2-[7-(diethylamino)-2-oxo-2H-1-benzopyran-3-yl]benzoxazole-5-sulphonamide

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:

03 November 2016 to 16 December 2016

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))

Version / remarks:

2001

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))

Version / remarks:

2008

Deviations:

no

GLP compliance:

yes

Type of method:

HPLC estimation method

Media:

soil

Radiolabelling:

no

Details on study design: HPLC method:

PERFORMANCE OF THE STUDY
While passing through a column along with the selected mobile phase, the test material interacts with the stationary phase. As a result of partitioning between mobile and stationary phases, the test material is retarded. The dual composition of a cyanopropyl stationary phase, having polar and non-polar sites allows for interaction of polar and non-polar groups of a molecule in a similar way as is the case for organic matter in soil or sewage sludge matrices. This enables the relationship between the retention time on the column and the Koc on organic matter to be established.
According to the guidelines, the determination of the Koc for test materials that are ionised for at least 10 % within pH 5.5 to 7.5 should be performed with both the ionised and non-ionised form. Therefore, the pKa values of the test material were calculated using the Perrin calculation method (pKalc 5.0, module in Pallas 3.0, CompuDrug International San Francisco, CA, USA). Based on the calculations, the HPLC method was performed at pH 7.
Solutions of reference substances with known log Koc values based on soil adsorption data and the test material were analysed. The capacity factor (k') of each compound was calculated from its retention time. The log k’ values of the reference substances were plotted against the known log Koc values. A linear regression program was used to calculate the calibration curve. Linear regression analysis was performed using the least squares method. The coefficient of correlation (r) was calculated. The log Koc value for the test material was calculated by substituting its mean log k’ in the calibration curve. The value of log Koc obtained from duplicate measurements was within ± 0.25 log units.

ANALYTICAL CONDITIONS
- Instrument: Acquity UPLC system (Waters, Milford, MA, USA)
- Detector: Acquity UPLC TUV (Waters)
Column: Acquity UPLC HSS Cyano, 100 mm x 2.1 mm i.d., dp = 1.8 μm (Waters)
- Column temperature: 35 ± 1 °C
- Mobile phase pH 7: 55/45 (v/v) methanol/ 0.01 M phosphate buffer pH 7
- Flow: 0.4 mL/min
- Injection volume: 5 μL
- UV detection: 210 nm

PREPARATION OF THE SOLUTIONS
- Solution of the unretained compound
A 5000 mg/L stock solution of formamide (99.2 %) in methanol was used. The stock solution was diluted to obtain an end solution of 55/45 (v/v) methanol/ 0.01 M phosphate buffer pH 7.
The formamide blank solution was 55/45 (v/v) methanol/ 0.01 M phosphate buffer pH 7.

- Reference substance solutions
Stock solutions of the reference substances at concentrations of 1000 mg/L (1108 mg/L for 4,4’-DDT) in methanol were used. The stock solutions were diluted to obtain an end solution of 55/45 (v/v) methanol/ 0.01 M phosphate buffer pH 7.
The blank solution for the mixture of reference substances was 55/45 (v/v) methanol/ 0.01 M phosphate buffer pH 7.

- Test solution
A 1000 mg/L stock solution of the test material was prepared in methanol. In order to dissolve the test material the stock solution was ultrasonicated for 10 minutes. The stock solution was diluted to obtain an end solution of 55/45 (v/v) methanol/0.01 M phosphate buffer pH 7. The final concentration of the test material solution was 10.0 mg/L.
The test material blank solution was 55/45 (v/v) methanol/ 0.01 M phosphate buffer pH 7.

INJECTIONS
The reference substance and test material solutions were injected in duplicate. Blank solutions were analysed by single injection.

