Benzenamine, N-phenyl-, styrenated

Water solubility

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2005-08-22 - 2005-10-24

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Version / remarks:

1995

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Version / remarks:

EC Directive 92/69 Method A.6 (1992)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

column elution method

Key result

Water solubility:

20.6 µg/L

Conc. based on:

test mat.

Remarks:

p-SDPA

Incubation duration:

2 d

Temp.:

20 °C

pH:

7

Key result

Water solubility:

< 58.8 µg/L

Conc. based on:

test mat.

Remarks:

p,p’-diSDPA

Incubation duration:

2 d

Temp.:

20 °C

pH:

7

Remarks on result:

not determinable

Remarks:

solubility was below the limit of quantification

Key result

Water solubility:

< 27.6 µg/L

Conc. based on:

test mat.

Remarks:

o,p,p’-triSDPA

Incubation duration:

2 d

Temp.:

20 °C

pH:

7

Remarks on result:

not determinable

Remarks:

solubility was below the limit of quantification

Details on results:

Method Validation
Linearity: The analytical system gave linear response in the range of 7.87 – 236 μg/L for p-SDPA, 49.0 - 1469 μg/L for p,p’-diSDPA and 23.0 - 691 μg/L for o,p,p’-triSDPA. Linearity R² was determined to be 0.9999 for p-SDPA , 1.0000 for p,p’-diSDPA and 0.9998 for o,p,p’-triSDPA
Accuracy, Precision: Response of blind values of test medium control samples was lower than 30 % of the LOQ.
Solubility Results: A pH value of 7 was measured for all samples. The Tyndall effect (check for colloidal matter) was negative for all samples.
Validity Criteria: The validity criteria were fulfilled according to the guideline:
Repeatability: The test item concentrations of all five consecutive fractions were constant within ± 30 %. The mean values obtained from two tests with different flow rate did not differ by more than 30 %.
Sensitivity: A HPLC method with a LOQ of 9.44, 58.8 and 27.6 μg/L, respectively, was used.

Conclusions:

The water solubility was determined according to a scientifically valid method, i.e. OECD TG 105 under GLP, in a well-documented study, the validity criteria were met, hence, the results for the test material can be considered as reliable. The test item consists of three component groups, mono-, di- and tri-styrenated diphenylamines (SDPA, diSDPA, triSDPA). For every group the major component was quantified as an acceptable value of the solubility of the whole component group.
The water solubility of the components of the test item was determined to be 20.6 μg/L for p-SDPA, < 58.8 μg/L (< LOQ) for p,p’-diSDPA, < 27.6 μg/L (< LOQ) for o,p,p’-triSDPA at 20 °C and a pH value of 7. As the water solubility decreases with an increasing number of styrene groups due to an increasing lipophilicity (estimation based on structure), it can be concluded that the actual water solubility of p,p’-diSDPA and o,p,p’-triSDPA would be way lower than their limit of quantification. So it can be reasonably concluded that the water solubility of the whole test item would be below 0.1 mg/l.

Executive summary:

The water solubility of styrenated diphenylamine using the column elution method was determined at 20 ± 0.5 °C according to OECD 105 and EC Directive 92/69 A.6 under GLP. Analyses were performed using HPLC-UV with a diode array detector (DAD). The water solubility was determined for the three component classes of the test item, mono-styrenated diphenylamines (SDPA), di-styrenated diphenylamines (diSDPA) and tri-styrenated diphenylamines (triSDPA). The classes were quantified by their major components, p-SDPA for mono-styrenated diphenylamines, p,p’-diSDPA for di-styrenated diphenylamines and o,p,p’-triSDPA for tri-styrenated diphenylamines. pH values were measured with indicator sticks. All sample were checked for colloidal material using the Tyndall effect. The water solubility of the components of the test item was determined to be

20.6 μg/L for p-SDPA

< 58.8 μg/L (< LOQ) for p,p’-diSDPA

< 27.6 μg/L (< LOQ) for o,p,p’-triSDPA

at 20 °C and a pH value of 7.

