Tag Archives: Particle Size Analysis

5 Reasons to Combine Laser Diffraction Particle Sizing and Image Analysis

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Particle size is by far one of the most important physical properties of particulate samples. The measurement of particle size distribution is routinely carried out across a wide range of industries for mainly two reasons; to better understand how particle size will affect their product performance and to optimise and control the quality of products and processes during manufacturing.

In addition to particle size, the shape or morphological surface properties of the particles can be equally as important or even interrelated eg. surface area and particle size. The size and shape of a particle can influence a variety of material properties. From dissolution rates of tablets, stability of paints, the texture of foods and coatings, to the flowability and packing density of powders, understanding particle size and shape can be critical when designing a product for a particular purpose or behaviour.

Why measure particle size using laser diffraction?

Laser diffraction technology for routine particle size analysis remains the method of choice across a diverse range of industrial sectors.  The speed and ease of use of this technology and the wide dynamic range (nm to mm)1 give users access to quick, reliable particle size data with minimal effort. 

Laser diffraction is a non-destructive ensemble technique, meaning it calculates particle size distribution for the whole sample rather than building up a size distribution from measurements of individual particles. A sample, dispersed either in solution or fed dry which is passed through a collimated laser beam, scatters light over a range of angles. Large particles generate a high scattering intensity at relatively narrow angles to the incident beam, while smaller particles produce a lower intensity signal but at much wider angles. Laser diffraction analysers like the Mastersizer 3000 record the angular dependence of the intensity of light scattered by a sample, using an array of detectors. The range of angles over which measurements are made directly relates to the particle size range which can be determined in a single measurement2. 

However, particles are 3-dimensional objects, and unless they are perfect spheres (e.g. emulsions or bubbles), they cannot be fully described by a single dimension such as a radius or diameter3. Therefore, to simplify the measurement process particle size is defined using the concept of equivalent spheres. The equivalent sphere concept works very well for regular-shaped particles, but for particles that are shaped like needles or plates, the size in at least one dimension can differ significantly from that of the other dimensions.

For this reason, many groups also employ low-cost sieve analysis to evaluate the large particle content. However, in addition to being slow and manually intensive, sieving lacks sensitivity at the fine fraction of the distribution, particularly at < 38 µm which is known as the sub-sieve size region4. Excessive fines in this size range tend to cause attraction or bridging of particles and are often combined with humidity or sticking issues. Wet sieving may help, but screen blocking is still common especially in smaller sizes.  Laser diffraction using wet or dry dispersion methods overcomes these issues and enables faster, simpler analysis with better resolution and control of agglomerates. 

How can imaging help measure particle size more accurately?

Imaging allows users to visually see the particles to determine particle size and shape and is complementary to laser diffraction particle sizing, allowing more data to be collected and measured. 

The Hydro Insight is a dynamic imaging tool that sits alongside the Mastersizer 3000 particle size analyser. It provides real-time images of individual particles as well as quantitative data on particle shape at the same time as laser diffraction size measurements. Particles dispersed by the Mastersizer 3000’s wet accessories flow through the Hydro Insight and are then photographed by a high-resolution digital camera at up to 127 frames per second. The camera takes images of the suspended particles in the analysis cell, converts them to a digital format, and sends the information to the software for final analysis in real-time. Individual particle images are viewed directly and captured as image files for post-run processing. More than 30 size and shape metrics available such as circularity, ellipticity, opacity, mean diameter, and aspect ratio allows the user to understand how the combination of particle size and shape affects material behaviour. 

Adding the Hydro Insight to your Mastersizer 3000, combines shape data with size data to enable the following benefits:  

#1 Gain a deeper understanding of why materials behave the way they do 

Hydro Insight provides real-time images of liquid dispersions of individual particles to provide quantitative data on particle shape. Circularity and aspect ratio (width and length) can be used to distinguish between particles that have regular symmetry, such as spheres or cubes, and particles with different dimensions along one axis, such as needle shapes. Other shape parameters that can be used to characterise particle form include elongation and roundness. This plays a significant role in applications such as powder processes where size and shape can influence powder flowability/ blending properties, cohesion/ formation of agglomerates, tableting/ compaction behaviour, porosity/ reactivity, and even health and safety. When assessing pharmaceutical drug products the size and shape of particles can influence drug delivery within the body, dissolution behaviour, bioavailability, and drug efficacy. 

#2 Speed up method development

When setting up a method to measure particle size using laser diffraction, achieving optimal dispersion is important to prevent agglomerates and to ensure the reproducibility of results. This can involve multiple steps from varying the dispersant type or amount of surfactant to the amount of mechanical mixing or ultrasound needed. By combining size analysis with imaging, particles can be seen live in a liquid and any agglomerates that form can quickly be identified and dispersed using optimal conditions. Users can see their dispersion as they develop laser diffraction methods, saving time for other projects.

