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Reference
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
6 September - 10 October 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
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))
Version / remarks:
2001
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))
Version / remarks:
2008
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of method:
HPLC estimation method
Test temperature:
25°C
Details on study design: HPLC method:
EQUIPMENT
HPLC system:
Pump VWR-Hitachi Chromaster 5160
Autosampler VWR-Hitachi Chromaster 5260 AS
UV Detector VWR-Hitachi Chromaster 5420
Column Agilent, Zorbax CN, 150 x 4.6 mm; 5 µm
Conditions The experiment was run at 25°C and for detection a wavelength of 210 nm was used.

MOBILE PHASES
- Type: The mobile phase was ultra-pure water1:methanol (55:45; v:v) adjusted to a pH of 6.8. Isocratic conditions with a flow rate of 1 ml/min were applied.
- Solutes for dissolving test and reference substances:
Stock solutions of the test item and of the reference items were prepared in in a suitable solvent (For more details see any other information on materials and methods incl. tables). All stock solutions were diluted by a factor of 100 using the mobile phase, for the single as well as the mixed injections.

DETERMINATION OF DEAD TIME
The dead time (t0) was determined with Sodium nitrate, which is unretained under the applied conditions.

REFERENCE SUBSTANCES
see any other information on materials and methods incl. tables

DETERMINATION OF RETENTION TIMES
The Software EZChrom Elite 3.3.2 SP2, Agilent Technologies was used to analyse retention times.
- Quantity of test substance / reference substances introduced in the column:
Stock solutions of the test item and of the reference items were prepared in in a suitable solvent (For more details see any other information on materials and methods incl. tables). All stock solutions were diluted by a factor of 100 using the mobile phase, for the single as well as the mixed injections.

MEASUREMENTS / REPETITIONS
- Number of determinations: 2
The selected set of reference items was used to conduct two determinations of log KOC. First, the reference items were injected individually to identify them via their retention time. Secondly, the reference items were injected as a mixture of all of them together to calibrate the system followed by two injections of the single test item solution. Finally, the reference items were again injected as a mixture to re-confirm the initial calibration.
The first test item injection was evaluated using the initial calibration with the mixed reference items solution and the second test item injection was evaluated using the second calibration with the mixed reference items solution.

EVALUATION
- Calculation of capacity factors k': k = (tR - t0) / t0 with tR = retention time, t0 dead time
The calculation was done using the program Microsoft Excel.

- Calculation of retention times: Retention times were analysed with the software EZChrom Elite.

- Determination of the log Koc value:
With the determined k values of the reference items a correlation between log k versus log KOC was plotted in Microsoft Excel with a subsequent linear regression analysis

Key result
Sample No.:
#1
Type:
log Koc
Value:
ca. 2.1 dimensionless
pH:
6.8
Temp.:
25 °C
Remarks on result:
other: component N-Propylphthalimide, average logKoc from two determinations, 95% confidence interval for logKoc: 1.99 - 2.2
Key result
Sample No.:
#1
Type:
log Koc
Value:
ca. 2.4 dimensionless
pH:
6.8
Temp.:
25 °C
Remarks on result:
other: component N-sec-Butylphthalimide, average logKoc from two determinations, 95% confidence interval for logKoc: 2.3 - 2.5
Key result
Sample No.:
#1
Type:
log Koc
Value:
ca. 2.46 dimensionless
pH:
6.8
Temp.:
25 °C
Remarks on result:
other: component N-Butylphthalimide, average logKoc from two determinations, 95% confidence interval for logKoc: 2.35 - 2.56
Details on results (HPLC method):
see details in field any other information on results incl. tables

- Retention times of Sodium nitrate (dead time): 1.10 min (three determinations)

- Retention times of reference substances used for calibration:

Item   First determination retention time (min)   Second determination retention time (min)
 Acetanilide  3.35  3.34
 Phenol  3.45  3 -45
 Methyl benzoate  5.46  5.44
 Napthalene  12.71  12.63
 1,2,3 -Trichlorobenzene  16.83  16.73
 Pyrazophos  36.19  35.79