Reference 2

Endpoint:

water solubility

Type of information:

(Q)SAR

Adequacy of study:

supporting 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:

SOFTWARE
EPIWIN software by US-EPA

2. MODEL (incl. version number)
WATERNT v1.01 and WSKOW v1.42

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
p-SDPA: c1(C(C)c2ccc(Nc3ccccc3)cc2)ccccc1
p,p'-diSDP: c1(Nc4ccc(C(C)c3ccccc3)cc4)c(C(C)c2ccccc2)cccc1
o,p,p'-triSDPA: c1(Nc4ccc(C(C)c3ccccc3)cc4)c(C(C)c5ccccc5)cc(C(C)c2ccccc2)cc1

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
[Explain how the model fulfils the OECD principles for (Q)SAR model validation. Consider attaching the QMRF or providing a link]
- Defined endpoint: The models and the training and validation sets are published by US Environmental Protection Agency (USA). A complete description of the estimation methodology used by WSKOWWIN is available in two documents prepared for the U.S. Environmental Protection Agency, Office of Pollution Prevention and Toxics (Meylan and Howard, 1994a,b). A database of more than 8400 compounds with reliably measured log Kow values had already been compiled from available sources. Most experimental values were taken from a "star-list" compilation of Hansch and Leo (1985) that had already been critically evaluated (see also Hansch et al, 1995) or an extensive compilation by Sangster (1993) that includes many "recommended" values based upon critical evaluation. Other log Kow values were taken from sources located through the Environmental Fate Data Base (EFDB) system (Howard et al, 1982, 1986). A few values were taken from Section 4a, 8d, and 8e submissions the to U.S. EPA under the Toxic Substances Control Act (see http://www.syrres.com/esc/tscats_info.htm).
Water solubilities were collected from the AQUASOL dATAbASETM of the University of Arizona (Yalkowsky and Dannenfelser, 1990), Syracuse Research Corporation's PHYSPROP© Database (SRC,1994), and sources located through the Environmental Fate Data Base (EFDB) system (Howard et al, 1982, 1986). Water solubilities were primarily constrained to the 20-25oC temperature range with 25oC being preferred.

- Unambiguous algorithm:
WATERNT uses a "fragment constant" methodology to predict water solubility. In a "fragment constant" method, a structure is divided into fragments (atom or larger functional groups) and coefficient values of each fragment or group are summed together to yield the solubility estimate. We call WATERNTs methodology the Atom/Fragment Contribution (AFC) method. Coefficients for individual fragments and groups in WATERNT were derived by multiple regression of 1000 reliably measured water solubility values.
To estimate water solubility, WATERNT initially separates a molecule into distinct atom/fragments. In general, each non-hydrogen atom (e.g. carbon, nitrogen, oxygen, sulfur, etc.) in a structure is a "core" for a fragment; the exact fragment is determined by what is connected to the atom. Several functional groups are treated as core "atoms"; these include carbonyl (C=O), thiocarbonyl (C=S), nitro (-NO2), nitrate (ONO2), cyano (-C/N), and isothiocyanate (-N=C=S). Connections to each core "atom" are either general or specific; specific connections take precedence over general connections. For example, aromatic carbon, aromatic oxygen and aromatic sulfur atoms have nothing but general connections; i.e., the fragment is the same no matter what is connected to the atom. In contrast, there are 5 aromatic nitrogen fragments: (a) in a five-member ring, (b) in a six-member ring, (c) if the nitrogen is an oxide-type {i.e. pyridine oxide}, (d) if the nitrogen has a fused ring location {i.e. indolizine}, and (e) if the nitrogen has a +5 valence {i.e. N-methyl pyridinium iodide}; since the oxide-type is most specific, it takes precedence over the other four. The aliphatic carbon atom is another example; it does not matter what is connected to -CH3, -CH2-, or -CH< , the fragment is the same; however, an aliphatic carbon with no hydrogens has two possible fragments: (a) if there are four single bonds with 3 or more carbon connections and (b) any other not meeting the first criteria.
It became apparent, for various types of structures, that water solubility estimates made from atom/fragment values alone could or needed to be improved by inclusion of substructures larger or more complex than "atoms"; hence, correction factors were added to the AFC method. The term "correction factor" is appropriate because their values are derived from the differences between the water solubility estimates from atoms alone and the measured water solubility values. The correction factors have two main groupings: first, factors involving aromatic ring substituent positions and second, miscellaneous factors. In general, the correction factors are values for various steric interactions, hydrogen-bondings, and effects from polar functional substructures. Individual correction factors were selected through a tedious process of correlating the differences (between solubility estimates from atom/fragments alone and measured solubility values) with common substructures.
Results of two successive multiple regressions (first for atom/fragments and second for correction factors) yield the following general equation for estimating water solubility of any organic compound:
log WatSol (moles/L) = Σ(fi * ni) + Σ(cj * nj) + 0.24922
(n = 1128, correlation coef (r2) = 0.940, standard deviation = 0.537, avg deviation = 0.355)
where Σ(fi * ni) is the summation of fi (the coefficient for each atom/fragment) times ni (the number of times the atom/fragment occurs in the structure) and Σ(cj * nj) is the summation of cj (the coefficient for each correction factor) times nj (the number of times the correction factor is applied in the molecule).