#3 Build confidence in product quality

Laser diffraction is an ensemble technique able to measure particle size and particle size distribution for a wide range of samples over a wide dynamic range. However, for materials that require narrow polydispersity, the presence of just a few large or outlying particles can make a big difference to their performance. Large particles can block printing nozzles or cause imperfections in coatings or even be a source of immunogenicity when developing pharmaceutical drugs. Adding the Hydro Insight to the Mastersizer 3000 provides images of individual particles and gives a number-based particle size distribution, so it becomes sensitive to even small numbers of oversized particles leading to enhanced resolution. 

#4 Quickly troubleshoot

Laser diffraction offers a simple, fast, and reproducible technique to measure particle size reliably; however, samples can sometimes present results that are unexpected, contain artifacts or simply be “out of spec”. Looking at your material on a microscope often needs a different sample preparation method and that can make the picture more complicated. 

By adding imaging to laser diffraction workflows, the process of troubleshooting can be automated and therefore speed up analytical processes. With Hydro Insight, any anomalies in results can be assessed to determine whether they were caused by oversized particles, agglomerates, bubbles, or something else.

#5 Faster method transfer

Sieving is one of the oldest and simplest techniques for separating particles based on their size. However, the time it takes to obtain accurate results, the poor resolution, and problems associated with particle agglomeration and sieve blockage, have seen sieving being replaced in most industries with laser diffraction. Laser diffraction and sieving can provide similar results when characterising spherical or semi-spherical particles, however, differences can be observed for non-spherical particles because each technique measures different particle properties. Laser diffraction measures light scattering from a group of particles and reports size as a volume distribution of spheres that would produce the recorded pattern. In comparison to sieving, a mixture of size, shape, and density generates a weight distribution. Therefore using sieving, an elongated particle will be reported using the smaller dimension and will appear smaller when compared to laser diffraction results.  

The Hydro Insight provides a window or a set of eyes into the Mastersizer. It records thumbnail images of a dispersion of particles and measures quantitative particle shape data. It can report different size parameters for irregular particles such as particle width and elongation data that may correlate better with sieve analysis and thus simplify the transfer process from sieves to laser diffraction.  

Laser diffraction provides fast, reproducible particle size data for a range of applications. Image analysis is often used in combination with laser diffraction to provide a further understanding of how materials behave as well as being an orthogonal technique that helps with method validation.

So why choose the MASTERSIZER 3000 with the Hydro Insight?

The MALVERN MASTERSIZER 3000 system has a unique, compact design that uses laser diffraction to measure particle size distribution. The Hydro Insight sits alongside the Mastersizer 3000 and provides real-time images of particles, as well as quantitative particle shape data. This enables users to gain a deeper understanding of their products for easier troubleshooting and quicker method development.  Learn more about the Malvern Mastersizer 3000 and Hydro Insight system, speak to ATA Scientific today.

Particle Imaging Techniques

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What is particle imaging used for?

Where particle size analysis is used to produce a distribution curve showing how large the majority of particles in a given solution are, particle imaging also provides the ability quantify morphological (ie. shape) characteristics of particles.

Determining particle shape parameters

When reporting particle size, we try to report just one single number for each particle; the equivalent spherical size. In image analysis reports, this is often termed the CE diameter (or Circular Equivalent diameter). However, when it comes to reporting particle shape, there are many numerical descriptions that can be used, including: length/width, aspect ratio, circularity, compactness, roughness, convexity and elongation. Most image analysis system also report parameters such as lightness/darkness, opacity and intensity. All of these parameters help differentiate one type of particle to another, which is one of the real strengths of image analysis.

Where particle sizing can only report a size distribution, image analysis can be used to quantify subtle differences in shape or optical properties. New image analysis systems also provide powerful software packages that enable classification of particles into different groups. This in turn enables users to quantify different types of materials in the one sample.

How FlowCAM works

FlowCAM is one of the more popular of the new age particle imaging systems. This system counts, sizes and images particles in a sample. The FlowCAM also provides the option of colour analysis and detection of living organisms by means of fluorescence. The measurement process is as follows:

  • Particles are suspended in water
  • The water is pumped through a flow cell
  • Optics and a CCD camera magnify and capture an image of each particle, measuring its shape and size
  • The results are displayed as a scattergram.
  • The user selects distributions to display, and regions in the scattergram of particular interest can be selected and displayed in more detail.
  • A library of information is housed in the system for screening future samples, if necessary.

