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Water solubility

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water solubility
Type of information:
experimental study
Adequacy of study:
key study
Study period:
May 2015 - June 2015
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
according to guideline
OECD Guideline 105 (Water Solubility)
GLP compliance:
yes (incl. QA statement)
Type of method:
flask method
Water solubility:
< 0.05 mg/L
Conc. based on:
test mat.
20 °C
Details on results:
The results represents the mean value taken from four measurements.
The water solubilty of MBTS was determined to be <0.05 mg/L.
Executive summary:

The water solubility of Rubator MBTS in demineralized water was investigated by the flask method according to guideline OECD 105. A value of the water solubility was determined via HPLC to be <0.05 mg/L at 20°C at a pH = 5 (Currenta 2015).

Description of key information

MBTS is expected to be insoluble in water at pH 7 due to big molecule and

negligible dissociation constant. Indeed, an experimental study performing the flask method in combination with HPLC analytics according to OECD guideline 105 showed a poor water solubility of <0.05 mg/L at 20 °C and a pH = 5 (Currenta, 2015). The manufacture information from Bayer (1993) , Lanxess (2007) and General Quimica (2007) further support this very low value with a water solubility of MBTS smaller than 0.2 mg/l at 20°C.

Key value for chemical safety assessment

Water solubility:
0.05 mg/L
at the temperature of:
20 °C

Additional information

The experimentally confirmed poor water solubility of MBTS of <0.05 mg/L at 20 °C (Currenta 2015) is further supported by the information from other resources, such as:

- estimated value of 0.27- 0.37 mg/L at 25°C and pH = 7 using WSKOW, v. 1.41 (Currenta, 2010)

- expert judgment according to rather big molecule and negligible dissociation constant at environmentally relevant pH (i.e. pH of 5-9): insoluble at pH 7 and room temperature

- peer-reviewed literatures: Merck Index (2009) and NIOSH (1997) reported MBTS as insoluble

- observations from ecotoxicity studies: precipitation and cloudiness in test solutions of MBTS in water and actual concentrations below detection limit (<0.3 mg/L).

In contrast, Monsanto (1980) using column elution method reported a water solubility of MBTS in the range of 49-88 mg/L at 22°C. This result does not match with information from any other resources and considered as doubtful according to expert judgment; and hence will not be taken into account for further assessment.