Tetrasodium hydrogen 2-phosphonatobutane-1,2,4-tricarboxylate

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Remarks:

adsorption

Type of information:

(Q)SAR

Adequacy of study:

key study

Study period:

10/2012

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with limited documentation / justification

Justification for type of information:

QSAR prediction

Guideline:

other: REACH guidance QSARs R6, May/July 2008

Principles of method if other than guideline:

Estimation Program Interface (EPI) Suite v4.10: KOCWIN (v2.00) for the estimation of the organic carbon-normalized sorption coefficient for soil and sediment (Koc).
The Estimation Program Interface was developed by the US Environmental Agency's Office of Pollution Prevention and Toxics, and Syracuse Research Corporation (SRC). © 2000 - 2011 U.S. Environmental Protection Agency for EPI SuiteTM (Published online in January 2011).

GLP compliance:

no

Type of method:

other: Estimation

Media:

soil

Radiolabelling:

no

Type:

log Koc

Value:

-2.756

Remarks on result:

other: calculation (logKow method)

Type:

log Koc

Value:

1.405

Remarks on result:

other: calculation (MCI method)

Key result

Phase system:

other: Koc

Type:

other: Koc

Value:

0.002 L/kg

Remarks on result:

other: calculation (logKow method)

Phase system:

other: Koc

Type:

other: Koc

Value:

25.38 L/kg

Remarks on result:

other: calculation (MCI method)

Validity of the model:

1. Defined Endpoint: Organic carbon partition coefficient, given as logarithmic Koc and Koc

2. Unambigous algorithm: The molecule is first classified as a polar substance. Based on structure of the molecule, the following fragment descriptors (correction coefficients) were applied: organic acid (-COOH) and organo phosphorus, aliphatic (P=O). For the number of times of the fragments that occurs in the structure of the substance default values are applied by the program. For estimation of logKoc according to the log Kow method the estimated logKow of -5.45 was used.

3. Applicable domain: With a molecular weight of 358.07 g/mole the substance is within the range of the training set (32 - 665 g/mole) as well as in the validation set (27 - 991 g/mole). Regarding the structure of the substance, the fragment descriptors found by the program are complete.

4a. Statistical characteristics (MCI method): N training set without corrections = 69; N training set with correction = 447; N validation set = 158; Correction coefficient of the total training set without corrections r² = 0.967; Correlation coefficient of the total training set with corrections r² = 0.900; Correlation coefficient of the total validation set r² = 0.850.

4b. Statistical characteristics (Kow method): N training set without corrections = 68; N training set with correction = 447; N validation set = 150; Correction coefficient of the total training set without corrections r² = 0.877; Correlation coefficient of the total training set with corrections r² = 0.855; Correlation coefficient of the total validation set r² = 0.778.

5. Mechanistic interpretation: Log Koc is estimated based on the likeliness of a substance for sorption to surfaces of soil/sediment particles. The log Koc is a physical inherent property used extensively to describe a chemical's likeliness to adsob to organic carbon. Adequacy of prediction:

The result for tetrasodium hydrogen 2-phosphonatobutane-1,2,4-tricarboxylate falls within the applicability domain described above and the estimation rules applied for the substance appears appropriate.

Validity criteria fulfilled:

not applicable

Conclusions:

The QSAR determination of the carbon partition coefficient for tetrasodium hydrogen 2-phosphonatobutane-1,2,4-tricarboxylate using the model KOCWIN included in the Estimation Program Interface (EPI) Suite v4.10 revealed values of 0.001756 L/kg (log Kow method) and 25.38 L/kg (MCI method).

Executive summary:

The organic carbon partition coefficient (Koc) for tetrasodium hydrogen 2-phosphonatobutane-1,2,4-tricarboxylate was predicted using the QSAR calculation of the Estimation Program Interface (EPI) Suite v4.10. The program uses two methods for the prediction: the first-order Molecular Connectivity Index (MCI method) and a method using the log Kow of the substance (log Kow method). With the log Kow method a Koc of 0.001756 L/kg was estimated relating to the dissociated form of the substance, as the substance is identified as a polar compound by the program , and its log Kow for the dissociated form was used for calculation. Based on the MCI method a Koc of 25.38 L/kg was predicted. As predictions for a salt cannot be performed by the program, metals (Na) has been removed to allow estimation via MCI. Thus, prediction relates to the non-water based parent acid of the substance. Additionally, the fragment descriptor "organic acid: -COOH is counted only once per structure, regardless of number of occurrences in the melocule, leading to an overestimation, as the substance containes 4 fragment descriptors. Taking the limitations of the program into account, the Koc of 0.001756 L/kg estimated by the log Kow method is the preferred value to describe the adsorption potential of the substance.

Description of key information

The QSAR determination of the carbon partition coefficient for tetrasodium hydrogen 2-phosphonatobutane-1,2,4-tricarboxylate using the model KOCWIN included in the Estimation Program Interface (EPI) Suite v4.10 revealed values of 0.001756 L/kg (logKow method) and 25.38 L/kg (MCI method) for the substance.

Key value for chemical safety assessment

Koc at 20 °C:

0.002

Additional information

The organic carbon partition coefficient (Koc) for tetrasodium hydrogen 2-phosphonatobutane-1,2,4-tricarboxylate was predicted using the QSAR calculation of the Estimation Program Interface (EPI) Suite v4.10. The program uses two methods for the prediction: the first-order Molecular Connectivity Index (MCI method) and a method using the log Kow of the substance (log Kow method). With the log Kow method a Koc of 0.001756 L/kg was estimated relating to the dissociated form of the substance, as the substance is identified as a polar compound by the program , and its log Kow for the dissociated form was used for calculation. Based on the MCI method a Koc of 25.38 L/kg was predicted. As predictions for a salt cannot be performed by the program, metals (Na) has been removed to allow estimation via MCI. Thus, prediction relates to the non-water based parent acid of the substance. Additionally, the fragment descriptor "organic acid: -COOH is counted only once per structure, regardless of number of occurrences in the melocule, leading to an overestimation, as the substance containes 4 fragment descriptors. Taking the limitations of the program into account, the Koc of 0.001756 L/kg estimated by the log Kow method is the preferred value to describe the adsorption potential of the substance.

Nevertheless, both predicted values indicate no adsorption/desorption potential for the substance.