Real life applications

In real life, particle size and shape determining technologies like those FlowCAM incorporates are used in applications like:

  • Water analysis for environmental purposes, measuring things like plankton, algal blooms and levels of sedimentation
  • Biotechnological settings, where quantification of enzymes or fermentation processes is needed
  • Process monitoring, which covers most industrial applications – monitoring emulsions and dispersions, and in the polymer and pharmaceutical industries.
  • Formulation monitoring, used for solid substances like topical cosmetics, flavour carriers, inks or pigments.

Find an imaging instrument

If you want to undertake particle imaging, the first step is to get the right instrument for the job. ATA Scientific carries a range of quality scientific instruments suited to your needs. Contact us to find out which instrument you need for particle imaging today.

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Particle Size Analysis: A Glossary of Terms

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In the fascinating world of particle size analysis, there are many difficult terms that you may need to get to grips with. Here we’ve provided a glossary of terms from Agglomeration through to Zeta Potential — it’s truly an A to Z of particle size analysis.

Agglomeration

A jumbled collection or mass of particles that have collected together; furthermore, the collection of these particles is known as “agglomeration”.

Aqueous solubility

Measured by weight, this refers to the maximum percentage of a substance that dissolves in a unit volume of water.

Bioavailability

The extent to which a living organism is able to absorb a drug into its systemic circulation. Bioavailability is important in ensuring drugs have their desired effect in the body.

Chromatography

A method of separating a mixture of compounds by passing them through a medium in which the components progress at different rates.

Coarse particle fraction

The percentage of a material which is composed of large particles.

Dose uniformity

The extent to which the active material within a sample of dosage units remains uniform. It is usually expressed as a percentage of the average content.

Hydrodynamic volume

The overall volume of a polymer when it is situated within a solution. The hydrodynamic volume can be measured by the way the polymer behaves in that solution.

Laser diffraction

A technique for measuring particle size which is predicated on the idea that particles moving through a laser beam will scatter light at an angle directly proportional to their own size. Laser diffraction is one of the most effective methods of particle size analysis.

Milling

The grinding of materials into smaller particles.

Oligomer

A molecule that consists of just a few repeating units, or monomers, which bind together chemically.

Particulate

Small subdivisions of matter that can be found suspended in a gas or liquid.

Percutaneous

Anything which is administered or absorbed through the skin, such as an injection or transdermal drug.

Polydisperity

The state of having a broad range of particle sizes within a semisolid; this stands in opposition to monodispersity, where the particles are all of the same size. Polydispersed materials tend to pack better than monidspersed materials.

Polymer

A large molecule composed of many repeating units, or monomers, which bind together chemically.

Rheology

The study of the deformation and flow of matter, usually in reference to the flow of liquids but also sometimes to semisolids.

Sedimentation

A naturally-occurring process whereby solid particles settle out of the fluid carrying them and come to rest against a barrier.

Semisolid drug

Otherwise referred to as simply a ‘semisolid’, it’s a pharmaceutical product that has some properties of solids and some properties of liquids. Common examples include creams, ointments or gels.

Shear rate

The rate that contiguous fluid layers move in relation to each other.

Size Exclusion Chromatography

A form of chromatography whereby molecules in a solution are separated based on their varying hydrodynamic volume.

Transdermal patch

A patch which is applied to the body in order to administer a certain amount of drugs through the skin and, subsequently, into the bloodstream.

Viscosity

The resistance that a liquid shows to being deformed by sheer stress.

Zeta potential

The effective charge on a particle that is immersed in a liquid.  This can have a significant effect on the stability of particles in suspension.

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The Methods of Gel Permeation Chromatography

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In this particle size analysis article, we’ll take a look at two brilliant new methods of gel permeation chromatography (shortened to GPC). Specifically, we’ll look at the benefits of using light scattering detectors and viscosity detectors, as well as how these methods can be combined with more traditional GPC methods such as refractive index detection in order to get the best results.

What is GPC?

In its traditional form, gel permeation chromatography (GPC) is a proven and effective method for determining average molecular weight of polymers and small molecules. It also enables us to ascertain the overall molecular weight distribution. However, conventional GPC does have its limitations. For example, the molecular masses provided by conventional GPC are all relative. In GPC molecules are separated according to hydrodynamic volume, not molecular weigh.  Molecular weights and molecular weight distributions are determined by comparing retention times with molecular weight standards. A calibration curve is utilised in order to achieve this.

Since this really depends on the polymer that is being used, true molecular masses can only be determined if the samples are precisely the same structure. This shortcoming can lead to large deviations occurring in branched samples, as their molecular density is significantly higher than that of linear chains.

The most common detectors used in conventional GPC are:

  • Refractive Index (RI)
  • Ultraviolet (UV)

However, their signals rely on concentration only, not on polymer size or molecular weight. As we’ve already mentioned earlier in this article, light scattering detectors and viscosity detectors have been shown to fix the problems that have for a long time been associated with conventional GPC.

