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Adsorption / desorption

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adsorption / desorption, other
Type of information:
Adequacy of study:
key study
Study period:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
accepted calculation method
Justification for type of information:
Estimation Programs Interface (EPI) SuiteTM
(Developed by the US Environmental Protection Agency's Office of Pollution Prevention and Toxics and Syracuse Research Corporation (SRC). )

2. MODEL (incl. version number)
BIOWIN (v4.10)

CAS Number: 2157-01-9
CHEM : 2-Propenoic acid, 2-methyl-, octyl ester
MOL FOR: C12 H22 O2
MOL WT : 198.31


EPI Suite™ is a screening-level tool and should not be used if acceptable measured values are available.
EPI Suite™ is a peer reviewed prediction program.
EPA's Office of Pollution Prevention and Toxics (OPPT) requested that the EPA Science Advisory Board (SAB) review the supporting science, functionality, and appropriate use of software known as the Estimation Programs Interface (EPI) Suite. OPPT has supported the development of this software for estimating the behavior of chemical substances in a biological or environmental system based on their physical, chemical and environmental properties. EPI Suite is routinely used in evaluating new chemicals under EPA's Premanufacture Notices (PMNs) for new chemicals under section 5 of the Toxic Substances Control Act, and is widely used for predicting physical/chemical properties and environmental fate and transport properties for chemicals already in commerce.

The Soil Adsorption Coefficient Program (KOCWIN) estimates the soil adsorption coeffiecient (Koc) of organic compounds.  Koc can be defined as "the ratio of the amount of chemical adsorbed per unit weight of organic carbon (oc) in the soil or sediment to the concentration of the chemical in solution at equilibrium" (Lyman, 1990); it is represented by the following equation (Lyman, 1990):

 Koc =  (ug adsorbed/g organic carbon) / (ug/mL solution)

The units of Koc are typically expressed as either L/kg or mL/g.

Koc provides an indication of the extent to which a chemical partitions between solid and solution phases in soil, or between water and sediment in aquatic ecosystems.  Estimated values of Koc are often used in environmental fate assessment because measurement of Koc is expensive.  Traditional estimation methods rely upon the octanol/water partition coefficient or related parameters, but the first-order molecular connectivity index (MCI) has been used successfully to predict Koc values for hydrophobic organic compounds (Sabljic, 1984, 1987; Bahnick and Doucette, 1988).  The original KOCWIN program (PCKOC) used MCI and a series of group contribution factors to predict Koc (Meylan et al., 1992).  This group contribution method was shown to outperform traditional estimation methods based on octanol/water partition coefficients and water solubility.

Since the introduction of the original PCKOC program in 1992, the number of available experimental Koc values has grown significantly.  Using an expanded experimental dataset and the original PCKOC methodology, the QSAR equations were re-regressed to derive updated coefficient values.  In addition, several new group contribution factors (correction factors) were added to improve estimation accuracy.  Also, the updated KOCWIN program includes a separate Koc estimate based upon Log Kow (rather than MCI).  A brief description of the estimation methodology and accuracy is presented in the Methodology section and Accuracy section of this help file.

KOCWIN requires only a chemical structure to make these predictions.  Structures are entered into KOCWIN by SMILES (Simplified Molecular Input Line Entry System) notations.  A discussion of the encoding rules for SMILES notation can be found in the document "A Brief Description of SMILES Notation".  

The following journal article explains the MCI prediction methodology and its use:

(1) Meylan, W., P.H. Howard and R.S. Boethling, "Molecular Topology/Fragment Contribution Method for Predicting Soil Sorption Coefficients", Environ. Sci. Technol. 26: 1560-7 (1992).

Journal abstract:

"The first-order molecular connectivity index (MCI) has been successfully used to predict soil sorption coefficients (Koc) for nonpolar organics, but extension of the model to polar compounds has been problematic.  To address this, we developed a new estimation method based on MCI and series of statistically derived fragment contribution factors for polar compounds. After developing an extensive database of measured Koc values, we divided the dataset into a training set of 189 chemicals and an independent validation set of 205 chemicals.  Two linear regressions were then performed.  First, measured log Koc values for nonpolar compounds in the training set were correlated with MCI.  The second regression was developed by using the deviations between measured log Koc and the log Koc estimated with the nonpolar equation and the number of certain structural fragments in the polar compounds.  The final equation for predicting log Koc accounts for 96% and 86% of the variation in the measured values for the training and validation sets, respectively.  Results also show that the model outperforms and covers a wider range of chemical structures than do models based on octanol-water partition coefficients (Kow) or water solubility."


EPI SuiteTM cannot be used for all chemical substances. The intended application domain is organic chemicals. Inorganic and organometallic chemicals generally are outside the domain.

Data source

Reference Type:
other company data
Report date:

Materials and methods

Test guideline
no guideline required
Version / remarks:
EPIWIN prediction
Principles of method if other than guideline:
A Adsorpion/Desorption was calculated using the KocWIN v4.10 model within EPI Suite ver. 4.10 (US-EPA, 2008)
GLP compliance:

Test material

Constituent 1
Chemical structure
Reference substance name:
Octyl methacrylate
EC Number:
EC Name:
Octyl methacrylate
Cas Number:
Molecular formula:
octyl 2-methylprop-2-enoate
Test material form:
Details on test material:

Study design

Batch equilibrium or other method

Computational methods:
Koc Estimate from Log Kow:
Log Kow (User entered ) ......................... : 5.24
Non-Corrected Log Koc (0.55313 logKow + 0.9251) .... : 3.8235
Fragment Correction(s):
1 Ester (-C-CO-O-C-) or (HCO-O-C) ...... : -0.0656
Corrected Log Koc .................................. : 3.7579

Estimated Koc: 5727 L/kg <===========

Results and discussion

Adsorption coefficient
Key result
5 727 L/kg

Applicant's summary and conclusion

Executive summary:

According to a KocWIN calculation the Koc of the test item n-Octylmethacrylate is predicted to be 5727 L/kg.

NOTE: Any of data in this dataset are disseminated by the European Union on a right-to-know basis and this is not a publication in the same sense as a book or an article in a journal. The right of ownership in any part of this information is reserved by the data owner(s). The use of this information for any other, e.g. commercial purpose is strictly reserved to the data owners and those persons or legal entities having paid the respective access fee for the intended purpose.

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