Webinar recap: Mastering the basics of dynamic light scattering with Zetasizer
In 2024, we hosted a masterclass series with one goal in mind: to guide light-scattering novices and veterans toward the mastery of this technology’ essential techniques. In the first webinar of this series, DLS method development, we explored the essential steps to achieve reliable dynamic light scattering (DLS) measurements using Zetasizer Advance instruments.
Many users encounter challenges in obtaining consistent DLS measurement results due to improper method setup, incorrect cell selection, or inadequate sample preparation. These issues can compromise data accuracy and make it difficult to achieve reliable particle size analysis.
With increasing demands for precise and repeatable particle size measurements across industries – from pharmaceuticals to materials science – there is an urgent need for users to optimize their DLS techniques. In this webinar, Technical Support Manager Mike Kaszuba shared his DLS expertise for every step from setup to results analysis.
Key takeaways
- Instrument verification is crucial
Dynamic light scattering is an absolute technique that does not require calibration. However, regular verification is essential. This involves using certified standards, such as a 100 nm polystyrene latex standard, and following ISO guidelines. - Choosing the right cell can make or break your measurement
Selecting the appropriate cell for your sample type and measurement angle is critical for reliable results. The Zetasizer Advance range offers various cuvettes, from disposable plastic cuvettes for aqueous samples to quartz cuvettes for solvent-based measurements. - Proper sample preparation is key to accurate results
Ensure your sample is well-dispersed and free of contaminants. Pay attention to concentration levels: too low may result in insufficient scattering, while too high can cause multiple scattering issues. Filtration and dilution should be performed carefully to maintain sample integrity.
Verification involves measuring a certified standard and ensuring your instrument meets ISO specifications. Regular verification is essential to maintaining accuracy.
Mike Kaszuba
Instrument Verification
Regular instrument verification ensures that your Zetasizer is operating correctly and delivering reliable results. Use certified standards and follow ISO 22412 guidelines to verify that your measurements fall within the acceptable range for mean size, PDI, and relative standard deviation.
Cell selection and sample preparation
The right cell selection depends on your sample type and the measurement technique you are using. Disposable plastic cuvettes are ideal for aqueous samples, while quartz or glass cuvettes are better suited for solvent-based samples. Proper handling and preparation of cells and samples are critical to avoid contamination and ensure accurate measurements.
Proper cell selection and sample preparation are fundamental to obtaining reliable and accurate results.
Mike Kaszuba
Measurement Setup and Advanced Techniques
ZS Xplorer software allows users to configure sample details, measurement parameters, and detection angles. Automatic attenuation is recommended to ensure optimal light intensity reaching the detector. Multi-angle DLS (MADLS) and particle concentration measurements require additional considerations, such as selecting appropriate cells for multi-angle detection and measuring scattering intensity from the dispersant.
Highlights from the Q&A Session
During the Q&A, Mike addressed several key questions from participants:
Q: I ordered a 60 nm polystyrene standard for verification, but my measurements consistently show 63-64 nm. How can I troubleshoot this?
A: Ensure you are looking at the hydrodynamic diameter on the ≈, not the certified diameter from electron microscopy. Also, verify that you are preparing the latex size standard in 10 mM sodium chloride solution. Based on your readings, you appear to be within the acceptable range.
Q: For quality control methods, should we use manual attenuation?
A: We recommend automatic attenuation to avoid detector saturation. However, if you find a consistent attenuator position for your sample, you can manually set it. Just be cautious – if your sample changes, manual settings might lead to detector saturation.
Q: What is the minimum sample volume required?
A: It depends on the cell and detection angle. For side scatter, the minimum is 3 µL. For backscatter, it’s 12 µL with a quartz cell or 40 µL with a disposable cell.
Q: How many angles does the Nano series have?
A: It depends on the model. For example, the ZS Nano has two angles (forward and backscatter), while others may vary.
Q: What parameters indicate a reliable measurement?
A: Check for repeatability in Z-average diameter and PDI values. Consistent size distributions across repeat measurements indicate reliability.
For more insights on improving your particle size measurements and a demo of the Zetasizer Advance, contact our experts today.