Light scattering detectors

The signals that are provided by static light scattering detectors are directly proportional to the molecular weight of the polymer, as well as concentration of molecules and their refractive index. So the advantage of using static light scattering detectors in GPC is that molecular weight can be gleaned without the need to create a calibration curve.

Viscosity detectors

The signal provided by viscosity detection is relative to intrinsic viscosity and polymer concentration. Intrinsic viscosity is inverse to molecular density, so measurement of intrinsic viscosity gives a good indication of molecular structure.

The famous Mark-Houwink plot shows the double logarithmic plot of molecular weight against intrinsic viscosity. It’s an important plot when it comes to polymer structure analysis, as it mirrors structural changes in the polymer (such as chain rigidity).

By their powers combined

By using the advantages of refractive index detectors, light scattering detectors and viscosity detectors, triple detection can be achieved. Light scattering enables accurate molecular weights to be determined; intrinsic viscosity provides structure information; and concentration gives quantitative ratios of different species. It also enables the differentiation of monomers, dimers, trimers and aggregates.

ATA Scientific offers scientific instruments that can be used for GPC and other associated processes. Contact us today for more information on how we can help you find the right instrument.

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The Benefits of the Zetasizer

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In order to be effective, topical oil-based products, or ‘semisolid’ drugs, need to be able to penetrate the skin in a manner that allows them to be delivered to the body’s circulation. Whether it’s for beauty, medicine or any other purpose, the challenge of delivering semisolids into the body is crucial to the success of any given semisolid product.

Measuring the size of particles within these semisolids is the key to ensuring the product is delivered in the most effective manner. Various methods of particle size measurement or analysis are used to measure these materials, including laser diffraction and dynamic light scattering. Further to this, by using an instrument called the Zetasizer, scientists can also understand the variable effects of pH and temperature on the delivery system.

Dynamic light scattering

In order to guarantee the size of the nanoparticles remains consistent at the pH and temperature that will be found on the human body, the process of dynamic light scattering (DLS) can be used. DLS measures the intensity of scattered light from particles suspended under Brownian motion, before analysing fluctuations. DLS is so sensitive that it can track changes in particle size to less than 1nm across, making it very nicely suited to examining potential particle size shifts in the human body.

pH and temperature changes

By studying the effect of pH changes on the nanoparticles, we can finely tune the molecular change that may result when being applied to the human body. For example, when pH values are low, the diameter of the particles increases; if the pH level is raised again, then it will be restored to its former size. Using this technique allows us to control the size of the nanoparticles in the body. Alternatively, we can also use temperature instead of pH; higher temperatures make nanoparticles more hydrophobic, resulting in larger particle sizes.

An example

Take, for example, the Lipodisq delivery system, which copies the way naturally-occurring HDLs [high-density lipoproteins] bind cholesterol in the body. The nanoparticles of the Lipodisq system are able to find a way through the skin while still carrying the pharmaceutical agents with them to be delivered into the bloodstream – but they need to be exactly the right size. In fact, the suitable size range is very small; if the nanoparticles are larger than 50nm (nanometres) in size, they will not be able to breach the outer layer of the skin. If they’re less than 5-10nm, they will be too unstable to properly transport the required ingredients. Therefore, these nanoparticles must fall somewhere between 10nm and 50nm in order to be effective.

Using the Zetasizer

Particle size analysis technology is already having dramatic benefits to the pharmaceutical industry as the ability for executing controlled releases of semisolids into the body is increased. Any method that achieves particle size measurement can go a long way to aiding in this regard, but the fact that the Zetasizer is capable of taking into account variables such as pH and temperature make it an outstanding tool and one that will undoubtedly be used on a more regular basis.

ATS Scientific offers a range of Zetasizer instruments, so browse our product range today to find the right one for you.

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Using Dynamic Imaging Particle Analysis to Characterise Biologics

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In recent years we have seen an increase in the role of biologics in medicine. Biologics are medicinal products that are created by biologic processes instead of chemical synthesis; these include products such as blood, vaccines, gene therapy, allergenics or somatic cells. Because of the increased role of biologics, the need to characterise particulate matter within those biologics has increased as well. In this article, we’ll take a look at how dynamic imaging particle size analysis is being used to characterise particulates in biologics, as well as some of the factors that need to be considered when using the technology.

The early days: Light Obscuration

In the early days of particle analysis in biologics, analysts used light obscuration techniques to attempt characterisation, but this method meant they faced a few hurdles. These were as follows:

The transparency of aggregated proteins

Biologics are subject to protein aggregation — that is, the formation of larger particles from a combination of smaller ones. Because aggregated proteins are transparent or “soft”, they are much tougher to detect than opaque particles, and light obscuration technology was not always able to detect them.

