Phosphoric acid, decyl octyl ester

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Type of information:

(Q)SAR

Adequacy of study:

key study

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 adequate and reliable documentation / justification

Justification for type of information:

QSAR prediction from an well known and acknowledged tool. See below under 'Overall remarks, attachments' for applicability domain.

Qualifier:

according to guideline

Guideline:

other: REACH guidance on QSARs: Chapter R.6. QSARs and grouping of chemicals

Principles of method if other than guideline:

Since the test substance is a UVCB with similar constituents varying mainly in carbon chain lengths, the Koc values were estimated for the individual components using the MCI (Molecular Connectivity Index) approach of the KOCWIN v2.00 program followed by the determination of an overall weighted-average value using the mole fractions of all the individual components.

Computational methods:

Since the test substance is an UVCB with several constituents varying mainly in carbon chain lengths, the Koc values were estimated for the individual components using the MCI (Molecular Connectivity Index) approach of the KOCWIN v2.00 program followed by an determination of an overall weighted-average value using the mole fractions of all the individual components.

MCI based methodology:
PCKOCWIN (version 1) estimated Koc solely with a QSAR utilizing First Order Molecular Connectivity Index (MCI). This QSAR estimation methodology is described completely in a journal article (Meylan et al, 1992) and in a report prepared for the EPA (SRC, 1991). PCKOCWIN (version 2) utilizes the same methodology, but the QSAR has been re-regressed using a larger database of experimental Koc values that includes many new chemicals and structure types.

Log Kow based methodology:
A traditional method of estimating soil adsorption Koc involves correlations developed with log octanol-water partition coefficient (log Kow) (Doucette, 2000). Since an expanded experimental Koc database was available from the new MCI regression, it was decided to develop a log Kow estimation methodology that was potentially more accurate than existing log Kow QSARs for diverse structure datasets. Effectively, the new log Kow methodology simply replaces the MCI descriptor with log Kow and derives similar equations. The derivation uses the same training and validation data sets. The training set is divided into the same non-polar (no correction factors) and correction factor sets. The same correction factors are also used. Separate equations correlating log Koc with log Kow were derived for nonpolar and polar compounds because it was statistically more accurate to do so than to use the approach taken with the MCI-based method.

Reference:
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).
Doucette, W.J., Soil and sediment sorption coefficients, Handbook of Property Estimation Methods, Environmental and Health Sciences. R.S. Boethling & D. Mackay (Eds.), Boca Raton, FL: Lewis Publishers (ISBN 1-56670-456-1), 2000.

Validity of model
1. Defined endpoint: log Koc – soil adsorption coefficient of organic compounds.
2. (a) MCI method algorithm: log Koc = 0.5213 MCI + 0.60 + ΣPfN
(b) Log Kow method algorithm: log Koc  =  0.55313 Log Kow  +  0.9251 + ΣPfN
MCI – molecular connectivity index, ΣPfN - summation of the products of all applicable correction factor coefficients available in the data set multiplied by the number of times (N) that factor is counted for the structure.
3. Applicability domain: Currently, there is no universally accepted definition of model domain. The training set of the model contains diverse molecules, so that the fragment library is abundant. It is however possible that a compound has functional groups or other structural features that are not represented in the training set and for which no fragment coefficients were developed. Additionally, there can be more instances of a given fragment than the maximum for all training set compounds. These points should be taken into consideration while interpreting test results.
Molecular weight limits of the training set: 32-665 g/mol
Log Kow limits: -2.11-9.10
4. Appropriate measures of goodness of fit, robustness and predictivity: for the statistics, training data set has been split up into two subsets: the one containing non-polar substances with no fragments subjected to corrections (i.e. those with ΣPfN = 0) and the one containing the remaining ones.
(a) MCI: For the non-polar set: N = 69 compounds, correlation coefficient R2= 0.967, standard deviation sd = 0.247 and average deviation ad = 0.199. For the second set: N = 447 compounds, correlation coefficient R2= 0.9, standard deviation sd = 0.34 and average deviation ad = 0.273. For the external validation data set: N = 158 compounds, correlation coefficient R2= 0.85, standard deviation sd = 0.583 and average deviation ad = 0.459. For the 516 compounds in the training set, 93% are within 0.6 log units and 100% within 1 log unit.
(b) Log Kow: For the non-polar set: N = 68 compounds, correlation coefficient R2= 0.877, standard deviation sd = 0.478 and average deviation ad = 0.371. For the second set: N = 447 compounds, correlation coefficient R2= 0.855, standard deviation sd = 0.396 and average deviation ad = 0.307. For the external validation data set: N = 150** compounds, correlation coefficient R2= 0.778, standard deviation sd = 0.679 and average deviation ad = 0.494.
** eight ammonium and metal salt compounds were removed from the Validation dataset
Overall, the MCI methodology is somewhat more accurate than the Log Kow methodology, although both methods yield good results.  If the Training datasets are combined in to one dataset of 516 compounds (69 having no corrections plus 447 with corrections), the MCI methodology has an r2, standard deviation and average deviation of 0.916, 0.330 and 0.263, respectively, versus 0.86, 0.429 and 0.321 for the Log Kow methodology.
For the accuracry graphs, please refer to the PDF under 'attached background material'.
5. Mechanistic interpretation if possible: The methodology and relationship between the first order molecular connectivity index (MCI) and adsorption coefficient is outlined in the reference paper: 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). MCI was initially successfully used to predict soil sorption coefficients for non-polar organics, and the developed new estimation method based on MCI and series of statistically derived fragment contribution factors made it useful also for the polar ones.

