Acetic acid, 2,2-difluoro-2-[[2,2,4,5-tetrafluoro-5-(trifluoromethoxy)-1,3-dioxolan-4-yl]oxy]-, ammonium salt (1:1)

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:

2011-10-21 until 2011-01-02

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

.

Qualifier:

according to guideline

Guideline:

OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)

Qualifier:

according to guideline

Guideline:

EU Method C.18 (Adsorption / Desorption Using a Batch Equilibrium Method)

GLP compliance:

yes (incl. QA statement)

Type of method:

batch equilibrium method

Media:

soil

Specific details on test material used for the study:

TEST ITEM: cyclic C6O4 - NH4 Salt
Batch number: 3ac3EV
Total formula: C6H4F9NO6
Molecular weight: 357 g/mol
Appearance: Liquid, pale amber – yellowish brown, clear
Water solubility: Completely soluble
Recommended storage: 18 ± 4 °C, humidity < 65 %
Storage at test facility: Room temperature, protected from light in the original container
Retention of test item: At least 1 g was retained and stored at 6 ± 2 °C

Radiolabelling:

no

Test temperature:

22 ± 2 °C

Analytical monitoring:

yes

Matrix no.:

#1

Matrix type:

other: EUROSOIL 4

% Clay:

20.3

% Org. carbon:

1.31

pH:

6.8

Matrix no.:

#2

Matrix type:

other: EUROSOIL 5

% Clay:

6

% Org. carbon:

5.96

pH:

3.1

Details on matrix:

Two soils were employed as test systems: One with a high organic carbon and a low clay content (EUROSOIL No. 5) and one with high clay and low organic carbon content (EUROSOIL No.4) .

Properties of Standard EURO Soils (All data were taken from their respective certificate and IRMM information on reference materials -Report EUR 20152 EN-, respectively):

EUROSOIL 4
Soil site Normandy, F Schl.-Holst., D
FAO soil unit Orthic, Luvizol
CLAY total [%] 20.3 6.00
pH in 0.01 M CaCl2 6.80 3.10
Total carbon [%] 1.45 6.43
Organic carbon [%] 1.31 5.96
Nitrogen [%] 0.16 0.23
C/N ratio (1) 8.19 25.9
Dry mass [%] (2) 97.2 98.8

EUROSOIL 5
Soil site Schl.-Holst., D
FAO soil unit Orthic, Podzol
CLAY total [%] 6.00
pH in 0.01 M CaCl2 3.10
Total carbon [%] 6.43
Organic carbon [%] 5.96
Nitrogen [%] 0.23
C/N ratio (1) 25.9
Dry mass [%] (2) 98.8
(1) Organic carbon content divided by the content of nitrogen
(2) Determined at DR.U.NOACK-LABORATORIEN (mean value of three replicates)

Details on test conditions:

TEST SYSTEM
EUROSOIL No. 4 and 5 in contact to 0.01 mol/L CaCl2 solution.
CaCl2 solution: Deionised water was used to prepare the CaCl2 solution (0.01 mol/L)
Storage at test facility: Room temperature, dark, in closed containers (brown glass bottles)

Test concentrations: 5 mg/L (dry salt) in aqueous phase at test start
Stock solutions:A stock solution of 10000 mg test item/L (corresponding to 3611 mg dry salt/L) was prepared in 0.01 M CaCl2 solution and kept in the dark at 4 to 6 °C.
Application solutions: Out of the stock solution, a dilution of 50 mg/L (dry salt) were prepared with 0.01 M CaCl2 solution.
Vehicle: None
Dispersion treatment: Agitation

Samples were prepared in parallel method; were shaken at approx. 80 rpm (rotary shaker) to reach adsorption equilibrium. The aqueous phase was decanted after centrifugation with 3000 rpm for 5 minutes and analysed.
For mass balance testing, the wet soil was extracted as described below and the extract was analysed.
Test vessel: Centrifuge tubes with screw caps, tube mat: Polypropylene,
Soil : solution ratio 1 : 1, 1 : 4, 1 : 5 and 1 : 50
Test volume aqueous phase:
- 50 mL for soil : solution ratio 1 : 50
- 10 mL for soil : solution ratio 1 : 5
- 8 mL for soil : solution ratio 1 : 5
- 5 mL for soil : solution ratio 1 : 5
Amount of soil:
- 1 g at soil / solution ratio 1 : 50
- 2 g at soil / solution ratio 1 : 5 and 1 : 4
- 5 g at soil / solution ratio 1 : 1

Preparation of the test soils: The soil samples were equilibrated by shaking with 0.01 mol/L CaCl2 solution overnight (12 h minimum).
Application: To the equilibrated soil the respective application solution volume was given (10 % of the final volume, dilution factor 10).

