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Adsorption / desorption

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Reference
Endpoint:
adsorption / desorption
Remarks:
adsorption
Type of information:
calculation (if not (Q)SAR)
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
accepted calculation method
Justification for type of information:
Estimated data generated using the EPI Suite model developed by the USEPA.
Qualifier:
according to
Guideline:
other: Modeling database
Principles of method if other than guideline:
Prediction done using KOCWIN Program (v2.00)
GLP compliance:
not specified
Type of method:
other: MCI Method
Media:
soil
Specific details on test material used for the study:
- Name of test material : 2-Hydroxy-4-methylbenzoic acid
- Molecular formula :C8H8O3
- Molecular weight :152.148 g/mol
- Smiles notation : Cc1ccc(c(c1)O)C(=O)O
- InChl :1S/C8H8O3/c1-5-2-3-6(8(10)11)7(9)4-5/h2-4,9H,1H3,(H,10,11)
- Substance Type: Organic
- Physical State: Solid
Radiolabelling:
not specified
Test temperature:
25 deg.C
Analytical monitoring:
not specified
Key result
Type:
Koc
Value:
34.81 L/kg
Temp.:
25 °C
Remarks on result:
other: log Koc = 1.5417 (estimated by MCI method)
Transformation products:
not specified

KOCWIN Program (v2.00) Results:

==============================

SMILES : Cc1ccc(C(=O)(O))c(O)c1

CHEM : Benzoic acid, 2-hydroxy-4-methyl-

MOL FOR: C8 H8 O3

Koc may be sensitive to pH!

--------------------------- KOCWIN v2.00 Results ---------------------------

Koc Estimate from MCI:

---------------------

First Order Molecular Connectivity Index ........... : 5.109

Non-Corrected Log Koc (0.5213 MCI + 0.60) .......... : 3.2632

Fragment Correction(s):

* Organic Acid (-CO-OH) ............... : -1.62498

1 Aromatic Hydroxy (aromatic-OH) ....... : -0.0966

Corrected Log Koc .................................. : 1.5417

Estimated Koc: 34.81 L/kg <===========

Validity criteria fulfilled:
not specified
Conclusions:
The soil adsorption coefficient i.e Koc value of 2-Hydroxy-4-methylbenzoic acid was estimated to be 34.81 L/kg (log Koc=1.5417) by means of MCI method (at 25 deg C). This Koc value indicates that the substance 2-Hydroxy-4-methylbenzoic acid has a low sorption to soil and sediment and therefore have moderate migration potential to ground water.
Executive summary:

KOCWIN model (v2.00) of Estimation Programs Interface (EPI Suite, 2017) was used to predict the soil adsorption coefficient i.e Koc value of test chemical 2-Hydroxy-4-methylbenzoic acid (CAS No. 50 -85 -1). The soil adsorption coefficient i.e Koc value of 2-Hydroxy-4-methylbenzoic acid was estimated to be 34.81 L/kg (log Koc=1.5417)  by means of MCI method (at 25 deg C). This Koc value indicates that the substance 2-Hydroxy-4-methylbenzoic acid has a low sorption to soil and sediment and therefore have moderate migration potential to ground water.

Description of key information

KOCWIN model (v2.00) of Estimation Programs Interface (EPI Suite, 2017) was used to predict the soil adsorption coefficient i.e Koc value of test chemical 2-Hydroxy-4-methylbenzoic acid (CAS No. 50 -85 -1). The soil adsorption coefficient i.e Koc value of 2-Hydroxy-4-methylbenzoic acid was estimated to be 34.81 L/kg (log Koc=1.5417)  by means of MCI method (at 25 deg C). This Koc value indicates that the substance 2-Hydroxy-4-methylbenzoic acid has a low sorption to soil and sediment and therefore have moderate migration potential to ground water.

Key value for chemical safety assessment

Koc at 20 °C:
34.81

Additional information

Various predicted data for the target compound 2-Hydroxy-4-methylbenzoic acid (CAS No. 50-85-1) and experimental studies for its structurally similar read across chemical were reviewed for the adsorption endpoint and results of all the studies are summarized below:

In first predicted data study Koc value of test chemical 2-Hydroxy-4-methylbenzoic acid (CAS No. 50 -85 -1) was estimated by using the KOCWIN Program (v2.00) of Estimation Programs Interface (EPI Suite, 2017). The soil adsorption coefficient i.e., Koc value of 2-Hydroxy-4-methylbenzoic acid was estimated to be 34.81 L/kg (log Koc=1.5417) by means of MCI method (at 25 deg C). This Koc value indicates that the substance 2-Hydroxy-4-methylbenzoic acid has a low sorption to soil and sediment and therefore has moderate migration potential to ground water.