Key result

Type:

Koc

Value:

ca. 30 423.56 L/kg

Remarks on result:

other: weighted average estimation using MCI method of KOCWIN v.2.00

Remarks:

log Koc: 4.48

Details on results:

Chemical names	SMILES	Mole fraction Xi = (mi/Mi)/∑ (mi/Mi)	Koc	log Koc	Koc * xi	log Koc * xi	Domain evaluation
C8	CCCCCCCCOP(O)(O)=O	0.277827505	184	2.27	52.35	0.643762726	ID (Molecular weight and molecular fragments)
C10	CCCCCCCCCCOP(O)(O)=O	0.258478574	612	2.79	161.73	0.736743728	ID (Molecular weight and molecular fragments)
C8-10	CCCCCCCCCCOP(O)(=O)OCCCCCCCC	0.368868569	80050	4.90	30203.68	1.850088067	ID (Molecular weight and molecular fragments)
Decanol	CCCCCCCCCCO	0.03270296	127	2.10	4.25	0.070386552	ID (Molecular weight and molecular fragments)
Octanol	CCCCCCCCO	0.039749301	38	1.58	1.56	0.064362005	ID (Molecular weight and molecular fragments)
					30423.56	3.37
				Log Koc =	4.48

ID: In domain

Koc
SMILES : CCCCCCCCCCOP(O)(O)=O
CHEM  :
MOL FOR: C10 H23 O4 P1	Domain evaluation	MW (Training set)
MOL WT : 238.27	ID	665.02
--------------------------- KOCWIN v2.00 Results ---------------------------
Koc Estimate from MCI:
---------------------
First Order Molecular Connectivity Index ........... : 7.061
Non-Corrected Log Koc (0.5213 MCI + 0.60) .......... : 4.2805
Fragment Correction(s):		Training set
*  OrganoPhosphorus [P=O], aliphatic ..... : -1.4940	ID	1
Corrected Log Koc .................................. : 2.7866
Estimated Koc: 611.7 L/kg  <===========
Koc Estimate from Log Kow:
-------------------------
Log Kow (Kowwin estimate) ......................... : 3.71
Non-Corrected Log Koc (0.55313 logKow + 0.9251) .... : 2.9772
Fragment Correction(s):
*  OrganoPhosphorus [P=O], aliphatic ..... : 0.1033
Corrected Log Koc .................................. : 3.0806
Estimated Koc: 1204 L/kg  <===========
SMILES : CCCCCCCCCCOP(O)(=O)OCCCCCCCC
CHEM  :
MOL FOR: C18 H39 O4 P1	Domain evaluation	MW (Training set)
MOL WT : 350.48	ID	665.02
--------------------------- KOCWIN v2.00 Results ---------------------------
Koc Estimate from MCI:
---------------------
First Order Molecular Connectivity Index ........... : 11.121
Non-Corrected Log Koc (0.5213 MCI + 0.60) .......... : 6.3973
Fragment Correction(s):		Training set
*  OrganoPhosphorus [P=O], aliphatic ..... : -1.4940	ID	1
Corrected Log Koc .................................. : 4.9034
Estimated Koc: 8.005e+004 L/kg  <===========
Koc Estimate from Log Kow:
-------------------------
Log Kow (Kowwin estimate) ......................... : 7.20
Non-Corrected Log Koc (0.55313 logKow + 0.9251) .... : 4.9076
Fragment Correction(s):
*  OrganoPhosphorus [P=O], aliphatic ..... : 0.1033
Corrected Log Koc .................................. : 5.0110
Estimated Koc: 1.026e+005 L/kg  <===========
SMILES : OP(=O)(O)OP(=O)(O)O
CHEM  :
MOL FOR: H4 O7 P2	Domain evaluation	MW (Training set)
MOL WT : 177.98	ID	665.02
--------------------------- KOCWIN v2.00 Results ---------------------------
********************************************************************
* WARNING - The entered structure is an INORGANIC Compound.      *
*   Inorganic compounds were not included in the training data   *
*   set for the methodology utilized in this program. Therefore, *
*   inorganic compounds are outside the estimation domain.       *
********************************************************************
Koc Estimate from MCI:
---------------------
First Order Molecular Connectivity Index ........... : 3.707
Non-Corrected Log Koc (0.5213 MCI + 0.60) .......... : 2.5323
Fragment Correction(s):		Training set