The amorphousness of aggregated proteins

The shape of the aggregates vary from circular to strand-like shapes. Light obscuration devices are capable of measuring size, but they assume that the particles are spherical in shape. Because aggregates could be absolutely any shape, many measurements were inaccurate.

The biologics are delivered through pre-filled syringes

This could result in silicone droplets being present, and might also result in inflated particle counts.

The introduction of Dynamic Imaging

A dynamic imaging particle size analyser, on the other hand, is capable of making various measurements even if the particle is transparent. It works by capturing digital microscopic images of biologic particles as they make their way through a flow cell. The result is a more detailed description of the particle and its shape, which also allows for analysts to recognise the difference between aggregates and silicone droplets.

Dynamic Imaging limitations

It would seem, then, that dynamic imaging has solved the problem of characterising biologics — but that’s not to say that the technology is perfect. In particular, there are three factors that analysts must consider whenever characterising biologics with the use of dynamic imaging. These are:

Resolution

Digital images don’t show the real world in the same way that the human eye does. Instead, images are pixelated, which means dynamic imaging systems can only count particles that are no smaller than 1µm, and can only differentiate shape for particles larger than 2-3µm. Electron microscopy is needed to measure particles smaller than these limits, but such a technique has many shortcomings of its own.

Colour threshold

Images are not only limited in size; they are also limited in their colour scale. Because imaging systems are backlit, particles in the optical path reduce the light that passes through to the camera sensor and, as such, the incoming pixel intensity becomes darker. This works fine for opaque particles, but not so well for the transparent protein aggregates. Additionally, the amorphous nature of the aggregates causes light to bend awkwardly around the structure, creating further confusion.

Image quality and sharpness

This great effects on the precision of particle measurements. The less sharp the image, the lower the accuracy when attempting biologic characterisation.

Finding a particle size analyser

Particle size analysers play a key role in biologics, so it’s important that you one you use is of a high quality and from a trusted supplier. ATA Scientific offers a range of quality particle size analysers perfect for characterising particulates in biologics. Contact us today for more information.

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A Guide to Understanding Laser Diffraction Principles + Theory

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Laser diffraction has emerged as one of the most important and effective techniques in the world of particle size analysis thanks to its fast, non-destructive properties, its suitability for a broad range of particle sizes, and its ability to be fully automated. As a technique that measures particle size distribution for both wet and dry dispersions, it offers many advantages, including a high level of precision, fast response, high potential for the repetition of results, and a wide measurable particle diameter range.

The Role of Laser Diffraction in Particle Analysis

Over the last twenty years, laser diffraction has, to a large extent, replaced traditional methods of particle size analysis, such as sieving and sedimentation (a previously common practice for granular material).

Recognised for its capacity to reproduce results and size range spanning five orders of magnitude, laser diffraction has emerged as the technique of choice throughout the pharmaceutical industry where examining particle size is crucial in determining the performance of a product or process.

One example of this is the efficacy of ‘semisolid’ drugs, that are often used in ointments, creams, gels or lotions. Semisolid drugs have some of the properties of solids and some of the properties of liquids, so understanding the size of the particles they contain is crucial in knowing how each particular product should be delivered to the human body.

The scope for automation means modern particle size analysis can often be a matter of loading the sample and hitting a button, which is an exciting prospect for pharmaceutical companies looking to scale their research.

How Does Laser Diffraction Work

Laser diffraction is grounded in the relationship between light and surfaces (in our case particles). When light and surfaces interact, it results in either solely or a mix of refraction, reflection, absorption or diffraction. The latter offers the greatest scope for accurate particle size analysis assuming the diffraction system contains the following:

  • A laser – This is necessary as a source of intense and coherent light that’s of a defined wavelength.
  • A sample presentation system – This ensures that the material being tested successfully travels through the laser beam as a stream of particles that have a known state of dispersion and can be reproduced.
  • Detectors – Specialised detectors (typically an array of photo-sensitive silicon diodes) are applied to measure the light pattern produced across a range of angles.

Laser diffraction is what is known as a ‘cloud’ or ‘ensemble’ technique meaning it offers a result for the entire sample, as opposed to providing information for individual particles. Ensemble techniques use a broadened beam of laser light which scatters the light on to a specialised lens to offer a greater collection. During a laser diffraction experiment, particles are illuminated in a collimated laser beam – producing a scattered pattern of light – allowing scientists to deduce particle size and shape.

As a general rule, the bigger particles will bring about a high intensity of scattering at low angles to the beam and the smaller particles, on the other hand, create a low-intensity signal at far wider angles. These angular scattering patterns are measured with various specially-designed detectors and particle size distribution is determined from the resulting data.

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Laser Diffraction Models

Laser diffraction relies on optical models to help scientists understand data produced. The Mie scattering theory and the Fraunhofer diffraction approximation are two key theories used to calculate the type of light intensity distribution patterns produced by particles of various sizes.

