N-(carboxymethyl)-N-(phosphonomethyl)glycine

Adsorption / desorption

Administrative data

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

Not reported

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study was conducted according to OECD Guideline 121.

Justification for data waiving:

other:

Cross-reference

Cross-reference 1

Reason / purpose for cross-reference:

reference to same study

Cross-reference 2

Reason / purpose for cross-reference:

reference to other study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1986

Report date:

1986

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 121 (Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC))

Deviations:

no

Principles of method if other than guideline:

Not applicable

GLP compliance:

no

Media:

soil

Test material

Test material information

Constituent 1

Reference substance name:

N-(carboxymethyl)-N-(phosphonomethyl)glycine

EC Number:

227-824-5

EC Name:

N-(carboxymethyl)-N-(phosphonomethyl)glycine

Cas Number:

5994-61-6

Molecular formula:

C5H10NO7P

IUPAC Name:

2-[(carboxymethyl)(phosphonomethyl)amino]acetic acid

Details on test material:

- Name of test material (as cited in study report): N-(Phosphonomethyl)iminodiacetic acid (glyphosate intermediate)-14C labeled
- Radiochemical purity (if radiolabelling): 97.6 % (HPLC)
- Specific activity (if radiolabelling): 8.27 mCi/mM
- Other:
Specific activity of the stock solution: 80,839 dpm/µg for this stock solution(calculated by liquid scintillation counting)

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
Not applicable

Radiolabelling:

yes

Study design

Test temperature:

26°C

HPLC method

Details on study design: HPLC method:

EQUIPMENT
- Apparatus: HPLC
- Type: Waters U6K injector
- Type, material and dimension of analytical (guard) column: Partisil-10-SAX column which was eluted with Burns buffer
- Detection system: Chart recorder and Monsanto Automated Chromatography System (MACS)


- Tracor Mark III TM Analytic liquid scintillation counting instruments were used to determine the dpms in each vial from quench curves maintained for each instrument

REPETITIONS
- Number of determinations: Triplicate

- Triplicate soil samples (150 to 200 mg) were weighed, Combusto-cones and oxidized quantitatively to 14CO2 with the use of Combustaid.
- The combustion instrument automatically prepared samples for LSC as explained above in the analytical method for glyphosate.
- The extraction of soils was accomplished with triplicate soil samples (150 to 200 mg) weighed into 1.5 mL microcentrifuge tubes and extracted with 4 X 1 mL of 0.5 M NH4OH solution. The extracts were combined and filtered through 0.22 µ Cameo II filters and triplicate aliquots were analyzed by LSC.

COLLECTION OF SOIL AND STORAGE
- Geographic location: Decatur, IL.
- Soil preparation (e.g.: 2 mm sieved; air dried etc.): Air-dried overnight and were sieved to a uniform particle size of diameter 425 µm or less (Tyler equivalent 35 mesh). Portions of each soil type were weighed, dried in an oven at 100°C overnight, and then re-weighed with the weight percentage of water calculated from the difference in weight.
For adsorption experiments, the soil was first weighed into centrifuge tubes and then equilibrated by 24 h of shaking with twice the weight of deionized water.

PROPERTIES
Please refer to "Table 1. Physical and chemical properties of soils used in conjunction with adsorption tests' in attached background material

Batch equilibrium or other method

Details on sampling:

Not applicable

Details on matrix:

Not applicable

Details on test conditions:

No data

Computational methods:

- Adsorption coefficients (K'): Adsorption coefficient (x/m/Ce)
- Adsorption coefficient per organic carbon (Koc): (K'/% organic carbonx100).

Results and discussion

Adsorption coefficient

Type:

Koc

Value:

> 6 200 - <= 39 600

Results: HPLC method

Details on results (HPLC method):

Freundlich constant(Koc):
- Spinks loamy sand soil: 6,200 (1.10% organic carbon)
- Dupo silt loam soil: 11,400 (0.87% organic carbon)
- Drummer silty clay loam soil: 39,600 (1.45% organic carbon)

Results: Batch equilibrium or other method

Adsorption and desorption constants:

Not applicable

Recovery of test material:

Not applicable

Concentration of test substance at end of adsorption equilibration period:

Not applicable

Concentration of test substance at end of desorption equilibration period:

Not applicable

Transformation products:

not measured

Details on results (Batch equilibrium method):

Not applicable

Statistics:

- Freundlich constants were evaluated by software programs on a VAX system and a DEC 10 system with essentially identical results.
- Analyses on the DEC 10 system used a Monsanto developed model for environmental chemistry studies labeled DATP which uses the subroutine ZXSSQ of the IMSL library of mathematical subroutines.

Any other information on results incl. tables

Please refer to "Table 2. Adsorption/desorption data" in attached background material section.

Applicant's summary and conclusion

Validity criteria fulfilled:

not specified

Conclusions:

Under the test conditions, the calculated Freundlich constants (K), ranged from 68 in Spinks soil to 575 in Drummer soil. The average adsorption coefficient (K') values, ranging from 9.050 to 21.340 in Spinks soil up to 201.854 to 309.023 in Drummer soil, indicating that the chemical does not have the potential to leach, and that it will be practically immobile in the soil. Therefore, the soil environment appears to be a likely trap for test material and its potential to leach should be minimal.

Executive summary:

A study was performed to assess the soil adsorption and desorption of the test material on three soil types. The study was conducted according to OECD Guideline 121.

The average percentage adsorbed from dilute aqueous solutions ranging in initial concentration from 0.04 ppm to 5 ppm ranged between 95.3 and 99.9% and only 0.05 to 4.33% of the adsorbed chemical was desorbed in two sequential treatments with a solution of 0.01 M CaCl2.

Adsorption coefficient, K' ranged from 9.050 to 309.023 for the different concentrations in all three soils. The values for the Freundlich constants K and 1/n were also determined by a computerized fit of the Freundlich equation to the adsorption data in the three soils. The Freundlich K constants were computed to be 68 (Spinks loamy sand), 99 (Dupo silt loam), and 575 (Drummer silty clay loam) indicating test material does not have the potential for soil leaching.

Under the test conditions, the average K’(adsorption coefficient) ranged from 9.050 to 21.340 in Spinks soil up to 201.854 to 309.023 in Drummer soil, indicating that the chemical does not have the potential to leach and that it will be practically immobile in the soil. Therefore, the soil environment appears to be a likely trap for test material.