Tag Archives: Particle Size Analysis

What is Particle Size Analysis?

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Particle size analysis: it sounds tricky, but mark our words, it’s something that everyone would be well-served learning more about. Whether you realise it or not, particle size analysis plays an extremely important role in many of the products we use, consume and interact with in our everyday lives. In this article, we’re going to offer you a brief introduction to particle size analysis, listing some of its most common applications as well as its most established methods. We’ll also take a look at zeta potential, a measurement that is often used along side particle size analysis.

What is particle size analysis?

There are a huge number of industries which rely on methods of particle size analysis to ensure products are of the highest quality. From powders to creams, gels, lotions, and other mixtures, the size and characteristics of the particles contained within can have dramatic effects on properties such as stability, appearance, flow and chemical reactivity. As a result, a highly important industry has developed centred on particle size analysis, with constant innovation in methods that provide more and more accurate ways of analysing particle size.

What are the applications of particle size analysis?

As we’ve already mentioned, the applications of particle size analysis are numerous; too numerous to mention here. However, some of the industries that rely heavily on the understanding of particle size distribution include:

  • The cosmetics industry
  • The pharmaceutical industry
  • The cement industry
  • The food and beverage industry
  • The plastics industry
  • The pigments and inks industry
  • The ceramics industry
  • The metal powders industry

What are some common particle size analysis methods?

Probably the most popular method of particle size analysis is laser diffraction , which involves particles being illuminated by a laser beam, causing the light to be scattered in various directions. The scattering patterns are then measured with specially-designed detectors and particle size distribution can be calculated from this data. For example, larger particles bring about a higher intensity of scattering at lower angles to the beam, while smaller particles offer a low intensity of scattering at higher angles.

Laser diffraction has the advantage of offering real-time particle analysis that allows for several benefits, including:

  • Increased return of investment
  • Lower energy consumption
  • Better troubleshooting
  • Increased efficiency
  • Reduced operator risk

What is Zeta Potential?

When measuring particle size distribution, it’s also important to consider the particle’s zeta potential or ‘charge’ measurement. Most particles will gain a charge on their surface when dispersed in an aqueous system. These charges change the distribution of the surrounding ions, leaving a layer around the particle that does not have the same properties as the rest of the solution. Zeta potential determines how particles interact within solution and measurement of zetapotential can give valuable insight into stability and reactivity of a material.

Laser Diffraction – Why is it Such an Important Particle Sizing Technique?

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As a technique of particle size analysis, laser diffraction offers the ability to learn more about particle size and shape with a high level of accuracy. This information is incredibly useful to industries and for research and the information generated is influential in streamlining and enhancing processes used.

Particle sizing technologies are intended to provide a reliable measurement (that can be reproduced) for different sized particles. There are multiple technologies for particle size analysis and it is vital to appreciate that no one piece of technology is appropriate for every job. There are advantages and also drawbacks to each piece of measurement technology and different devices are best suited to particular industries or tasks.

Why is measuring particle size and shape important?

Today, many industries rely on the ability to use a particle size analyser to measure the size of particles of varying sizes, including those that are incredibly fine. We know that for all materials that are milled or ground, the resulting particle size is typically the factor that determines performance of the product and efficiency of the process.

As a result, analysis of particle size has become crucial to industries such as the pharmaceutical, food and beverage, building and chemical industries.

Why is laser diffraction one of the most important and used particle size analysis techniques?

As it can be used to determine particle size of liquid suspensions, dry substances and aerosols, laser diffraction is most popular for its dynamic nature and range.

However, different particle size analysis technologies can quite often produce different results for the same sample. There is a logical reason for this, being that each particle analysis measurement technique measures a different part of aspect of the same material. For this reason, all particle size analysis results must be considered as the best indications possible rather than definitive and exact measurements.

Why is ‘Equivalent Sphere’ Theory used?

Even the smallest particles are multi-dimensional and it is very hard, not to mention problematic, to describe a multi-dimensional particle using one dimension only.

As only one shape, a sphere, can be described by one dimension, all techniques that measure particle size relate this to an ‘equivalent sphere’.

What are the most common particle sizing techniques used?

  • Sedimentation techniques
  • Sieve technique
  • Aerodynamic sizing technique
  • Laser diffraction
  • Image analysis technique

With so many techniques for measurement available, which should be used?

Ultimately, there is no simple and definitive answer to this question. Because different products and processes can be measured, the most suitable measurement technology for the product and process needs to be chosen and applied. Having said this, of all of the technologies, the one that can be used most widely is laser diffraction.

The advantage of laser diffraction as a tool for determining particle size and shape is that it can be used to gain information about a wide range of particle sizes and sample types. This technique is suitable for materials such as sprays, powders, suspensions and emulsions and results are able to be delivered in the form of a ‘volume’ distribution, which is the most significant and logical description when bulk material properties are being analysed.

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Particle Size Analysis – What You Need to Know

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Particle size analysis has many important uses for many industries. While many people may not immediately recognise or understand the benefits of determining particle size and shape, processes and systems in a variety of industries are enhanced and made more efficient when this intelligence is known. Specialised equipment has been developed to assist with such analysis and is vital in ensuring quality control and product standards.