Fraunhofer Theory

In the late 1970s, when laser diffraction systems were first introduced, limited computing power made it difficult, and impractical, to rigorously apply Mie theory. The Fraunhofer approximation of the Mie theory was a much easier model to use and was therefore widely adopted at this stage. It provides a simpler approach by additionally assuming that:

  • The particle size must be relatively large. It is recommended that 10x the laser wavelength is the minimum for this approximation.
  • The particles being measured are opaque discs.
  • Light is scattered only at narrow angles.
  • Particles of all sizes scatter light with the same efficiency.
  • The refractive index difference between the particle and the surrounding medium is infinite.

Mie Scattering Theory

Mie theory uses the refractive index difference between the particle and the dispersing medium to predict the intensity of the scattered light. It also describes how the absorption characteristics of the particle affect the amount of light which is transmitted through the particle and either absorbed or refracted. This capability to account for the impact of light refraction within the particle is especially important for particles of less than 50µm in diameter and/or those that are transparent.

Mie theory is based on the following assumptions:

  • The particles being measured are spherical.
  • The suspension is diluted, so that light is scattered by one particle and detected before it interacts with other particles.
  • The optical properties of the particles and the medium surrounding them are known.
  • The particles are homogeneous.

Choosing the Right Scientific Solution

Advances in computing power allow modern laser diffraction-based particle analysers to fully exploit the description of light scattering developed by Mie 100 years ago. The examples included here demonstrate how the ability of Mie theory to correctly predict the effect of particle transparency and changes in scattering efficiency make it superior to the Fraunhofer approximation, particularly for particles less than 50µm in diameter. ISO13320 recognises these benefits, concluding that the Mie theory provides an appropriate optical model across the full laser diffraction measurement range.

Modern measurement systems enable easier access to the powerful capabilities of the Mie theory through the inclusion of, for example, a database of refractive indices. These systems provide the greatest accuracy for the widest possible range of materials.

The Mastersizer range of laser diffraction particle size analysers set the standard for delivering rapid, accurate particle size distributions for both wet and dry dispersions.

Find Your Particle Size Analysis Solution

The team at ATA Scientific are experienced leaders in the scientific instruments industry, specialising in particle size analysis. Contact a member of the ATA Scientific team to find the right solution for your needs today.

10 Applications for Particle Size Analysis

10 Applications for Particle Size Analysis

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Particle size analysis involves using methods such as laser diffraction to measure the size of particles within a sample. By measuring and controlling particle size, manufacturers are able to deliver higher quality products. Here we look at 10 industries or products that have benefited from the application of particle size analysis.

1. Asthma puffers

For asthma sufferers, inhalers can help relieve respiratory discomfort on a day-to-day basis, and may even be the difference between life and death.

Studies have shown that asthma sufferers don’t always use their puffers according to directions, and the effectiveness of an inhaler can vary between users. In fact there are several factors that determine the efficacy of a puffer, including;

  • Construction of the device
  • Particle size of the drug
  • Technique of the user
  • Respiratory flow of the user

It is near impossible to ensure that asthma sufferers always chose the right puffer or consistently use the correct technique. Particle size, however, is one factor that manufacturers can control to ensure that asthma medication is delivered as efficiently as possible. Particle size analysis plays a key role in developing aerosols for effective delivery into the asthma sufferer’s lungs.

2. Inks

From pens, to computer printers, to professional book and screen printing – ink applications are wide ranging. Ink is essentially a fluid used to mark solids and there is low tolerance for error when it comes to the manufacturing quality of ink.

Particle size in pen ink relates largely to pigments which can affect:

  • Viscosity of the ink
  • Colour
  • Stability of the ink

Through careful analysis, manufacturers can gain control over the performance of fundamental ink properties, resulting in a better overall product and manufacturing process.

3. Cement

In cement manufacturing, there are two key areas where laser diffraction particle size analysis can have a material impact:

  • Controlling manufacturing costs
  • Increasing performance

Prior to the wide availability of particle size analysis equipment, common methods included the use of sieve and air permeability tests. While these methods are still in use, laser diffraction through particle size analysis is faster, cheaper and easier to use and automate.

When particle size in cement manufacturing plays such an important role in both price and performance, it’s no wonder particle size analysis is so widely used in this industry.

4. Road safety

The effectiveness of reflective surfaces used in road safety measures is dependent on the particulate size and distribution of reflective material.

Glass beads are typically used as the reflective surface. The reduction of impurities and promotion of desirable particle distribution can aid manufacturers in the production of glass beads that:

  • Reflect over greater distances
  • Reflect more uniformly
  • Last longer

Given the importance of providing clearly visible and reflective markings on long stretches of road and highway, accurate testing using particle size analysis is vital to ensure consistency and improvement.

