Registration Dossier

Data platform availability banner - registered substances factsheets

Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Environmental fate & pathways

Phototransformation in water

Currently viewing:

Administrative data

Link to relevant study record(s)

Reference
Endpoint:
phototransformation in water
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: The study was conducted in accordance with international guidelines (OECD 316) and in accordance with GLP. All relevant validity criteria were fulfilled.
Study type:
direct photolysis
Qualifier:
according to guideline
Guideline:
other: OECD test 316 guideline: Phototransformation of chemcials in water - Direct photolysis (2008)
GLP compliance:
yes (incl. QA statement)
Radiolabelling:
no
Analytical method:
gas chromatography
Details on sampling:
One millilitre samples were taken at day 0 (initial), 1, 2, 3, 4, 5, 6, and 7.
Buffers:
Citrate buffer (Citric acid, sodium hydroxide and hydrogen chloride) pH 4
Phosphate buffer (Di-sodium hydrogen phosphate and potassium dihydrogen phosphate) pH 7
Borate buffer (Boric acid, potassium chloride and sodium hydroxide) pH 9
Borate buffer (Boric acid, potassium chloride and sodium hydroxide) pH 10
Light source:
Xenon lamp
Light spectrum: wavelength in nm:
> 290 - < 800
Relative light intensity:
> 31.8 - < 35
Details on light source:
Artificial sunlight: Light from a xenon arc lamp, filtered to simulate natural sunlight over the range of 290-800 nm.
Details on test conditions:
Before the test was performed maximum solubility of the test substance was determined under the test conditions.

Tier 1

A stock of tris(2-ethylhexyl)phosphate was prepared by dissolving 4.1 mg of the test substance in 1 mL of tetrahydrofuran in a volumetric flask which was then made up to 100 mL with milli-Q water. The preparation led to a stock solution of tris(2-ethylhexyl) phosphate at a concentration of 40.586 mg/L. From this stock a series of 10 serial dilutions were made. These were produced in aliquots of 5 mL. The 5 mL aliquots were added to 5 mL of the appropriate buffered solution (i.e. pH 4, 7 or 9) to give final concentrations. Each solution was filtered (0.22 µm pore size).

Tests were conducted at 20.7-21.5 °C. For each pH, blank data were collected first, followed by each of the tris(2-ethylhexyl) phosphate solutions, in the sequence from lower to higher concentration. Intensity data was measured in quadruplicate for each solution. Absorbance as a function of wavelength for each solution was computed by the workstation attached to the spectrophotometer, and stored as average and standard deviation of the absorbance as a function of wavelength at 1 nm intervals.

Tier 1 tests led to tier 2 tests being required. Tier 2 test was conducted as follows.

Tier II

Flasks with 6.0 mL of each work solution and identical flask were prepared and covered with aluminum foil, to provide control samples. Flasks were filled to the top leaving no headspace to minimize volatilization. All manipulations were carried out inside a laminar flow chamber in order to avoid microbiological contamination. Sample tubes were placed in attificial sunlight inside a Suntest XLS + unit. This unit was fitted with a Xenon-arc lamp (250W.m-2) and a special UV-glass filter, which eliminate light with wavelengths lower than 290 nm. The irradiance inside the chamber was monitored by a sensor (light meter). The temperatures and pH of the samples were also monitored during the test. For each sample 4 aliquots of 1.0 mL; two from the test flasks and two from the control flask. Immediately after collecting the samples were stored in a freezer at -20 °C until analysis.

For anaylasis of all smaples a calibration curve was derived using known concentrations of the test substance on GC-MS, to enable quantification of test substance in the testing vessels. For identification of degradation product were used a reference standards of 2-Ethyl Hexanoic Acid and 2-Ethyl Hexanol. The identification was performed by compared between retention times in an Agilent GC 6890 with mass spectrometry MS 5973.
Duration:
7 d
Temp.:
21 °C
Initial conc. measured:
19 mg/L
Reference substance:
yes
Remarks:
p-nitroacetophenoe-pyridine
Dark controls:
yes
Computational methods:
Linear regression and graphical presentation of the results in the report were done on Excel. Linear regression of the raw absorbance (Awavelength), and molar concentration was determined. The Beer-Lambert Law calculation was performed on an Excel spreadsheet using the worksheet function LINEST. The data for all of the wavelengths (190 to 1100 nm, with 1 nm steps) was processed, giving the absorption spectrum of the active ingredient as the molar decadic absorption coefficient versus the wavelength (Awavelength).

