bis(diethylamino)-N,N-diethylmethaniminium chloride

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:

March 24, 2003 to March 28, 2003

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

1993

Deviations:

no

GLP compliance:

yes

Remarks:

OECD GLP

Type of method:

batch equilibrium method

Media:

soil

Radiolabelling:

no

Test temperature:

25 °C

Analytical monitoring:

yes

Matrix no.:

#1

Matrix type:

Spodsol

% Clay:

3

% Org. carbon:

1.9

pH:

5.1

Matrix no.:

#2

Matrix type:

Alfisol

% Clay:

25

% Org. carbon:

0.4

pH:

5.7

Matrix no.:

#3

Matrix type:

Entisol

% Clay:

30

% Org. carbon:

7.8

pH:

9

Details on matrix:

Three soils, covering a range of soil organic matter content (0.4 to 7.8%), clay content (3 to 30%) and pH (5.1 to 9.0), were obtained from Soilcon Laboratories (Richmond, BC) for use in this study. Although there was a significant difference between some of the soil parameters recommended by the OECD and those of the test soils used in this study, this was acceptable as indicated in OECD Method 106.

Details on test conditions:

A primary aqueous stock solution (0.871 mg/mL) of the test substance was used to prepare a secondary stock (609.7 microliters/mL).

Soil (2.0 ± 0.1 g) and 10 mL of aqueous CaCl2 solution were added to 15-mL polypropylene centrifuge tubes and the contents of the tubes were mixed (tumbled end-over-end; ~1 rev./5 sec.) overnight to pre-equilibrate the soils. After soil hydration, the tubes containing soil were spiked with small volumes (0.1 mL) of the secondary aqueous test substance stock solution (609.7 microliters/mL). The contents of the tubes were mixed (tumbled end-over-end; ~1 rev/5 sec) for 23 hours.

The tubes were centrifuged (~2000 rpm, 20 min). The levels of the supernatants (in all tubes) were marked with a permanent felt pen on the sides of the tubes. The volumes of soil and aqueous solution above the soil in the tubes based on tube graduations were recorded. The pHs of the blank soil solutions were measured using a calibrated pH meter. Aliquots (~1.5 mL) of the clear supernatants were transferred to 1.8-mL glass crimp-top vials and stored at ~22°C in the dark prior to analysis by high performance liquid chromatography (HPLC). The remaining supernatant in the 15-mL polypropylene centrifuge tubes were discarded, leaving the damp soil pellets in the tubes. The soil pellets were washed twice with CaCl2 solution and both washes were also analyzed for the test substance.

The concentrations of the test substance in the adsorption and wash solutions were calculated using the peak area of the test substance peak and the slope and y-intercept of the calibration curve. The calibration curve from the calibration solutions showed a linear relationship with correlation coefficient of 0.9994, indicating acceptable method linearity for the analysis of the test substance in calcium chloride solution. The extent of soil adsorption and desorption of the test substance was calculated according to equations in the guidelines.

Duration:

16 h

Key result

Sample No.:

#1

Type:

Koc

Value:

>= 66 - <= 68 other: mL/g

pH:

5.1

Temp.:

25 °C

Matrix:

Soil 1: Very strongly to strongly acid sandy soil (Spodosol)

% Org. carbon:

1.9

Key result

Sample No.:

#2

Type:

Koc

Value:

> 93 750 other: mL/g

pH:

5.7

Temp.:

25 °C

Matrix:

Soil 2: Moderately or slightly acid loamy soil (Alfisol)

% Org. carbon:

0.4

Key result

Sample No.:

#3

Type:

Koc

Value:

>= 411 - <= 461 other: mL/g

pH:

9

Temp.:

25 °C

Matrix:

Soil 3: Slightly alkaline loamy soil (Entisol).

