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Reference
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From 19 February 2019 to 27 March 2020
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
other: The Guidelines for the Testing of Chemicals, Physical-Chemical Properties and Physical Hazards, 121 Estimation of the adsorption coefficient (Koc) on soil and on sewage sludge using high performance liquid chromatography (HPLC)
Version / remarks:
Second Edition Beijing: China Environmental Press. 2013, page 190-198
Deviations:
no
Qualifier:
according to guideline
Guideline:
OECD Guideline 121 (Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC))
Version / remarks:
Adopted 22 Jan, 2001
Deviations:
no
Qualifier:
according to guideline
Guideline:
other: Standardization Administration of the People's Republic of China. GB/T 21860-2011 Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC)
Version / remarks:
BeiJing: Standards Press of China, 2011
GLP compliance:
yes
Type of method:
HPLC estimation method
Specific details on test material used for the study:
- Storage: Ambient temperature (10-30°C)
- Stability under storage conditions: Stable
- Water solubility: Insoluble
- Solubility in organic solvents: Soluble in dimethyl sulfoxide and acetone
Radiolabelling:
no
Test temperature:
Column oven is within the range of 25.0 +/- 0.1°C during the test
Details on study design: HPLC method:
EQUIPMENT
- Apparatus: Agilent 1260 HPLC, Instrument No. TTE20172376
- Type, material and dimension of analytical (guard) column: Guard column = Agilent ZORBAX Eclipse XDB-CN, 4.6 x 12.5 mm, 5 µm; Column = Agilent ZORBAX Eclipse XDB-CN, 4.6 x 150 mm, 5 µm; Oven = 25°C; Flow = 1.0 mL/min; Injection volume = 10 µL
- Detection system: Detection wavelength = 210 nm;

MOBILE PHASES
- Type: Acetonitrile:water (55:45% V/V)
- Solutes for dissolving test and reference substances: Acetonitrile

DETERMINATION OF DEAD TIME
- Method: 25.9 mg and 31.6 mg of Sodium nitrate were accurately weighted into 25 mL volumetric flask and dissolved in ultrapure water to make a stock concentration of 1036 mg/L and 1264 mg/L. The stock solutions were diluted with mobile phase to obtain the test solution of 100 mg/L. The test solution was injected individually. The average retention time of duplicate injection was calculated as the dead-time t0.

REFERENCE SUBSTANCES
- Identity: 4-Methylbenzamide (log Koc = 1.78), Aniline (log Koc = 2.07), Naphthalene (log Koc = 2.75), 1,2,3-Trichlorobenzene (log Koc = 3.16), Phenanthrene (log Koc = 4.09), 4,4'-DDT (log Koc = 5.63).

TEST SYSTEM
- Method of preparation of test solution: 24.3 mg and 24.2 mg of the test item were accurately weighed in 25 mL volumetric flask and diluted with acetonitrile to the mark to obtain the stock solution with the concentration of 972 mg/L and 968 mg/L. The two stock solutions were diluted with mobile phase to obtain working solution to 500 mg/L.
- Method of preparation of reference substance solution: The stock solution for reference substances was prepared in methanol. Then, the stock solutions were diluted with mobile phase into a mixed reference solution.

DETERMINATION OF RETENTION TIMES
Test solution of test item were analyzed in duplicates and the retention time of test item was calculated as the average of the two determinations. Before and after the injection of the test item, the mixed calibration solution of reference substances was analyzed in duplicates. The retention time of all reference substances was obtained and calculated as the average of the two determinations.

REPETITIONS
- Number of determinations: The test solution was analyzed in duplicates and the retention time was calculated as the average of the two determinations.

EVALUATION
According to the result of t0 and tR, the capacity factors (k) of reference and test item was be calculated. Calibration graph of log Koc versus log k was plotted to get the linear fitting regression curve of log Koc. According to the regression equation, the log k of test item was used to calculate log Koc.
Key result
Sample No.:
#1
Type:
log Koc
Value:
5.65 dimensionless
Temp.:
25 °C
Remarks on result:
other: Mean value for Group I
Key result
Sample No.:
#2
Type:
log Koc
Value:
6.42 dimensionless
Temp.:
25 °C
Remarks on result:
other: Mean value for Group II
Key result
Sample No.:
#3
Type:
log Koc
Value:
7.25 dimensionless
Temp.:
25 °C
Remarks on result:
other: Mean value for Group III
Details on results (HPLC method):
- Dead time t0: Sodium Nitrate solution was analyzed in duplicates and the retention time was determined to be 2.076 min and 2.089 min, respectively. The average value was 2.083 min which was used as the dead-time t0.
- Retention times of reference substances used for calibration: See table 5.4.1/1 in "Any other information on results incl. tables". The average retention time of 4-Methylbenzamide was 3.162 min; the average retention time of Aniline was 4.005 min; the average retention time of Naphthalene was 4.846 min; the average retention time of 1,2,3-Trichlorobenzene was 5.170 min; the average retention time of Phenanthrene was 5.718 min; the average retention time of 4,4'-DDT was 8.903 min.
- Details of fitted regression line (log k' vs. log Koc): The linear regression equation of log k to log Koc was log Koc = 5.0164*log k + 2.6357 (R²=0.8946)
- Graph of regression line attached
- Average retention data for test substance: See table 5.4.1/2 in "Any other information on results incl. tables". The retention time of each single component of the test item was 10.383 min, 13.919 min and 19.371 min, respectively. The capacity factors (k) were 3.986, 5.684 and 8.302, respectively. According to the linear regression equation and log k of the test item of two replicates, the log Koc was in the range of 5.65 -7.25 (the deviations were in the range of -0.04 --0.03, so within the limit of +/-0.5 log Koc).
Transformation products:
not measured

