Advancements In Laser Diffraction Particle Sizing

Interview conducted by G.P. ThomasSep 11 2013

In September 2011 Malvern Panalytical launched the successor to its market-leading laser diffraction particle size analyzer. Two years on, the company has further extended its laser diffraction family. Product Group Manager Paul Kippax talks about the importance of customer input in both initial and continuing product development, and how the market for laser diffraction sizing is changing.

What were the chief considerations in planning a new generation instrument when you already held a market-leading position?

Since the launch of the Mastersizer 2000 in the late 1990s, the applications for laser diffraction particle sizing have grown enormously in scope and scale. For processors of particulate materials, particle size measurement is an almost universal requirement and in many industries is essential at every stage of the production cycle.  

Within this, laser diffraction technology has gained increasing acceptance as a go-to technique for size analysis, replacing other forms of measurement, such as sieving, in critical quality control applications.

As a result, the use of laser diffraction has broadened, not only in terms of the types of materials being measured, but also because it has crossed the chasm from being a high-end research instrument applied by expert users to being used as a routine tool for quality control.

Furthermore there was, and continues to be, pressure to develop and characterize materials at the nanoscale. So overall we were looking at serving a diversifying set of needs, with some requiring enhanced performance and a broader measurement range, and others focusing more on simplicity of use.

Mastersizer 2000. Image credit Malvern Panalytical

How did you define what was needed next?

With more than 11,000 Mastersizer installations around the world, we were fortunate in being able to tap into a great deal of real-world user experience and expertise.

Laser diffraction users across industry, not just our own customers but those using competing systems, told us there was a clear need for increasingly smart, automated and robust technology that could operate seamlessly across a wide measurement range. Essentially it should be designed and supported in a way that meant anyone could obtain good measurement results.

In some organizations an instrument will have multiple users analyzing a diverse range of samples, so measurement range and sample dispersion flexibility are key requirements.  At the other end of the spectrum, simpler QC requirements mean repetitive analysis on a narrow range of sample types and sizes, often by relatively unskilled users.

So we needed to cover all bases in terms of software operation, method development flexibility and the ergonomics associated with the use and maintenance of the system. The limited bench space associated with modern QC labs also meant that a small footprint instrument would also be essential.  

Our users also highlighted the dispersion method applied in making measurements as an area where improvements could be made. In particular, the general feeling was that no laser diffraction manufacturer seemed to have fully mastered dry dispersion in a way that could effectively handle both fragile and strongly-agglomerated samples and measure over the wide particle size range demanded by many applications. This put the development of a new dry powder dispersion module at the heart of the project to develop the next Mastersizer system.

When you launched the Mastersizer 3000 in 2011 what did you expect to be the most appreciated of its capabilities and has that proved to be the case?

The small size of the system definitely got people really excited but, as we’d anticipated, the development of an overall system architecture aimed at achieving improved ease of use and maintenance, along with increased data accessibility, won people over. The performance of many of today’s analytical instruments - and laser diffraction is no exception - is extremely high, generating very large amounts of data that require interpretation.

Making that performance accessible, by providing an intelligent operating environment that guides users towards the robust reporting of results appropriate for the application, is absolutely critical.   Simplification of the report customization features within the software means people can easily produce exactly the reports they need for their specific applications, while data trending and statistical analysis displayed live during the measurement process reassure users as to the validity of their results.

With productivity a critical consideration, especially in routine particle sizing applications, users demanded simplified sample preparation for all sample types. The revolutionary dry dispersion system for the Mastersizer 3000, developed as an open innovation project with UK academia, has extended the applications for which direct powder measurement can be used. Given the choice, most people working with powder materials tend to prefer to make measurements using dry dispersion, as it’s the simplest and fastest method for laser diffraction measurement and the process of method development is conceptually easier.

Another important factor highlighted by users is the possibility for continuous development. Supported by the agile development processes we now follow within Malvern Panalytical, this has enabled us to make further additions to the software in response to continued customer feedback. As a result of this, we now provide data correlation and analysis functions to enable the transfer of methods and specifications from older laser diffraction systems and other measurement techniques.  We’ve also developed new measurement and analysis tools to support the process of method development.

Mastersizer 3000. Image credit Malvern Panalytical.

You mentioned ‘open innovation’ in connection with development of the dry dispersion system. What did that involve?

The Aero S dry powder disperser was developed in collaboration with Prof Mojtaba Ghadiri’s group at The University of Leeds in the UK. Redeveloping products when you are the industry leader can be challenging, but open innovation enabled the introduction of fresh viewpoints and new ideas, moving the whole technology to a new level.

