Reaction mass of disodium hexatitanium tridecaoxide and disodium trititanium heptaoxide

Surface tension

Administrative data

Endpoint:

surface tension

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because water solubility is below 1 mg/L at 20°C

Cross-reference

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2010-07-19 to 2010-08-31

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Remarks:

Only measured titanium solublity; fails to take into account possible dissociation/hydrolysis

Justification for type of information:

The water solubility was measured in deionised water by measuring dissolved titanium.
The method used will not detect potential dissociation / hydrolysis.
Disodium titanate substance (EC 234-802-9) has the molecular formula Na2TiO3 and its composition is expressed as (Na2O)x(TiO2), where x is ranging from 0.1 to 6 according to the SIP. This substance, Reaction mass of Disodium Hexatitanate and Sodium Metatitanate, has a value of x = 0.21, calculated from XRF results, has been identified as a mixture of two specific types of disodium titanate and is therefore within the scope of the disodium titanate SIP. It is assessed therefore that disodium titanate is an acceptable read-across substance for Reaction mass of Disodium Hexatitanate and Sodium Metatitanate

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

signed, 2010-09-20

Type of method:

flask method

Remarks:

metal analysis via ICP-OES

Key result

Water solubility:

0.222 mg/L

Temp.:

20 °C

pH:

10.47

Method validation summary:

Method Principle:	Test mediumsamples delivered by eurofins-GAB GmbH (stabilized with nitric acid 65% (1 % v/v) at the test site) were used for analysis by ICP-OES without any further preparation. Final analysis was done by ICP-OES at titanium emission wavelengths of323.452 nm (quantification) and 338.376 nm (confirmation).
Specificity:	The concentrations of titanium in test medium samples were determined by ICP-OES at two emission wavelengths (quantification and confirmation). No significant interferences from the test medium matrix were detected at the emission wavelengths corresponding to titanium in any of the control specimens. The analytical method can therefore be regarded as highly specific for titanium.
Linearity:	The calibrationcurves used for titanium analysis at 323.452 nm were linear within the range from 0.0025 mg/L to 2.5 mg/L with a correlation coefficient of r = 1.0000 (r^2= 1.0000).
Precision (Repeatability):	At concentration levels of 0.115 mg/Ldisodium titanate(equivalent tomg/L titanium (LOQ)),mg/L disodium titanate (equivalent tomg/L titanium) and 2.3 mg/Ldisodium titanate(equivalent tomg/L titanium) the variation was ascertained by performing at least five determinations each in fortified test matrix. The relative standard deviations (at least five determinations each) were found to be 2.4 % at the 0.115mg/L, 2.5% at themg/L fortification level and 0.4 % at the 2.3 mg/L fortification level.
Accuracy (Recovery):	The accuracy is given as the recovery of titanium from test medium at three different concentration levels.The mean recoveries in the test medium ranged from 89 % to 100 % for titanium. The overall recovery was found to be 94% with a relative standard deviation of 5.1%.
Limit of Quantification:	The LOQ was defined at 0.115 mg/L regarding disodium titanate detection (0.05 mg/L regarding titanium).The limit of quantification (LOQ) was defined as the lowest fortification level with mean recoveries ranging from 70 % to 110 % at a relative standard deviation (RSD) of£ 20 % and blanks not exceeding 30 % of the LOQ. This requirement was fulfilled for the0.115mg/L test item (0.05 mg/L Ti) fortification level regarding titanium analysis in test medium.The limit of detection (LOD) was defined as 30 % of the limit of quantification (= 0.0345 mg/L regarding test item, 0.0150 mg/L

Results of the Flask Test:

The measurement of the samples taken from each bottle after 1 week plus 0 h, 24 h and 48 h and after 168 h, 192 h and 216 h were not used to determine the solubility because the results determined were not constant. Therefore the sampling procedure had to be modified twice as described.

The calculation from the content of titanium to the content of the test item based on the given titanium content of 43.5 %. In the following section single values are discussed. Due to rounding effects, presented values might slightly differ from values calculated manually.

Measured Titanium concentrations and pH in bidistilled water free from oxygen and carbon dioxide at 20 ± 0.5 °C: 

Time (1 week plus)	Sample No.	Titanium	Titanium (Mean)	Disodium titanate (Mean)	pH
[h]		[mg/L]	[mg/L]	[mg/L]
336	1	0.0843	0.091	0.209	10.48
	2	0.0976			10.46
360	1	0.0883	0.0984	0.226	10.51
	2	0.1085			10.44
384	1	0.1062	0.1005	0.231	10.47
	2	0.0947			10.47
	Mean:		0.097	0.222	10.47
	SD:		0.005	0.01	0.03
	RSD:		5.2	4.5	0.3

Conclusions:

Interpretation of results: slightly soluble (0.1-100 mg/L)
The water solubility of Disodium titanate in bidistilled water free from oxygen and carbon dioxide at 20 ± 0.5 °C is determined to be 0.222 mg/L (with a loading of 250 mg/L). The average pH of the saturated solution was pH 10.5.