*  OrganoPhosphorus [P=O], aliphatic ..... : -1.4940	ID	1
Corrected Log Koc .................................. : 1.0384
Estimated Koc: 10.92 L/kg  <===========
Koc Estimate from Log Kow:
-------------------------
Log Kow (Kowwin estimate) ......................... : -1.74
Non-Corrected Log Koc (0.55313 logKow + 0.9251) .... : -0.0373
Fragment Correction(s):
*  OrganoPhosphorus [P=O], aliphatic ..... : 0.1033
Corrected Log Koc .................................. : 0.0660
Estimated Koc: 1.164 L/kg  <===========
SMILES : CCCCCCCCCCO
CHEM  :
MOL FOR: C10 H22 O1	Domain evaluation	MW (Training set)
MOL WT : 158.29	ID	665.02
-------------------------------------
Experimental Database Structure Match:
Name    : 1-DECANOL
CAS Num : 000112-30-1
Exp LogKoc: 2.59
Exp Ref : Schuurmann,G et al (2006)
--------------------------- KOCWIN v2.00 Results ---------------------------
Koc Estimate from MCI:
---------------------
First Order Molecular Connectivity Index ........... : 5.414
Non-Corrected Log Koc (0.5213 MCI + 0.60) .......... : 3.4222
Fragment Correction(s):		Training set
1  Aliphatic Alcohol (-C-OH) ........... : -1.3179	ID	1
Corrected Log Koc .................................. : 2.1043
Estimated Koc: 127.1 L/kg  <===========
Koc Estimate from Log Kow:
-------------------------
Log Kow (experimental DB) ......................... : 4.57
Non-Corrected Log Koc (0.55313 logKow + 0.9251) .... : 3.4529
Fragment Correction(s):
1  Aliphatic Alcohol (-C-OH) ........... : -0.4114
Corrected Log Koc .................................. : 3.0415
Estimated Koc: 1100 L/kg  <===========
SMILES : CCCCCCCCO
CHEM  :
MOL FOR: C8 H18 O1	Domain evaluation	MW (Training set)
MOL WT : 130.23	ID	665.02
-------------------------------------
Experimental Database Structure Match:
Name    : 1-OCTANOL
CAS Num : 000111-87-5
Exp LogKoc: 1.56
Exp Ref : Schuurmann,G et al (2006)
--------------------------- KOCWIN v2.00 Results ---------------------------
Koc Estimate from MCI:
---------------------
First Order Molecular Connectivity Index ........... : 4.414
Non-Corrected Log Koc (0.5213 MCI + 0.60) .......... : 2.9009
Fragment Correction(s):		Training set
1  Aliphatic Alcohol (-C-OH) ........... : -1.3179	ID	1
Corrected Log Koc .................................. : 1.5830
Estimated Koc: 38.28 L/kg  <===========
Koc Estimate from Log Kow:
-------------------------
Log Kow (experimental DB) ......................... : 3.00
Non-Corrected Log Koc (0.55313 logKow + 0.9251) .... : 2.5845
Fragment Correction(s):
1  Aliphatic Alcohol (-C-OH) ........... : -0.4114
Corrected Log Koc .................................. : 2.1730
Estimated Koc: 149 L/kg  <===========
SMILES : CCCCCCCCOP(O)(O)=O
CHEM  :
MOL FOR: C8 H19 O4 P1	MW (Training set)
MOL WT : 210.21	665.02
--------------------------- KOCWIN v2.00 Results ---------------------------
Koc Estimate from MCI:
---------------------
First Order Molecular Connectivity Index ........... : 6.061
Non-Corrected Log Koc (0.5213 MCI + 0.60) .......... : 3.7592
Fragment Correction(s):	Training set
*  OrganoPhosphorus [P=O], aliphatic ..... : -1.4940	1
Corrected Log Koc .................................. : 2.2653
Estimated Koc: 184.2 L/kg  <===========
Koc Estimate from Log Kow:
-------------------------
Log Kow (Kowwin estimate) ......................... : 2.72
Non-Corrected Log Koc (0.55313 logKow + 0.9251) .... : 2.4296
Fragment Correction(s):
*  OrganoPhosphorus [P=O], aliphatic ..... : 0.1033
Corrected Log Koc .................................. : 2.5330
Estimated Koc: 341.2 L/kg  <===========