In next predicted data study the Soil Adsorption Coefficient i.e Koc value of test substance 2-Hydroxy-4-methylbenzoic acid (CAS no. 50 -85 -1) was estimated using Adsorption Coefficient module (v12.1.0.50374) program as Koc 558, 534, 377, 96.0, 11.7, 1.55 and 1.0 at pH range 0, 1, 2, 3, 4, 5 and 6-14, respectively (log Koc value ranges from 0 to 2.7 ± 1.0) of (ACD (Advanced Chemistry Development)/I-Lab predictive module, 2017). This Koc values indicate that the test substance 2-Hydroxy-4-methylbenzoic acid has a negligible sorption to soil and sediment and therefore have rapid migration potential to groundwater.

In an another prediction done by using ChemSpider Database (2017),the Soil Adsorption Coefficient i.e Koc value of test substance 2-Hydroxy-4-methylbenzoic acid (CAS no. 50 -85 -1) was estimated. The adsorption coefficient (Koc) value of test substance 2-Hydroxy-4-methylbenzoic acid was estimated to be 1.0 (Log Koc = 0) at pH 5.5 and 7.4, respectively. This Koc value indicates that the test substance 2-Hydroxy-4-methylbenzoic acid has a negligible sorption to soil and sediment and therefore has rapid migration potential to groundwater.

Additional soil adsorption coefficient i.e., Koc value of test chemical 2-Hydroxy-4-methylbenzoic acid (CAS No. 50 -85 -1)was estimated using the SciFinder database (American Chemical Society (ACS), 2017).The soil adsorption coefficient i.e., Koc value of 2-Hydroxy-4-methylbenzoic acid was estimated to be 464, 328, 83.5, 10.2, 1.34 and 1.0 at pH range 1, 2, 3, 4, 5 and 6-10, respectively (log Koc value ranges from 0 to 2.66) (at 25 deg C). This Koc value indicates that the substance 2-Hydroxy-4-methylbenzoic acid has a negligible sorption to soil and sediment and therefore has rapid migration potential to ground water.

From CompTox Chemistry Dashboard using OPERA (OPEn (quantitative) structure-activity Relationship Application)  V1.02 model in which calculation based on PaDEL descriptors (calculate molecular descriptors and fingerprints of chemical), the adsorption coefficient i.e., KOC for test substance 2-Hydroxy-4-methylbenzoic acid was estimated to be 44.5 L/kg (log Koc = 1.648).The predicted KOC result based on the 5 OECD principles. This Koc value indicates that the substance 2-Hydroxy-4-methylbenzoic acid has a low sorption to soil and sediment and therefore has moderate migration potential to ground water.

Next study was experimental study done by Sustainability Support Services (2017) for read across chemical 2-methoxybenzoic acid (2-MBA) (CAS No. 579 -75 -9) in this study the adsorption coefficient Koc in soil and in sewage sludge of read across chemical 2-methoxybenzoic acid (2-MBA) (CAS No. 579 -75 -9) was determined by the Reverse Phase High Performance Liquid Chromatographic method. The reference substances were chosen according to estimated Koc range of the read across substance and generalized calibration graph was prepared. Five reference substances, Xylene, Ethylbenzene, Toluene, Naphthalene and Phenanthrene were chosen having Koc value range from 2.369 to 4.09. The Log Koc value of read across chemical 2-methoxybenzoic acid (2-MBA) (CAS No. 579 -75 -9) was determined to be 0.9919 dimensionless at 25°C. Based on the value of log Koc it is concluded that this read across chemical has negligible sorption to soil and sediments and therefore has rapid migration potential to ground water.

Next both the experimental studies were done from authoritative database HSDB, 2017 for two different read across chemicals salicylic acid and acetylsalicylic acid the adsorption coefficient (Koc) of substance salicylic acid was determined to be 404 using a log Kow of 2.26 and a regression-derived equation and the adsorption coefficient (Koc) of substance acetylsalicylic acid was determined to be 100(log Koc =2.00) using a log Kow of 1.19 and a regression-derived equation. Both Koc values suggest that acetylsalicylic acid and salicylic acid is expected to have high mobility in soil.

One more experimental study was done from authoritative database (HSDB, 2017) for read across chemical phthalic acid in this study the Koc values were determined for an acidic forest soil (Podzol, 4.85% organic carbon, pH 2.8), an agricultural soil (Alfisol, 1.25% organic carbon, pH 6.7) and a sublimnic soil (sediment from Lake Constance, Germany, 1.58% organic carbon, pH 7) as 31, 2 and 2, respectively. Koc values suggest that phthalic acid is expected to have very high mobility in soil.

On the basis of above overall results for target chemical 2-Hydroxy-4-methylbenzoic acid(from EPI suite, ACD labs, ChemSpider, SciFinder database and CompTox Chemistry Dashboard, 2017) and its read across chemical (from HSDB, and SSS) , it can be concluded that the Koc value of test substance 2-Hydroxy-4-methylbenzoic acid ranges from 1 to 558 dimensionless indicating that the test chemical 2-Hydroxy-4-methylbenzoic acid has a negligible to low sorption to soil and sediment and therefore have rapid to moderate migration potential to ground water.

[LogKoc: 1.5417]