Duration:

48 h

Initial conc. measured:

5 other: ug/cm^3

pH:

2.91

Temp.:

22 °C

Key result

Type:

Koc

Value:

11 L/kg

Temp.:

22 °C

% Org. carbon:

5.96

Remarks on result:

other: Soil 5

Key result

Type:

Kd

Value:

0.653 L/kg

Temp.:

22 °C

% Org. carbon:

5.96

Remarks on result:

other: Soil 5

Key result

Type:

Kd

Temp.:

22 °C

% Org. carbon:

1.31

Remarks on result:

not determinable

Remarks:

no significant adsorption for soil 4

Recovery of test material:

Mean Recovery rate, related to initial nominal mass of test item [μg], at 48 hours in soil 5 = 96.8%

Concentration of test substance at end of adsorption equilibration period:

For soil no. 4 no adsorption to soil could be observed. For soil no. 5 adsorption could only be observed at a soil to solution ratio of 1:1.
For soil 5 the adsorption equilibrium, at the soil to solution ratio of 1 : 1, was reached after at least 2 hours. The percentage of adsorption at 48h was 39.5%.

Sample no.:

#1

Duration:

2 h

% Adsorption:

32.88

Remarks on result:

other:

Remarks:

EUROSOIL No.5

Sample no.:

#2

Duration:

2 h

% Adsorption:

34.23

Remarks on result:

other:

Remarks:

EUROSOIL No.5

Sample no.:

#3

Duration:

4 h

% Adsorption:

32.97

Remarks on result:

other:

Remarks:

EUROSOIL No.5

Sample no.:

#4

Remarks on result:

not measured/tested

Remarks:

sample was erroneously interchanged

Sample no.:

#5

Duration:

6 h

% Adsorption:

35.26

Remarks on result:

other:

Remarks:

EUROSOIL No.5

Sample no.:

#6

Duration:

6 h

% Adsorption:

32.02

Remarks on result:

other:

Remarks:

EUROSOIL No.5

Sample no.:

#7

Duration:

24 h

% Adsorption:

35.21

Remarks on result:

other:

Remarks:

EUROSOIL No.5

Sample no.:

#8

Duration:

24 h

% Adsorption:

37.34

Remarks on result:

other:

Remarks:

EUROSOIL No.5

Sample no.:

#9

Duration:

48 h

% Adsorption:

34.6

Remarks on result:

other:

Remarks:

EUROSOIL No.5

Sample no.:

#10

Duration:

48 h

% Adsorption:

37.73

Remarks on result:

other:

Remarks:

EUROSOIL No.5

Transformation products:

not specified

Details on results (Batch equilibrium method):

For soil No. 4 no significant adsorption (> 20 %) could be observed, even with a soil : solution ratio of 1 : 1, at a test period of 48 h.

For soil No.5 a two step testing was employed. In the first step the optimal soil to solution ratio was determined and in the second step the time for reaching adsorption equilibrium was measured. During step one, cyclic C6O4 - NH4 Salt showed significant adsorption only at a soil : solution ratio of 1 : 1 with a maximum adsorption rate of 29 %. Soil no. 5 was used for the determination of the adsorption equilibration time.
In step two the adsorption equilibrium, at the soil to solution ratio of 1 : 1, was reached after at least 2 hours with a mass balance of ≥ 90 %. The test item was stable at test conditions over test duration and no significant adsorption to the test vessels was observed. From the obtained data, the distribution coefficient (Kd) and the organic carbon normalised adsorption coefficient (KOC) were calculated.

pH-Stability and Adsorption to the Test Vessel

The stability and test vessel adoption of cyclic C6O4 - NH4 Salt was tested with a concentration of 5 mg/L in aqueous phase adjusted to pH 3 and pH 7, respectively, over 72 h and found to be stable and non adsorptive.

pH	Time (h)	Meas.Conc. (mg/l)	Recovery Rate related to initial conc. (%)
3.0	0	4.13	-
	72	4.79	116
7.0	0	4.13	-
	72	4.64	112

pH-Values of the Aqueous Phase after Contact with Soils

The pH of the aqueous phase was measured before and after contact with soil at the selected soil : solution ratio

Soil no.	Soil/solution ratio	pH of aqueous phasebefore contact with soil	pH of aqueous phase after contact with soil
5	1:1	6.18	2.91
4	1:50	6.32	6.78

