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Reference
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
03 August 2010- 21 October 2010
Reliability:
1 (reliable without restriction)
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
Qualifier:
according to
Guideline:
EU Method C.19 (Estimation of the Adsorption Coefficient (KOC) on Soil and Sewage Sludge Using High Performance Liquid Chromatography (HPLC))
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of method:
HPLC estimation method
Media:
soil/sewage sludge
Radiolabelling:
no
Test temperature:
25 ±1 °C
Details on study design: HPLC method:
EQUIPMENT
Pump: Dionex P580 Pump
Injector: Rheodyne 8125)
Column: Reprosil-Pur CN Dr. Maisch, 4.6 mm i.D., 125 mm length, particle size 3 µm
Detector: Dionex, UVD 170S; RI-Detektor RI 101
Program: ChromeleonTM, Version 6.80
Evaluation reference mix: UV, Wavelength 228 nm
Evaluation test item RI

Column temperature was room temperature, 25 ±1 °C.

MOBILE PHASES
A mixture of 55% methanol and 45% water, isocratic, was used. The mix was produced by the pump.

DETERMINATION OF DEAD TIME
The dead time t0 was measured by using an un-retained compound (sodium nitrate) which was included in the mix of the reference items.

REFERENCE SUBSTANCES
- Identity:
Sodium nitrate
Phenole
Methylbenzoate
3,5-Dinitrobenzamide
Naphthaline
1,2,3-Trichlorbenzene
Pyrazophos
- purity of reference substances: analytical grade
Type:
log Koc
Value:
0.968 - 2.12
Temp.:
25 °C
Remarks on result:
other: mean of 3 replicates
Details on results (HPLC method):
- Retention times of reference substances used for calibration: see tables in "any other information on materials and methods"
- Details of fitted regression line (log k' vs. log Koc):

Equation of the regression:
log (k’) = 0.2837 * log KOC – 0.2908
with a coefficient of determination r2 = 0.9541.

- Graph of regression line attached: see attached graph
- Average retention data for test substance: see section "any other information on results"

Pre-Tests

A solution of the test item in eluent with a concentration of 10.85 g/L was prepared and injected in order to check detectability and to find an approximate range for log KOC. Additionally, eluent and solutions of diisopropyl ether and tert-butanol were injected to check the detectability of the main compound.

The test item solution gave two not resoluted peaks at 2.5 – 2.9 minutes and a third peak at 3.9 minutes. The retention time of tert-butanol was 2.5 minutes and the retention time of diisopropyl ether was 2.9 minutes.

Based on this result, a suitable mix of reference items was chosen (with pyrazophos as substance with the highest log KOC and a retention time of approx. 9.0 minutes). The undiluted test item solution was used for the determination of the log KOC of the test item under the same conditions like in the pre-test.

Measurement Data

The following data were acquired for the test itemreaction mass of 2,2'-oxybisbutane (DSBE), DIPE, SBA and 2-methylpropan-2-ol (TBA).

The test item solution was measured on 21. Oct. 2010. The retention times and areas of the peaks are presented in the following tables:

Retention Times Test Item

Measurement

Peak 1

Peak 2

Peak 3

 

RT [min.]

RT [min.]

RT [min.]

Measurement 1

2.529

2.913

3.919

Measurement 2

2.529

2.913

3.926

Measurement 3

2.529

2.913

3.923

Mean

2.529

2.913

3.923

Standard Deviation

0.000

0.000

0.004

Areas Test Item

Measurement

Area

Peak 1

Rel.AreaPeak1

Area

Peak 2

Rel.AreaPeak2

Area

Peak 3

Rel.AreaPeak3

 

mAU*min

%

mAU*min

%

mAU*min

%

Measurement 1

5.0256

50.86

4.5743

46.30

0.2808

2.84

Measurement 2

5.0519

51.82

4.4566

45.71

0.2412

2.47

Measurement 3

5.0747

52.39

4.3777

45.20

0.2337

2.41

Mean

5.0507

51.69

4.4695

45.73

0.2519

2.58

Standard Deviation

0.49%

1.49%

2.21%

1.20%

10.04%

9.01%

 

Peak Identification

Solutions of diisopropyl ether and tert-butanol were injected for comparison purposes. The retention time of tert-butanol was 2.5 minutes. The retention time of diisopropyl ether was 2.9 minutes. Peak 1 of the test item solution was identified as tert-butanol, peak 2 of the test item solution was identified as diisopropyl ether.

Calculated Values

The calculated values are presented in the following table:

Capacity Factor, log Capacity Factor, log KOC Test Item Peaks

Peak

Measurement No.

k’

logk’

log KOC

1

1

0.9633

-0.0163

0.968

2

0.9633

-0.0163

0.968

3

0.9633

-0.0163

0.968

Mean

 

 

0.968

Stand. Dev.

 

 

0.000

2

1

1.2614

0.1008

1.380

2

1.2614

0.1008

1.380

3

1.2614

0.1008

1.380

Mean

 

 

1.380

Stand. Dev.

 

 

0.000

3

1

2.0423

0.3101

2.118

2

2.0477

0.3113

2.122

3

2.0454

0.3108

2.120

Mean

 

 

2.120

Stand. Dev.

