N-(2-nitrophenyl)phosphoric triamide

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:

2005-08-03 - 2006-02-01

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: The GLP study was conducted according to an internationally accepted guideline. All study parameters are based on the specific guideline.

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

HPLC estimation method

Media:

soil

Radiolabelling:

no

Test temperature:

20°C

Details on study design: HPLC method:

The analysis of the water phases (blank values and equilibrium concentrations) is based on the highly specific high performance liquid chromatography with mass-spectrometric detection (LC/MS-MS).

The analytical method for the determination of N-(2-nitrophenyl)phosphoricacid triamide in water was developed by SGS INSTITUT FRESENIUS GmbH. The validity check of the analytical method was performed within the course of the study.

The detection mode is based on an electrospray ionization technique (EST positive). For N-(2-nitropbenyl)phosphoricacid triamide the calibration and evaluation of specimens was performed on the basis of two N-(2-nitrophenyl)pliosphoricacid triamide daughter ion recordings (transitions): m/z 217 ► m/z200andm/z217 ► m/z 121.

The specimens (water phases) were subjected to mass-spectrometric investigations after being diluted with a mixture of acetonitrile:water (25:75; v/v).

The adsorbed N-(2-nitrophenyl)phosphoricacid triamide in the solid phase (soil) was calculated.

Details on test conditions:

Three German soil systems (soil textures according to USDA classification were: sand for LIJFA 2.1 soil, loamy sand for LUFA 2.2 soil, sandy loam for LUFA 2.3) were used.

Key result

Type:

Koc

Remarks:

LUFA 2.1 (60 g dry soil and 60 mL of 0.01 mol/L CaCl2)

Value:

38

Temp.:

20 °C

% Org. carbon:

1.21

Key result

Type:

Koc

Remarks:

LUFA 2.1 (12 g dry soil and 60 mL of 0,01 mol/L CaCl2)

Value:

20

Temp.:

20 °C

% Org. carbon:

1.21

Key result

Type:

Koc

Remarks:

LUFA 2.2 (60 g dry soil and 60 mL of 0.01 mol/L CaCl2)

Value:

125

Temp.:

20 °C

% Org. carbon:

2.29

Key result

Type:

Koc

Remarks:

(12 g dry soil and 60 mL of 0,01 mol/L CaCl2)

Value:

103

Temp.:

20 °C

% Org. carbon:

2.29

Key result

Type:

Koc

Remarks:

LUFA 2.3 (60 g dry soil and 60 mL of 0.01 mol/L CaCl2)

Value:

180

Temp.:

20 °C

% Org. carbon:

1.02

Key result

Type:

Koc

Remarks:

LUFA 2.3 (12 g dry soil and 60 mL of 0,01 mol/L CaCl2)

Value:

132

Temp.:

20 °C

% Org. carbon:

1.02

Details on results (HPLC method):

Adsorption Test

The selection of soil/solution ratios was performed on

• 60 mL aqueous test item solution/60 g dry soil (ratio 1:1)

• 60 mL aqueous test item solution/12 g dry soil (ratio 5:1) The test item concentration was adjusted to 0.1 mg/L,

The test systems were tumbled for 16 hours. A time period of 16 h maximum was assumed to be sufficient for reaching equilibrium. Aliquots of the supernatants were sampled after centrifugation at 16 hours. The equilibrium concentration of N-(2-nitrophenyl)phosphoricacid triamide in the water phases was determined by LC-MS/MS. The detection mode is based on an electrospray ionization technique (ESI positive).
The amount of test item adsorbed onto soil, the adsorption coefficient (K), the adsorption coefficient 011 basis of soil organic carbon content (Koc) were calculated for each specimen of the experimental setup.

