6-Amino-5-chloro-2-cyclopyrimidine-4-carboxylic acid

Adsorption / desorption

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

20 Sep 2007 - 22 May 2008

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:

2000

GLP compliance:

yes (incl. QA statement)

Remarks:

Food and Consumer Product Safety Authority, Den Haag, The Netherlands

Type of method:

batch equilibrium method

Media:

soil

Radiolabelling:

yes

Test temperature:

20 ± 2°C

Analytical monitoring:

yes

Details on sampling:

- Concentrations: Five different soils at five concentrations: 0.45, 0.225, 0.045, 0.0225 and 0.0045 µg/mL
- Triplicate aliquots (500 µL from 0.0045, 0.0225, 0.045 levels and 200 µL from 0.225 and 0.45 µg/mL levels) of supernatants were added directly to scintillant and counted by LSC.
- To determine test item stability the supernatants of the highest concentration (0.45-µg/mL concentration) of the adsorption experiments were analyzed by HPLC with fraction collection.
- Sampling interval: At equilibrium (after 24 hours)

Matrix no.:

#1

Matrix type:

clay loam

% Clay:

31

% Silt:

48

% Sand:

21

% Org. carbon:

3.8

pH:

6.4

CEC:

34.5 meq/100 g soil d.w.

Bulk density (g/cm³):

1.1

Matrix no.:

#2

Matrix type:

loam

% Clay:

15

% Silt:

44

% Sand:

41

% Org. carbon:

0.5

pH:

8.73

CEC:

8.8 meq/100 g soil d.w.

Bulk density (g/cm³):

1.2

Matrix no.:

#3

Matrix type:

sandy loam

% Clay:

7

% Silt:

34

% Sand:

59

% Org. carbon:

1.3

pH:

8.09

CEC:

6.4 meq/100 g soil d.w.

Bulk density (g/cm³):

1.2

Matrix no.:

#4

Matrix type:

silty clay

% Clay:

45

% Silt:

48

% Sand:

7

% Org. carbon:

1.6

pH:

7.83

CEC:

16.6 meq/100 g soil d.w.

Bulk density (g/cm³):

1.1

Matrix no.:

#5

Matrix type:

sandy loam

% Clay:

13

% Silt:

20

% Sand:

67

% Org. carbon:

1.2

pH:

5.67

CEC:

8.3 meq/100 g soil d.w.

Bulk density (g/cm³):

1.3

Details on matrix:

COLLECTION AND STORAGE
- Geographic location: #1: Drummer (clay loam), #2: California (loam), #3: Nambsheim (sandy loam), #4: Lleida (silty clay), #5: Sassafras (sandy loam)
- Soil preparation: air-dried and sieved through a 2-mm sieve

Details on test conditions:

TEST SYSTEM
- Desorption experiments were conducted only on those samples treated at the highest test solution concentration
- Type, size and further details on reaction vessel: Tarson’s polypropylene centrifuge tubes
- Number of reaction vessels/concentration: 2
- Method of preparation of test solution: the two highest treatment solutions were prepared by transferring radiolabeled stock solution to a 10-mL volumetric flask and drying the contents under nitrogen. The residue was then reconstituted in 0.01 M CaCl2 by sonicating for less than a minute and bringing to volume with 0.01 M CaCl2. Treatment solutions of 0.45, 0.225 and 0.045 µg/L were prepared by further diluting 1000µL of the prepared treatment solutions to 10-mL volumetric flask using appropriate volumes of 0.01 M CaCl2. The radioactive concentrations of the test item were determined by LSC analysis of triplicate aliquots.
- 5 g (oven dry weight equivalent) soil was weighed into centrifuge tube, the total moisture content: 4.5 mL and mixed overnight via mechanical agitation, test samples were then treated with 0.5 mL of the treatment solution and placed on the mechanical agitator for 24 h; desorption (after supernatant removal): fresh 0.01 M CaCl2 solution (equivalent to that removed following adsorption) was added to each of the soil samples from the highest test item solution concentration (nominal 0.45 µg/mL). A second desorption equilibration and analysis was immediately repeated as described above. After the second desorption, the soil samples were air-dried, and triplicate aliquots of the dried soil sample were combusted prior to LSC analysis.