For WSKOWWIN, a dataset of 1450 compounds (941 solids, 509 liquids) having reliably measured water solubility, log Kow and melting point was used as the training set for developing the new estimation algorithms for water solubility. Standard linear regressions were used to fit water solubility (as log S) with log Kow, melting point and molecular weight.
Residual errors from the initial regression fit were examined for compounds sharing common structural features with relatively consistent errors. On that basis, 12 compound classes were initially identified and added to the regression to comprise a multi-linear regression including log Kow, melting point and/or molecular weight plus 12 correction factors. Each correction factor is counted a maximum of once per structure [if applicable], no matter how many times the applicable fragment occurs. For example, the nitro factor in 1,4-dinitrobenzene is counted just once. A compound either contains a correction factor or it doesn't; therefore, the matrix for the multi-linear regression contained either a 0 or 1 for each correction factor.
WSKOWWIN estimates water solubility for any compound with one of two possible equations. The equations are equations 19 and 20 from Meylan and Howard (1994a) or equations 11 and 12 from the journal article (Meylan et al., 1996). The equations are:
log S (mol/L) = 0.796 - 0.854 log Kow - 0.00728 MW + ΣCorrections
log S (mol/L) = 0.693 - 0.96 log Kow - 0.0092(Tm-25) - 0.00314 MW + ΣCorrections
(where MW is molecular weight, Tm is melting point (MP) in deg C [used only for solids]). When a measured MP is available, that equation is used; otherwise, the equation with just MW is used.

- Defined domain of applicability:
In WATERNT, the current fragment constants were developed almost entirely from a sub-set of the 1450 compound database used to train the WSKOWWIN program.
For WSKOWWIN, a dataset of 1450 compounds (941 solids, 509 liquids) having reliably measured water solubility, log Kow and melting point was used as the training set.
- Appropriate measures of goodness-of-fit and robustness and predictivity:
Training sets were chosen large enough, deviation from prediction with the training set are considered acceptable:
The WATERNT Program training set with 1128 compounds gave an equation for logWSolubility with r² = 0.940 resulted in a std dev = 0.537, acd dev = 0.355

The regression equations used by the WSKOWWIN program were trained with a dataset of 1450 compounds, equation for logSolubility with r² = 0.970 resulted in a std dev = 0.409, acd dev = 0.313
The WSKOWWIN estimation equations were initially validated on two datasets of compounds that were not included in the model training. A relatively small dataset was tested that consisted of 85 compounds having experimental log Kow values, but no available melting points. Many compounds in the 85 compound test set decompose before melting and would theoretically have very high melting points (e.g. amino acids and compounds having multiple nitrogens). The accuracy statistics for the equation used by WSKOWWIN are:
number 85
r2 0.865
std deviation 0.961
avg deviation 0.714
A much larger dataset of 817 compounds was also tested. All 817 compounds had experimental melting points, but none of the 817 compounds had a reliable experimental log Kow. The log Kow values used for the validation-testing were estimated (primarily using the KOWWIN program available at that time); therefore, the water solubility estimates are based on estimates for log Kow. Typically, estimates based on estimates reduce estimation accuracy, but this type of validation can provide insight into the ability of the method. The accuracy statistics for this dataset are:
number 817
r2 0.902
std deviation 0.615
avg deviation 0.480


5. APPLICABILITY DOMAIN
The intended application domain is organic chemicals. Inorganic and organometallic chemicals generally are outside the domain.

In WATERNT, the minimum and maximum values for molecular weight are the following:

Training Set Molecular Weights:
Minimum MW: 30.30 (formaldehyde)
Maximum MW: 627.62 (hexabromobiphenyl)
Average MW: 187.73

Training Set Water Solubility Ranges:
Minimum Solubility (mg/L): 0.0000004 (octachlorodibenzo-p-dioxin)
Minimum Solubility (log moles/L): -12.0605 (octachlorodibenzo-p-dioxin)
Maximum Solubility (mg/L): miscible (various)
Maximum Solubility (log moles/L): 1.3561 (acetaldehyde)

Regarding the estimation domain, the WSKOWWIN program applies an individual correction factor only once per structure [if at all] regardless of how many instances of the applicable structural feature occur in the structure. The minimum number of instances is zero and the maximum is one.

