

 

Loading 1 mg/L pH 6 with blank subtraction:

Lead: The observed variations within the test flasks were in compliance with the guidance except for the within-vessel variations of vessel 1 and 2 (23.3 and 10.9 %) after 2 h , vessel 2 (10.1 %) after 6h and vessel 2 (11.9 %) after 504 h. The observed variations between the test flasks over the experimental period were in the range of 11.1 – 28.7 %.

 

Loading 1 mg/L pH 7 without blank subtraction:

Lead: The observed variations within the test flasks were in compliance with the guidance except for the within-vessel variations of vessel 1 (19.5 %) after 672 h. The observed variations between the test flasks over the experimental period were in the range of 5.81 – 12.6 %.

 

Loading 1 mg/L pH 7 with blank subtraction:

Lead: The observed variations within the test flasks were in compliance with the guidance except for the within-vessel variations of vessel 1 (19.6 %) after 672 h. The observed variations between the test flasks over the experimental period were in the range of 5.81 – 12.6 %.

 

Loading 1 mg/L pH 8 without blank subtraction:

Lead: The observed variations within the test flasks were in compliance with the guidance except for the within-vessel variations of vessel 2 (10.5 %) after 24 h. The observed variations between the test flasks over the experimental period were in the range of 3.82 – 15.3 %.

 

Loading 1 mg/L pH 8 with blank subtraction:

Lead: The observed variations within the test flasks were in compliance with the guidance except for the within-vessel variations of vessel 2 (10.6 %) after 24 h. The observed variations between the test flasks over the experimental period were in the range of 3.97 – 15.4 %.

 

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 observed increased between-vessel variations may be due to the wider particle size distribution of the test item. 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 between-vessel variations may be observed in tests of materials with wider particle size distributions.

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information): slightly soluble (0.1-100 mg/L)
Under the described conditions of this test with inorganic glass (optical glass), the following dissolved concentrations were measured at the respective loading, exposure and solution pH:
 
1 mg/L loading after 7 days pH 6 with blank subtraction: Lead: 18.7 ± 2.08 µg/L
 
1 mg/L loading after 28 days pH 6 with blank subtraction: Lead: 60.1 ± 17.2 µg/L
 
1 mg/L loading after 7 days pH 7 with blank subtraction: Lead: 17.7 ± 1.36 µg/L
 
1 mg/L loading after 28 days pH 7 with blank subtraction: Lead: 46.3 ± 5.83 µg/L
  
1 mg/L loading after 7 days pH 8 with blank subtraction: Lead: 17.0 ± 1.99 µg/L
 
1 mg/L loading after 28 days pH 8 with blank subtraction: Lead: 37.8 ± 3.64 µg/L

The maximum dissolution of Pb from the test item is 6.01% (w/w).