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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, 2018). The solutions of the test substance and reference substances were prepared in appropriate solvents. A test item solution was prepared by accurately weighing 4 mg of test item and diluted with Acetonitrile up to 10 ml. Thus, the test solution concentration was 400 mg/l. The pH of test substance was 4.8. 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-naphtol, Direct Red 81, Benzoic acid methylester, Carbendazim, Benzoic acid phenylester, Xylene, Ethylbenzene, Toluene, Naphthalene, 1,2,3-trichlorobenzene, Pentachlorophenol, 3,5-dinitrobenzamide, Benzamide, phenanthrene having Koc value ranging from 1.25 to 4.09. The Log Koc value of test chemical was determined to be 0.992± 0.053 dimensionless at 25°C.This log Koc value indicates that the substance has a negligiblesorption to soil and sediment and therefore have rapid migration potential to ground water.

Additional information

Adsorption / desorption

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

In an experimental study from study report (2018),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 4 mg of test item and diluted with Acetonitrile up to 10 ml. Thus, the test solution concentration was 400 mg/l. The pH of test substance was 4.8. 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-naphtol, Direct Red 81, Benzoic acid methylester, Carbendazim, Benzoic acid phenylester, Xylene, Ethylbenzene, Toluene, Naphthalene, 1,2,3-trichlorobenzene, Pentachlorophenol, 3,5-dinitrobenzamide, Benzamide, phenanthrene having Koc value ranging from 1.25 to 4.09. The Log Koc value of test chemical was determined to be 0.992± 0.053 dimensionless at 25°C.This log Koc value indicates that the substance has a negligible sorption to soil and sediment and therefore have rapid migration potential to ground water.

 

Another adsorption study was conducted for estimating the adsorption coefficient (Koc) value of test chemical (authoritative databases, 2017). The adsorption coefficient (Koc) value was calculated using a structure estimation method based on molecular connectivity indices. The adsorption coefficient (Koc) value of test chemical was estimated to be 67 (Log Koc = 1.826). 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 results of test chemical (from study report and authoritative databases), it can be concluded that the logKoc value of test chemical was evaluated to be ranges from 0.992 to1.826, 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.