Calcium 1,4-bis(2-ethylhexyl) bis(2-sulphosuccinate)

Melting point / freezing point

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

melting point/freezing point

Type of information:

(Q)SAR

Adequacy of study:

key study

Study period:

May 2018

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:

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

Qualifier:

no guideline followed

Principles of method if other than guideline:

Within the US EPA EPI Suite MPBPWIN v.143 model, MPBPWIN estimates melting point by two different methods.  The first is an adaptation of the Joback group contribution method for melting point (Joback, 1982; Reid et al; 1987) and the second is a simple Gold and Ogle method suggested by Lyman (1985).

The original Joback methodology used a data set of 388 compounds to derive 41 chemical structure group descriptors via multiple linear regression (Joback, 1982).  The Joback adaptation in MPBPWIN is an extension of the original method to include the same groups as in the adapted Stein and Brown boiling point method (see Boiling Point).  In addition, MPBPWIN also uses melting point correction factors for specific structures. Appendix F contains a complete list the group descriptors and coefficient values.

The second estimation method (Gold and Ogle, 1969), simply relates melting point (Tm) to boiling point (Tb) as follows (both values in K):

Tm  =  0.5839 Tb

MPBPWIN averages the adapted Joback and the Gold and Ogle estimates and reports the average estimate as well as both individual estimates.

MPBPWIN then goes one step further.  It reports a "suggested" melting point (MP) that is based upon the two individual estimates and several criteria.  First, MPBPWIN looks at the difference between the two estimates.  If the difference is small (< 30 K), the suggested MP is simply the average.  When this criteria fails (which occurs quite often), MPBPWIN examines the structure type and the magnitude of the difference.  It then decides which estimate is more likely to be accurate and "weights" the suggested MP accordingly.  For example, when MPBPWIN detects an amino-acid structure, it uses a 75% weighting factor for the higher estimate and 25% for the lower estimate to derive the suggested MP.  Weighting factors in MPBPWIN were approximated through observation of estimated versus experimental MP.

The adapted Joback method can significantly over-estimate MP for some structures.  A similar error occurs in the Stein and Brown (1994) boiling point method (when BP > 500 K) before a  quadratic or linear equation corrects the error.  This type of correction was not developed for MPBPWIN.  Instead, MPBPWIN applies a "cut-off" MP at approximately 350 deg C; that is, any MP estimate above 350 deg C is reduced to 350 deg C.  When MPBPWIN detects a large difference between a very high adapted Joback estimate and a much lower Gold and Ogle estimate, it usually weights the suggested MP strongly to the Gold and Ogle estimate (again, it depends on structure).  When used alone, the adapted Joback MP method can be very inaccurate for some structures (usually by estimating too high).  The simplistic Gold and Ogle method is also inaccurate for various structures.  However, when combined in the MPBPWIN format, estimation accuracy  improves significantly for very large, diverse datasets.

GLP compliance:

no

Type of method:

other: QSAR Prediction (MPBPWIN v1.43)

Specific details on test material used for the study:

The following SMILES string was used as input to the MPBPWIN v1.43 model for predicting the melting point of Docusate Calcium:
[Ca]CCCCC(CC)COC(=O)CC(C(=O)OCC(CC)CCCC)S([O-])(=O)=OCCCCC(CC)COC(=O)CC(C(=O)OCC(CC)CCCC)S([O-])(=O)=O

Key result

Melting / freezing pt.:

ca. 349.8 <= °C

Decomposition:

no

Decomp. temp.:

> °C

Conclusions:

The melting point of docusate calcium is predicted to be 349.8°C

Executive summary:

The US EPA EPI Suite QSAR model software package (MPBPWIN v.143) was used to predict the melting point of docusate calcium.

The following SMILES string was used as input to the model:

[Ca]CCCCC(CC)COC(=O)CC(C(=O)OCC(CC)CCCC)S([O-])(=O)=OCCCCC(CC)COC(=O)CC(C(=O)OCC(CC)CCCC)S([O-])(=O)=O

The melting point of the substance is predicted to be 349.8°C

Reference 2

Endpoint:

melting point/freezing point

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 102 (Melting point / Melting Range)

Principles of method if other than guideline:

The test is conducted in accordance with the procedure described in EU Regulation (EC) 440/2008, Annex Part A test A.1 and OECD Test Guideline 102 - Differential Scanning Calorimetry (DSC)

GLP compliance:

no

Type of method:

differential scanning calorimetry

Specific details on test material used for the study:

Batch FPAC1822263.
Substance tested is a 56%wt solution of calcium docusate in corn oil. Attempts were made to obtain neat/pure test material but the substance is extremely difficult to handle in the neat form. The form of the substance tested reflects how the substance will be supplied and placed on the market.

