Dichlorobis(η-cyclopentadienyl)titanium

Partition coefficient

Link to relevant study record(s)

Reference

Endpoint:

partition coefficient

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Experimental starting date: 05 November 2016 Experimental completion date: 10 July 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method A.8 (Partition Coefficient - Shake Flask Method)

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 107 (Partition Coefficient (n-octanol / water), Shake Flask Method)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

flask method

Partition coefficient type:

octanol-water

Specific details on test material used for the study:

Identification: Dichlorobis(η-cyclopentadienyl)titanium
(CAS# 1271-19-8)
Appearance/physical state: red powder
Batch: 07088501022
Purity: 99.8%
Expiry date: 04 March 2019
Storage conditions: room temperature, in the dark

Analytical method:

photometric method

Key result

Type:

log Pow

Partition coefficient:

-1.35

Temp.:

20 °C

pH:

< 7

Details on results:

Discussion
The test item was demonstrated to be insoluble in n-octanol at a nominal concentration of 1.0 g/L. It was therefore necessary to prepare the stock solution in the aqueous phase (n octanol saturated water). However, from available literature, the test item was expected to hydrolyze very rapidly on contact with water and dissolution may in fact be directly linked to this hydrolysis process. However, as the test item demonstrated significant solubility in water, testing continued to quantify the partitioning characteristics of the resulting products, irrespective of the final species in solution.
Standard solutions were also prepared directly in matrices containing at least a proportion of aqueous media, such that quantification was performed on the test item in the same form as the partitioned sample solutions, and thus allowing calculation of concentrations relative to the parent test item.
Due to the potential complexity of the test item chemistry in the environment, the inherent acidity of aqueous test item solutions due to the liberation of hydrochloric acid and observed insolubility of the test item in aqueous buffer solutions, no manipulation of the test systems’ pH was performed and the determination was carried out at the natural pH achieved on dissolution of the test item.
Quantification of the partition coefficient of the test item hydrolysis products was performed using absorbance at a wavelength of 330 nm, which monitored a characteristic shoulder on the spectrum profile of the solubilized products. This allowed determination of the stock and the individual phase concentrations, working within the linear response range of the instrument, without having to employ the extreme dilution factor as was needed for the water solubility determination.
On evaluation of the relevant aqueous phase standard solutions, the diluted stock sample solutions and the diluted aqueous phase sample solutions, essentially identical spectra were generated, both with respect to the profile and the magnitude of absorbance, indicating the hydrolysis products generated as being highly hydrophilic and predominantly retained in the aqueous phase. Analyzed aqueous phase concentrations were in the range 94.6 to 97.2% of the mean analyzed stock solution concentration.
Evaluating the spectra originating from the organic phase analysis; standard solution spectra were similar to that observed for the aqueous phase analysis, with some minor differences expected due to the possible matrix specific absorbance characteristics of the hydrolysis product complexes. However, significant differences were observed between standard and sample solution spectra; indicating that the species that did partition into the organic phase were extremely limited. For example the absorbance maxima observed at approximately 250 nm in the standard solutions was not replicated in the organic phase sample solutions. The region of absorbance that was used for quantification however was dominant in the organic phase sample solutions and therefore allowed for presentation of a worst case scenario for lipophilic behaviour, although this still remained negligible.

Definitive Test

The mean peak absorbances obtained for the standard, stock and sample solutions are shown in the following two tables:

Solution	Absorbance
Standard 5.02 mg/L	0.0275
Standard 10.0 mg/L	0.0458
Standard 20.1 mg/L	0.0951
Standard 20.1 mg/L	0.0804
Standard 40.2 mg/L	0.1675
Organic phase matrix blank	no significant response
Sample 1	0.0978
Sample 2	0.1031
Sample 3	0.0469
Sample 4	0.0697
Sample 5	0.1631
Sample 6	0.1671

Aqueous Phase

Solution	Absorbance
Standard 25.1 mg/L	0.2359
Standard 50.2 mg/L	0.4595
Standard 50.3 mg/L	0.4515
Standard 75.3 mg/L	0.6968
Standard 100 mg/L	0.9561
Aqueous phase matrix blank	no significant response
Sample 1	0.4769
Sample 2	0.4640
Sample 3	0.4688
Sample 4	0.4699
Sample 5	0.4676
Sample 6	0.4724
Stock solution A	0.4911
Stock solution B	0.4913

The total weights (mg) and analyzed concentration (mg/L) of the respective phases are shown in the following table:

Sample number	Total weight (mg)^[1]	Organic phase		Aqueous phase			% recovery
		Analyzed concentration (mg/L)	Weight (mg)^[2]	Analyzed concentration (mg/L)	Weight (mg)^[2]	pH
1	95.6	45.4	4.09	1.03 x 10^3	92.9	2.5	101
2	95.6	48.1	4.33	1.01 x 10^3	90.5	2.5	99.2
3	68.0	20.0	2.56	1.02 x 10^3	65.0	2.5	99.3
4	59.5	31.4	3.51	1.02 x 10^3	57.0	2.5	102
5	127	78.0	4.68	1.01 x 10^3	122	2.5	99.1
6	119	80.0	4.48	1.02 x 10^3	115	2.5	100

Mean stock solution concentration:   1.06 x 10³mg/L

pH of stock solution:                        2.5
Temperature:                                    20.0 ± 0.5 °C

[1]From analysis of the stock solution

[2]From analysis of the respective phase

The partition coefficient determined for each sample is shown in the following table:

Sample number	Organic/aqueous volume ratio	Partition coefficient	Log10Pow	Mean partition coefficient
1	1:1	4.40 x 10^-2	-1.36	4.59 x 10^-2
2		4.78 x 10^-2	-1.32
3	2:1	1.97 x 10^-2	-1.71	2.53 x 10^-2
4		3.08 x 10^-2	-1.51
5	1:2	7.70 x 10^-2	-1.11	7.76 x 10^-2
6		7.82 x 10^-2	-1.11

Mean P_ow : 4.96 x 10^-2           log₁₀P_ow: -1.35          P_owstandard deviation : 2.39 x 10^-2

Conclusions:

The partition coefficient of the test item has been determined to be 4.96 x 10-2 at 20.0 ± 0.5 °C, log10 Pow -1.35, monitoring responses attributed to test item hydrolysis products, reflective of the species expected to form rapidly on accidental release into the environment.

Executive summary:

4.96 x 10^-2at 20.0±0.5 °C, log₁₀P_ow-1.35,monitoring responses attributed to test item hydrolysis products, reflective of the species expected to form rapidly on accidental release into the environment. Testing used ashake-flask method designed to be compatible with Method A.8 Partition Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008andMethod 107 of the OECD Guidelines for Testing of Chemicals, 27 July 1995. 

Description of key information

The endpoint is waived as the substance is hydrolytically unstable

Key value for chemical safety assessment

Log Kow (Log Pow):

-1.35

at the temperature of:

20 °C

Additional information

The substance is hydrolytically unstable. The measured log Kow is attributed to hydrolysis byproducts.