N,N-Dimethyl-9-dodecenamide

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

17 - 19 January 2022

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

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))

Deviations:

no

Qualifier:

according to guideline

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. QA statement)

Type of method:

HPLC estimation method

Radiolabelling:

no

Test temperature:

29.8°C - 29.9°C

Details on study design: HPLC method:

EQUIPMENT
- Apparatus: HPLC-DAD
- Type: WATERS 996
- Column; Roc Cyano (4.6 x 150 mm, 5µm), RESTEK
- Detection system: UV
- Detection wavelength: 200 nm
- Injection volume: 50 µL
- Column flow : 1 mL/min
- Column temperature: 30 ± 1 °C

MOBILE PHASES
- Type: Methanol: 55%/Ultrapure water: 45%
- Experiments with additives carried out on separate columns: no
- pH: 5
- Solutes for dissolving test and reference substances:
Test substance: A stock solution of the test item was prepared at a concentration of 1 g/L in acetone. A diluted solution at 5 mg/L was prepared in the HPLC mobile phase with sodium nitrate at 1 mg/L.
For the preliminary test a solution of the test item was prepared at a concentration of 9.7 mg/L in the HPLC mobile phase with sodium nitrate at 1 mg/L.
Reference substances: A stock solution of each reference substance was prepared at a concentration of approximately 1 g/L in acetone. These solutions were kept at 1 - 5 °C for 6 months. Two diluted reference solutions containing all the reference substances were prepared in the HPLC mobile phase with sodium nitrate at 1 mg/L.
For the preliminary test, individual solutions of six reference items were also prepared in the HPLC mobile phase with sodium nitrate at 1 mg/L.

DETERMINATION OF DEAD TIME
- Method: The dead time t0 was measured by using a non-retained compound (sodium nitrate) which was present in the reference items mixes and in the test item solution

REFERENCE SUBSTANCES
- Identity: phenol (CAS 108-95-2); methylbenzoate (CAS 93-58-3);aniline (CAS 62-53-3); pyrazophos (CAS 13457-18-6); phenanthrene (CAS 85-01-8); DDT (CAS 50-29-3)

DETERMINATION OF RETENTION TIMES
- Quantity of test substance introduced in the column: 50 µL of a 5 mg/L solution
- Quantity of reference substances: see table below

REPETITIONS
- Number of determinations: 2

EVALUATION
- Calculation of capacity factors k':
The capacity factor k for every peak was calculated using the following equation:

k = (tR- t0)/t0

where
tR is the HPLC retention time of test or reference substance (min);
t0 is the HPLC dead-time = retention time of sodium nitrate (min).

- Determination of the log Koc value:
The calibration function was drawn up from the two measurements of the capacity factors of each reference item. The log k was plotted as a function of the corresponding logarithms of the adsorption coefficient, log KOC. A linear regression was performed and a calibration function was obtained.
The partition coefficient of the test item was obtained for the two measurements by interpolation of the calculated capacity factor on the calibration graph.
Mean and standard deviations of the log KOC were calculated.

Sample No.:

#1

Type:

log Koc

Value:

3.15 dimensionless

pH:

5

Temp.:

29.8 °C

Sample No.:

#2

Type:

log Koc

Value:

3.15 dimensionless

pH:

5

Temp.:

29.8 °C

Details on results (HPLC method):

- Retention times of reference substances used for calibration: The retention times of the reference items are presented in the table in the section on any other information on results.
- Details of fitted regression line (log k' vs. log Koc): See section on any other information on results
- Graph of regression line attached: yes
- Average retention data for test substance: See section on any other information on results

Preliminary test:

A preliminary study was carried out in order to check the retention times and the signal areas of the test and the reference items.

A solution of the test item was prepared at a concentration of 9.7 mg/L in the HPLC mobile phase with sodium nitrate at 1 mg/L. Individual solutions of six reference items were also prepared in the HPLC mobile phase with sodium nitrate at 1 mg/L. These solutions were injected in the chromatographic system using the same analytical parameters as for the main study except for the method duration (20 minutes).

A peak was observed for the test item with a retention times of 3.68 minutes. The dead time t₀, determined with the peak of sodium nitrate, was 1.06 minutes.

Compound	Concentration	tR(min)	t0(min)	k	log k	log KOC
phenol	10 mg/L	2.38	1.06	1.25	0.10	1.32
methylbenzoate	10 mg/L	2.63	1.06	1.48	0.17	1.80
aniline	10 mg/L	2.47	1.06	1.33	0.12	2.07
pyrazophos	10 mg/L	4.36	1.06	3.11	0.49	3.65
phenanthrene	10 mg/L	4.63	1.06	3.37	0.53	4.09
DDT	10 mg/L	8.02	1.06	6.57	0.82	5.63

A linear regression of log k versus log K_OCfor these reference items was carried out and the following equation was obtained:

log k = 0.1736 x log K_OC– 0.1653                         with R = 0.9903 and R²= 0.9807.

The log K_OCvalue corresponding to the peak of the test item was then deduced from the previous equation:

log K_OC= 3.20

The coefficient of determination obtained with the reference solutions is higher than 0.95 and the retention times of the peak of the test item are included in the range of the retention times of the reference items. Therefore, these reference items were used for the main test.

