Phenylacetic acid

Endpoint summary

Description of key information

Adsorption / desorption

The adsorption coefficient Koc in soil and in sewage sludge of test chemical was determined by the Reverse Phase High Performance Liquid Chromatographic method according to OECD Guideline No. 121 for testing of Chemicals (Experimental study report, 2017). The solutions of the test substance and reference substances were prepared in appropriate solvents. A test item solution was prepared by accurately weighing 5 mg of test item and diluted with ACN up to 10 ml. Thus, the test solution concentration was 500 mg/l. The pH of test substance was 5.6. Each of the reference substance and test substance were analysed by HPLC at 210 nm. After equilibration of the HPLC system, Urea was injected first, the reference substances were injected in duplicate, followed by the test chemical solution in duplicate. Reference substances were injected again after test sample, no change in retention time of reference substances was observed. Retention time tR were measured, averaged and the decimal logarithms of the capacity factors k were calculated. The graph was plotted between log Koc versus log k(Annex - 2).The linear regression parameter of the relationship log Koc vs log k were also calculated from the data obtained with calibration samples and therewith, log Koc of the test substance was determined from its measured capacity factor. The reference substances were chosen according to estimated Koc range of the test substance and generalized calibration graph was prepared. The reference substances were Acetanilide, 4-chloroaniline, 4-methylaniline(p-Tolouidine), N-methylaniline, p-toluamide, Aniline, 2,5- Dichloroaniline, 4 -nitrophenol, 2 - nitrophenol, 2-nitrobenzamide, 3-nitrobenzamide, Nitrobenzene, 4 - Nitrobenzamide, 1-naphthylamine, 1-naphtol, Direct Red 81, Benzoic acid methylester, Carbendazim, Xylene, Ethylbenzene, Toluene, Naphthalene, 1,2,3 -trichlorobenzene, Pentachlorophenol, Phenol, N,Ndimethylbenzamide, 3,5-dinitrobenzamide, N-methylbenzamide, Benzamide, phenanthrene, DDT having Koc value ranging from 1.25 to 5.63. The Log Koc value of test chemical was determined to be 1.932± 0.001dimensionless at 25°C.This log Koc value indicates that the substance has a low sorption to soil and sediment and therefore have moderate migration potential to ground water.

Additional information

Adsorption / desorption

Various experimental studies of the test chemical were reviewed for the adsorption end point which are summarized as below:

 

In an experimental key study from study report (2017),the adsorption coefficient Koc in soil and in sewage sludge of test chemical was determined by the Reverse Phase High Performance Liquid Chromatographic method according to OECD Guideline No. 121 for testing of Chemicals. The solutions of the test substance and reference substances were prepared in appropriate solvents. A test item solution was prepared by accurately weighing 5 mg of test item and diluted with ACN up to 10 ml. Thus, the test solution concentration was 500 mg/l. The pH of test substance was 5.6. Each of the reference substance and test substance were analysed by HPLC at 210 nm. After equilibration of the HPLC system, Urea was injected first, the reference substances were injected in duplicate, followed by the test chemical solution in duplicate. Reference substances were injected again after test sample, no change in retention time of reference substances was observed. Retention time tR were measured, averaged and the decimal logarithms of the capacity factors k were calculated. The graph was plotted between log Koc versus log k(Annex - 2).The linear regression parameter of the relationship log Koc vs log k were also calculated from the data obtained with calibration samples and therewith, log Koc of the test substance was determined from its measured capacity factor. The reference substances were chosen according to estimated Koc range of the test substance and generalized calibration graph was prepared. The reference substances were Acetanilide, 4-chloroaniline, 4-methylaniline(p-Tolouidine), N-methylaniline, p-toluamide, Aniline, 2,5- Dichloroaniline, 4 -nitrophenol, 2 - nitrophenol, 2-nitrobenzamide, 3-nitrobenzamide, Nitrobenzene, 4 - Nitrobenzamide, 1-naphthylamine, 1-naphtol, Direct Red 81, Benzoic acid methylester, Carbendazim, Xylene, Ethylbenzene, Toluene, Naphthalene, 1,2,3 -trichlorobenzene, Pentachlorophenol, Phenol, N,Ndimethylbenzamide, 3,5-dinitrobenzamide, N-methylbenzamide, Benzamide, phenanthrene, DDT having Koc value ranging from 1.25 to 5.63. The Log Koc value of test chemical was determined to be 1.932± 0.001dimensionless at 25°C.This log Koc value indicates that the substance has a low sorption to soil and sediment and therefore have moderate migration potential to ground water.

