OECD TG 105 is the “Water Solubility” standard, which is listed in Section 1 (Physicochemical Properties) of the OECD Test Guidelines for the Testing of Chemicals.
Water solubility is the measure of the amount of a substance that can be dissolved in pure water at a specific temperature (usually 20 °C), expressed as mass/volume or mass/mass. OECD TG 105 is particularly suitable for substances with low to moderate solubility. For highly soluble substances, other approaches may be necessary.
The basic principle of the test is to bring the test substance into equilibrium with water and to determine the concentration of the dissolved substance using a suitable analytical method. OECD TG 105 includes two basic methods:
The shaking flask method:
- The test substance is shaken together with water in a closed container
- Wait until equilibrium is reached (usually 24–48 hours)
After phase separation, the concentration of the substance in the solution is determined analytically
Suitable for substances with moderate and relatively high solubility
Column elution method:
- The test substance is applied to an inert carrier material and loaded into a column
- Water is passed through the column; the dissolved substance is collected in the eluate
- The concentration in the eluate is measured analytically
- Suitable for substances with low solubility; requires less sample material
The basic parameters reported in the study are:
- Water solubility (mg/L or g/L)
- Measured Temperature (°C)
- pH (solubility may depend on the pH)
- Method Used (Bottle or Column Elution)
- Analytical Measurement Method and Limit of Detection
- Data on Measurement Uncertainty and Repeatability
Why is this being done?
OECD TG 105 is being conducted for the following scientific and regulatory purposes:
- Substance Characterization: Water solubility is a fundamental physicochemical property of a substance and is used for identification purposes.
- Predicting Environmental Behavior: Solubility provides clues about the distribution, bioavailability, transport, and fate of the substance in water
- Design of Ecotoxicity Tests: Solubility is a critical factor in selecting test concentrations and dosages
- Assessment of Bioaccumulation Potential: Low water solubility may be an indicator of a tendency toward bioaccumulation
- Classification and Labeling: Solubility is taken into account when classifying chemicals based on physical and environmental hazards.
- Assistance with the preparation of regulatory submissions: Used for REACH, biocidal product, plant protection, and drug safety assessments
- Quality Control: Monitoring the consistency of raw materials, intermediate products, and finished products in production processes
- Weighing the Evidence: A Contribution to the Comprehensive Assessment of the Substance in Conjunction with Other Physicochemical, Toxicological, and Environmental Data
OECD TG 105 is not a standalone toxicity or hazard assessment. It is intended for physicochemical characterization; the results must be interpreted in conjunction with other physicochemical properties, toxicological data, and exposure assessment.
As part of our nano-testing services, we conduct water solubility determinations in accordance with OECD TG 105 with scientific rigor, leveraging our accredited laboratory infrastructure and quality management system. Our scope of services includes the following:
Method Selection and Validation
Selection of the appropriate method (bottle or column elution) based on the expected solubility range and the properties of the test substance
Validation of the selected method and verification using appropriate reference substances; selection, calibration, and determination of the limit of detection for the analytical measurement method (HPLC, GC, spectrophotometry, etc.); evaluation and reporting of measurement uncertainty; documentation of method-specific limitations and conditions of use
For information on method selection, analytical measurement strategies, sample acceptance criteria, the testing schedule, and reporting procedures for your water solubility determinations in accordance with OECD TG 105, please feel free to contact Nano-Test.