Older DLS systems using 90-degree scattering angles indeed made it difficult to perform DLS measurements in the presence of dust or aggregates. Always Filter Samples before Light Scattering Analysis - FalseĪlthough it is better to filter samples before light scattering analysis to ensure they are dust free, it is not needed in the majority of instruments.
When loading or studying biological samples, special care may be required, and appropriate instruments will automatically enable flexibility and user discretion in selecting the exact measurement settings.īased on the conductivity of the measured sample, instruments with good zeta potential can automatically adjust the applied voltage to produce a field strength that causes electrophoresis and yet is gentle enough to not denature biological samples. Commercial Electrophoretic Light Scattering Measurements Denature Biological Samples – False The detection and quantitation of these larger aggregates is as important as the characterization of the main particle or molecule itself. This makes DLS very sensitive in the detection of even trace amounts of agglomerates or aggregates, making it extremely useful in a variety of applications. If some amount of light (X) is scattered by a particle of a given size, the particle size doubles the scattered light intensity to 84x more light. DLS is not Suitable for Samples Containing Aggregated Materials - FalseĪs the size of a particle increases, the amount of light dispersed by the particle also increases considerably. DLS Analysis Needs Dilute Samples for Successful Measurement - FalseĪlthough some light scattering devices need dilute samples to disperse within the optimal response range for the detector(s), contemporary light scattering instruments can employ a method of auto-attenuation of laser or alter the measurement position inside the sample to off-set multiple scattering and sample concentration without the necessity for altering the sample. However, both SLS and DLS techniques produce the weight average molecular size or weight of everything in the batch sample in the absence of a separation technique. Likewise, when DLS is combined with a separation or fractionation technique, higher resolution can also be obtained over batch-mode measurements when the sample contains oligomers. SLS can measure molar mass or weight average molecular weight and needs fractionation or separation technique to resolve different oligomeric states. SLS Offers Improved Resolution than DLS when Analyzing Different Oligomeric States – False When below the size limit of 1/20 the wavelength of the laser, there will be no angular dependence in the scattered light and no extra information can be obtained by adding multiple detectors. SLS measurements can be performed by examining the intensity of light as either a virtue of concentration or angle.
It is a common misconception that multi angle instrumentation is important for absolute molecular weight measurements. SLS can examine either the concentration or angular-dependent scattering relationship, or both concentration and angle. Molecular Weight Measurements through SLS Need Multiple Angles – False It is then possible to measure the radius of gyration (Rg), the weight average molecular weight (Mw), and the second virial coefficient (A2) for the samples under study. This is usually summarized in a Debye or Zimm. In SLS, the total scattered intensity of light is measured as a virtue of concentration or angle. DLS investigates the fluctuations of scattered light over time and processes this signal by means of an auto-correlation technique, which in turn gives a particle's translational diffusion coefficient (DT) and then determines its size distribution, mean hydrodynamic radius (Rh), or polydispersity. DLS and SLS are Same Methods – FalseĭLS and Static light scattering (SLS) are two different techniques and measure different things. This article exposes some of these common misconceptions and provides answers for each.
Over the years, several myths have evolved regarding the value of light scattering and its usage in various applications. Sponsored by Malvern Panalytical Jan 6 2014ĭynamic light scattering (DLS) is a popular method used for measuring the size and size distribution of particles and molecules.
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