 

In a supporting study,adsorption experiment was conducted for evaluating the adsorption capacity of test chemical onto three different soils (from peer reviewed journal (B. von Oepen et. al., 1991) and authoritative databases, 2017). The study was performed in accordance with the Modified OECD-Guideline 106 Adsorption/Desorption using the batch equilibrium method. The soils used for testing covers a broad spectrum of sorption relevant properties e.g. organic carbon content (% oc), clay content, pH value, Cation Exchange Capacity etc. The soils used for testing were an acidic forest soil, a Podzol and an agricultural soil (Alfisol). Additionally the sorption behaviour of a sublimnic soil, a sediment of the Lake Constance, was investigated .Initial test chemical concentrations used for the study were about 0.15, 0.5, 5 and 15 mg/l, respectively. For sorption experiments,50 ml of the test solution were added to 10 g (dry weight) of the specific soils. The soil samples were shaken for 0.5, 1, 1.5, 5, 24 respectively 72 hours. Then an aliquot of 1 ml of the water-phase was removed and the concentration of the test chemical in the aqueous phase was determined. As for test chemical, the sorption equilibrium was reached within 16 hours, the Freundlich isotherms were determined after an incubation period of 16 hours. The initial concentrations used were about 15 mg/l, 5 mg/1, 0.5 and 0.15 mg/l. After reaching the equilibrium the soil samples were centrifuged, decanted, and the concentrations in the supernatant were determined by means of GC, HPLC or scintillation measurements. All samples were determined in parallel. One control and one blank were investigated additionally. Alter the adsorption step, a two step desorption test was performed with an equilibrium time of 8 hours followed by a desorption period of 16 hours. The Freundlich constants and Koc values were calculated. For the test chemical, the sorption equilibrium was reached within 16 hrs. The soil with the highest organic carbon content, the Podzol, has the highest sorption capacity towards the test chemical as compared to the Alfisolsoil and Sublimnic soil. Consequently the sorption coefficients determined for Alfisol and the sediment are lower than those determined for the Podzol. The desorption data revealed that sorption was reversible to a great extent for all substances under study. The mass balance resulted in a recovery of ˃ 80%. The adsorption coefficient (Koc) value of test chemical onto three different soils, a Podzol, an alfisol and sediment was determined to be 31 (Log Koc= 1.491), 26 (Log Koc= 1.414) and 28 (Log Koc= 1.447) dimensionless with a corresponding Freundlich constant (Kf) value of 1.48, 0.33 and 0.44, respectively. This logKoc value indicates that the test chemical has a negligible sorption to soil and sediment and therefore has rapid migration potential to ground water.

 

For the test chemical from peer reviewed journal (S. Bintein et. al., 1994), adsorption study was conducted for estimating the adsorption coefficient (Koc) value of test chemical. The adsorption coefficient (Koc) value was calculated using the QSAR model. This model involves a variety of abiotic and biotic parameters as inputs, among which one such parameter is the soil or sediment sorption coefficient of test chemical (Kp) in models used to estimate the environmental mobility and fate of the test chemical. The QSAR model involves the use of quantitative structure activity relationship (QSAR) equation. Equations used in developing QSAR model for describing the sorption behavior of test chemical in soil or sediments were Koc = (Kp X 100)/%OC and logKp = 0.93 logKow + 1.09 log fOC+ 0.32 CFa – 0.55 CFb’ + 0.25, respectively, in which, the Kp, logKow and pKa value were obtained from the different literatures. Thus, the adsorption coefficient (Koc) value of test chemical was estimated to be ranges from 29.85 to 71.42 (Log Koc= 1.47 to 1.85), respectively, calculated using a QSAR equation. This Koc value indicates that the test chemical has a low sorption to soil and sediment and therefore have moderate migration potential to ground water.

 

On the basis of above overall results for test chemical (from study report, peer reviewed journals, and authoritative databases), it can be concluded that the logKoc value of test chemical ranges from 1.41–1.9, respectively, indicating that the test chemical has a negligible to low sorption to soil and sediment and therefore have rapid to moderate migration potential to ground water.

 

In addition to the above information, adsorption endpoint can also be considered for waiver as per in accordance with column 2 of Annex VIII of the REACH regulation, testing for this endpointis scientifically not necessary and does not need to be conducted since the test chemical has a low octanol water partition coefficient and the adsorption potential of this substance is related to this parameter.