DLS, ELS, and data reliability: What you need to know
Dynamic light scattering (DLS) and electrophoretic light scattering (ELS) are two highly sensitive measuring techniques. Of course, this sensitivity is what makes them so valuable in materials applications – but it also comes with a downside.
From sample variations and instrumental imperfections to changes in environmental conditions, all kinds of unwanted factors can affect your DLS or ELS results. So, when buying a light-scattering instrument, make sure you consider the small details that will make a big difference when it comes to data quality and reliability.
Dust
Unwanted particles in samples are inevitable, but the unreliable measurements they cause aren’t. Malvern Panalytical’s Adaptive Correlation method removes (and stores) data from these transient scattering events from the steady-state data before carrying out DLS particle size calculations. You can rest easy, knowing that the system takes dust into account, leaving your results uncontaminated by contaminants.
Temperature
Fluctuations in temperature during measurements lead to viscosity changes, which in turn affect particle mobility, which ultimately causes errors in the DLS or ELS results. When selecting an instrument, consider the quality of its components and ask whether it is designed to ensure the temperature is stable before taking readings.
Cuvettes
Different instruments are compatible with different types of cuvette. At Malvern Panalytical, we always recommend those with high optical quality, simply because they provide the most reliable results. Find out more here, including information on which cuvettes can be used with our Zetasizer range.
Multiple particle sizes
By taking measurements from different angles, some DLS instruments can provide more in-depth information on samples that contain particles of different sizes. Bear in mind, though, that not all these instruments will offer a single, simple result: some models will take the measurements and leave you to run the calculations. Let our Zetasizer systems and our MADLS® algorithm do the hard work for you!
Charge shielding
Highly conductive samples can compromise the accuracy of ELS measurements, by reducing the current when ions build up on the electrodes. For more reliable data, consider choosing a system that can mitigate this issue, such as our Constant Current Zeta method, which uses a real-time compensating circuit.
Electro-osmosis
Another risk with high-conductivity samples is electro-osmosis, a net flow of charged particles that can distort the zeta potential data when measured at low frequency. It’s a good idea to opt for an ELS solution that can overcome this unreliability; for example, Malvern Panalytical’s M3-PALS method. This measures the mobility of the particles at high frequency and uses this reading to correct the low-frequency data.
Behind-the-scenes support from our specialist software
With so many factors to consider, it’s reassuring to know that Malvern Panalytical provides a range of solutions to bolster data quality. But that’s not all: to make things even easier for you, our Zetasizer systems are set up to give you extra confidence in your results, thanks to our Data Quality Guidance software.
This program not only assesses the raw data against a database of known issues, letting you know if your initial results are in line with expectations before you continue, but it also provides advice on correcting any problems. Data Quality Guidance is just one more way in which we support your materials analysis and ensure its reliability – so you can make the most of your measurements!
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