Main test:

The retention times of the reference items are presented in the table below:

Compound	tR1 (min)	tR2 (min)	ΔtR(min)	tRmean (min)	ΔtR/ tRmean	Equilibrium?
phenol	2.40	2.40	0.00	2.40	0.00%	YES
methylbenzoate	2.65	2.65	0.00	2.65	0.00%	YES
aniline	2.79	2.84	0.05	2.82	1.77%	YES
pyrazophos	4.38	4.41	0.03	4.40	0.68%	YES
phenanthrene	4.66	4.64	0.02	4.65	0.43%	YES
DDT	8.06	8.16	0.10	8.11	1.23%	YES

with       t_R: retention time

Δt_R: absolute value of the retention times difference

The retention times observed for the peak of sodium nitrate, used for the determination of the dead time (t₀) were:

	Mix 1	Mix 2
Injection 1	1.06	1.07
Injection 2	1.05	1.07

The equilibrium state of the system was declared since the difference of the reference items retention times (Δt_R/ t_Rmean) did not exceed 5% between two analyses.

log k over log K_OC

The following table presents for each reference item their log K_OC, the calculated retention factor for the two injections (k₁and k₂), the mean of k₁and k₂(k mean), and the log (k mean):

Compound	log KOC	k1	k2	k mean	log (k mean)
phenol	1.32	1.26	1.29	1.28	0.11
methylbenzoate	1.80	1.50	1.52	1.51	0.18
aniline	2.07	1.61	1.65	1.63	0.21
pyrazophos	3.65	3.09	3.12	3.11	0.49
phenanthrene	4.09	3.40	3.42	3.41	0.53
DDT	5.63	6.53	6.63	6.58	0.82

The logarithms of the adsorption coefficients, log K_OC, are plotted as a function of the mean capacity factors, log k. The linear regression obtained with the reference items is presented in the attached graph with the representation of the confidence interval (in orange) calculated with a 98% confidence level.

The determination coefficient R²observed is 0.9971 and the correlation coefficient R is 0.9985. According to the guideline, a typical correlation for the relationship between log K_OCand log k for a set of test substances is around 0.95. Therefore, the obtained coefficients are satisfactory.

The equation of the line issued from this linear regression (y = 0.1646x – 0.1190) was used for the test item log K_OCcalculation.

Test item:

Retention times and capacity factors

A typical chromatogram of the test item is constituted of one peak. The retention times obtained are presented below:

	Injection 1 tR(min)	Injection 2 tR(min)	tRmean (min)	Relative standard deviation
Dead time t0	1.06	1.05	1.06	0.7%
Test item peak	3.71	3.71	3.71	0.0%

Calculation of k, log k and log KOC

The calculated values for the peak of the test item are presented in the following table. log K_OCis calculated using the regression equation obtained from the reference items:

log K_OC= ( log k + 0.1190 ) / 0.1646

Measurement No.	k	log k	log KOC
1	2.50	0.40	3.15
2	2.53	0.40	3.15
	log KOCmean		3.15
	Standard deviation		0.000

The study was considered as valid since:

- the system was in an equilibrium state: the difference of the reference items retention times did not exceed 5 % (calculated as the retention times difference divided by the mean);

- the separation efficiency of the column was verified (log k was superior to 0.0 for log KOC of 3.0 and superior to -0.4 for log KOC of 2.0);

- the correlation coefficient R of the calibration function was superior to 0.95;

- repeatability of individual log KOW determinations did not differ by more than ± 0.25 unit.

Validity criteria fulfilled:

yes

Executive summary:

A study was performed to estimate the Adsorption Coefficient (log KOC) on Soil and Sewage Sludge of the test item N,N-dimethyldodec-9-enamide using HPLC. The method followed was designed to be compliant with OECD TG 121 and EU Method C.19.

Six reference items with different retention times were used to produce the calibration curve. They were chosen in relation to the expected retention time of the test item. For each reference item, two determinations were performed. The capacity factor k was calculated from the retention time of sodium nitrate (dead time) and the retention time of the respective reference item. A calibration function (log k versus log KOC, linear fit) was determined based on literature values of KOC for the reference items.

The following adsorption coefficient was determined for the test item: log K_OC= 3.15.

This value is the mean of two independent measurements.

Description of key information

A study was performed to estimate the Adsorption Coefficient (log KOC) on Soil and Sewage Sludge of the test item N,N-dimethyldodec-9-enamide using HPLC. The method followed was designed to be compliant with OECD TG 121 and EU Method C.19.

Six reference items with different retention times were used to produce the calibration curve. They were chosen in relation to the expected retention time of the test item. For each reference item, two determinations were performed. The capacity factor k was calculated from the retention time of sodium nitrate (dead time) and the retention time of the respective reference item. A calibration function (log k versus log KOC, linear fit) was determined based on literature values of KOC for the reference items.

The following adsorption coefficient was determined for the test item: log K_OC= 3.15.

This value is the mean of two independent measurements.

Key value for chemical safety assessment

Koc at 20 °C:

1 412