ABIWAS was used to model the photodegradation in water by solar irradiation. ABIWAS takes in values for the molar decadic absorption coefficient, and the quantum yield, together with the molar concentration of the active ingredient, and the depth of water over which the photodegradation rate is to be averaged. ABIWAS returns a mean half-life, averaged over the depth and the daily solar cycle for photodegradation during different months at a single latitude, 55 °N. The use of low values for the molar concentration and the depth gives the optically thin case required to estimate the photodegradation half-life in surface waters.
Preliminary study:
For June, the half-lives are 4.38x10^-5 days (pH 4), 4.94x10^-5 days (pH 7), and 5.21x10^-5 days (pH 9). These values represent short half-lives, indicating that the water in the natural environment tris (2- ethylhexyl) phosphate is susceptible to photolysis, therefore tier II tests at pH 4, 7 and 9 were reuired.

The solutions W21, W31 and W41 were injected to confirm concentration and the chromatograms were showmen in Figures 5, 6 and 7, respectively.
Test performance:
pH was monitiored throughout the test as was temperature, these remained constant.
Key result
DT50:
0.93 d
Test condition:
pH 4
Key result
DT50:
1.64 d
Test condition:
pH 7
Key result
DT50:
3.5 d
Test condition:
pH 9
Predicted environmental photolytic half-life:
The results of definitive test showed half-lives like 0.93 days at pH 4, 1.64 days at pH 7 and
3.50 days at pH 9.
Transformation products:
yes
No.:
#1
No.:
#2
Details on results:
The results of definitive test showed half-lives like 0.93 days at pH 4, 1.64 days at pH 7 and
3.50 days at pH 9. For pH 4, 7 and 9 the rate constant of degradation/transformation are 0.7436, 0.4223 and 0.1980 days-1, respectively

There were identified two degradation products, the 2-Ethyl Hexanol and 2-Ethyl Hexanoic Acid.

Table 1. Concentration of tris(2-ethylhexyl)phosphate (control (dark) and irradiated (light) samples) and degradation products during photolysis at pH 4, 7 and 9.

Concentration µg/mL

 

 

pH 4

pH 7

pH 9

Time

Time (days)

Light

Dark

Light

Dark

Light

Dark

T0

 

20.62

20.62

18.91

18.91

19.35

19.35

T1

 

20.65

23.00

19.15

22.00

18.44

20.70

T2

 

16.91

22.62

15.72

20.98

15.93

19.88

T3

 

12.03

22.02

11.49

19.09

10.88

16.93

T4

 

3.57

21.97

3.45

19.09

3.19

17.14

T5

 

2.98

21.96

2.91

18.71

2.76

16.60

T6

 

1.34

21.92

1.32

19.62

1.37

16.26

T7

 

<LOQ

21.81

<LOQ

20.45

<LOQ

15.80

 

Table 2. Photolysis rate constant (K) and half-life (T1/2) of tris(2-ehtylhexyl)phosphate.

 

pH 4

pH 7

pH 9

K (per day)

0.74

0.42

0.20

T ½ (days)

0.93

1.64

3.50

Validity criteria fulfilled:
yes
Remarks:
as per OECD quality guidelines, the study fulfills these recommendations
Conclusions:
The Tris(2-ethylhexyl) phosphate is function ofpH is considered unstable at photolysis.
Executive summary:

The study was conducted according to OECD 316 guidelines to determine to determine the photolysis of tris(2 -ethylhexyl) phosphate.

The test substance showed varying half-lives dependent on pH. However all photolytic degradation half-lives were under 4 days. Half-lives were 0.93 days (pH 4), 1.64 days (pH 7) and 3.50 days (pH 9). Validity/ quality criteria were met in accordance with those documeted by the OECD test guideline. Two degradation products were identified, and were 2-ethyl hexanol and 2 -ethyl hexanoic acid.

Tris(2 -ethylhexyl)phosphate is photolytically unstable at all tested pH levels.

Description of key information

Phototransformation in water half-life: 0.93d (pH=4), 1.64d (pH=7), 3.5d (pH=9); OECD 316; Severino (2013)

Identification of Degradation Products: 2 -ethylhexanol and 2 -ethylhexanoic acid (Severino, 2013)

Key value for chemical safety assessment

Half-life in water:
1.64 d

Additional information

In a single key study, an assessment of photolysis was conducted according to OECD 316 (Severino, 2013). The test substance showed varying half-lives dependent on pH. However all photolytic degradation half-lives were under 4 days. Half-lives were 0.93 days (pH 4), 1.64 days (pH 7) and 3.50 days (pH 9). Validity/ quality criteria were met in accordance with those documeted by the OECD test guideline. Two degradation products were identified, and were 2-ethyl hexanol and 2 -ethyl hexanoic acid. Tris(2 -ethylhexyl)phosphate is photolytically unstable at all tested pH levels