FORMULAE
Capacity factor k’:
k' = (tr – t0) / t0
Where:
tr = retention time
t0 = mean column dead time

Calibration curve:
logk’ = a logKoc + b
Where:
a = slope
b = intercept

Key result

Type:

Koc

Value:

10 000 dimensionless

pH:

7

Temp.:

35 °C

Matrix:

Soil

Key result

Type:

log Koc

Value:

4.01 dimensionless

pH:

7

Temp.:

35 °C

Matrix:

Soil

Details on results (HPLC method):

CALCULATION OF pKa VALUES
The following pKa values in the logarithm range of 1 - 14 for acidic and basic groups in the molecular structure of the test material were calculated using the Perrin calculation method:
Acidic: RC6H4SO2NH2 pKa 9.38
Basic: RARN(R1R2) pKa 5.20

DETERMINATION OF THE Koc
In the chromatogram of the test solution, one test material peak was observed.
The results of the HPLC method show the calibration curve of the log k’ of the reference substances as function of log Koc. The equation of the regression line was: log k’ = 0.304 x log Koc – 0.852 (r = 0.98, n = 16).

Table 2: Koc of the test material at pH 7

Substance	tr,1 [min]	tr,2 [min]	Mean tr (n = 2)	logKoc	Koc
Formamide (t0)	0.733	0.729	0.731
Acetanilide	0.943	0.934		1.26
Monuron	1.141	1.129		1.99
2,5-Dichloroaniline	1.258	1.247		2.55
Naphthalene	1.457	1.443		2.75
Benzoic acid phenylester	1.721	1.702		2.87
Fenthion	2.179	2.156		3.31
Phenanthrene	2.409	2.383		4.09
4,4’-DDT	5.317	5.251		5.63
Test material	2.429	2.423	2.426	4.01	1.0 x 10^4

Validity criteria fulfilled:

not applicable

Conclusions:

Under the conditions of this study, the Koc of the test material was 1.0 x 10^4 and the logKoc was 4.01.

Executive summary:

The Koc of the test material was assessed in accordance with the standardised guidelines OECD 121 and EU Method C.19 under GLP conditions using an HPLC Method.

The pKa values of the test material were calculated and based on the calculations, the HPLC method was performed at pH 7. Solutions of reference substances with known log Koc values based on soil adsorption data and the test material were analysed. The capacity factor (k') of each compound was calculated from its retention time. The log k’ values of the references substances were plotted against the known log Koc values. A linear regression program was used to calculate the calibration curve. Linear regression analysis was performed using the least squares method. The coefficient of correlation (r) was calculated. The log Koc value for the test material was calculated by substituting its mean log k’ in the calibration curve. The value of log Koc obtained from duplicate measurements was within ± 0.25 log units.

In the chromatogram of the test solution, one test material peak was observed.

Under the conditions of this study, the Koc of the test material was 1.0 x 10^4 and the logKoc was 4.01.

Description of key information

Under the conditions of this study, the Koc of the test material was 1.0 x 10^4 and the logKoc was 4.01.

Key value for chemical safety assessment

Koc at 20 °C:

10 000

Additional information

The Koc of the test material was assessed in accordance with the standardised guidelines OECD 121 and EU Method C.19 under GLP conditions using an HPLC Method. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

The pKa values of the test material were calculated and based on the calculations, the HPLC method was performed at pH 7. Solutions of reference substances with known log Koc values based on soil adsorption data and the test material were analysed. The capacity factor (k') of each compound was calculated from its retention time. The log k’ values of the references substances were plotted against the known log Koc values. A linear regression program was used to calculate the calibration curve. Linear regression analysis was performed using the least squares method. The coefficient of correlation (r) was calculated. The log Koc value for the test material was calculated by substituting its mean log k’ in the calibration curve. The value of log Koc obtained from duplicate measurements was within ± 0.25 log units.

In the chromatogram of the test solution, one test material peak was observed.

Under the conditions of this study, the Koc of the test material was 1.0 x 10^4 and the logKoc was 4.01.

[LogKoc: 4.01]