Range of water solubilities in the Training set:
Minimum = 4 x 10-7 mg/L (octachlorodibenzo-p-dioxin)
Maximum = completely soluble (various)

Range of Molecular Weights in the Training set:
Minimum = 27.03 (hydrocyanic acid)
Maximum = 627.62 (hexabromobiphenyl)

Range of Log Kow values in the Training set:
Minimum = -3.89 (aspartic acid)
Maximum = 8.27 (decachlorobiphenyl)

Currently there is no universally accepted definition of model domain. However, users may wish to consider the possibility that water solubility estimates are less accurate for compounds outside the MW range of the training set compounds, and/or that have more instances of a given fragment than the maximum for all training set compounds. It is also possible that a compound may have a functional group(s) or other structural features not represented in the training set, and for which no fragment coefficient was developed. These points should be taken into consideration when interpreting model results.

- Similarity with analogues in the training set:
The following information is available on the three representative structures
p-SDPA: MW = 273.38 g/mol, logPow = 5.45 (estimated, KOWWIN Program (v1.68)), water solubility = 0.047109 mg/L (estimated, WATERNT) / 0.3889 mg/L (estimated, WSKOWWIN); Log Water Sol = -6.7637 moles/L (estimated, WATERNT) / -5.847 moles/L (estimated, WSKOWWIN)
p,p’-diSDPA: MW = 377.53 g/mol, logPow = 7.61 (estimated, KOWWIN Program (v1.68)), water solubility = 3.4684e-005 mg/L (estimated, WATERNT) / 0.001348 mg/L (estimated, WSKOWWIN); Log Water Sol = -10.0368 moles/L (estimated, WATERNT) / -8.447 moles/L (estimated, WSKOWWIN)
o,p,p’-triSDPA: MW = 481.69 g/mol, logPow = 9.76 (estimated, KOWWIN Program (v1.68)), water solubility = 4.8169e-007 mg/L (estimated, WATERNT) / 4.319e-006 mg/L (estimated, WSKOWWIN); Log Water Sol = -12.0000 moles/L (estimated, WATERNT) / -11.047 moles/L (estimated, WSKOWWIN)

So, all constituents fit in the validated molecular weight range of both models. All structures are covered by the respective validation data sets. Also, the resulting estimated water solubilities of all components are covered by the values of the components used in the training set. Only the estimated logPow of o,p,p’-triSDPA, which is only relevant for the WSKOWWIN program, is with 9.96 slightly above the range of the domain (8.27). However it is recommended that users may wish to consider the possibility that water solubility estimates are less accurate for compounds outside the MW range, water solubility range and log Kow range of the training set compounds. Nevertheless a clear trend in water solubility changes with the amount of substitutions is evident.

6. ADEQUACY OF THE RESULT
The prediction fits is purpose to support the conclusions drawn from the experimentally derived values.

Guideline:

other: REACH guidance on QSARs Chapter R.6

Version / remarks:

May 2008

Principles of method if other than guideline:

Water solubility is estimated via 2 different models, WATERNT v1.01 ("fragment constant" methodology) and WSKOW v1.42, on representative structures of the registered substance.

GLP compliance:

no

Water solubility:

47.1 µg/L

Conc. based on:

other: p-SDPA

Remarks:

WATERNT

Temp.:

25 °C

Water solubility:

0.035 µg/L

Conc. based on:

other: p,p’-diSDPA

Remarks:

WATERNT

Temp.:

25 °C

Water solubility:

0 µg/L

Conc. based on:

other: o,p,p’-triSDPA

Remarks:

WATERNT

Temp.:

25 °C

Water solubility:

388.9 µg/L

Conc. based on:

other: p-SDPA

Remarks:

WSKOWWIN

Temp.:

25 °C

Water solubility:

1.348 µg/L

Conc. based on:

other: p,p’-diSDPA

Remarks:

WSKOWWIN

Temp.:

25 °C

Water solubility:

0.004 µg/L

Conc. based on:

other: o,p,p’-triSDPA

Remarks:

WSKOWWIN

Temp.:

25 °C

Conclusions:

The present entry describes a scientifically accepted calculation method for the water solubility of the single components (representative structures) of styrenated diphenylamine using the US-EPA software WATERNT v1.01 and WSKOW v1.42. No GLP criteria are applicable for the usage of this tool and the QSAR estimation is easily repeatable. The compounds fit into the validation data sets of the models. The result is adequate for the regulatory purpose. A clear decrease in water solubility is evident with an increasing number of styrene moieties present in the molecule.

