Tag Archives: Laser Diffraction

5 Reasons to Combine Laser Diffraction Particle Sizing and Image Analysis

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.

Different Methods of Particle Size Measurement

Particle size analysis can seem a complex and intricate area. The thought of attempting to measure and draw conclusions about microscopically small particles can seem incredibly confusing and the techniques used to measure particles can perhaps seem daunting. Particle size analysers are of great use in achieving such measurements and techniques such as laser diffraction assist us to understand more about the properties of materials.

However, in order to understand some of the higher level concepts related to this area, it is necessary to have a sound grasp of the concepts that inform results.

Mean, median and mode

These three terms are too often confused and thought to mean the same thing. Far from being one and the same, these terms require definition:

Mean – Mean relates to the arithmetic average of the data.

Median – When concerned with particles, median is the value of the particle size that precisely divides the population into two halves. This means that there is 50% of the population above and 50% of the population below the value.

Mode – Mode defines the most common value in a frequency distribution. This also corresponds to the highest point of the frequency curve.

Common methods of particle size measurement

Because different dimensions of the particle are measured when different techniques are used, different results are obtained. Of the different methods of measurement, each has its own advantages and disadvantages.


While this is an old technique, it has the advantage of being cheap and particularly useful for the measurement of large particles. In industries such as mining, this can be particularly useful.

The main disadvantages associated with this technique include: it is not possible to measure sprays or emulsions and measurement of dry powders is also difficult when particles become small. Wet sieving can help to overcome this problem, but it is then very difficult to reproduce results. Materials such as clay, which are cohesive and agglomerated, are also difficult to measure.

As particles tend to orientate themselves through the sieve, operating methods and measurement times need to be standardised if accurate and meaningful results are to be obtained.


This has been a common method used (historically) in clay and ceramics industries.

There are two main problems with this process: the density of the material is needed and so it is not useful for determining particle size of emulsions where the material does not settle or for dense materials where the material settles quickly. Samples containing components of mixed density can not be accurately resolved. Measurement of small particles is very slow and therefore the process of repeating testing can be tedious.

Electrozone testing

This technique is very good for measuring red blood cells, but for real, industrial materials there are quite a few problems. It is very difficult to measure emulsions and dry powders and it is impossible to measure sprays. It is necessary to measure in an electrolyte and the required calibration standards are expensive.

Laser Diffraction

This is an often favoured technique that is considered to be one of the most accurate and reliable. It has a number of important advantages:

  • It is very flexible and can measure all types of particles (powders, emulsions, suspensions and sprays)
  • It is very rapid (answers can be produced in less than sixty seconds)
  • It offers an absolute method of particle analysis that is grounded in scientific principles and makes it possible for measurements to be taken without the need to calibrate any instrument against the standard
  • The technique provides a very wide and dynamic range
  • It is possible to measure an entire sample
  • The technique is highly repeatable.

Combine technique with instrument

The technique used to measure particle size will depend on the material being analysed, and the instrument used should be one of the highest quality. ATA Scientific is a trusted brand selling a range of scientific instruments suited to measuring particle size. Contact us today to find the right instrument for you.

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Using Laser Diffraction for Semisolid Formulations

Because they provide a solution to issues of bioavailability often seen in new drug candidates, semisolid drug formulations are becoming more and more common. These days, they make up a significant proportion of pharmaceutical dosage. When it comes to semisolid drug production, particle size is an undeniably crucial parameter. For this reason, finding an appropriate particle size analyser is of the utmost importance.

In this article, we’ll look at laser diffraction, a widely used method of particle size analysis that can be used for semisolid formulations at elevated temperature.

Why semisolids?

Something like 40 per cent of new chemical entities are challenging to modern drug delivery systems because of their poor aqueous solubility and low bioavailability. Semisolid formulations offer an answer to this problem. Additionally, patient compliance is improved, as semisolid products can be delivered painlessly and with minimal side effects.