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5. Ceramics

Ceramics are most commonly produced from powders. The size and distribution of particles within these powders has significant effects on both the function and manufacturing of ceramic products. Depending on the function of the ceramic, particle size analysis can aid in:

  • Densification
  • Transport
  • Mechanical properties

A single gram of ceramic powder can have billions of particles, with a total surface area of several square meters. Particle size analysis allows an understanding of both particle distribution and percentage of impurities within the powder. Using laser diffraction, the appraisal process is much faster and easier to accomplish than with a manual sieve.

6. Semisolid pharmaceuticals

In general terms, semisolids possess properties of both liquids and solids. In pharmaceuticals, semisolids are used for specific applications or in situations where the delivery of the drug is critical for patients who can’t accept traditional delivery types.

Example of semisolid pharmaceuticals include:

  • Ointments
  • Gels
  • Lotions
  • Creams

Because medicine is critical to our health and wellbeing, there is little room for error. With the help of particle size analysis, pharmacists and manufacturers can gain more accuracy in drug design and quality control, benefiting both patients and companies.

7. Cosmetics

The beauty industry is heavily reliant on semisolid products such as powders and creams. Particle size is a key factor in the consistency of these materials and laser diffraction can benefit analysis and development of a variety of cosmetic products.

  • Generally, moisturisers are oil in water emulsions, the formulation of which requires knowledge of both the particle size distribution of the oil dispersal and the zeta potential, which is the charge on the surface of the droplets.
  • Lipstick colour is related to the use and selection of pigments. Particle size affects the colour and effect of the product. Larger particles, for example, create sparkle and other lustre effects, while small particles typically create a ‘silky’ finish.
  • The particle size and distribution of foundations and other facial powders can affect the stability of the product, as well as appearance and capacity to provide sun protection through the use of light scattering components like zinc oxide.

When it comes to the highly competitive cosmetics industry, most manufacturers strive for perfection. Particle size analysis is therefore an indispensable tool in research and development of cosmetic products.

8. Soils and sediments

From farming and agriculture to building, construction, conservation and mining – soil and sediment are critical materials in a range of high value industries.

Soil and sediment can be classified into categories, most commonly:

  • Sand
  • Silt
  • Clay

Each type exhibits different qualities and varying levels of stability, water retention, aeration and drainage. Across all industries that require knowledge of soil properties, laser diffraction particle analysis can offer insight into the distribution of particulate types and the potential risks and benefits of given soil samples.

9. Food and drink

Size and distribution of particles in food and drink products can affect the taste, texture, appearance and stability of the product.

For example, coffee beans need to be ground into fine particulates after roasting and before brewing. Optimal levels of particulate size will depend on the type of bean, desired flavour and method of brewing. For coffee roasters, control over particle size is therefore extremely important for consumer experience.

Chocolate is another product that can benefit from laser diffraction. ‘Mouth feel’, which describes the optimal creaminess of eating chocolate, is a key factor in delivering a superior consumer experience. As chocolate is primarily a combination of milk solids and cocoa powder, particle size analysis can help chocolate producers manipulate their production process to maximise customer satisfaction.

10. Plastics

Plastics and polymers invariably benefit from particle size analysis. Polystyrene, for example, has particle sizes ranging from 20 nanometers to 1000 microns.

In most plastic manufacturing processes, the starting material is a pellet or powder. These feeder materials must meet a number of criteria, including:

  • Melting point
  • Flexural strength
  • Compressive strength
  • Impact resistance
  • Chemical resistance
  • Density
  • Tensile strength
  • Chemical composition

Each of these criteria are greatly affected by the particle size distribution of the pellets or powder. Particle size analysis can also improve transport and packaging processes – pellets and powders are easier to ship than heated slurries.

The benefits of particle size analysis

By using laser diffraction to measure particle size, this technique allows analysis of particle behaviour and consistency in a range of products. Understanding particle size gives manufacturers the information and control needed to ensure delivery of high quality products across a variety of industries.

If you’re in an industry that relies on particle size analysis, you’ll benefit from investing in quality instruments to measure particle size. ATA Scientific offers a range of products perfect for this application, so browse our product range today.

Basic Principles of Particle Size Analysis

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What is particle size analysis?

Particle size analysis is used to characterise the size distribution of particles in a given sample. Particle size analysis can be applied to solid materials, suspensions, emulsions and even aerosols. There are many different methods employed to measure particle size. Some particle sizing methods can be used for a wide range of samples, but some can only be used for specific applications. It is quite important to select the most suitable method for different samples as different methods can produce quite different results for the same material.

Who uses particle size analysis?