 

 

0.002

 

log KOC was calculated from the capacity factor as follows:

 

log KOC= (log k’ + 0.32) / 0.2934

Validity criteria fulfilled:
yes
Conclusions:
Using the correlation log k’ / log KOC, the log KOC of the peak of the test item 2-propanol and 2-butanol production, distn. residues was calculated in the range of 0.968 – 2.120.
The log Koc is not used for classification purposes. In the risk assessment, the log Koc data are used for modelling of environmental fate.
Executive summary:

The adsorption coefficient on soil and on sewage sludge of 2-propanol and 2-butanol production, distn. residues (consisting mainly of di-isobutyl ether, di-isopropyl ether, C3- and C4-alcohols and C6-hydrocarbons) was estimated using HPLC according to OECD 121 resp. EU C.19.

The study was performed using a HPLC with a cyanopropyl chemical bound resin on a silica base column. Six reference items with different retention times were used to produce a calibration curve, since retention time on cyanopropyl columns and KOC are correlated. The reference items were chosen on behalf of the retention time of the test item 2-propanol and 2-butanol production, distn. residues (consisting mainly of di-isobutyl ether, di-isopropyl ether, C3- and C4-alcohols and C6-hydrocarbons) on the column.

First, the study was performed using UV-detection. With UV-detection the main compounds diisopropyl ether, tert-butanol and 2,2'-oxybisbutane (DSBE) (see analytical certificate) weren’t detected. Only minor compounds were analysed. The results of this experiment were reported in the original final report, but are considered as not valid. Therefore, a study plan amendment was issued, the final report was invalidated, and the experiment was repeated using RI detection. The raw data of the first experiment will be kept in the GLP Document Archive together with all other data collected in this study. Only the data of the repetition experiment (solutions, instruments, program, results) are reported. The repetition experiment was performed using HPLC with UV- and RI-detection. The refractive index (RI) is the ratio of the speed of light in vacuum relative to the speed in the considered medium.

For the evaluation of the chromatograms of the reference mix, the UV-signals were used. For the evaluation of the chromatograms of the test item, the RI-signals were used. Additionally, solutions of tert-butanol and di-isopropyl ether were injected for comparison purposes. The retention time of tert-butanol was 2.5 minutes and the retention time of di-isopropyl ether was 2.9 minutes.

First, a solution of the reference items was analysed three times with HPLC, then a solution of the test item (three times) and finally three more times the solution with the references. For each reference item, the capacity factor k’ was calculated from the retention time of sodium nitrate and the retention time of the respective reference item. A calibration function was set up using the literature values for KOC of the reference items and the mean capacity factor of the six determinations. In the graph Log k’ versus Log KOC, linear regression was performed, giving r² = 0.954 and r = 0.9770.

The chromatogram of the test item gave three peaks. Peak 1 is assigned to tert-butanol and peak 2 is assigned to di-isopropyl ether. Peaks 1 and 2 weren’t resoluted. Peak 3 is a smaller peak. With the help of the calibration function log K versus log Koc, the corresponding log Kocs were determined as:

Peak 1, Mean area [mAU*min] 5.0507, Rel. Area % 51.69, Mean retention time [min] 2.529, Log Koc ±SD 0.968 ± 0.000

Peak 2, Mean area [mAU*min] 4.4695, Rel. Area % 45.73, Mean retention time [min] 2.913, Log Koc ±SD 1.380 ± 0.000

Peak 3, Mean area [mAU*min] 0.2519, Rel. Area % 2.58, Mean retention time [min] 3.923, Log Koc ±SD 2.120 ± 0.002

These values are the means ± standard deviation of three independent determinations.

The first peak lay outside the range limited by the reference items. However, since this peak corresponds to the substance tert-butanol and corresponds well to the measured log Pow for this substance, the value was regarded as valid.

For this reason, peaks 1 - 3 are included in the estimation of the log Koc and the log Koc should be stated as range 0.968 – 2.120.

Description of key information

Using the correlation log k’ / log KOC, the log KOC corresponding to the peaks of the test item of “2-propanol and 2-butanol production, distn. residues” (consisting mainly of di-isobutyl ether, di-isopropyl ether, C3- and C4-alcohols and C6-hydrocarbons) was in the range of 0.968 – 2.120.

Key value for chemical safety assessment

Koc at 20 °C:
132

Additional information

The chromatogram of the test item gave three peaks. With the help of the calibration, the log KOC was determined in the range of 0.968 – 2.120.

Variations in the retention times of reference items and test item are very small. Therefore, a stable configuration of the HPLC-column can be assumed.

The correlation log k’/log KOC is sufficiently accurate, as calibration gave a coefficient of determination r² = 0.9541. No observations were made which might give doubts concerning the validity of the study outcome. The result is considered as valid.

 

Literature / (Q)SAR log Koc values of the main components of the reaction mass lie within the same range as the experimentally determined values discussed above: DSBE: 2.2 (1); DIPE: 1.5 (1); SBA: 0.63 (1); TBA: 0.48 (1), thus confirming the validity of the measured data.

 

References:

(1) Estimation Program Interface (EPI) Suite,2000 - 2009, U.S. Environmental Protection Agency

[LogKoc: 2.12]