Key result

Melting / freezing pt.:

ca. -14 °C

Atm. press.:

ca. 101 kPa

Decomposition:

no

Remarks on result:

other: The first endothermic event starting at approximately -14°C which is the melting/freezing point of the test item which correlates with the melting/freezing point value for pure corn oil (-11°C to -8°C)*

Melting / freezing pt.:

ca. 224 °C

Atm. press.:

ca. 101 kPa

Decomposition:

no

Remarks on result:

other: The second endothermic event started at 224°C which correlates well with smoke point data for pure corn oil (230 -238°C)

Atm. press.:

ca. 101 kPa

Decomposition:

yes

Decomp. temp.:

339 °C

Remarks on result:

other: The third exothermic event started at 339°C which is assumed to be the onset of decomposition of the test item (docusate calcium and/or corn oil)

Three transition events were detected in the test item DSC thermograms.

The first was an endothermic event starting at approximately -14°C which is the melting/freezing point of the test item which correlates with the melting/freezing point value for pure corn oil (-11°C to -8°C)*

The second endothermic event started at 224°C which correlates well with smoke point data for pure corn oil (230 -238°C)*

The third exothermic event started at 339°C which is assumed to be the onset of decomposition of the test item (docusate calcium and/or corn oil).

*Ullmans encyclopedia of industrial chemistry Vol A 10, Fats and Oils VCH Weinheim 1995 and Baileys industrial oil & fat products, 6th Edition 2005, Wiley-Interscience New York.

Conclusions:

According to the DSC method, the melting/freezing point of the test item was determined to be -14°C which is attributed to corn oil, not calcium docusate (which is solid at ambient temperature). Due to the nature of the sample tested (56% w/w docusate calcium in corn oil) it was not possible to determine an accurate freezing/melting temperature of the registered substance.

Executive summary:

A melting point test for Docusate Calcium (56% w/w in corn oil) was conducted in accordance with the procedure described in EU Regulation (EC) 440/2008, Annex Part A test A.1 and OECD Test Guideline 102 (DSC method)

According to the DSC method, the melting/freezing point of the test item was determined to be -14°C which is attributed to the corn oil present in the sample and not calcium docusate (which is a solid at ambient temperature). Due to the nature of the sample tested (56% w/w docusate calcium in corn oil) it was not possible to determine an accurate freezing/melting temperature of the registered substance. This information is therefore considered as supplementary and cannot be taken as a reliable result which reflects the true melting/freezing point of the registered substance.

Description of key information

A melting point test for Docusate Calcium (56% w/w in corn oil) was conducted in accordance with the procedure described in EU Regulation (EC) 440/2008, Annex Part A test A.1 and OECD Test Guideline 102 (DSC method)

According to the DSC method, the melting/freezing point of the test item was determined to be -14°C which is attributed to the corn oil present in the sample and not calcium docusate (which is a solid at ambient temperature). Due to the nature of the sample tested (56% w/w docusate calcium in corn oil) it was not possible to determine an accurate freezing/melting temperature of the registered substance. This information is therefore considered as supplementary and cannot be taken as a reliable result which reflects the true melting/freezing point of the registered substance.

In the absence of reliable experimental data QSAR has been used to determine a predicted melting point value for the registered substance. The melting point of the substance is predicted to be 349.8°C. This predicted value is selected as the key study for this endpoint.

Key value for chemical safety assessment

Melting / freezing point at 101 325 Pa:

349.8 °C

Additional information

The US EPA EPI Suite QSAR model software package (MPBPWIN v.143) was used to predict the melting point of docusate calcium.

The following SMILES string was used as input to the model:

[Ca]CCCCC(CC)COC(=O)CC(C(=O)OCC(CC)CCCC)S([O-])(=O)=OCCCCC(CC)COC(=O)CC(C(=O)OCC(CC)CCCC)S([O-])(=O)=O