OECD TG-123 Partition Coefficient (1-Octanol/Water): Slow-Stirring Method
OECD GLP Physical-Mechanical Test
WESHIN INSPECTION TECH CO., LTD_

OECD TG 123: Partition Coefficient (1-Octanol/Water) – Slow-Stirring Method

 

The gold standard for high-hydrophobicity substances, delivering superior accuracy for bioaccumulation assessment.
 

For highly lipophilic chemicals, determining an accurate n-octanol/water partition coefficient log Pow is essential yet technically demanding. At Weshin Inspection Tech , we conduct specialized studies following OECD Test Guideline 123 (TG 123), utilizing the Slow-Stirring Method to provide high-fidelity data for substances with extreme hydrophobicity.

 

Why the Slow-Stirring Method is Crucial

 

The Slow-Stirring Method is designed to overcome the limitations of traditional techniques for substances with high log Pow values:

  • Eliminating Emulsification: Unlike the shake-flask method, slow stirring prevents the formation of micro-droplets (emulsions) at the phase interface, ensuring the measured concentration represents true dissolved solubility.

  • Extended Range Capability: Specifically optimized for substances with log Powvalues between 5 and 8.2, filling the gap where other methods lose precision.

  • Regulatory Compliance: Essential for high-tier chemical evaluations under REACH and for identifying Persistent, Bioaccumulative, and Toxic (PBT) substances.
     

Our Technical Excellence

 

Weshin Inspection Tech employs advanced experimental setups to manage the long-term equilibration required by TG 123:

  • Precision Agitation Control: Maintaining ultra-stable, vortex-free stirring (typically 20–50 rpm) to facilitate mass transfer without disrupting the phase boundary.

  • Equilibrium Verification: Sequential sampling of both octanol and aqueous phases to confirm that thermodynamic equilibrium has been reached.

  • Trace Analytical Detection: Leveraging high-sensitivity GC-MS or LC-MS/MS to quantify exceptionally low concentrations of the test substance in the water phase.
     

Why Partner with Weshin Inspection Tech?

 

  • Strict Thermal Stability: Measurements are performed in high-precision incubators at 25±0.1°C to minimize uncertainty in partitioning data.

  • Expertise in Complex Matrices: Specialized handling of volatile or poorly soluble substances to prevent loss during the extended stirring period.

  • Audit-Ready Documentation: We deliver comprehensive reports featuring kinetic plots of concentration versus time, ensuring full transparency for regulatory audits.


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