Greetings from the Malvern development labs!

You may have seen that we have recently launched Hydro Sight, an imaging accessory for the Mastersizer range. This is a very exciting time for us (and not just because they’ve given us some cake and snazzy green t-shirts to celebrate…) – Hydro Sight is the first Mastersizer Cake product of the brand-sparkly new Analytical Imaging development team!

I’m Katy and I work on application development within the team and wanted to give you a behind-the-scenes look at what we do. One of the novel features I’ve been working on with Hydro Sight is the Dispersion Index (DI) parameter and how it can be used to assist laser diffraction method development.

The Dispersion Index (DI) is effectively a measure of disorder within an image frame. Every frame is composed of a series of pixels, each of which has a greyscale intensity value which can range from 0 (black) to 255 (white). The DI is a measure of the variation in this greyscale intensity across the frame.

So that’s the maths bit (and the somewhat tenuous excuse for my title…) – what does it translate to in a practical sense and how can it actually be used in an applications setting? Well, it turns out you can use this property to monitor changes in the dispersion state of your sample in support of the data provided by the Mastersizer.

Take toner, for example. Initially it contains a few agglomerates alongside the primary particles, but with stirring and the application of ultrasound the agglomerates are dispersed. Images captured during this transition process will become increasingly non-uniform: the DI will increase, alongside an increase in the laser obscuration of the Mastersizer. Once fully dispersed the size distribution and laser obscuration from the Mastersizer will remain stable and the DI will plateau, indicating that the dispersion is stable.

toner dispersion profile

Of course, sometimes samples misbehave and start to agglomerate. In this case, the second parameter – the Relative Standard Deviation (RSD) of the DI – can help. It became apparent during our studies that looking at the variability of the DI across a number of frames could yield more information about the state of the sample. If a sample has become more disperse (more homogeneous) the variation in DI between frames is reduced: overall the RSD drops over the course of the measurement. Conversely, if a sample is agglomerating (becoming less homogeneous due to the presence of agglomerates) the variation in DI between frames increases: overall the RSD increases over the course of the measurement. Consequently, the DI and RSD profiles can help to confirm conclusions drawn from the Mastersizer results.

Should you want to discover more about the DI and RSD head over to these technical and application notes. As for me, I hope to be blogging very soon about ways in which the Hydro Sight can help identify when more than one sample process is occurring.

Further Resources:

Playback the Hydro Sight & Hydro SV launch event

Download an instant demo of the Hydro Sight software

Technical Note: Dispersion Index and Dispersion Index RSD Parameters Measured on the Hydro Sight

Application Note: Applying image analysis to support development of sizing methods

Related Blog Posts:

A picture paints a thousand particles

Powtech Vox Pops – First Reactions to New Mastersizer Capabilities

A Sneaky Peek Backstage @Powtech

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