OECD TG 111: Hydrolysis as a function of pH

Sterile aqueous buffer solutions of different pH values (pH = 4, 7 and 9) are treated with the test substance and incubated in the dark under controlled laboratory conditions of temperature. After appropriate time intervals, buffer solutions are analysed for the test substance content and (if required) for hydrolysis products. The test should normally runs until 90% hydrolysis of the test substance is observed or for 30 days whichever comes first. A plot of the test substance concentrations versus time allows an estimation of its hydrolysis half-life/DT50. Major hydrolysis products can be identified and their concentrations versus time plotted to show their rates of formation and decline. Sterility checks are usually planned at the start and at the end of the study in order to ensure that all test phases are carried out in abiotic conditions.

Preliminary test-Tier 1 (if required) is performed at 50 ± 0.5°C and pH 4.0, 7.0 and 9.0. If after 5 days hydrolysis < 10%, the test substance is considered hydrolytically stable and, normally, no additional testing is required.

1 concentration of the the test substance at different pH and temperature conditions.
Analytical determination of the parent substance and major hydrolysis products content in sterile buffer samples:
Treated sample: 2 replicates for sampling date for each pH/temperature condition
Untreated sample: 1 replicate for each pH/temperature condition at first and last sampling planned
Additional replicates for sterility check:
Untreated sample: 1 replicate for each pH/temperature condition at first and last sampling planned
Additional replicates as spare samples.

Recovery quality check at 2 fortification levels:
1 replicate for sampling for untreated buffer solution

Repeatability of the anlytical method:
Duplicate analysis of the same extract of buffer solution at proper sampling dates.

LOD (for the test substance and the transformation products):
≤ 3% of the initial amount applied to the solutions.

LOQ ≤10% of the initial amount.

Analyses performed using a method validated according to SANCO/3029/99 rev.4 guidance document

Kinetics analysis and calculation of DT50 and DT90 values.
Major hydrolysis identification/quantification (if required).
Study includes GLP management and reporting.

OECD Guideline for Testing of Chemicals, No. 111 (13thApril 2004) - Hydrolysis as a function of pH.
SANCO/3029/99 rev. 4 (11/07/2000) - Residues: guidance for generating and reporting methods of analysis in support of pre-registration data requirements for Annex II (Part A, section 4) and Annex III (Part A, section 5) of Directive 91/414.


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