Particle size analysis is a very important test and is used for quality control in many different industries. In just about every industry where milling or grinding is used, particle size is a critical factor in determining the efficiency of manufacturing processes and performance of the final product. Some industries and product types where particle sizing is used includes:

  • Pharmaceuticals
  • Building materials
  • Paints and coatings
  • Food and beverages
  • Aerosols

Equivalent sphere theory

One basic problem in particle size analysis is characterizing particles using just one number. Most particle sizing techniques aim report particle size distributions on a two dimensional graph (ie. particle size on the x-axis and quantity of material on the y-axis). However, the difficulty with this is that there is only one shape that can be described by a single unique number, and that is the sphere. Only a sphere measures the same across every dimension. If we say we have a 100 micron sphere, this describes it exactly. We cannot say the same for a cube, where the 100 micron may describe the length of one edge, or even a diagonal transect.

For this reason, all particle sizing techniques measure a one dimensional property of a particle and relate this to the size of an “equivalent sphere”. One example is to measure the surface area of a particle and then report the size of sphere which has the same surface area. Probably the most common method is to measure the “volume” of each particle in a sample and report the size of a sphere which has the same volume as the particles being measured (this is what is done in Laser Diffraction methods).

Particle Sizing by laser diffraction

Laser diffraction has become one of the most commonly used particle sizing methods, especially for particles in the range of 0.5 to 1000 microns. It works on the principle that when a beam of light (a laser) is scattered by a group of particles, the angle of light scattering is inversely proportional to particle size (ie. the smaller the particle size, the larger the angle of light scattering). Laser diffraction has become very popular because it can be applied to many different sample types, including dry powders, suspensions, emulsions and even aerosols. It is also a very fast, reliable and reproducible technique and can measure over a very wide size range.

Other methods

There are many other methods for analysing particle size, other than laser diffraction. Sieving is one of the oldest particle sizing methods and is still widely used for relatively large particles (ie. > 1mm). When measuring very small particles (ie. < 0.5um), Dynamic Light Scattering is by far the easiest methods to use. And if you need to measure morphological properties of particles, (ie. shape as well as size), then image analysis methods are the only way to gain the extra information.

Contact ATA Scientific today for a free consultation.

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Methods of Measuring Molecular Shape, Weight and Size

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Who wants to measure molecules?

The answer is a surprisingly broad range of people and companies. Molecular weight and size is most often used in identification of proteins, and in characterisation of polymers.

Molecular Weight is commonly measured in industries such as::

  • Pharmaceutical industry
  • Biotech research
  • Medical analysis
  • The food industry
  • Petroleum and polymer industries

Measurement methods for molecules

Molecules are not simple shapes – unlike the fairly compliant, mathematically-uncomplicated atom, which is spherical, molecules are difficult to define as a simple shape. Hence, two measurements have become industry standards – the radius of gyration and the hydrodynamic radius – and analytical instruments are geared towards obtaining these.

Radius of gyration

Scientific instruments can be used to identify the centre of mass and dimensions of a molecule; this is its radius of gyration. It is measured directly using static light scattering; however this method has limitations at sizes lower than 10-15nm, and also for large molecules like polysaccharides. Viscometers are the tool which is most often used for determining radius of gyration, using the Flory-Fox equation.

Hydrodynamic radius

This is a behavioural property of a substance – a measurement of size based on how it moves, which means that it is much more useful in industrial or practical settings.

Size exclusion chromatography

Size exclusion chromatography is the method by which scientists determine the molecular size (not the weight!), of a particular substance.  Molecules are separated in columns packed with porous substances, which might include glass beads, polystyrene gels, silica gel, etc. Larger molecules elute more quickly through the columns, since the molecules cannot fit into as many spaces.    A concentration detector is placed at the bottom of the GPC columns to determine the amount of material of each size fraction. In traditional SEC/GPC systems, operators need to pass known standards through the columns before the sample.  By creating a calibration curve of size versus elution time, particle size of unknown samples can be calculated.

In more recent times, addition of other detection techniques such as Static Light Scattering and the Intrinsic Viscosity detector provide direct measurement of molecular weight and size so that traditional calibration techniques are not required.

Gel permeation chromatography

SEC is also commonly referred to by other names. When an aqueous solution is used to carry the sample through the column, the technique is often called “Gel Filtration Chromatography”, and the name “Gel Permeation Chromatography” is often used when solvents are used to carry the substance in question through the packed columns.

Get the right instrument

Using the right method to measure molecules is very important, just as using the right instrument for measuring molecules is essential too. ATA Scientific offers a range of scientific instruments, including the Malvern Omnisec – Advanced Multi-Detection SEC/GPC, that can assist you in undertaking your measurements, so contact us today to find the instrument you need.

Looking for the perfect analytics instrument for YOUR next big discovery?

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