1,2,3-trichloropropane

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

The study followed the principles laid down in EU Method C.7 (Degradation - Abiotic degradation: Hydrolysis as a function of pH) with restrictions. However, the publicly available project summary does not contain all the relevant information and results. Therefore, the results are considered as reliable with restrictions.

Qualifier:

equivalent or similar to guideline

Guideline:

EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)

Principles of method if other than guideline:

Hydrolysis rates were measured under sterile conditions at precisely controlled temperatures and at pH levels of 3, 7 and 11. Conditions were adjusted to provide sufficiently precise rate constants.

GLP compliance:

not specified

Specific details on test material used for the study:

Source: Chem. Serv.
Purity: unknown

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

A typical hydrolysis experiment consisted of 5 to six ampules and the following steps: preparing a spiking solution of the substance, preparing buffer solutions, transferring spiked buffer to 15-mL Teflon lined screw cap or sealed ampules, monitoring degradation by sacrificing individual tubes and determining percentage of the substance remaining. Spiking solutions were prepared by dissolving substrate in water. The concentration was such that 0.1 mL diluted to 100 mL buffer gave a concentration of 0.00001 M or 50 % of the water solubility or less. Initial hydrolysis runs were performed at pH 3, 7 and 11 to set the pH conditions, temperatures and sampling times for the definite experiments.

Buffers:

Buffer stock solutions were prepared at 0.1 M using sterile water. To prepare pH 3 buffer, 0.1 M potassium hydrogen phthalate was diluted to 0.005 M and final pH adjustment made with 0.1 M HCl. The pH 7 buffer was prepared from 0.1 M potassium dihydrogen phosphate diluted to 0.005 M with final pH adjustment using 0.1 M NaOH. Buffers for pH 9 and 11 were made by diluting 0.1 M sodium phosphate heptahydrate to 0.005 M with final pH adjustment using 0.1 M NaOH.

Details on test conditions:

Water was unchlorinated groundwater that was processed through a high-capacity reverse osmosis unit and a deionizer unit. This water was further purified by passage through a Barnstead Nanopure II deionizer, 4-module unit with pretreatment, high capacity and Z-Ultrapure cartridges. Water treated in this way has a resistance of greater than 16 meg ohms. This double-deinonised water was autoclaved for 30 minutes. The sterile water was stored in a sterile cotton-plugged container. All hydrolysis experiments were conducted in screw cap tubes. Buffer stock solutions were prepared with autoclaved water. Sterile checks on the water were performed intermittently. Buffer solutions also were checked for bacterial growth.

Duration:

36 h

Initial conc. measured:

0.9 other: ppm

Number of replicates:

In general, each experiment was carried out with three replicates.

Positive controls:

yes

Remarks:

benzyl chloride

Preliminary study:

The preliminary study was used to set the pH and temperature conditions and the sampling times.

Transformation products:

not specified

pH:

7

Temp.:

25 °C

Hydrolysis rate constant:

0.02 a-1

DT50:

44 yr

St. dev.:

0

Type:

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

Details on results:

Details on the results are not reported in the publicly available project summary.

Validity criteria fulfilled:

yes

Conclusions:

The experimentally determined half-life for hydrolysis of 44 years indicate that this process is not relevant with regard to the environmental degradation of 1,2,3-trichloropropane.

Executive summary:

The hydrolysis of 1,2,3-trichloropropane was studied according to the principles of the EU Method C.7. Hydrolysis rate constants were determined under sterile conditions at precisely controlled temperatures and at pH levels of 3, 7 and 11. The rate constant for 1,2,3-trichloropropane at 25 °C (as calculated from the experimentally determined rate constants) was 1.8e-6 +/- 0.6e-6 per hour at neutral conditions, which results in a half-life of approximately 44 years.

Conditions were adjusted to provide sufficiently precise rate constants. The appropriate pH and temperature conditions and good sampling durations were set in a preliminary test. Each hydrolysis experiment was conducted in three replicates with a starting concentration of approximately 1 ppm and normally six ampules were used that were sacrificed in the course of the experiment for determination of remaining test substance. The study took up to about 36 hours. Buffer solutions were prepared from potassium hydrogen phthalate (pH 3), potassium dihydrogen phosphate (pH 7) and sodium phosphate heptahydrogen (pH 9, pH 11). The substance in the spiked buffer solution was determined by high performance liquid chromatography. Hydrolysis rates for chlorostilbene oxide (acidic conditions), 2,4-D methyl ester (basic conditions) and benzyl chloride (neutral conditions) were measured repetitively to assess the effect of undetected changes in the experimental conditions.

Description of key information

Hydrolysis is not a relevant environmental abiotic degradation pathway for 1,2,3-trichloropropane.

Additional information

Rate constants for hydrolysis of TCP have been studied experimentally (Ellington et al. 1987). The experimental rate constant for neutral reactions was 1.8 x 10-6 and that for basic reactions was 9.9 x 10-4. The half-life of the substance in water due to hydrolysis at environmentally relevant conditions that can be calculated from these rate constants is 44 years (WHO 2003) indicating that this abiotic degradation pathway is not relevant for TCP.