Validity criteria fulfilled:

not applicable

Conclusions:

Using the MCI (Molecular Connectivity Index) approach of the KOCWIN v2.00 program (EPI Suite v4.11), the estimated log Koc of the individual constituents ranged from 38 to 80050 L/kg, leading to a weighted average Koc value of 30423.56 L/kg (or log Koc: 4.48).

Executive summary:

The soil adsorption coefficient (Koc) value for the test substance, mono- and di- C8-10 PSE, was estimated using the MCI (Molecular Connectivity Index) approach of the KOCWIN v2.00 program of EPI Suite v4.11. Since the test substance is a UVCB with similar constituents varying mainly in carbon chain lengths, the Koc values were estimated for the individual components followed by the determination of an overall weighted-average value using the mole fractions of all the individual components. SMILES codes were used as the input parameter for the log Koc estimation for the individual constituents. The estimated log Koc of the individual constituents ranged from 38 to 80050 L/kg, leading to a weighted average Koc value of 30423.56 L/kg (or log Koc: 4.48) (US EPA, 2018). This indicates moderate sorption to soil /sediment, or slow migration to ground water (US EPA, 2012).The estimates for the major constituents are considered to be reliable, as they fall within of the applicability domain.

Description of key information

Using the MCI (Molecular Connectivity Index) approach of the KOCWIN v2.00 program (EPISuite v4.1), the estimated log Koc of the individual constituents ranged from 38 to 80050 L/kg, leading to a weighted average Koc value of 30423.56 L/kg (or log Koc: 4.48).

Key value for chemical safety assessment

Koc at 20 °C:

30 423.56

Additional information

The soil adsorption coefficient (Koc) value for the test substance, mono- and di- C8-10 PSE, was estimated using the MCI (Molecular Connectivity Index) approach of the KOCWIN v2.00 program of EPI Suite v4.11. Since the test substance is a UVCB with similar constituents varying mainly in carbon chain lengths, the Koc values were estimated for the individual components followed by the determination of an overall weighted-average value using the mole fractions of all the individual components. SMILES codes were used as the input parameter for the log Koc estimation for the individual constituents. The estimated log Koc of the individual constituents ranged from 38 to 80050 L/kg, leading to a weighted average Koc value of 30423.56 L/kg (or log Koc: 4.48) (US EPA, 2018). This indicates moderate sorption to soil /sediment, or slow migration to ground water (US EPA, 2012).The estimates for the major constituents are considered to be reliable, as they fall within of the applicability domain.

[LogKoc: 4.48]