Duration:

24 h

Temp.:

20 °C

Duration:

24 h

Temp.:

20 °C

Sample No.:

#1

Type:

Koc

Value:

25.5 L/kg

Temp.:

20 °C

Matrix:

clay loam

Sample No.:

#2

Type:

Koc

Value:

4.9 L/kg

Temp.:

20 °C

Matrix:

loam

Sample No.:

#3

Type:

Koc

Value:

2.4 L/kg

Temp.:

20 °C

Matrix:

sandy loam

Sample No.:

#4

Type:

Koc

Value:

3.8 L/kg

Temp.:

20 °C

Matrix:

silty clay

Sample No.:

#5

Type:

Koc

Value:

24.3 L/kg

Temp.:

20 °C

Matrix:

sandy loam

Adsorption and desorption constants:

Adsorption constants KF: #1 (clay loam): 0.941, #2 (loam): 0.004, #3 (sandy loam): 0.016, #4 (silty clay): 0.066, #5 (sandy laom): 0.217

Recovery of test material:

98.2 - 99.8% of injected radioactivity among all test soils

Details on results (Batch equilibrium method):

A relationship of adsorption with soil pH was observed. The two soils with pH (CaCl2) <6 exhibited the strongest sorption (Koc approximately 25 mL/g) and three soils with pH >7 exhibited weaker sorption (Koc ≤5mL/g.).

Table 1: Summary of the average sorption coefficients for each soil

SOIL	KD(mL/g)	KOM(mL/g)	KOC(mL/g)
#1 (clay loam)	0.97	14.9	25.5
#2 (loam)	0.02	3.1	4.9
#3 (sandy loam)	0.03	1.4	2.4
#4 (silty clay)	0.06	2.2	3.8
#5 (sandy loam)	0.29	14.6	24.3
Average	0.28	7.2	12.2

Table 2: Freundlich adsorption isotherm parameter derived from the linear function of the Freundlich equation

SOIL	KF	KFOM	KFOC	1/n	R2
#1 (clay loam)	0.941	14.5	24.8	1.0007	0.9780
#2 (loam)	0.004	0.5	0.8	0.5167	0.6113
#3 (sandy loam)	0.016	0.7	1.2	0.8071	0.9475
#4 (silty clay)	0.066	2.4	4.1	1.0460	0.9615
#5 (sandy loam)	0.217	10.9	18.1	0.9163	0.9841
Average	0.249	5.8	9.8	0.8574	0.8965

Table 3: Average percent desorption for each soil

SOIL	D1(%)	D2(%)	DT(%)
#1 (clay loam)	15.7	17.4	33.1
#2 (loam)	8.6	15.9	24.5
#3 (sandy loam)	42.3	27.6	69.9
#5 (sandy loam)	26.3	20.4	46.7
Sassafras #16	38.2	20.6	58.8

Validity criteria fulfilled:

not applicable

Reference 2

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

28 Apr - 26 May 2008

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:

2000

GLP compliance:

yes (incl. QA statement)

Remarks:

Food and Consumer Product Safety Authority, Den Haag, The Netherlands; Bundesinstitut für Risikobewertung, Berlin, Germany; National GLP Compliance Monitoring Authority, Department of Science & Technology, New Dlhi, India

Type of method:

batch equilibrium method

Media:

soil

Radiolabelling:

yes

Test temperature:

20 ± 2°C

Analytical monitoring:

yes

Details on sampling:

- Concentrations: 20 different soils at a concentration of 4.5 µg/mL
- Triplicate aliquots (200 µL) of supernatants were added directly to scintillant and counted by LSC. A 500-μL aliquot of the supernatant from each soil was analysed by HPLC and 1 minute fractions were collected.
- Sampling interval: At equilibrium (after 24 hours)

Matrix no.:

#1

Matrix type:

silty clay loam

% Clay:

33

% Silt:

67

% Sand:

0

% Org. carbon:

2.6

pH:

6.72

CEC:

21.9 meq/100 g soil d.w.

Bulk density (g/cm³):

1

Matrix no.:

#2

Matrix type:

sandy loam

% Clay:

9

% Silt:

20

% Sand:

71

% Org. carbon:

0.5

pH:

6.43

CEC:

3.4 meq/100 g soil d.w.

Bulk density (g/cm³):

1.4

Matrix no.:

#3

Matrix type:

silt loam

% Clay:

25

% Silt:

58

% Sand:

17

% Org. carbon:

3

pH:

6.6

CEC:

16.6 meq/100 g soil d.w.

Bulk density (g/cm³):

1.02

Matrix no.:

#4

% Org. carbon:

1.3

pH:

5.5

Bulk density (g/cm³):

1.16

Matrix no.:

#5

% Org. carbon:

2.8

pH:

5.4

Bulk density (g/cm³):

1.12

Matrix no.:

#6

% Org. carbon:

2

pH:

5.4

Matrix no.:

#7

% Org. carbon:

2.6

pH:

4.2

Matrix no.:

#8

% Org. carbon:

0.6

pH:

7.2

CEC:

4.6 meq/100 g soil d.w.

