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Adsorption / desorption

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Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
The study was performed on the primary hydrolysis product of BPA-DA, 4,4-Bisphenol A Tetra-Acid (BPA-TA; CAS 38103-05-8).
Reason / purpose:
other: read-across target
Qualifier:
according to
Guideline:
OECD Guideline 121 (Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC))
Deviations:
no
GLP compliance:
yes
Type of method:
HPLC estimation method
Test temperature:
25 °C
Details on study design: HPLC method:
A 1.00 mg/mL 4,4'-Bisphenol A Tetra-Acid stock solution was prepared by placing 0.0512 g of the test substance (0.0502 g as active ingredient) in a 50.0-mL volumetric flask and bringing it to volume with methanol. This stock solution was divided into separate aliquots and stored refrigerated until injected on the instrument. A 1.00 mg/mL sodium nitrate reference standard stock solution was prepared by placing 0.00500 g of sodium nitrate in a 5.00-mL volumetric flask and bringing it to volume with acetonitrile. This stock solution was used to determine the dead time (t0) of the instrument, and was stored refrigerated until injected.

Reference standard stock solutions used in the determination of the Koc were prepared using the following substances: acetanilide, aniline, benzoic acid phenylester, and phenanthrene.

HPLC method: Samples were analysed by automated injection on a high performance liquid chromatographic system equipped with ultraviolet detection (HPLC/UV). The following instrumental conditions were utilised: Hewlett Packard quaternary solvent pump Series 1100 equipped with a Hewlett Packard Series 1100 degasser and autosampler, a Hewlett Packard variable wavelength detector, a column heater and Hewlett Packard Version A.09.01 for data acquisition; Column: Zorbax SB-CN, 5-micrometers, 250 mm x 4.6 mm; Column Temperature: 25 °C; Mobile Phases: A: 100% 0.01 M sodium citrate tribasic; B: 100% acetonitrile; Flow Rate: 1.00 mL/minute; Injection Volume: 10.0 microL; and Wavelength: 210 nm. The dead time (t0) of the system was determined by making duplicate injections of sodium nitrate. Each remaining reference substance was analysed in duplicate. A calibration graph was determined by plotting the log k’ versus corresponding log (Koc) for the reference substances.

The test substance was analysed in duplicate. The capacity factor and log k’ were calculated and the log (Koc) determined from the calibration curve. The values of the log (Koc) from the duplicate measurement are considered acceptable when they fall within a range of ± 0.25 log units.

The adsorption distribution coefficient (Kd) is the ratio of the concentration of the test substance in the sewage sludge (Cs), and the concentration of the test substance in the aqueous phase (Caq) at the point of equilibrium. The adsorption coefficient (Koc) is the adsorption distribution coefficient (Kd) normalised with the organic carbon content of the sewage sludge (foc). The equations below show these relationships:

Kd = (Cs/Caq)

and

Koc= (Kd/foc)

where:
Cs is generally in units of µg/g and Caq is generally in units of µg/mL

The capacity factors (k’) for each reference standard compound with a known Koc value are determined by the equation:

k’=(tR-to)/to

where:
tR = the retention time of the test substance
to= the dead time (the average time a solvent molecule needs to pass through the column)
Key result
Type:
Koc
Value:
< 33.1
Temp.:
25 °C
Key result
Type:
log Koc
Value:
< 1.52
Temp.:
25 °C
Validity criteria fulfilled:
not applicable
Conclusions:
The mathematical extrapolation of the Koc given the retention time of 4,4-Bisphenol A Tetra-Acid compared to the standards employed in the study was estimated to be < 0.000000740 (mean log Koc = -6.13). Since the retention time of 4,4-Bisphenol A Tetra-Acid was lower than the retention time for acetanilide (the earliest eluting calibration standard identified in the OECD 121 guidelines), the Koc for 4,4-Bisphenol A Tetra-Acid was reported as less than 33.1, the Koc of acetanilide (log Koc <1.52).
Endpoint:
adsorption / desorption: screening
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
the study does not need to be conducted because the physicochemical properties of the substance indicate that it can be expected to have a low potential for adsorption
Justification for type of information:
The registered substance is unstable in water due to hydrolysis; therefore a test conducted with the hydrolysis product 4,4'-Bisphenol A Tetra-Acid (BPA-TA, CAS # 38103-05-8) is more appropriate. However, in accordance with point 9.3.1 and 9.3.3, Column 2 (Specific rules for adaptation from Column 1) of Annex VIII and Annex IX of Regulation (EC) No. 1907/2006, adsorption/desorption screening is not required if the substance has a low potential for adsorption (eg the substance has a low octanol water partition coefficient). The partition coefficient of BPA-TA is lower than 3 (Log Pow 0.7 at pH 5, <-2.22 at pH 7 and <-2.2 at pH 9). On this basis, adsorption/desorption testing with the registered substance has been omitted.

Description of key information

The adsorption coefficient (Koc) of BPA-TA is < 33.1, log Koc <1.52 at 25 °C.

Key value for chemical safety assessment

Additional information

Due to BPA-DA being hydrolytically unstable, the adsorption coefficient of the hydrolysis product BPA-TA (4,4-Bisphenol A Tetra-Acid, CAS # 38103-05-8) was determined in accordance with OECD 121 under GLP conditions (Springborn Smithers Laboratories, 2009).The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

The mathematical extrapolation of the Koc given the retention time of BPA-TA compared to the standards employed in the study was estimated to be < 0.000000740 (mean log Koc = -6.13). Since the retention time of BPA-TA was lower than the retention time for acetanilide (the earliest eluting calibration standard identified in the OECD 121 guideline), the Koc for BPA-TA was reported as less than 33.1, the Koc of acetanilide (log Koc <1.52).

The adsorption coefficient (Koc) of BPA-TA is < 33.1, log Koc <1.52 at 25 °C.

The registered substance is unstable in water due to hydrolysis; therefore a test conducted with the hydrolysis product 4,4'-Bisphenol A Tetra-Acid (BPA-TA, CAS # 38103-05-8) is more appropriate. However, in accordance with point 9.3.3 of Column 2 of REACH Annex IX, the study does not need to be performed if based on the physicochemical properties the substance can be expected to have a low potential for adsorption. The result obtained for the adsorption screening study conducted to fulfil the Annex VIII data requirements indicates that the substance has a low adsorption potential. It is therefore considered justified to omit this study.