Dimethyldioctylammonium chloride

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption, other

Type of information:

experimental study

Adequacy of study:

key study

Study period:

June 9 1988 to December 29 1989

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Remarks:

The purity of the non radiolabelled test chemical was only 42%. However this comprised only approximately 1/4 of the test substance used (radiolabeled test material comprised the rest) and was accounted for in the stock calculations.

Qualifier:

equivalent or similar to guideline

Guideline:

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

Version / remarks:

The study report does not mention the OECD 106 Guideline, nor does it state compliance with it.

Deviations:

yes

Remarks:

See below

Principles of method if other than guideline:

Various deviations noted compared to the OECD 106 guideline:
-Information missing regarding characteristics of the soil collection locations.
-Only four soil types have been tested, rather than the 5 suggested in the Guideline.
- Tier 2 of testing was ommitted from the testing regime, however this was largely due to the data gathered under the preliminary testing.
- Soil solution ratio of 1:200 used (greater than suggested maximum 1:100) however they did maintain a 1g soil content.

GLP compliance:

yes

Type of method:

batch equilibrium method

Media:

soil

Specific details on test material used for the study:

Preliminary study test material
- lot number: 7499-E
- purity: 99%
- radiolablelled: yes, 14C
- source: Lonza Inc.
- storage: refridgerated
- amount received: 2mCi contained in 2 vials labelled 1.52% w/w in water, 1 mCi per vial.
- radiochemical purity: determined at the laboratory as 98.0%

Definitive study test material
- lot number: 7499-E
- stated radiochemical purity: 99%
- radiolablelled: yes, 14C
- source: Biological Test Centre, Irvine, California
- storage: refridgerated
- amount received: 1mCi contained in 1 vial labelled 1.52% w/w in water.
- radiochemical purity: determined at the laboratory as 97.5%
- specific activity: 9.01 mCi/mmole

An error was noted in the specific activity used in the study, however this discrepany was considered small and the resulting error in calculation of the results also small, therefore correction of the data was not considered necessary.

Non radiolabelled test substance
- Lot number: #7807-E
- Purity: 41.2% active ingredient
- Apperance: light yellow liquid
- Source: Lonza Inc.

Radiolabelling:

yes

Test temperature:

25 ± 1°C average daily temperature

Details on study design: HPLC method:

N/A

Analytical monitoring:

yes

Matrix type:

sand

% Clay:

4

% Silt:

4

% Sand:

92

% Org. carbon:

0.5

pH:

7.4

CEC:

0.3

Bulk density (g/cm³):

1.64

Matrix type:

sandy loam

% Clay:

12

% Silt:

10

% Sand:

78

% Org. carbon:

1.8

pH:

6.3

CEC:

0.7

Bulk density (g/cm³):

1.23

Matrix type:

silty clay loam

% Clay:

32

% Silt:

52

% Sand:

16

% Org. carbon:

4.1

pH:

7.9

CEC:

32.3

Bulk density (g/cm³):

1.1

Matrix type:

silt loam

% Clay:

24

% Silt:

52

% Sand:

24

% Org. carbon:

4.2

pH:

7.4

CEC:

22.7

Bulk density (g/cm³):

1.08

Details on matrix:

-Supplier of soils: AGVISE, Northwood, North Dakoata
-Treatment of soils: air dried for 24 hours and then sieved through a 2mm mesh screen.
-Analysis of soil characteristics: subsamples of each soil were collected and shipped to A and L Mid West Agricultural Laboratories Inc., 13611 B Street, Omaha, Nebraska 68144-3693
-Sterilisation of soils: homogeneously distributing a one percent addition of sodium azide throughout the soil
- No details provided on characteristics of the site collection locations, storage,

Details on test conditions:

Definitive study details
- soil to water ratio: 1 to 200
- test solution preparation: aqueous solutions of 14C DDCA were prepared by adding a 46.8ml aliquot of 14C DDAC primary stock solution (concentration 853 mg/L) to a flask and adding sterile 0.01M CaCl2 to a final volume of 5700ml to give a nominal concentration of 7.0 mg/L. The 7 mg/L aqueous test solution was diluted to prepare nominal concentrations of 5.25, 3.5 and 0.7 mg/L. The measured concentrations of test solutions by LSC were 7.4, 5.36, 3.69 and 0.665 mg/L.
- Time 0 purity analysis: the purity of time 0, 7 mg/L nominal test concentration was analysed by TLC and was determined to have a radiochemical purity of 14C DDAC in the aqueous test solution of 97.9%.
- Adorption procedure: one gram of each soil type were weighed into sterile, tared Nalgene bottles. Triplicate 200ml aliquots of each standard solution with nominal concentrations of 0, 0.7, 3.5, 5.25 and 7 mg/L were added to the Nalgene bottle for each soil type. The soil suspensions were shaken in darkness on a mechanical shaker in an environmentally controlled chamber for 24 hours. The suspensions were then centrifuged for 15 minites at approximately 2000 rpm. The pH was measured and then the supernatants were removed and volumes measured and recorded. Triplicate samples were taken for LSC.
- Desorption procedure: aliquots of fresh solution of 0.01M CaCl2 were added to each sample according to the volume removed after the adsorption phase. The soil suspensions were shaken in the darkness on a mechanical shaker for 24 hours in an environmentally controlled chamber. After shaking the suspensions were centrifuged for 15 minutes at approximately 2000 rpm, the supernatants removed, volumes measured and recorded and triplicate samples taken for LSC analysis. The 7 mg/L test samples were subjected to 2 additional 24 hour desorption cycles. The sandy loam, siilty clay and silt loam soil samples were combusted. The fourth soil, the sand, the samples were extracted rather than combusted, using three 10ml aliquots of dimethylformide: acetic acid by shaking for 15 minutes, centrifuging and analysing the extract by LSC.

Sample No.:

#1

Duration:

24 h

Initial conc. measured:

0 other: mg/L

Temp.:

25.1 °C

Sample No.:

#2

Duration:

24 h

Initial conc. measured:

0.7 other: mg/L

Temp.:

25.1 °C

Sample No.:

#3

Duration:

24 h

Initial conc. measured:

3.5 other: mg/L

Temp.:

25.1 °C

Sample No.:

#4

Duration:

24 h

Initial conc. measured:

5.25 other: mg/L

Temp.:

25.1 °C

Sample No.:

#5

Duration:

24 h

Initial conc. measured:

7 other: mg/L

Temp.:

25.1 °C

Key result

Type:

Kd

Value:

1 095

Temp.:

25.1 °C

Matrix:

Sand

% Org. carbon:

0.25

Remarks on result:

other: KOC of 437803

Key result

Type:

Kd

Value:

8 179

Temp.:

25.1 °C

Matrix:

Sandy Loam

% Org. carbon:

0.9

Remarks on result:

other: KOC 908757

Key result

Type:

Kd

Value:

32 791

Temp.:

25.1 °C

Matrix:

Silty Clay Loam

% Org. carbon:

2.05

Remarks on result:

other: KOC 1469081

Key result

Type:

Kd

Value:

30 851

Temp.:

25.1 °C

Matrix:

Silt loam

% Org. carbon:

2.1

Remarks on result:

other: KOC 1469081

Phase system:

soil-water

Type:

other: Kd

Value:

591

Temp.:

25.1 °C

Matrix:

Sand

% Org. carbon:

0.25

Remarks on result:

other: KOC 236473, desoption phase

Phase system:

soil-water

Type:

other: Kd

Value:

2 074

Temp.:

25.1 °C

Matrix:

Sandy loam

% Org. carbon:

0.9

Remarks on result:

other: KOC 230498, desorption phase

Phase system:

soil-water

Type:

other: Kd

Value:

8 309

Temp.:

25.1 °C

Matrix:

Silty clay loam

% Org. carbon:

2.05

Remarks on result:

other: Koc 405328, desorption phase

Phase system:

soil-water

Type:

other: Kd

Value:

7 714

Temp.:

25.1 °C

Matrix:

Silt loam

% Org. carbon:

2.1

Remarks on result:

other: Koc 367334, desorption

Details on results (HPLC method):

N/A

Adsorption and desorption constants:

- adsorption correlation coefficients ranged from 0.9265 to 0.9970, implying the data adequately fits the Freundlich model.
- desorption correlation coefficients ranged from 0.8515 to 0.9361.

Recovery of test material:

Test initiation: TLC of the test solution at time 0 on the nominal 7.0 mg/L concentration showed a recovery of 97.9% DDAC, indicating mainly parent compound.
End of test: TLC of the soil extract at the end of the study showed that 93% of the 14C material remained as parent chemical.