- Details of fitted regression line (log k' vs. log Koc):

 First injection  Second injection
   Coefficient of regression (r^2)  0.994  0.994
  Intercept (A)  0.622  0.622
 Slope (B)  2.07  2.08

- Graph of regression line attached (see attached background material)

- Retention times for test substance:

 First determination retention time (min)   Second determination retention time (min)
 component 1:  N-propylphthalimide  6.76  6.74
 component 2: N-sec-Butylphthalimide  9.03  9.00
 component 3: N-Butylphthalimide  9.53  9.50
Validity criteria fulfilled:
yes
Conclusions:
In this study according to OECD guideline 121, the log KOC values of the three main components of the test item “Reaction mass of N-butylphthalimide and N-propylphthalimide and N-sec-butylphthalimide” calculated as the mean of both determinations, are 2.10 for N-propylphthalimide (KOC = 125), 2.40 for N-sec-butylphthalimide (KOC = 252) and 2.46 for N-butylphthalimide (KOC = 286).
Executive summary:

The log KOC of the three main components of the test item “Reaction mass of N-butylphthalimide and N-propylphthalimide and N-sec-butylphthalimide” was determined according to TG OECD 121. This determination is based upon a regression analysis of the log KOC values of reference items against their respective retention times as determined by HPLC analysis.

The following reference items were used: Acetanilide, Phenol, Methyl benzoate, Naphthalene, 1,2,3-Trichlorobenzene and Pyrazophos. The dead time of the HPLC system was determined with Sodium nitrate.

This set of reference items yielded a calibration with log KOC values ranging from 1.25 to 3.65 and retention times ranging from 3.34 min to 36.2 min. The dead time of the HPLC system was 1.10 min.

The log KOC value for the first test item component (N-propylphthalimide) was found to be 2.10 (95% confidence limits: 1.99–2.20) in both determinations.

The log KOC value for the second test item component (N-sec-butylphthalimide) was found to be 2.40 (95% confidence limits: 2.30–2.50) in both determinations.

The log KOC value for the third test item component (N-butylphthalimide) was found to be 2.46 (95% confidence limits: 2.35–2.56) in both determinations.

The determinations are valid since the values of log KOC derived from these two repeated measure-ments fall within a range of 0.25 log units.

Consequently, the log KOC values of the three main components of the test item “Reaction mass of N-butylphthalimide and N-propylphthalimide and N-sec-butylphthalimide” calculated as the mean of both determinations, are 2.10 for N-propylphthalimide (KOC = 125), 2.40 for N-sec-butylphthalimide (KOC = 252) and 2.46 for N-butylphthalimide (KOC = 286).

Description of key information

The log KOC of the three main components of the test item “Reaction mass of N-butylphthalimide and N-propylphthalimide and N-sec-butylphthalimide” was determined in a GLP study according to TG OECD 121 (Tobler, N, 2017).

The log KOC values of the three main components of the test item “Reaction mass of N-butylphthalimide and N-propylphthalimide and N-sec-butylphthalimide” calculated as the mean of both determinations, are 2.10 for N-propylphthalimide (KOC = 125), 2.40 for N-sec-butylphthalimide (KOC = 252) and 2.46 for N-butylphthalimide (KOC = 286).

The determinations are valid since the values of log KOC derived from these two repeated measurements fall within a range of 0.25 log units.

Key value for chemical safety assessment

Koc at 20 °C:
125

Additional information

The following reference items were used: Acetanilide, Phenol, Methyl benzoate, Naphthalene, 1,2,3-Trichlorobenzene and Pyrazophos. The dead time of the HPLC system was determined with Sodium nitrate.

With the determined k values of the reference items a correlation between log k versus log KOC was plotted in Microsoft Excel with a subsequent linear regression analysis.

As key value the lowest KOC among the three test item components was selected. The KOC was determined at 25°C. It was assumed that the KOC at 20°C is in the same range.