tert-butylphenyldiphenyl phosphate (tBuTPP)

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

June - August 2021

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)

Qualifier:

according to guideline

Guideline:

other: OPPTS 835.1230, Adsorption/Desorption (Batch Equilibrium).

GLP compliance:

no

Type of method:

batch equilibrium method

Media:

soil

Radiolabelling:

no

Test temperature:

All tests were conducted in a temperature-controlled laboratory room at ambient room temperature. The temperature was monitored with NIST traceable thermometer and was recorded at least hourly with a data logger. Room temperature during the tests ranged from 18.7 to 20.0 oC.

Analytical monitoring:

yes

Remarks:

LC/MS/MS

Details on sampling:

Sampling was performed by placing 500 μL of the solution in HPLC vial using 1000- μL digital pipette, rinsing the pipette tip by taking 500 μL of 0.2% formic acid in methanol, and placing the rinse in the same HPLC vial.
The solutions equilibrated for 24 hours were analyzed both without filtration and after filtration through Whatman Nylon membrane filters with a pore size of 0.2 μm to check whether these filters were appropriate to remove particles >0.2 μm prior to the analysis in the subsequent tests. Retention of tBuTPP low TPP by the walls of high-speed micro-centrifuge tubes was assessed by micro-centrifugation of a sample of the test substance solution with subsequent analysis of the supernatant.

Matrix no.:

#1

Matrix type:

sandy loam

% Clay:

8.8

% Silt:

8.1

% Sand:

83.1

% Org. carbon:

0.8

pH:

4.7

CEC:

9.7 meq/100 g soil d.w.

Details on matrix:

Laboratory ID RMN-LS-103114
Soil taxonomy class Coarse-loamy, mixed, superactive, frigid Pachic Hapludolls
Soil name Embden
Geographical location of
the site (latitude, longitude) N 47o 42.056’ W 097 o 31.018’

Use pattern Agricultural
Date of sampling October 31, 2014
Depth of sampling 0-6”
Collection and storage
of the sample Collected with a shovel, sieved to pass a 2-mm sieve,
and stored at ambient temperature.

Sample No.:

#1

Duration:

2 h

Initial conc. measured:

60 other: ug/L

pH:

4.7

Temp.:

20 °C

Sample no.:

#1

Duration:

48 h

Conc. of adsorbed test mat.:

60 other: ug/L

pH:

4.7

Temp.:

20 °C

Key result

Sample No.:

#1

Type:

Koc

Value:

4.81 dimensionless

pH:

4.7

Temp.:

20 °C

% Org. carbon:

0.81

Adsorption and desorption constants:

Adsorption distribution coefficient (Kads) of tBuTPP low TPP in aqueous (0.01 M CaCl2) suspension of Loamy Sand soil was 516±49.6 L/kg (average ± standard deviation).
3. Organic carbon normalized adsorption distribution coefficient (adsOCK) of tBuTPP low TPP in soil system was 6.45×104 L/kg and log(Kads) was 4.81.

Recovery of test material:

Recovery of tBuTPP low TPP in aqueous 0.01 M CaCl2 solution after 24-hour equilibration with subsequent 3-day refrigerated storage was 43.9%-53.9% of dosed amount (Table 7). After storage, the solutions were poured out of the tubes and each tube was extracted three times with 5-mL aliquots of methanol. The recovery in the extracts from each tube was 32.6% - 34.2% providing total recovery 78.1%-86.5% of dosed amount. Losses of the test material might be caused by adsorption to the outer surface of pipette tips used for sampling. Average recovery (82.8% of dosed) was within 100±20% considered as acceptable for this type of tests.

Concentration of test substance at end of adsorption equilibration period:

Concentration of tBuTPP low TPP after equilibration with the soil was 10.2±0.8 μg/L

Details on results (Batch equilibrium method):

Adsorption of tBuTPP low TPP by RMN-LS soil remained stable over the period from 2 to 48-hour equilibration. The pH of the aqueous phase was 4.6 - 4.7. Concentration of tBuTPP low TPP after equilibration with the soil was 10.2±0.8 μg/L (average value ± standard deviation) and adsorption distribution coefficient (Kads) was 516±49.6 L/kg (average ± standard deviation). The value of organic carbon normalized adsorption distribution coefficient (Kads) was 6.45×104 L/kg and log(adsOCK) was 4.81.
Recovery of tBuTPP low TPP in solutions equilibrated in Control vessels (no soil) in adsorption kinetics test was 37.5% to 62.9% of the applied dose, with average recovery 51.2%. This recovery was similar to those found in Tier 1 (66.1% - 75.3% after 24- hour equilibration and 43.9% - 53.9% after subsequent storage of the vessels), taking into account variability caused likely by some variability in the properties of the walls of the tubes.

Validity criteria fulfilled:

yes

Conclusions:

1.Adsorption equilibrium (quasi-equilibrium) in soil test systems was reached after 2-hour equilibration period and solution concentration remained stable over a 48-hour period.
2. Adsorption distribution coefficient (Kads) of tBuTPP low TPP in aqueous (0.01 M CaCl2) suspension of Loamy Sand soil was 516±49.6 L/kg (average ± standard deviation).
3. Organic carbon normalized adsorption distribution coefficient (Kads) of tBuTPP low TPP in soil system was 6.45×104 L/kg and log(Kads) was 4.81.

Key value for chemical safety assessment

Koc at 20 °C:

4.81