Bulk density (g/cm³):

1.44

Matrix no.:

#9

Matrix type:

sandy loam

% Clay:

18

% Silt:

22

% Sand:

60

% Org. carbon:

5.5

pH:

4.6

CEC:

14.9 meq/100 g soil d.w.

Bulk density (g/cm³):

0.87

Matrix no.:

#10

Matrix type:

sandy loam

% Clay:

13

% Silt:

19

% Sand:

68

% Org. carbon:

1

pH:

5.87

CEC:

6.5 meq/100 g soil d.w.

Bulk density (g/cm³):

1.2

Matrix no.:

#11

% Org. carbon:

3.8

pH:

7.6

Bulk density (g/cm³):

1.1

Matrix no.:

#12

Matrix type:

sandy loam

% Clay:

15

% Silt:

16

% Sand:

69

% Org. carbon:

10.9

pH:

4.4

CEC:

17.2 meq/100 g soil d.w.

Bulk density (g/cm³):

0.71

Matrix no.:

#13

Matrix type:

sandy clay loam

% Clay:

28

% Silt:

18

% Sand:

54

% Org. carbon:

0.3

pH:

8.23

CEC:

14.6 meq/100 g soil d.w.

Bulk density (g/cm³):

1.2

Matrix no.:

#14

% Org. carbon:

1.8

pH:

4.9

Bulk density (g/cm³):

0.75

Matrix no.:

#15

Matrix type:

loam

% Clay:

20

% Silt:

48

% Sand:

32

% Org. carbon:

1.2

pH:

7.6

CEC:

10.2 meq/100 g soil d.w.

Bulk density (g/cm³):

1.2

Matrix no.:

#16

Matrix type:

silty clay loam

% Clay:

35

% Silt:

64

% Sand:

1

% Org. carbon:

2.5

pH:

6.71

CEC:

22.5 meq/100 g soil d.w.

Bulk density (g/cm³):

1.1

Matrix no.:

#17

% Org. carbon:

0.6

pH:

6

Matrix no.:

#18

% Org. carbon:

2

pH:

5.2

Matrix no.:

#19

Matrix type:

clay loam

% Clay:

30.8

% Silt:

45.6

% Sand:

23.6

% Org. carbon:

2.6

pH:

6.2

CEC:

34.6 meq/100 g soil d.w.

Bulk density (g/cm³):

1.11

Matrix no.:

#20

% Org. carbon:

3.8

pH:

7

Bulk density (g/cm³):

1.07

Details on matrix:

COLLECTION AND STORAGE
- Geographic location: #1: Lleida, Spain (silty clay loam), #2: Bojac, USA (Virginia, sandy loam), #3: Tama, USA (silt loam), #4: Champenoux (texture not determined), France, #5: Paynesville, USA (Minnesota, texture not determined), #6: Speyer 2.2, Germany (texture not determined), #7: Bukit Rotan, Malasia (texture not determined), #8: Baura, Brazil (texture not determined), #9: Glei Humico, Brazil (sandy loam), #10: Woodstown, USA (Delaware, sandy loam) , #11: Fargo, USA (North Dakota, texture not determined) , #12: Cape Fear, USA (South Carolina, sandy loam) , #13: Hidalago, USA (sandy clay loam), #14: Latassolo, Roxo Brazil (texture not determined), #15: Gross-Umstadt, Germany (loam), #16: Tama, USA (silty clay loam), #17: Saitama, Japan (texture not determined), #18: Fujishiro, Japan (texture not determined), #19: Drummer, USA (Illinois, clay loam), #20: Drummer # 2, USA (Illinois, texture not determined)
- Soil preparation: air-dried and sieved through a 2-mm sieve

Details on test conditions:

TEST SYSTEM
- Type, size and further details on reaction vessel: Tarson’s polypropylene centrifuge tubes
- Number of reaction vessels/concentration: 2
- Method of preparation of test solution: A treatment solution at a nominal concentration of 4.5 μg/mL was prepared by transferring 650 μL of radiolabeled stock solution (169.2 μg/mL) to a 25-mL volumetric flask and drying the contents under nitrogen. Reconstitution in0.01 M CaCl2 by sonicating for about a minute and brought to volume with 0.01 M CaCl2 to get a nominal concentration of 4.3992 μg/mL. The radioactive concentrations of the test item were determined by LSC analysis of triplicate aliquots.
- 5 g (oven dry weight equivalent) soil was weighed into centrifuge tube, the total moisture content: 4.5 mL and mixed overnight via mechanical agitation, test samples were then treated with 0.5 mL of the treatment solution and placed on the mechanical agitator for 24 h; desorption (after supernatant removal): fresh 0.01 M CaCl2 solution (equivalent to that removed following adsorption) was added to each of the soil samples. A second desorption equilibration and analysis was immediately repeated as described above. After the second desorption, the soil samples were air-dried, and triplicate aliquots of the dried soil sample were combusted prior to LSC analysis.