Some examples of semisolid drugs include topical creams used for localised skin layer action (eg. Antiseptics and anaesthetics); as well as transdermal drugs that enter the body percutaneously. Semisolids have gained particular traction in transdermal delivery thanks to advances in delivery technology, such as slow release patches. When a transdermal patch is applied to the skin, the drug will enter the blood either through sweat ducts, hair follicles or the stratum corneum (the outer layer of the epidermis). However, the potential of the transdermal drugs to deliver the active ingredient is reliant on the semisolid’s rheological properties.

What makes a good semisolid?

The efficacy and safety of semisolid compounds are largely down to particle size and size distribution. These can have profound effects on bioavailability, dose uniformity and more. The relationship between product performance and particle size can be examined with data generated from the laser diffraction method of particle size analysis, which rests on the idea that particles that move through a laser beam will scatter light at an angle proportional to their size.

By applying stringent techniques in designing its particle size, the local efficacy of a drug’s entry can be maximised, and adverse reactions can be prevented. However, if settling or sedimentation occurs, efficacy will often be compromised due to irregular delivery.

Some of the methods of particle size analysis that have been used over the years include X-ray tomography, confocal imaging and scanning electron microscopy. However, these can usually only be applied while the product is being developed, and usually only with a small amount of material, which can cause problems when trying to characterise larger samples.

Laser diffraction: Why it’s the way forward

Laser diffraction, on the other hand, allows for very rapid measurement, accurate analysis, a broader measurement range, and the capability of looking at many sample types. One of its best properties is its sensitivity to changes in coarse particle fraction which makes it great for studying the instability that results from sedimentation or agglomeration. Additionally, the latest laser diffraction systems are completely automated and user-friendly.

One of the problems with using laser diffraction for semi-solids, however, is that samples are not liquid at room temperature. To deal with this, the laser diffraction system can be equipped with a dispersion cell and water bath, elevating the temperature to make more detailed particle size measurements.

Find the right particle size analyser

It’s important that you not only use the best method for analysing semisolid formulations at elevated temperature, but also use the best instrument. ATS Scientific is a trusted brand that offers a range of quality particle size analysers. Contact us today for more information.

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Particle Size Analysis: A Glossary of Terms

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.


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.


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.


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.


The grinding of materials into smaller particles.


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


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


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


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.


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


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


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.


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 Benefits of the Zetasizer

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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How to Choose a Scientific Equipment Supplier

When you’re investing money in scientific equipment, such as a laser diffraction particle size analyser, it’s important to investigate your options before making a final decision. These days getting value for money is just one of the important considerations you need to make.

Naturally, the complexity of scientific equipment means that it is important not only to choose the equipment itself but also the supplier as well. After all, equipment of such high sensitivity and precision will undoubtedly require the backup of a supplier capable of continued support long after the deal is sealed.

That’s why it’s important to look at the supplier with a critical eye to make sure you are going to get value for money and also professional backup when you need it. Whilst it is true that all manufacturers have a legal responsibility when it comes to supplying any piece of equipment, it will be of little comfort to an aggrieved purchaser if the supplier only wants to perform its legal requirements.

What you need is reassurance that your supplying company will stand beside you over the long term and be capable of providing any assistance necessary to keep your equipment in prime operating condition.

Criteria for choosing a supplier

With this in mind, let’s take a look at some of the criteria against which you should assess your scientific equipment supplier.


In the first place, you should be looking for the equipment to receive pre-sales testing to ensure that it is properly certified and that the manufacturers requirements are being met. This is often the first sign of a quality supplier and it should be offered upfront at no cost.


Don’t underestimate the training requirements. New pieces of equipment often require some time to get used to, that’s why it’s important to anticipate any training needs that will be necessary to bring your staff up to speed with the new purchase. It is at this point that you need to reassure yourself that the supplier can also provide the on-site training you will need.


All equipment needs to be maintained in accordance with the manufacturer’s specifications and with any regulatory requirements that are in place. Make sure your scientific equipment supplier is in a position to offer this.