What is Particle Size Analysis used for?

Particle size analysis is used to learn more about the size and shape of grains and particles within a particular sample. This analysis is so sophisticated and versatile that it is applicable to solid materials and also suspensions, emulsions and aerosols.

As some particle size analysis methods can only be used for particular materials, it is important that the most appropriate method of analysis be used. Varying and inconsistent results can occur if an inappropriate method for determining size is used.

What are Particle Size Analysis results used for?

Quality control and efficient functioning of processes is better assured for many industries if particle size analysis testing is done. For any industry where milling or grinding is undertaken, it is important to know particle size and shape in order to maximise the efficient functioning of processes and the ultimate quality of products.

While an array of industries and products benefit from particle size analysis, some of the industries in which analysis is commonly and widely used are:

  • Pharmaceutical
  • Building
  • Paints and coatings
  • Food and beverages
  • Aerosols

What are some of the difficulties with Particle Size Analysis?

Problems can arise when particle size analysis attempts to reduce the size of particles to only one number. A two dimensional graph is usually used to report particle size and quantity. However, only the shape of a sphere can truly be expressed as a single number, as it is the only shape that has the same measurement across every dimension. This does not apply to shapes of other types and sizes; they do not consistently measure the same across all of their dimensions.

In light of this, a one dimensional property of a particle is related to the size of an ‘equivalent sphere’ in all particle sizing techniques. Commonly, the volume of each particle in a sample is measured and equated to the size of a sphere with the same volume as the measured particles. This is referred to as an ‘equivalent sphere’ and is often applied in laser diffraction methods.

What is Laser Diffraction?

One of the most often used particle sizing methods, laser diffraction operates from the principle that when a laser (beam of light) is broken and scattered by particles, the smaller the particle size, the larger the angle of light scattering will be.

Laser diffraction is so popularly used because of its application to many different sample types. Further advantages of this particle size analysis technique are that it is fast, reliable and a technique that can be reproduced. It is also possible to use this measurement technique over a wide size range.

Particle size analysis is vital for enhancing the processes used in a variety of industries. Modern, sophisticated equipment is specifically designed to provide accurate and reliable results pertaining to a range of materials. It is little surprise that particle size analysis is so popularly used when the specific information that it provides are so significant and important to companies and industries.

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Particle Sizing Techniques and Laser Diffraction

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The ability to measure the size of very fine particles is an integral part of many industries today. For every material that goes through a grinding or milling process, the final particle size is usually the primary factor that governs product performance or process efficiency. This is why particle sizing has become essential in areas such as the pharmaceutical industry, foods and beverages, cement and building materials and for manufacturers of chemical compounds for industrial and residential uses.

One of the most popular and widely used particle sizing technologies available today is Laser Diffraction. Laser Diffraction has become so popular because it offers a very wide dynamic range; it can be applied to liquid suspensions, dry substances and aerosols and provides a very rapid and reliable measurement process.

The goal of all particle sizing technologies is to provide a systematic and reliable measurement for a range of different sized particles. However it is important to understand that there is a wide range of particle sizing technologies available and no one technology is suitable for every job. Each measurement technology has its own advantages and each is often best suited to specific industries or applications.

It is also important to understand that different measurement technologies can often give different particle results for the same sample. This is because each measurement technique measures a different aspect of the same material.

Sphere Approximations

When reporting particle size, we tend to display a graph showing “particle size” on one axis and “percent of material” on the other axis. However, it is very difficult to describe a multi-dimensional particle using one dimension. In fact there is only one shape that can be described by one dimension, and that is the diameter of a sphere.
For this reason, all particle sizing techniques measure some property of material and then relate this to an “equivalent sphere”.

Some common particle sizing techniques and there reporting methods are as follows:

  • Sedimentation techniques – measures the rate at which particles settle in a liquid column and reports the size of a sphere with the same settling rate.
  • Sieve technique – measures the mass of material retained on a series of screens and reports the amount of material between spherical hole sizes.
  • Aerodynamic sizing technique – measures the behaviour of particles in an airstream and reports the size of a sphere that has the same behaviour.
  • Laser diffraction – measures light scattering from a group of particles and reports the size of a sphere that produces the same scattering.

So, with so many different measurement techniques available. The question is: which techniques are the best?

Getting the Answer as Right as Possible

Like most questions in the world of science, the answer has multiple parts. In short, you need to choose the most suitable measurement technology for your product and your process. However, if you had to pick a single technology that can universally applied then it would have to be Laser Diffraction.

Laser diffraction is the best general technique as it can be used with a very wide range of particle sizes and also a very wide range of sample types. Laser diffraction works very well for sprays, dry powders, suspensions and emulsions. The results reported are also displayed in terms of a “volume” distribution, which is the most appropriate description for bulk material properties.

Apart from Laser Diffraction, another technique that is gaining popularity is Image Analysis. Image Analysis is also considered a particle sizing technique, but it does offer one significant difference. It is the only methodology that provides any information on particle “shape”! If particle shape is known to have an influence on product performance, then image analysis may be the most appropriate option.

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