The pH-value of the test system was measured after contact with the soil

• LUFA2.1 pH 5.5

• LUFA 2.2 pH 6.5

• LUFA2.3 pH 5.8

The respective adsorption coefficients on the basis of soil organic carbon content (Koc) were calculated to be

• LUFA 2.1 soil test system 38 mL/g (ratio 1:1) and 20 mL/g (ratio 5:1 ) at 1.21 % org. carbon

• LUFA 2.2 soil test system 125 mL/g (ratio 1:1) and 103 mL/g (ratio 5:1 ) at 2.29 % org. carbon

• LUFA 2.3 soil test system 180 mL/g (ratio 1:1) and 132 mL/g (ratio 5:1 ) at 1.02 % org. carbon

Validity criteria fulfilled:

yes

Conclusions:

N-(2-nitrophenyl)phosphoricacid triamide showed a significant adsorption onto the experimental soils (reflected by values > 25 %).
The respective adsorption coefficients on the basis of soil organic carbon content (Koc) were calculated to be

• LUFA 2.1 soil test system 38 mL/g (ratio 1:1) and 20 mL/g (ratio 5:1) at 1.21 % org. carbon

• LUFA 2.2 soil test system 125 mL/g (ratio 1:1) and 103 mL/g (ratio 5:1) at 2.29 % org. carbon

• LUFA 2.3 soil test system 180 mL/g (ratio 1:1) and 132 mL/g (ratio 5:1) at 1.02 % org. carbon

Executive summary:

The extent of adsorption of N-(2-nitrophenyl)phosphoricacid triamide was studied on basis of the OECD Guideline no.106 for the testing of chemicals, adopted January 21, 2000. The study was conducted with N-(2-nitrophenyl)phosphoricacid triamide analytical grade (99 % minimum) test item. Following the equilibration of the three German soil systems (soil textures according to USDA classification were: sand for LUFA 2.1 soil, loamy sand for LUFA 2,2 soil, sandy loam for LUFA 2.3) with 60 mL of 0.01 mol/L CaCl2 the test item was applied in 0.01 mol/L CaCl2. The co-solvent (acetonitrile) in the test systems did not exceed 0.1 vol. %. The adsorption test was performed on two soil/solution ratio of 1:1 (60 g dry soil and 60 mL of 0.01 mol/L CaCl2) and 5:1 (12 g dry soil and 60 mL of 0,01 mol/L CaCL) using one test concentration of N-(2-nitrophenyl)-phosphoricacid triamide (0.1 mg test item/L). After agitation for 16 hours at 20 °C in the dark, the distribution of N-(2-nitrophenyl)phosphoricacid triamide between the aqueous phase and the solid phase (soil) was assayed. HPLC-MS coupling was used for the analysis of the equilibrium concentration in the water phases. The adsorbed N-(2-nitrophenyl)phosphoricacid triamide in the solid phase (soil) was calculated. The respective adsorption coefficients on the basis of soil organic carbon content (Koc) were calculated to be

•LUFA 2.1 soil test system38 mL/g (ratio 1:1) and 20 mL/g (ratio 5:1) at 1.21 % org. carbon

•LUFA 2.2 soil test system125 mL/g (ratio 1:1) and 103 mL/g (ratio 5:1) at 2.29 % org. carbon

•LUFA 2.3 soil test system180 mL/g (ratio 1:1) and 132 mL/g (ratio 5:1) at 1.02 % org. carbon

N-(2-nitrophenyl)phosphoricacid triamide showed a significant adsorption onto the experimental soils (reflected by values > 25 %). The clay content of soil is assumed to be a responsible factor for the adsorption of N-(2-nitrophenyl)-phosphoricacid triamide onto soils.

Description of key information

Adsorption of N-(2-nitrophenyl)phosphoricacid triamide  on Soils:

The extent of adsorption of N-(2-nitrophenyl)phosphoricacid triamide was studied on basis of the OECD/OCDE Guideline no.106 for the testing of chemicals, adopted January 21, 2000.

The respective adsorption coefficients on the basis of soil organic carbon content (Koc) were calculated to be

•LUFA 2.1 soil test system38 mL/g (ratio 1:1) and 20 mL/g (ratio 5:1) at 1.21 % org. carbon

•LUFA 2.2 soil test system125 mL/g (ratio 1:1) and 103 mL/g (ratio 5:1) at 2.29 % org. carbon

•LUFA 2.3 soil test system180 mL/g (ratio 1:1) and 132 mL/g (ratio 5:1) at 1.02 % org. carbon

N-(2-nitrophenyl)phosphoricacid triamide showed a significant adsorption onto the experimental soils (reflected by values > 25 %). The clay content of soil is assumed to be a responsible factor for the adsorption of N-(2-nitrophenyl)-phosphoricacid triamide onto soils.

A medium koc of 100 was claculated from figures above.

Key value for chemical safety assessment

Koc at 20 °C:

100

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