There will be times when equipment needs to be repaired so it is imperative to ensure that your supplier is in a position to do this. Every quality supplier should have a well equipped workshop and also be flexible enough to provide you with an on-site repair service.


If your equipment requires the regular supply of consumables, make sure your supplier is able to provide these for you ex-stock. There is nothing more frustrating than waiting for supplies to be imported not to mention the costly downtime you will experience.

Choose ATA Scientific as your supplier

These simple steps make it easier to purchase something like a particle size analyser by choosing a competent scientific equipment supplier which gives you the peace of mind that you need when making such a significant investment. ATA Scientific is a trusted supplier of scientific instruments, so contact us today to find out how we can help you find the instrument you need.

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10 Benefits of Real-Time Particle Size Analysis

If you’re looking for optimal performance in the particle size analysis process, then real-time or ‘on-line’ particle size analysis methods, such as laser diffraction, are the way to go. There are several applications for real-time particle size analysis, including sticky-wet concentrated slurries, liquid emulsions, and dry particulate streams. With the use of automated on-line analysis, the frequency of measurement increases significantly, enabling a reliable and efficient data stream to be delivered.

Benefits of real-time particle size analysis

There are several benefits that can occur as a result of utilising real-time particle size analysers, outline below.

1. Increased return of investment (ROI)

These online instruments have been shown to be extremely sturdy and capable of providing 24/7 operation with only a small amount of upkeep. You can achieve visible ROI within six to 12 months of operation, with both product quality and plant capacity enhanced by automatic real-time measurement.

2. Lower energy

While milling operations are generally quite energy-intensive, consumption has been shown to see an exponential increase as particle size becomes smaller. Quality control failure can occur as a result of under-milling, while over-grinding can result in too much energy being used. With real-time particle size analysis you will see minimal energy use to create products that meet specifications.

3. Real-time control

From metal powders to pharmaceuticals, particle size is a key performance parameter in a lot of particulate products. Real time particle size analysis, therefore, makes a lot of sense. The on-line systems are capable of measuring up to four particle size distributions per second.

4. Troubleshooting

By utilising continuous measurement, you’ll be able to see the outcome of every variable in real time, which makes troubleshooting a lot easier than viewing these variables with the disadvantage of occasional off-line analysis methods.

5. Increased efficiency

Using off-line analysis to examine process parameters and their effects can be time consuming. With real-time particle size analysis, you’ll be able to evaluate these situations in minutes instead of hours. Causal links become clear at a much quicker rate than normal.

6. More intelligent process development

Since the acquisition of knowledge is the main role of process development, real-time measurement has obvious advantages. Potential problems can be detected at an early stage, speeding up the knowledge gathering process.

7. Quicker product changeover

Since, during changeover, you’ll want to get to the set point as fast as the plant dynamics will allow, on-line systems are definitely the way forward. Waiting on lab results to ascertain whether or not it’s safe to switch to the in-spec collection silo is no longer necessary; instead, you’re fed this information in real time.

8. Immediate upset detection

In general, offline analysis is done on an hourly basis (at most). As a result, any upsets may not be detected for an hour at best and response to upsets may take even longer – enough time to spoil a batch. On-line analysis allows upsets to be detected immediately.

9. Higher sensitivity to quality

Real-time data is sensitive to changing conditions, allowing for tighter process control. Off-line data, on the other hand, is usually an average taken from composite samples, which lacks the sensitivity necessary to spot out-of-spec samples.

10. Reduced operator risk

Occupational health and safety problems can arise during the sample extraction process, especially when materials are highly toxic or volatile. The use of a real-time particle size analyser eliminates this risk.

Find the right product to get the benefits

ATA Scientific offers scientific instruments suited to many scientific endeavours, including real-time particle size analysers. Browse our range of particle science products today to find what you need.

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

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A Guide to Understanding Laser Diffraction Principles + Theory

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

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

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.

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