Table 5.4.1/1: The results of reference substances

Reference substance

Retention time (min)

Capacity factor k

Log k

Log Koc

1st

2nd

Mean

4-Methylbenzamide

3.161

3.163

3.162

0.518

-0.285

1.78

Aniline

3.999

4.010

4.005

0.923

-0.035

2.07

Naphthalene

4.839

4.852

4.846

1.327

0.123

2.75

1,2,3-Trichlorobenzene

5.162

5.178

5.170

1.483

0.171

3.16

Phenanthrene

5.708

5.728

5.718

1.746

0.242

4.09

4,4’-DDT

8.878

8.927

8.903

3.275

0.515

5.63

Dead-time t0 = 2.083 min

Table 5.4.1/2: The results of test item

Test item*

Replicate

Retention time (min)

Capacity factor k

Log k

Log Koc

Variance

Group I

1

2

Mean

10.330

10.435

10.383

3.960

4.011

3.986

0.598

0.603

0.600

5.64

5.66

5.65

-0.03

Group II

1

2

Mean

13.835

14.002

13.919

5.643

5.724

5.684

0.752

0.758

0.755

6.41

6.44

6.42

-0.03

Group III

1

2

Mean

19.228

19.514

19.371

8.233

8.370

8.302

0.916

0.923

0.919

7.23

7.27

7.25

-0.04

Variance is the difference of log Koc values for two replicates.

* Based on a qualitative analysis of the test substance, nine peaks were observed in the chromatograph for the test substance. A group evaluation of three major groups took place: group I with peaks 1 to 3, group II with peaks 4 to 6 and group III with peaks 7 to 9.

Validity criteria fulfilled:
yes
Conclusions:
The log Koc of the test item on soil was in the range of 5.65-7.25 as determined by HPLC method. Because the retention time of each single component of the test was longer than that of reference 4,4'-DDT, the log Koc of each single component of the test item was exceeded the range of calibration curve, so the log Koc of the test item was >5.63 (log Koc of reference DDT).
Executive summary:

In this study, the Koc of the test item was estimated by HPLC method. The Dead time t0 was determined by retention time of sodium nitrate. The 4-Methylbenzamide, Aniline, Naphthalene, 1,2,3-Trichlorobenzene, Phenanthrene and 4,4'-DDT were used as reference substance, then determined retention time tR of the test item and reference substance. According to the result of t0 and tR, the capacity factors (k) of reference and test item were calculated. A calibration graph of log Koc versus log k of reference substances was plotted to get the linear fitting regression curve of log Koc, and log Koc of test item was calculated.

The retention time of each single component of the test item was 10.383 min, 13.919 min and 19.371 min, respectively. The capacity factors (k) were 3.986, 5.684 and 8.302, respectively. The linear regression equation of log k to log Koc was log Koc = 5.0164*log k + 2.6357 (R²=0.8946). According to the linear regression equation and log k of the test item of two replicates, the log Koc was in the range of 5.65 -7.25 (the deviations were in the range of -0.04 --0.03, so within the limit of +/-0.5 log Koc).

Because the retention time of each single component of the test was longer than that of reference 4,4'-DDT, the log Koc of each single component of the test item was exceeded the range of calibration curve, so the log Koc of the test item was >5.63 (log Koc of reference DDT).

Description of key information

OECD Guideline 121, GLP, key study, validity 1:

log Koc > 5.63

Immobile in soil (according to P. J. McCall et al., 1980).

Key value for chemical safety assessment

Additional information

One valid key study is available to assess the adsorption coefficient of the registered substance. This study was performed according to OECD Guideline 121 with GLP compliance. Based on a qualitative analysis of the test substance, nine peaks were observed in the chromatograph for the test substance. A group evaluation of three major groups took place: group I with peaks 1 to 3, group II with peaks 4 to 6 and group III with peaks 7 to 9. The log Koc of each group of the test substance was in the range of 5.65 to 7.25. Because the retention time of each group of the test was longer than that of reference 4,4'-DDT, the log Koc of each group of the test item was exceeded the range of calibration curve, so the log Koc of the registered substance was > 5.63 (log Koc of reference DDT). This result indicates that the registered substance is immobile in soil (according to P.J. McCall et al., 1980).

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