Division 1.5 INFORMATION ON THE TEST SUBSTANCE

Non-labelled or labelled test substance can be used to measure the rate of transformation. Labelled material is required for studying the pathway of transformation and for establishing a mass balance. ¹⁴C-labelling is recommended but the use of other isotopes, such as ¹³C, ¹⁵N, ³H, ³²P, may also be useful. As far as possible, the label should be positioned in the most stable part(s) of the molecule^f1. The purity of the test substance should be at least 95 %.

Before carrying out a test on aerobic and anaerobic transformation in soil, the following information on the test substance should be available:

1. (a)

   solubility in water (Method A.6)

2. (b)

   solubility in organic solvents;

3. (c)

   vapour pressure (Method A.4) and Henry's law constant;

4. (d)

   n-octanol/water partition coefficient (Method A.8);

5. (e)

   chemical stability in dark (hydrolysis) (Method C.7);

6. (f)

   pK_a if a molecule is liable to protonation or deprotonation [OECD Guideline 112 ] (16).

Other useful information may include data on toxicity of the test substance to soil micro-organisms [Testing Methods C.21 and C.22] (16).

Analytical methods (including extraction and clean-up methods) for quantification and identification of the test substance and its transformation products should be available.