Application Note
Automated Size And Intensity Trend Measurements
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•Application Note: Automated Size And Intensity Trend Measurements
The ability to automate particle size and scattering intensity trend measurements can be a major advantage in many applications. Processes such as aggregation, sedimentation, solubilization and changes in molecular conformation can be followed by monitoring changes in the size and scattering intensity of the sample. The Zetasizer Nano range has the capability of automating the measurement of particle size and scattering intensity as a function of temperature or time. This application discusses the trend measurements options with application examples.
Time trend measurements, where the particle size and scattering intensity is plotted as a function of elapsed time, are useful for following processes such as particle aggregation, sedimentation, creaming or solubilization. Information on the kinetics of such processes can be obtained from these measurements.
The Zetasizer Nano range of instruments incorporates non-invasive backscatter (NIBS™) optics. The scattered light is detected at an angle of 173o. This optical configuration gives high sensitivity for the measurement of small, weakly scattering molecules such as proteins and polymers. In addition, NIBS™ minimizes multiple scattering effects and therefore also enables for the measurement of highly turbid, concentrated samples.
Measurements of a protein that undergoes polymerization were made on a Zetasizer Nano S instrument. Measurements of 20 seconds duration were taken over a period of over an hour. Figure 1 shows the zaverage diameter (the mean diameter based upon the intensity of scattered light) and the count rate (in kilo counts per second (kcps)) obtained as a function of the elapsed time after a polymerizing initiator was added to the protein sample. As the protein underwent polymerization to larger particles, an increase in the intensity of scattered light was observed. The effect of various inhibitors on this process could be studied by monitoring changes in the rate of size and/or scattering increases.
SOURCE: Malvern Instruments
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•Application Note: Automated Size And Intensity Trend Measurements
