N-cyclopropyl-1,3,5-triazine-2,4,6-triamine

Adsorption / desorption

Administrative data

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2002/08/23 to 2003/03/25

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2003

Report date:

2003

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

2000

Deviations:

yes

Remarks:

Deviations to SETAC are minor.

GLP compliance:

yes

Type of method:

batch equilibrium method

Media:

soil

Test material

Test material information

Constituent 1

Reference substance name:

N-cyclopropyl-1,3,5-triazine-2,4,6-triamine

EC Number:

266-257-8

EC Name:

N-cyclopropyl-1,3,5-triazine-2,4,6-triamine

Cas Number:

66215-27-8

Molecular formula:

C6H10N6

IUPAC Name:

N2-cyclopropyl-1,3,5-triazine-2,4,6-triamine

Test material form:

solid: particulate/powder

Radiolabelling:

no

Study design

Test temperature:

20 °C

Batch equilibrium or other method

Analytical monitoring:

yes

Matrix properties

Matrix properties 1

Matrix no.:

#3

Matrix type:

loamy sand

% Clay:

7.7

% Silt:

10.8

% Sand:

81.5

% Org. carbon:

1.8

pH:

6.8

CEC:

134 other: meq/kg

Matrix properties 2

Matrix no.:

#2

Matrix type:

loam

% Clay:

22.7

% Silt:

43.1

% Sand:

34.2

% Org. carbon:

1.5

pH:

7.5

CEC:

200 other: meq/kg

Matrix properties 3

Matrix no.:

#1

Matrix type:

loamy sand

% Clay:

4.1

% Silt:

16.9

% Sand:

79

% Org. carbon:

1.3

pH:

5.9

CEC:

106 other: meq/kg

Details on matrix:

Loamy Sand (#1) - Horst Soil
Loam (#2) - Westmaas soil
Loamy Sand (#3) - Naaldwijk soil

Details on test conditions:

Adsorption and desorption experiments were carried out at five concentration levels of the test compounds at 20°C in the dark. Initial concentrations of the test compounds in aqueous 0.01 M CaCl2- solution ranged from 0.07 to 6.0 µg/mL. 50 g of each soil type were pre-equilibrated with 0.01 M CaCl2-solution for 24 hours and the application solutions were added, resulting in a soil-to-solution ratio of 1:1. After equilibration, the phases were separated by centrifugation. The equilibrated water layer was removed. The concentration of test compound in the original solution and in the aqueous layer after equilibration was measured by HPLC, after which the adsorption was calculated from the difference. Following the adsorption experiment, desorption of the test compound was measured by replacing the removed aqueous phase by the same volume of 0.01 M CaCl2-solution. After this, the tubes were equilibrated again and the phases separated by centrifugation. The respective aqueous solutions were analysed by HPLC to quantify the amount of test item and to determine the distribution of the substances between solid and aqueous phase. The equilibration times for the adsorption and the desorption stages were 24 hours for cyromazine and 72 hours for melamine. After the desorption step, the soil layer was also subjected to chemical analysis in order to obtain a mass balance.

Duration of adsorption equilibration

Duration:

24 h

Remarks:

All soils

Duration of desorption equilibration

Duration:

24 h

Remarks:

All soils

Results and discussion

Adsorption coefficient

Adsorption coefficient 1

Key result

Sample No.:

#1

Type:

Koc

Remarks:

adsorption Kfoc

Value:

521 other: mL/g

pH:

5.9

Remarks on result:

other: 1/n 0.92

Adsorption coefficient 2

Key result

Sample No.:

#2

Type:

Koc

Remarks:

adsorption Kfoc

Value:

96 other: mL/g

pH:

7.5

Remarks on result:

other: 1/n 0.73

Adsorption coefficient 3

Key result

Sample No.:

#3

Type:

Koc

Remarks:

adsorption Kfoc

Value:

200 other: mL/g

pH:

6.8

Remarks on result:

other: 1/n 0.87

Partition coefficients

Remarks on result:

not determinable

Results: Batch equilibrium or other method

Adsorption and desorption constants:

For cyromazine, the mean adsorption coefficient KF was 3.94 mL/g, the mean adsorption KOC-value 272 ml/g. The compound is hence found to be of medium mobility (McCall). The slope N for the adsorption isotherms was on average 0.84, indicating a non-linear concentration dependence of KF (increasing KF with decreasing concentration). The adsorption coefficient strongly correlates with the pH value of the soils, whereas only a weak to medium correlation with the clay content and the cation exchange capacity was found. No significant correlation of KF with the organic carbon content of the soil was observed, indicating that the carbon content does not represent a measure for sorption. Nevertheless, the KOC-value correlates relatively strongly with the soil pH due to the dominant pH- dependence of KD and the low variation of the organic carbon content of the three soils. Adsorption of cyromazine was to some extent reversible in the tested soils, i.e. desorption coefficient was in the same range as the adsorption coefficient. For desorption a mean coefficient of 4.35 mL/g and a mean KOC-value of 296 mL/g were calculated.

Recovery of test material:

The mass balance during the sorption experiment for the soils Horst, Westmaas and Naaldwijk ranged for cyromazine from 83 to 86%. The lower recovery of cyromazine is partly the result of transformation of cyromazine into melamine.

Any other information on results incl. tables

Table 2: Freundlich adsorption and desorption constants of cyromazine

Cyromazine
Soil texture	Adsorption			Desorption
	KF (mL/g)	KOC(mL/g)	N	KF (mL/g)	KOC (mL/g)	N
Horst Loamy sand	6.77	521	0.92	6.56	505	0.84
Westmaas Loam	1.44	96	0.73	2.01	134	0.84
Naaldwijk Loamy sand	3.60	200	0.87	4.48	249	0.85
Mean	3.94	272	0.84	4.35	296	0.84

Applicant's summary and conclusion

Validity criteria fulfilled:

not specified

Conclusions:

The mean adsorption coefficient KF was 3.94 mL/g, the mean adsorption KOC-value 272 mL/g. The compound is hence found to be of medium mobility. For desorption a mean coefficient of 4.35 mL/g and a mean KOC-value of 296 mL/g were calculated.

Executive summary:

The adsorption and desorption of the test compounds cyromazine and melamine were investigated in three soils, using the batch equilibrium method following OECD Guideline 106. Adsorption and desorption experiments were carried out at five concentration levels of the test compounds at 20°C in the dark. Initial concentrations of the test compounds in aqueous 0.01 M CaCl₂- solution ranged from 0.07 to 2.0 µg/mL. 50 g of each soil type were pre-equilibrated with 0.01 M CaCl₂-solution for 24 hours and the application solutions were added, resulting in a soil-to-solution ratio of 1:1.

The mass balance during the sorption experiment for the soils Horst, Westmaas and Naaldwijk ranged for cyromazine from 83 to 86%. The lower recovery of cyromazine is partly the result of transformation of cyromazine into melamine. For cyromazine, the mean adsorption coefficient K_F was 3.94 mL/g, the mean adsorption K_OC-value 272 mL/g. The compound is hence found to be of medium mobility. For desorption a mean coefficient of 4.35 mL/g and a mean K_OC-value of 296 mL/g were calculated.