Powder dispersion is a complex phenomenon, governed by a number of competing mechanisms. The Aero S powder disperser was designed with reference to the most up to date dry powder dispersion theories and introduces a modular dispersion system that allows the user to easily select the most appropriate dispersion mechanism for their samples.

The ability to precisely configure and control the dispersion process enables the measurement of even friable pharmaceutical actives and other organic compounds that previously would have required wet dispersion methods.

The open sharing of information and expertise between Malvern Panalytical and Leeds University accelerated the development process by bringing together academic and commercial understanding, know-how and engineering expertise. Not only did this open, collaborative working result in the delivery of a innovative product designed to solve real-world challenges, it also offers an excellent example of successful technology transfer that has benefited all parties involved.

Below is a video demonstration of the Aero S dry powder disperser.

Does everyone who requires particle size data also need all the capabilities of an instrument like the Mastersizer 3000?

Much of what we’ve discussed so far points to the increasing diversification of particle sizing and the way it is being used.  When the Mastersizer 3000 was launched our aim was to offer highly accurate particle sizing to every operator, regardless of their level of experience, and to break new ground in terms of easing the analytical burden.

Two years on it remains the market leader and it’s great to see that the features we worked so hard to engineer are now delivering real value in industrial and academic laboratories. We’re continuing to introduce further software developments that enable access to the full performance capability of the system, and at the same time have added a new entry level system to the family, the Mastersizer 3000E.

Our aim has always been to deliver the most appropriate particle sizing technology to every user and help them benefit as fully as possible from the laser diffraction technique. While new software innovations meet the need for validated system operation and expert user interactions, the new entry level system extends the Mastersizer platform to those with more basic measurement requirements. It has a smaller measurement range and semi-automated wet dispersion units.  However, add-on software packages and upgrades can be used to extend the system’s capabilities as required. I hope that both systems will help us provide the very best solutions to all our customers.

So how do you go about deciding which laser diffraction system you really need?

There are many things to consider and, depending on your environment and measurement needs, some will be more important than others. Key issues to define from the outset are the types of samples that will be measured, who will be using the instrument and where the system will be installed. It is also vital to consider what particle sizing data are really required – that is, what questions will the data you obtain need to answer in terms of the performance of your products?

With respect to sample requirements, the measurement range of the system has to keep pace with your needs, and most people making this type of purchase want to access the widest possible range in order to future-proof their investment. Sample dispersion is also critical to success and, while different applications require different dispersers, the improvements we’ve made in dry dispersion mean that it can now be used for a much wider range of sample types than ever before. If wet dispersion is used,  it is important to select a sample handling unit which can measure a suitable volume of sample and provide for control of the sample dispersion process, for instance by providing built-in ultrasound dispersion capabilities.

The ease of use and maintenance of the system are important. However, the person using the system will spend most of their time interacting with the software that controls the hardware and reports results. Indeed, feedback from Mastersizer 3000 users suggests that, more than anything else, it is the software that comes with a laser diffraction system which really determines whether using the instrument and generating appropriate information will be a pleasure or a pain.

Some pertinent questions to ask include: is it genuinely easy to operate? How simple is it to access and configure the data, filter and review measurement records, compare methods? Software that helps with method transfer can be especially helpful when looking for instrumentation that will be rolled out across multiple sites or that will need to dovetail with, for example, production protocols. Access to tools for analyzing the quality of any results can also be critical, particularly within a QC setting.

For the installation, perhaps the biggest challenge is the cramped nature of many QC laboratories. Bench space is increasingly tight in many situations, so it’s important that both the laser diffraction system itself and any sample dispersion units take up the least space possible, especially if you are working in controlled areas.

Finally there is the requirement for support. Increasingly, expert support is embedded in the instrument and software, something I expect to be an on-going trend. However, sometimes nothing beats a knowledgeable expert on the other end of a phone. With laser diffraction, as with other methods, access to applications knowledge is key, as this allows you to make best use of the technique for your particular sample. So this is where we continue to invest significant time and energy in order to develop and share the expertise that underpins productive use of our systems.

Where next for laser diffraction?

This is a particle sizing technique that just goes from strength to strength and the range and number of applications for which it is now being used is truly impressive.

Automation, ease of use, support with method development, seamless method transfer and above all utterly reliable measurement across an appropriate size range, are all simply expected.

Continuing software developments are the key to opening up even greater access to the full measurement capabilities of this powerful technique and a major area of focus at Malvern Panalytical.

About Dr Paul Kippax

Dr Paul Kippax is Product Group Manager at Malvern Panalytical, and has responsibility for the company's Mastersizer, Spraytec and Analytical Imaging product ranges.

He joined the company in 1997, starting as an application scientist. Prior to this he obtained a degree in Chemistry and a PhD in Physical Chemistry, both at the University of Nottingham in the UK.