Executive summary:

The water solubility of the single components (representative structures) of styrenated diphenylamine were estimated using the US-EPA software WATERNT v1.01 and WSKOW v1.42to:

Substance	p-SDPA	p,p’-diSDPA	o,p,p’-triSDPA
Molecular weight	273.38g/mol	377.53g/mol	481.69g/mol
Water solubility (WATERNT)	0.047109 mg/L	3.4684e-005 mg/L	4.8169e-007 mg/L
Water solubility (WSKOWWIN)	0.3889mg/L	0.001348 mg/L	4.319e-006 mg/L
Log Water solubility (WATERNT)	-6.7637 moles/L	-10.0368 moles/L	-12.0000moles/L
Log Water solubility (WSKOWWIN)	-5.847moles/L	-8.447 moles/L	-11.047 moles/L

A clear decrease in water solubility is evident with an increasing number of styrene moieties present in the molecule.

Description of key information

Water solubility: 20.6 μg/L for p-SDPA, < 58.8 μg/L (< LOQ) for p,p’-diSDPA, < 27.6 μg/L (< LOQ) for o,p,p’-triSDPA at 20 °C and a pH value of 7(OECD 105, GLP)

Water solubility: p-SDPA: 0.047109 mg/L (estimated,WATERNT) / 0.3889 mg/L (estimated, WSKOWWIN); p,p’-diSDPA: 3.4684e-005 mg/L (estimated,WATERNT) / 0.001348 mg/L (estimated, WSKOWWIN); o,p,p’-triSDPA: 4.8169e-007 mg/L (estimated, WATERNT) / 4.319e-006 mg/L (estimated, WSKOWWIN) (WATERNT v1.01 / WSKOW v1.42,EpiSuite estimation)

Key value for chemical safety assessment

Water solubility:

20.6 µg/L

at the temperature of:

20 °C

Additional information

There is one reliable experimental study available which addresses the fact that the registered substance styrenated diphenylamine is an UVCB, for which the single constituents however can be qualified and quantified. In general these constituents can be divided into mono-, di-, and tri-styrenated diphenylamines, for which of course several constitutional isomers exist. Due to the identical molecular weight and groups contained it can be reasonably concluded that the single components within the same subgroup to not differ substantially from each other. The single subgroups however do. In the available study, for every group the major component was hence quantified as an acceptable value of the solubility of the whole component group. The limit of quantification (LOQ) was fixed to 9.44 μg/L of p-SDPA, 58.8 μg/L of p,p’-diSDPA and 27.6 μg/L o,p,p’-triSDPA. The water solubility of the components of the test item was determined to be 20.6 μg/L for p-SDPA, < 58.8 μg/L (< LOQ) for p,p’-diSDPA, and < 27.6 μg/L (< LOQ) for o,p,p’-triSDPA at 20 °C and a pH value of 7.

So the only quantifiable value was 20.6 μg/L for p-SDPA. To determine to which extent the solubility values of p,p’-diSDPA and o,p,p’-triSDPA were below their respective LOQs, an additional QSAR estimation was performed on the three major components of the respective groups. The chosen models were WATERNT v1.01 and WSKOW v1.42(EpiSuite), the models were considered suitable for the substances. The following values were determined:

 

Substance	p-SDPA	p,p’-diSDPA	o,p,p’-triSDPA
Molecular weight	273.38g/mol	377.53g/mol	481.69g/mol
Water solubility (WATERNT)	0.047109 mg/L	3.4684e-005 mg/L	4.8169e-007 mg/L
Water solubility (WSKOWWIN)	0.3889mg/L	0.001348 mg/L	4.319e-006 mg/L

 

As obvious, the determined values in the individual models differ about one magnitude, however, the solubility determined by WATERNT for p-SDPA is with 47.1 µg/l in the same range as the experimentally determined value of20.6 μg/L. So the results determined with WATERNT can be considered as rather consistent with the experimental ones.

As further obvious from the results obtained with both QSAR models, the water solubility decreases with an increasing number of styrene groups due to an increasing lipophilicity (estimation based on structure), it can be concluded that the actual water solubility of p,p’-diSDPA and o,p,p’-triSDPA would be way lower than their limit of quantification. In fact, the solubility of p,p’-diSDPA is about two to three magnitudes below the one of p-SDPA, and the solubility of o,p,p’-triSDPA is again about two to three magnitudes below the one of p,p’-diSDPA and even five magnitudes below the one of p-SDPA. Hence, the contribution of the di-, and tri-styrenated diphenylamine sto the water solubility of the whole registered substance can be considered negligible and can be disregarded.

So it can be reasonably concluded that the water solubility of the whole test item would be below 0.1 mg/l. The key value for chemical safety assessment was chosen as 20.6 µg/l (from p-SDPA) as it is the only reliably experimentally determined value, and the values for the higher substituted components are expected to be magnitudes below that value and do hence not contributed in a relevant manner to the water solubility of the registered substance. The substance should be considered insoluble in water.