Inert particle size assessment: handling in glovebox and dispersion in water-free organic “solvent”
Some powders are sensitive to air (oxygen) or moisture from humid air. For these types of samples, understanding the particle size remains essential. However, many particle-size instruments struggle with these samples due to the lack of an inert measurement option. To address this challenge, Delft Solids Solutions developed a method to measure particle size distribution in an inert environment. This approach ensures accurate measurements for air-sensitive materials.
Ensuring Inert Storage for Accurate Particle Size Analysis
First, technicians prepare and store the samples in an inert environment before particle size analysis. They use special screw cap septum vials to prevent air transfer between the inside and outside. Next, they place the material in a dry solvent, like water-free heptane, hexane, or a process liquid, inside the vial. They then flush the vial with nitrogen gas and securely seal it with a screw cap. After sealing, they store the vial in a specialized glovebox filled with nitrogen gas. This setup ensures that the material never comes into contact with humid air until the measurements are performed.
The dry solvent is also used during particle size measurements with laser diffraction. First, technicians flush the dispersion unit and measurement cell with the dry solvent at least four times. This step ensures the complete removal of any water. Next, they fill the dispersion unit with the dry solvent, preparing it for the sample transfer. Using a syringe and a needle with a large enough opening, they carefully transfer the material into the dispersion unit. Before the transfer, they rinse the syringe with the dry solvent. Additionally, they add some dry solvent into the syringe before taking the sample.
A Controlled Method for Measuring Air-Sensitive Particle Size Distribution
Technicians carefully insert the needle into the septum to disperse the sample in the vial. After homogenizing the vial, they draw some sample into the syringe and remove it from the septum. Next, they insert the syringe into the solvent in the dispersion unit and empty it without exposing the sample to air. The sample is then measured immediately to ensure accurate results, as the material may slightly change over time. After several investigations, this method has proven effective for measuring the particle size distribution of air-sensitive materials. We continue to explore more options to improve measurements for such materials.
Our conclusion of the week:
Even if it is wet outside – there are always possibilities to measure materials dry!