Duration:

24 h

Duration:

24 h

Sample No.:

#1

Type:

Koc

Value:

2.5 L/kg

Temp.:

20 °C

Matrix:

silty clay loam

Sample No.:

#2

Type:

Koc

Value:

26 L/kg

Temp.:

20 °C

Matrix:

sandy loam

Sample No.:

#3

Type:

Koc

Value:

12.5 L/kg

Temp.:

20 °C

Matrix:

silt loam

Sample No.:

#4

Type:

Koc

Value:

13.47 L/kg

Temp.:

20 °C

Matrix:

texture not determined

Sample No.:

#5

Type:

Koc

Value:

32.5 L/kg

Temp.:

20 °C

Matrix:

texture not determined

Sample No.:

#6

Type:

Koc

Value:

15.5 L/kg

Temp.:

20 °C

Matrix:

texture not determined

Sample No.:

#7

Type:

Koc

Value:

143.27 L/kg

Temp.:

20 °C

Matrix:

texture not determined

Sample No.:

#8

Type:

Koc

Value:

9.17 L/kg

Temp.:

20 °C

Matrix:

texture not determined

Sample No.:

#9

Type:

Koc

Value:

60.28 L/kg

Temp.:

20 °C

Matrix:

sandy loam

Sample No.:

#10

Type:

Koc

Value:

16.5 L/kg

Temp.:

20 °C

Matrix:

sandy loam

Sample No.:

#11

Type:

Koc

Value:

4.74 L/kg

Temp.:

20 °C

Matrix:

texture not determined

Sample No.:

#12

Type:

Koc

Value:

4.91 L/kg

Temp.:

20 °C

Matrix:

sandy loam

Sample No.:

#13

Type:

Koc

Value:

0 L/kg

Temp.:

20 °C

Matrix:

sandy clay loam

Sample No.:

#14

Type:

Koc

Value:

54.17 L/kg

Temp.:

20 °C

Matrix:

texture not determined

Sample No.:

#15

Type:

Koc

Value:

2.92 L/kg

Temp.:

20 °C

Matrix:

loam

Sample No.:

#16

Type:

Koc

Value:

19.4 L/kg

Temp.:

20 °C

Matrix:

silty clay loam

Sample No.:

#17

Type:

Koc

Value:

71.67 L/kg

Temp.:

20 °C

Matrix:

texture not determined

Sample No.:

#18

Type:

Koc

Value:

76.75 L/kg

Temp.:

20 °C

Matrix:

texture not determined

Sample No.:

#19

Type:

Koc

Value:

62.12 L/kg

Temp.:

20 °C

Matrix:

clay loam

Sample No.:

#20

Type:

Koc

Value:

7.11 L/kg

Temp.:

20 °C

Matrix:

texture not determined

Recovery of test material:

98.7 - 100% of injected radioactivity among all test soils

Table 1: Summary of the average sorption coefficients for each soil

SOIL	Kd(mL/g)	Kom(mL/g)	Koc(mL/g)
#1: Lleida, Spain (silty clay loam)	0.07	1.50	2.50
#2: Bojac, USA (Virginia, sandy loam)	0.13	16.25	26.00
#3: Tama, USA (silt loam)	0.38	7.35	12.50
#4: Champenoux (texture not determined)	0.18	7.96	13.47
#5: Paynesville, USA (Minnesota, texture not determined)	0.91	18.96	32.50
#6: Speyer 2.2, Germany (texture not determined)	0.31	9.12	15.50
#7: Bukit Rotan, Malasia (texture not determined)	3.73	82.78	143.27
#8: Baura, Brazil (texture not determined)	0.06	5.50	9.17
#9: Glei Humico, Brazil (sandy loam)	3.32	35.27	60.28
#10: Woodstown, USA (Delaware, sandy loam)	0.17	9.71	16.50
#11: Fargo, USA (North Dakota, texture not determined)	0.18	2.73	4.74
#12: Cape Fear, USA (South Carolina, sandy loam)	0.54	2.85	4.91
#13: Hidalago, USA (sandy clay loam),	0.00	0.00	0.00
#14: Latassolo, Roxo Brazil (texture not determined)	0.98	31.46	54.17
#15: Gross-Umstadt, Germany (loam)	0.04	1.75	2.92
#16: Tama, USA (silty clay loam)	0.49	11.28	19.40
#17: Saitama, Japan (texture not determined)	0.43	43.00	71.67
#18: Fujishiro, Japan (texture not determined)	1.54	43.86	76.75
#19: Drummer, USA (Illinois, clay loam)	1.62	36.71	62.12
#20: Drummer # 2, USA (Illinois, texture not determined)	0.27	4.09	7.11
Average	0.80	19.58	33.44