Adsorption Kinetics (Determination of the Distribution Coefficient Kd)

The samples for analysis after 48 h were used for the calculation of the distribution coefficient. According to the results of the mass balances the adsorption coefficient (Kd) was determined according to Guideline equations (1) – (3) by the indirect method:

Results for [%] Adsorption, Kd and KOC

Soil	C0[μg/cm3]	m0[μg]	teq[h]	Cads aq (eq)[μg/cm3]	Cads s (eq)[μg/g]
5	5.0	250	48	3.025	1.975

Soil	A [%]	Kd [cm3/g]	KOC [cm3/g]	McCall mobility class
5	39.5	0.653	11.0	Very high

C0, m0 = Initial concentration, initial amount

teq = Equilibration time

Cads aq (eq) = Content of the test item in aqueous phase at equilibrium (mean value of 2 replicates)

Cads s (eq) = Calculated content of the test item in soil at equilibrium (mean value of 2 replicates)

A = Adsorption percentage after 48 h

Kd = Distribution coefficient

KOC = Organic carbon (Table 2) normalized adsorption coefficient

Validity criteria fulfilled:

yes

Conclusions:

cC6O4 ammonium salt showed a low tendency to adsorb to the two tested soils.
Kd = 0.653 and KOC = 11 were calculated for EUROSOIL No.5 (5.96% OC content)
For EUROSOIL No.4 (1.31% OC content) no Kd and KOC could be derived as no significant adsorption was observed in the study.
A correlation between the degree of adsorption and the content of organic carbon of the soils might be concluded.
According to the MCCALL classification scheme cC6O4 ammonium salt can be considered to have very high mobility in soil.

Executive summary:

Preliminary studies for the determination of the adsorption/desorption behaviour of cC6O4 ammonium salt in soils was performed according to OECD Guideline 106 for Testing of Chemicals (2000) and Council Regulation (EC) No. 440/2008, Method C.18.

One soil with a high organic carbon and a low clay content (EUROSOIL No. 5) and one soil with high clay and low organic carbon content (EUROSOIL No.4) were used as test system. The test item was applied at test start with a test item concentration of 5 mg/L in the aqueous phase and at soil to solution ratios of 1:50, 1:5, 1:4 and 1:1.

Equilibrium adsorption coefficients on two soils were determined as a function of soil characteristics. These two soil types were used exemplarily in order to cover as widely as possible the interactions of the test item with natural soils, especially based on the organic carbon content.

For soil No.4 no significant adsorption (> 20 %) could be observed, even with a soil : solution ratio of 1 : 1, at a test period of 48 h.

For soil No.5 a two steps testing was employed. In the first step the optimal soil to solution ratio was determined and in the second step the time for reaching adsorption equilibrium was measured. During step one, cC6O4 ammonium salt showed significant adsorption only at a soil : solution ratio of 1 : 1 with a maximum adsorption rate of 29 %. In step two the adsorption equilibrium, at the soil to solution ratio of 1 : 1, was reached after at least 2 hours with a mass balance of ≥ 90 %.

The test item was stable at test conditions over test duration and no significant adsorption to the test vessels was observed. From the obtained data, a distribution coefficient (Kd) of 0.653 L/Kg and the organic carbon normalised adsorption coefficient (KOC) of 11 L/Kg were calculated.

cC6O4 ammonium salt showed a low tendency to adsorb to the two test soils. According to the MCCALL classification scheme the test item can be considered to have very high mobility in soil. A correlation between the degree of adsorption and the content of organic carbon of the soils might be concluded.

Description of key information

A study for the determination of the adsorption/desorption behaviour of cC6O4 ammonium salt in soil was performed according to OECD Guideline 106 for Testing of Chemicals (2000) and Council Regulation (EC) No. 440/2008, Method C.18. The study was performed under GLP without deviations.
cC6O4 ammonium salt showed a low tendency to adsorb to the two types of soil used in the study.

From the obtained data, the distribution coefficient (Kd) of 0.653 L/kg and the organic carbon normalised adsorption coefficient (KOC) of 11 L/kg were derived for the soil with the highest content of organic matter (EUROSOIL No. 5, 5.96% OC content).

For the soil type with the lowest organic matter content (EUROSOIL No.4, 1.31% OC content ) no Kd and KOC could be calculated as no significant adsorption was observed in the study.

According to the MCCALL classification scheme the test item can be considered to have very high mobility in soil. A correlation between the degree of adsorption and the content of organic carbon of the soils might be concluded.

Key value for chemical safety assessment

Koc at 20 °C:

11