Concentration of test substance at end of adsorption equilibration period:

- Sand soil: percentage absorbed onto soil average of 84.4% after 24 hours
- Sandy loam soil: percentage absorbed onto soil average of 97.3 % after 24 hours
- Silty clay loam soil: percentage absorbed onto soil average of 99.5% after 24 hours
- Silt loam soil: percentage absorbed onto soil average of 99.3% after 24 hours

Concentration of test substance at end of desorption equilibration period:

- Sand soil: percentage desorbed from soil on average 23.87% after 24 hours
- Sandy loam soil: percentage desorbed from soil on average 4.9% after 24 hours
- Silty clay loam soil: percentage desorbed from soil on average 0.7% after 24 hours
- Silt loam soil: percentage desorbed from soil on average 0.74% after 24 hours

Duration:

24 h

% Desorption:

97.7

Remarks on result:

other: Sand matrix

Remarks:

Based on all concentrations.

Duration:

24 h

% Desorption:

102

Remarks on result:

other: Sandy Loam soil.

Remarks:

Based on all concentrations.

Duration:

24 h

% Desorption:

92.5

Remarks on result:

other: Silty clay loam soil

Remarks:

Based on all concentrations.

Duration:

24 h

% Desorption:

104

Remarks on result:

other: Silt loam soil

Remarks:

Based on all concentrations.

Transformation products:

no

Details on results (Batch equilibrium method):

TLC was carried out on soil extracts at the end of the study showed that >93% of the 14C material remained as parent compound indicating no/little degradation.

Statistics:

Due to the immobility of DDAC, the percent adsorbed was not in the 20-80% range for which the Freundlich model typically describes sorption characteristics of a compound. However isotherms were determined with correlation coefficients ranging from 0.9265 to 0.9970for adsorption which implies that the data adequately fits the Freundlich model.

Table 1. Final results of Preliminary study two (1:50 soil to water ratio).

Soil type	Mean percent absorbed (%)	Mean percent desorbed (%)	Mean mass balance (%)
Sand	96.0	18.2	101
Sandy loam	96.2	2.93	106
Silty clay loam	99.2	1.90	92.6
Silt loam	99.0	1.34	105

Validity criteria fulfilled:

not specified

Conclusions:

The Kd (and Koc respectively) for each of the four soils ranged from 1095 to 32791 (437805 -1599564) for adsorption and 591 to 8309 (230498 - 405328) for desorption. A classification system based on Koc can be used to understand the leaching potential of a chemical. Koc values of greater that 5000 denote immobility in a soil. Based on this the chemical is classified as immobile in all soil types.

Executive summary:

A batch adsorption/desorption study was carried out to GLP and following the principles and methods outlined in OECD test guideline 106. Some deviations are noted from the guidelines, although these are not considered significant.

Two preliminary studies were conducted prior to the definitive study which indicated DDAC was highly adsorptive to the soils at the soil solution ratios and test concentrations used. As a result the definitive was run at a soil:solution ratio of 1:200, with four different concentrations, 0.7, 3.5, 5.25 and 7 mg/L and a control, for a 24 hour adsorption period followed by a 24 hour desorption period. Four different soils were tested, including a sand, a sandy loam, silty clay loam and a silt loam.

The Kd and Koc, respectively,  for each of the four soils ranged from 1,095 to 32,791 (437,805 to 1,599,564) for adsorption and 591 to 8,309 (230,498 to 405,328) for desorption. A classification system based on Koc can be used to understand the leaching potential of a chemical. Koc values of >5 000 suggest immobility in a soil. Based on this the chemical is classified as immobile in all soil types. Mass balances of between 97.7 and 104% were achieved for all the soils and no apparent degradation of the chemical was observed over the duration of the study. The test subanance is unlikely to pose a potential risk of migration to groundwater bodies.

Description of key information

There are no studies available for the estimation of adsorption/desorption of the test substance. However, there is a reliable (Klimisch 2) study available for the read-across, didecyldimethyl ammonium chloride (DDAC).

An adsorption/desorption study was carried out following the principles methods outlined in OECD test guideline 106. Following two preliminary studies indicating the test substance was highly adsorptive under the conditions of the test, a definitive test was performed. The definitive test was run at four concentrations (control and 0.7, 3.5, 5.25 and 7 mg/L) with a 24 hour adsorption period followed by 24 hours desorption. Four soils were used including a sand, sandy loam, silty clay loam and silt loam. The Koc for the four soils ranged from 437, 805 to 1,599,564 for adsorption and 230,498 to 405,328 for desorption. Therefore, the test substance may be classified immobile in a range soil types and is unlikely to pose a potential risk of migration to groundwater bodies.