Zinc isodecyl phosphorodithioate

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:

08 September 2017 - 23 November 2017

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:

January 22 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:

March 04 2016

Deviations:

no

GLP compliance:

yes

Type of method:

HPLC estimation method

Test temperature:

35°C +- 1°C (column temperature)

Details on study design: HPLC method:

EQUIPMENT
- Apparatus: Acquity UPLC system (Waters, Milford, MA, USA)
- Type, material and dimension of analytical (guard) column: Acquity UPLC HSS Cyano, 100 mm x 2.1 mm i.d., dp = 1.8 µm (Waters)
- Detection system: Acquity UPLC TUV detector (Waters), 210 nm; Xevo TQ-S mass spectrometer (Waters), m/z 409.1 → m/z 110.7.

MOBILE PHASES
- Type: 55% methanol (Solvent A); 45% buffer pH 7 (Solvent B)
- pH: 7

DETERMINATION OF DEAD TIME
- Method: By inert substances which are not retained by the column

REFERENCE SUBSTANCES
- Identity: Acetanilide (99.8%); Monuron (99.9%); Naphthalene (99.5%); Fenthion (97.5%); Phenanthrene (98.1%); 4,4’-DDT (98.7%)

DETERMINATION OF RETENTION TIMES
- Quantity of test substance introduced in the column: A 1000 mg/L stock solution of the test item was prepared in methanol. The solution was ultrasonicated for 60 minutes. The stock solution was 10000 fold diluted with 55/45 (v/v) methanol/buffer pH 7. The final concentration of the test item solution was 0.1 mg/L.The test item blank solution was 55/45 (v/v) methanol/buffer pH 7.
- Quantity of reference substances: Stock solutions of the reference substances at concentrations of approximately 1 g/L in methanol were used. The stock solutions were diluted to obtain an end solution of 55/45 (v/v) methanol/buffer pH 7. The blank solution for the mixture of reference substances was 55/45 (v/v) methanol/buffer pH 7.
- Injection volume: 5 µL

REPETITIONS
- Number of determinations: Reference substances and test item were injected in duplicate, blank solutions were analysed by single injection

EVALUATION
- Calculation of capacity factors k': Solutions of reference substances with known log Koc values based on soil adsorption data and the test item were analyzed. The capacity factor (k') of each compound was calculated from its retention time.
- Determination of the log Koc value: 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 item 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.

Key result

Sample No.:

#1

Type:

log Koc

Value:

2.67 dimensionless

pH:

7

Remarks on result:

other: 99% peak area

Key result

Sample No.:

#1

Type:

Koc

Value:

470 dimensionless

pH:

7

Remarks on result:

other: 99% peak area

Sample No.:

#3

Type:

log Koc

Value:

> 5.63 dimensionless

pH:

7

Remarks on result:

other: 1% peak area

Sample No.:

#4

Type:

Koc

Value:

> 430 000 dimensionless

pH:

7

Remarks on result:

other: 1% peak area

Table 1 K_ocof the Test Item

Substance			Retention time (min)			log Koc	Koc	Peak area (%)
	tr,1	tr,2	tr,2	tr,2	mean
Formamide (t0)	0.74	0.74			0.74
Acetanilide	0.93	0.93				1.26
Monuron	1.11	1.11				1.99
Naphthalene	1.41	1.41				2.75
Fenthion	2.08	2.09				3.31
Phenanthrene	2.30	2.31				4.09
4,4’-DDT	5.00	5.02				5.63
Test item – peak 1	1.35	1.35	1.35	1.35	1.35	2.67	4.7 x 10^2	99
Test item – peak 2	12.85	12.85	12.84	12.84	12.85	>5.63	>4.3 x 10^5	1

The K_ocand log K_ocvalues of the test item at pH 7 were:

	Koc	log Koc	Peak area (%)
Test item – peak 1	4.7 x 10^2	2.67	99
Test item – peak 2	>4.3 x 10^5	>5.63	1

Validity criteria fulfilled:

not applicable

Conclusions:

The log Koc of the test item was 2.67 (99% peak area) and >5.63 (1% peak area).

Executive summary:

Volic (2018) is a GLP-compliant study following OECD guideline 121, HPLC method. The study is reliable without restrictions (Klimisch 1) as it followed a standard method that is suitable for the test item. The Koc of the test item was determined using an LC-UV and LC-MS/MS system, by comparison with reference substances with known Koc values. The test item is a UVCB, but in the chromatogram of the test solution one major peak was observed. The log Koc of the test item was 2.67 (99% peak area) and >5.63 (1% peak area).

Description of key information

The log Koc values for the test item were determined to be 2.67 (peak 1, 99%) and >5.63 (peak 2, 1%).

Key value for chemical safety assessment

Koc at 20 °C:

470

Additional information

Volic (2018) is a GLP-compliant study following OECD guideline 123, HPLC method. The study is reliable without restrictions (Klimisch 1) as it followed a standard method that is suitable for the test item. The Koc of the test item was determined using an LC-UV and LC-MS/MS system, by comparison with reference substances with known Koc values. The test item is a UVCB, but in the chromatogram of the test solution one major peak was observed. The log Koc of the test item was 2.67 (99% peak area) and >5.63 (1% peak area).

[LogKoc: 2.67]