Test No. 322: Determination of the Solubility and Dissolution Rate of Nanomaterials for Environmental Fate Assessment

This Test Guideline describes methods recommended to determine the dissolution and dissolution rate of nanomaterials (NMs) for environmental fate assessment at environmentally relevant pH values, using passive pH control (buffers). The test procedures are performed at room temperature (in the range of 20 - 22 °C), and in the dark. This Test Guideline consists of two parts: Part A (simple batch test) and part B (extended, time-resolved batch test). Part A is a batch test that delivers the apparent solubility of a NM after 24h at pH 7 (as default; in addition, pH values between 5 and 8 can be applied). Testing at pH 7 serves as reference to enable the comparison of different studies and NMs. Testing of additional pH values might be of relevance depending on specific context and purpose. Part B is a time-resolved batch test that delivers the apparent solubility of a NM after 72h at pH 5, 7 and 8, and the dissolution rate, if depletion of the NM or saturation of the solution is not reached before 4 hours). If complete dissolution is observed, the solubility of the tested NM should be given as ≥ initial concentration. Once a choice for Part A or B has been made, user can directly consult the respective section of this Test Guideline. To estimate and report solubility and dissolution rate based on the Test Guideline, the use of the provided MS-Excel evaluation files for Part A and B are mandatory (these are available as supporting material).