Registration Dossier

Environmental fate & pathways

Hydrolysis

Currently viewing:

Administrative data

Link to relevant study record(s)

Description of key information

The hydrolysis as a function of pH of the test item 4-METHYL-3-THIOSEMICARBAZIDE was assessed according to the OECD guideline 111. According to the results of this study, 4-METHYL-3-THIOSEMICARBAZIDE can be considered as stable at pH 7 and pH 1.2 and unstable at pH 4 and 9. However, due to unexpected results obtained at the tested temperatures, it was not possible to extrapolate half-lives at 25 °C. These unexpected results may be explained by decomposition due to another phenomenon than hydrolysis, as e.g. thermic decomposition. As a consequence, the stability of the substance in water is not well defined.

Key value for chemical safety assessment

Additional information

The hydrolysis as a function of pH of the test item 4-METHYL-3-THIOSEMICARBAZIDE was assessed according to the OECD guideline 111. The objective of the study was to determine the rate of hydrolysis of the 4-METHYL-3-THIOSEMICARBAZIDE in different buffers and at different temperatures.

 

A first preliminary test showed that the test item was stable at pH 1.2, but unstable at pH 4, 7 and 9. However the hydrolysis at pH 7 was not confirmed in the corresponding definitive test.

Thus a second preliminary test was performed that confirm stability at pH 1.2 and 7, and decomposition at pH 4 and 9. Definitive tests were thus conducted at pH 4 and 9, at three temperatures: 15, 37 and 50 °C. Hydrolysis of the test item (1050 mg/L solution) was conducted in order to obtain an hydrolysis rate between 20 and 70 %.

 

At pH 4 and 50 °C, 49.4 % hydrolysis was observed after 31 days. For the other temperatures, after 31 days, 54.3 % of the test item was hydrolyzed at 37 °C and 6.6 % at 15 °C.

 

At pH 9, within 31 days, 49 % of the test item was hydrolyzed at 15 °C, 32 % at 37°C and 35 % at 50 °C.

 

Following table shows the half-life times calculated for4-METHYL-3-THIOSEMICARBAZIDE at pH 4 and 9 for the 3 temperatures tested. It was not possible to extrapolate half-lives at 25 °C, due to the results observed.

 

Half-lives of4-METHYL-3-THIOSEMICARBAZIDE at pH 4 and 9 according to the temperature

 

Temperature (°C)

pH 4: t1/2, h-1

pH 9: t1/2, h-1

15

7701

770

25

-

-

37

630

1386

50

990

1155

 

 

According to the results of this study, 4-METHYL-3-THIOSEMICARBAZIDE can be considered as stable at pH 7 and pH 1.2 and unstable at pH 4 and 9. How

due to unexpected results obtained at the tested temperatures, it was not possible to extrapolate half-lives at 25 °C.These unexpected results may be explained by decomposition due to another phenomenon than hydrolysis, as e.g. thermic decomposition.