Article updated on 8 July 2021.
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The ability to identify and characterize particles—be it micron-sized particles, nanoparticles or otherwise—in terms of their size, shape, and properties is of huge benefit to many industries. By analyzing particles, companies can understand how uniform their product is and better predict how the product is going to behave in certain scenarios, which in turn helps to produce high-quality particle-based products to the market. Here, we’re going to focus on the basics of particle size analysis and why it is important, rather than the specific methods.
Techniques for Measuring Particle Size
Many industries, from food and beverage, to pharmaceuticals, paints, coatings and other specialty chemical formulations, and composites, take advantage of particle size analysis instruments. It is also widely used in the quality control space to determine if a product meets a certain standard. Depending on the size of the particles in question, there are a number of techniques which can be utilized, such as static light scattering (SLS), dynamic light scattering (DLS), dynamic image analysis (DIA), and even sieves. The choice of method is often dependent upon the type of particles being analyzed and the size of the sample (in terms of sample volume).
The main reason for analyzing a sample is to determine their size and shape and in turn their uniformity (i.e. how polydisperse or monodisperse is the sample). Uniformity is key to any product, especially formulations, as highly polydisperse (non-uniform) formulations won’t work as intended, and in some cases, the properties of the formulation become localized, rather than throughout the whole formulation.
Importance of Particle Size and Shape
While formulations and particle suspensions are a big area, anything from aerosols to powders can be analyzed, including more chemically complex substances such as emulsions. The size and shape of the particles is important, regardless of whether they are nanoparticles or particles that you can see with the naked eye, as these parameters often determine a lot of the properties about the product as a whole system (not as individual particles) and can be used to identify their functional behavior.
For example, the size and shape of particles can affect the flow properties in a liquid-based sample and can affect the packing properties in powders. One example in terms of bulk (system) properties is that larger particles in liquid-based mediums can increase the flow of the liquid, whereas smaller particles can lead to higher suspension viscosities. While the size and shape are some of the most important identifiable parameters, the properties of the individual particles—such as the degree of functionalization or electronic properties of the particles—can also be determined by some particle size analysis methods. Another example is where small droplets with high surface charges can increase the stability of complex emulsions, and all this information is available if desired.
Significance of Particle Size Measurements
So, while understanding the properties of each particle is important, how they all work together as a complete system is the end goal for many in product development and quality control applications; especially if how the particles interplay together could have a big impact on either the safety or the quality of the product. But in the academic world, understanding the fundamental science (basic properties) and general dispersity is sometimes enough information for the intended research. The reasons for performing particle size measurements does depend on who is doing the analysis and for what purpose.
Aside from sieving, the general way of analyzing the particles are via a laser. However, in most cases, the laser only obtains information from one side of the particle (the one that’s facing the laser) and uses this to build up a 3D representation of the particle. This is because spheres measure the same across every dimension (assuming that the particle is spherical). The identification of the relative surface area of the side being analyzed also helps to determine the volume of the particle. Only certain methods are available to analyze the shape as well as the size, as a lot of methods assume that the particles are going to be spherical (as spherical particles are much more common).
The actual identification of the particles is performed by how much laser light is scattered by each particle, enabling the size and concentration of the particles in a sample to be determined with relative ease. For most analyses, the information is outputted as either an average particle size value (which is less desirable) or as a particle size distribution curve (with a central average point)—which is the preferred option.
Conclusion
Overall, particle size analysis methods are versatile techniques that can provide a lot of information about the particulate system being analyzed, in terms of both individual particles and the whole system. Their versatility for analyzing a wide range of particle mediums and particle types is why they are used across many different scientific industries.
Sources and Further Reading
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