Tetramethylthiuram monosulphide

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2013

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
Not applicable

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

I - Preliminary assay at 50°C and pH 4, 7 and 9

Sampling and analytical assays were performed at T0 and 5 days later.

II - Definitive assay at 15, 37 and 50°C and pH 4, 7 and 9

15°C / pH 4, 7 and 9: samplings at 0, 292, 528, 624, 696, 790 and 865 hours
37°C / pH 4, 7 and 9: samplings at 0, 236, 330, 402, 496, 571 and 667 hours
50°C / pH 4, 7 and 9: samplings at 0, 68, 96, 140, 168, 236 and 310 hours

Buffers:

I - Preparation of the buffer solution for the abiotic hydrolysis

0.1 N sodium hydroxide: in a 1-L volumetric flask, a quantity 4.0 g (to the nearest 0.01 g) of sodium hydroxide was weighed and the volume was made up with HPLC water.

Buffer pH 4
In a 500-mL volumetric flask, a quantity of 10.2 g (to the nearest 0.01 g) of potassium hydrogeno-phthalate was weighed and the volume was made up with HPLC water. A volume of 4 mL of a sodium hydroxide 0.1N solution was transferred into a 1-L volumetric flask. A volume of 500 mL of the potassium hydrogeno-phthalate solution was added. The volumetric flask was shaken, made up to volume with water and the pH was verified.

Buffer pH 7.0
In a 500-mL volumetric flask, a quantity of 6.8 g (to the nearest 0.01 g) of potassium dihydrogen phosphate was weighed and the volume was made up with HPLC water. A volume of 296 mL of a sodium hydroxide 0.1N solution was transferred into a 1-L volumetric flask. A volume of 500 mL of the potassium dihydrogen phosphate solution was added. The volumetric flask was shaken, made up to volume with water and the pH was verified.

Buffer pH 9.0
In a 500-mL volumetric flask, quantities of 3.8 g (to the nearest 0.01 g) of potassium chloride and 3.1 g (to the nearest 0.01 g) of boric acid was weighed and the volume was made up with HPLC water. A volume of 213 mL of a sodium hydroxide 0.1N solution was transferred into a 1-L volumetric flask. A volume of 500 mL of the boric acid solution was added. The volumetric flask was shaken, made up to volume with water and the pH was verified.

II - Preparation of the reference item solutions for the calibration

A quantity of 50 mg of the test item was weighed (to the nearest 0.01 mg) into a 50-mL volumetric flask and the volume was made up with acetonitrile. This solution was diluted 100 fold in a mixture of acetonitrile/water 9/1. The obtained solution was diluted 1.33, 2, 4 and 10 fold with a mixture of acetonitrile/water 9/1 in order to obtain the calibration solutions.

III - Preparation of the abiotic degradation solutions for the preliminary test

A quantity of 10 mg of the test item was weighed (to the nearest 0.01 mg) into a 100-mL volumetric flask and the volume was made up with the corresponding buffer solution. This solution was treated with ultrasounds for 10 minutes and manually shaken until complete dissolution. An aliquot was diluted 10 fold with acetonitrile for the analysis at T = 0 and the rest of the solution was transferred into a 60-mL glass flask which was placed into a thermostated oven at 50.0 °C +/- 0.5 °C during 5 days. After this time, the solution was cooled at room temperature and diluted 10 fold with acetonitrile for the analysis at T = 5 days. Two flasks were prepared for each pH solution.

IV - Preparation of the abiotic degradation solutions for the main test

A quantity of 10 mg of the test item was weighed (to the nearest 0.01 mg) into a 100-mL volumetric flask and the volume was made up with the corresponding buffer. This solution was treated with ultrasounds for 10 minutes and manually agitated until complete dissolution. The solution was diluted 10 fold with acetonitrile for the analysis at T = 0. Volumes of 5 mL of the solution were transferred into test tubes previously heated at 100 °C for one night to be sterilized, and placed into a thermostated oven at 15.0 °C +/- 0.5 °C. For each analysis time, the test tube was put at room temperature and diluted 10 fold with acetonitrile. Two flasks were prepared for each pH.

The same preparations were made and put into a water bath at 37.0 °C +/- 0.5 °C and into a thermostated oven at 50.0 °C +/- 0.5 °C. Two flasks were prepared for each pH and for each temperature.

Details on test conditions:

See the "details on sampling" section

Number of replicates:

Two replicates per temperature and per pH were used.

Positive controls:

no

Negative controls:

no

Preliminary study:

Hydrolysis at pH 4 at 50°C after 5 days: 35.2%
Hydrolysis at pH 7 at 50°C after 5 days: 24.4%
Hydrolysis at pH 9 at 50°C after 5 days: 24.4%

Test performance:

None.

Transformation products:

not specified

Details on hydrolysis and appearance of transformation product(s):

Not available

Key result

pH:

4

Temp.:

25 °C

Hydrolysis rate constant:

0 h-1

DT50:

146 d

Type:

(pseudo-)first order (= half-life)

Key result

pH:

7

Temp.:

25 °C

Hydrolysis rate constant:

0 h-1

DT50:

184.3 d

Type:

(pseudo-)first order (= half-life)

Key result

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

0 h-1

DT50:

237.3 d

Type:

(pseudo-)first order (= half-life)

Other kinetic parameters:

None.

Details on results:

Not available

Validity criteria fulfilled:

yes

Conclusions:

Half-life of TMTM at 25°C was 146, 184 and 237 days at pH 4, 7 and 9 respectively.

Executive summary:

Hydrolysis of TMTM was investigated at pH 4, 7 and 9. The preliminary experiment performed at 50°C for 5 days indicated that hydrolysis of TMTM was superior to 10% at all pH. Therefore, the half-life was investigated at all the three pH. The experiment was performed in duplicate. Half-life of TMTM at 25°C was 146, 184 and 237 days at pH 4, 7 and 9 respectively.

Key value for chemical safety assessment

Half-life for hydrolysis:

184 d

at the temperature of:

25 °C

Additional information

Hydrolysis of TMTM was investigated at pH 4, 7 and 9. The preliminary experiment performed at 50°C for 5 days indicated that hydrolysis of TMTM was superior to 10% at all pH. Therefore, the environmental half-life was investigated at all the three pH. The experiment was performed in duplicate. Half-life of TMTM at 25°C was 146, 184 and 237 days at pH 4, 7 and 9 respectively.