% Org. carbon:

7.8

Details on results (Batch equilibrium method):

The pHs of the blank adsorption solutions after mixing approximately 16 hours were 4.4, 5.1, and 7.4 for soil-1, soil-2, and soil-3, respectively.
The various adsorption parameters were calculated from the observed concentrations of the test substance detected in the adsorption and wash solutions. The results showed that 20.2 ± 0.3%, greater than 99%, and 87.2 ± 0.6% of test substance adsorbed to soil-1, soil-2, and soil-3, respectively. The extent of adsorption was directly related to soil clay content, i.e. 3%, 25%, and 30% for soil-1, soil-2, and soil-3, respectively. Analyses of the two calcium chloride solution soil washes showed that 33 ± 7%, less than 2%, and 8.3 ± 0.3% of the adsorbed test substance desorbed from soil-1, soil-2, and soil-3, respectively. The masses of the test substance, per gram of soil, which adsorbed to soil-1, soil-2, and soil-3 in the adsorption step were 6.2 ± 0.1 microg/g, ~ 30 microg/g, and 26.6 ± 0.2 microg/g, respectively.
The adsorption coefficients (K’; mL/g) were 1.26 ± 0.02, > 375, and 34 ± 2 for soil-1, soil-2, and soil-3, respectively. The adsorption coefficients expressed as a function of soil organic matter content (K’oc; mL/g) were 67 ± 1, > 93750, and 436 ± 25 for soil-1, soil-2, and soil-3, respectively.

Soil solutions in test tubes for adsorption/desorption study:

Tube Label	Soil	CaCl2 Solution (mL)	Test Substance Secondary Stock Solution (microL)	Test Solutions
				Adsorption Label	Wash-1 Label	Wash-2 Label
1a	Soil 1	10.0	100	A1a	W1-1a	W2-1a
1b	Soil 1	10.0	100	A1b	W1-1b	W2-1b
1BLK	Soil 1	10.0	0	A1BLK	W1-1BLK	W2-1BLK
2a	Soil 2	10.0	100	A2a	W1-2a	W2-2a
2b	Soil 2	10.0	100	A2b	W1-2b	W2-2b
2BLK	Soil 2	10.0	0	A2BLK	W1-2BLK	W2-BLK
3a	Soil 3	10.0	100	A3a	W1-3a	W2-3a
3b	Soil 3	10.0	100	A3b	W1-3b	W2-3b
3BLK	Soil 3	10.0	0	A3BLK	W1-3BLK	W2-3BLK

Observed concentrations of the Test Substance in Adsorption and Wash Solutions:

Sample Label	Peak Area	Test Substance Conc. (microg/mL)	Average	Deviation	% Relative Deviation
Adsorption Solutions
A1 BLK	0.00	Less than DL	---
A1a	1065.02	4.85	4.87	0.02	0%
A1b	1071.72	4.88
A2BLK	0.00	Less than DL	---
A2a	0.00	Less than DL
A2b	0.00	Less than DL
A3BLK	0.00	Less than DL
A3a	174.16	0.74	0.8	0.04	5%
A3b	191.27	0.82
Wash-1 Solutions
W1-1BLK	0.00	Less than DL	---
W1-1a	247.89	1.08	1.05	0.03	3%
W1-1b	234.18	1.02
W1-2BLK	0.00	Less than DL	---
W1-2a	0.00	Less than DL
W1-2b	0.00	Less than DL
W1-3BLK	0.00	Less than DL
W1-3a	101.87	0.41	0.4	0.02	4%
W1-3b	109.20	0.44
Wash-2 Solutions
W2-1BLK	0.00	Less than DL	---
W2-1a	75.02	0.29	0.3	0.004	1%
W2-1b	76.56	0.29
W2-2BLK	0.00	Less than DL	---
W2-2a	0.00	Less than DL
W2-2b	0.00	Less than DL
W2-3BLK	0.00	Less than DL
W2-3a	75.68	0.29	0.3	0.01	4%
W2-3b	80.44	0.31
Less than DL = Less than detection limit

Average adsorption parameters:

Parameter	Soil
	1^a		2^b		3^c
	Average	SD	Average	SD	Average	SD
%Adsorbed (A)	20.2%	0.3%	Greater than 99%	nd	87.2%	0.6%
Adsorbed (microgram/g)	6.2	0.1	Approx. 30	nd	26.6	0.2
% Desorbed (D)	33%	7%	Less than 2%	nd	8.3%	0.3%
% R	67%	7%	Approx. 60	nd	91.7%	0.3%
K’ (mL/g)	1.26	0.02	Greater than 375	nd	34	2
K’oc (mL/g)	67	1	Greater than 93750	nd	436	25
CEC (meq/100 g)^d	12.2		20.6		9.7
% Organic matter	1.9%		0.4%		7.8%
% Clay	3.0%		25.0%		30.0%
SD = standard deviation     nd = not defined ^a very strongly to strongly acidic sandy soil     ^b moderately or slightly acidic loamy soil     ^cslightly alkaline loamy soil     ^dCation exchange capacity; total for Ca, Mg, and K

Validity criteria fulfilled:

not specified

Conclusions:

Under the conditions of this study, the adsorption coefficients expressed as a function of soil organic matter content (K’oc; mL/g) were 67 ± 1, > 93750, and 436 ± 25 for soil-1, soil-2, and soil-3, respectively.

Executive summary:

The soil adsorption of the test material was investigated in accordance with the standardised guidelines OECD 106, under GLP conditions. 

During the study, soils were equilibrated with aqueous solutions of the test material for approx. 16 hr, after which the soil solutions were analysed for the test material. The soils were washed twice, and the washes were also analysed for the test material. Three soils were used in this study, representing a range of soil organic matter content (0.4 % – 7.8 %), clay content (3 % - 30 %), and pH (5.1 – 9.0).

The results showed that 20.2 ± 0.3 %, > 99 %, and 87.2 ± 0.6 % of test material adsorbed to soil-1, soil-2, and soil-3 respectively, and that 33 ± 7 %, < 2 %, and 8.3 ± 0.3 % of the adsorbed test material desorbed from soil-1, soil-2, and soil-3, respectively, after two washes with a Calcium Chloride solution. The extents of adsorption were directly related to soil clay contents.

The adsorption coefficients (K’; mL/g) were 1.26 ± 0.02, > 375, and 34 ± 2 for soil-1, soil-2, and soil-3, respectively.

Under the conditions of this study, the adsorption coefficients expressed as a function of soil organic matter content (K’oc; mL/g) were 67 ± 1, > 93750, and 436 ± 25 for soil-1, soil-2, and soil-3, respectively.

Description of key information

Under the conditions of this study, the adsorption coefficients expressed as a function of soil organic matter content (K’oc; mL/g) were 67 ± 1, > 93750, and 436 ± 25 for soil-1, soil-2, and soil-3, respectively.

Additional information

The soil adsorption of the test material was investigated in accordance with the standardised guidelines OECD 106, under GLP conditions. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

In this study, soils were equilibrated with aqueous solutions of the test material for approx. 16 hr, after which the soil solutions were analyzed for the test material. The soils were washed twice, and the washes were also analyzed for the test material. Three soils were used in this study, representing a range of soil organic matter content (0.4 % – 7.8 %), clay content (3 % - 30 %), and pH (5.1 – 9.0).

The results showed that 20.2 ± 0.3 %, > 99 %, and 87.2 ± 0.6 % of HEG-Cl adsorbed to soil-1, soil-2, and soil-3 respectively, and that 33 ± 7 %, < 2 %, and 8.3 ± 0.3 % of the adsorbed test material desorbed from soil-1, soil-2, and soil-3, respectively, after two washes with a Calcium Chloride solution. The extents of adsorption were directly related to soil clay contents.

The adsorption coefficients (K’; mL/g) were 1.26 ± 0.02, > 375, and 34 ± 2 for soil-1, soil-2, and soil-3, respectively.

Under the conditions of this study, the adsorption coefficients expressed as a function of soil organic matter content (K’oc; mL/g) were 67 ± 1, > 93750, and 436 ± 25 for soil-1, soil-2, and soil-3, respectively.