Table 2: Summary of the average percent desorption for each soil

SOIL	D1(%)	D2(%)	DT(%)
#1: Lleida, Spain (silty clay loam)	67.6	28.1	95.7
#2: Bojac, USA (Virginia, sandy loam)	75.2	20.1	95.3
#3: Tama, USA (silt loam)	26.8	24.3	51.1
#4: Champenoux, France (texture not determined)	11.7	31.0	45.7
#5: Paynesville, USA (Minnesota, texture not determined)	19.5	18.7	38.2
#6: Speyer 2.2, Germany (texture not determined)	17.7	28.8	46.5
#7: Bukit Rotan, Malasia (texture not determined)	3.3	6.5	9.7
#8: Baura, Brazil (texture not determined)	30.4	13.4	43.8
#9: Glei Humico, Brazil (sandy loam)	9.4	6.8	16.2
#10: Woodstown, USA (Delaware, sandy loam)	31.5	21.4	52.9
#11: Fargo, USA (North Dakota, texture not determined)	3.1	3.6	6.7
#12: Cape Fear, USA (South Carolina, sandy loam)	26.0	16.6	42.5
#13: Hidalago, USA (sandy clay loam),	0.0	0.0	0.0
#14: Latassolo, Roxo Brazil (texture not determined)	18.7	10.4	29.1
#15: Gross-Umstadt, Germany (loam)	10.2	2.5	12.7
#16: Tama, USA (silty clay loam)	25.3	17.0	42.3
#17: Saitama, Japan (texture not determined)	9.3	24.5	33.8
#18: Fujishiro, Japan (texture not determined)	7.1	9.8	16.9
#19: Drummer, USA (Illinois, clay loam)	15.0	12.9	27.9
#20: Drummer # 2, USA (Illinois, texture not determined)	30.6	18.2	48.8

Validity criteria fulfilled:

not applicable

Description of key information

logKoc = 0-2.16 (OECD 106)

The test item has a low adsorption potential to soil and sediment.

Additional information

The adsorption / desorption of the test substance was examined in two studies performing batch equilibrium experiments according to OECD guideline 106 under GLP conditions.

The first study was performed with five nominal test concentrations of radio labelled test item (0.45, 0.225, 0.045, 0.0225 and 0.0045µg/mL) in 0.01 M CaCl2 at 20°C. The test item concentrations were determined by liquid scintillation counting (LSC). The five representative soils cover a wide range of physico-chemical properties. Two desorption cycles were performed on samples treated at the highest test concentration. The adsorption parameters were calculated using the Freundlich adsorption isotherm. The material balance ranged from 94.1 to 105.1% and is within the acceptable guideline range of 90-110% of the applied radioactivity. The resulting Koc values for the adsorption of the test item and the five soils ranged between 2.4 and 25.5 L/kg (average 12.2 L/kg, LogKoc = 0.38 - 1.41). Furthermore, a relationship of adsorption with soil pH was observed. The two soils with pH (CaCl2) < 6 exhibited the strongest sorption (KOC approximately 25 mL/g) and three soils with pH > 7 exhibited weaker sorption (KOC ≤ 5 mL/g).

In a second study, adsorption and desorption properties of 0.45 µg/mL radiolabelled test item (in 0.01 M CaCl2) to a total of 20 soils was investigated. The percent organic matter of the soils ranged from 0.5-18.8%, and the pH in 0.01 M CaCl2 ranged from 4.0-7.83. Sorption coefficients and percent of the test item desorbed from the soil during two desorption intervals was calculated and totalled (DT) for all soils. The average material balance was in an acceptable range (91.4 - 108.8%). The derived KOC values were in a range between 0.00 and 143.27 L/kg (average: 33.44 L/kg, Log Koc = 0 - 2.16)