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Environmental fate & pathways

Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
February 2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Conducted according to OECD test guidelines and to GLP.
Qualifier:
according to
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
no
Principles of method if other than guideline:
Preliminary hydrolysis study only.
GLP compliance:
yes (incl. certificate)
Radiolabelling:
no
Analytical monitoring:
yes
Duration:
5 d
Temp.:
50
Preliminary study:
Upon review of the chromatography there was little, to no loss of substance at 50 deg C. If <10% hydrolysis is observed in the preliminary study the substance is considered stable, with an equivalent half life of >1 year at 25 deg C.
Transformation products:
not specified
% Recovery:
< 10
pH:
7
Temp.:
50 °C
Duration:
5 d
Key result
pH:
7
Temp.:
25 °C
DT50:
> 1 yr
Validity criteria fulfilled:
yes
Conclusions:
In a 5 day preliminary hydrolysis study, ZMB2 showed <10% hydrolysis with an equivalent half life of >1 year at 25 deg C. ZMB2, therefore, is not expected to hydrolyse within the environmental compartment.

Description of key information

In a 5 day preliminary hydrolysis study conducted according to OECD 111, ZMB2 showed <10% hydrolysis with an equivalent half life of >1 year at 25 deg C. ZMB2, therefore, is not expected to hydrolyse within the environmental compartment (Harlan Laboratories, 2013).

Key value for chemical safety assessment

Half-life for hydrolysis:
1 yr
at the temperature of:
25 °C

Additional information

When considering the results of the investigations carried out to support the read-across from 1,3-dihydro-4(or 5)-methyl-2H-benzimidazole-2-thione (MB2) to 2H-Benzimidazole-2-thione, 1,3-dihydro-4(or 5)-methyl-, zinc salt (2:1) (ZMB2) (LANXESS, 2018), the results of the hydrolysis as a function of pH study conducted with this substance must be reconsidered in light of new information.  The overall conclusion in LANXESS (2018) is that ZMB2 exhibits its salt characteristic in aqueous solution, i.e., dissolving in water to MB2 and zinc ions in a matter of seconds.  For full details of the investigations conducted relating to hydrolysis, refer to Section 13.2 of IUCLID.

In the HPLC-UV analysis performed in this study, a mobile phase consisting of acetonitrile:water (30:70 v/v) was applied. Under these aqueous conditions, based on the weight of evidence presented in this document, it is clear that ZMB2 will instantly dissociate to MB2 (LANXESS, 2018). Thus in this study it would not have been possible to detect ZMB2 in undissociated form, only MB2 was observable at pHs 4-9.