Ask an Expert: Things I wish I knew about Laser Diffraction before writing my Thesis

經過 Steve Ward-Smith, Wednesday, 12th May 2021

Mastersizer 3000 Laser Diffraction system

A couple of weeks ago, my favorite radio station had a 1990’s throwback day. One of the DJs was asking people what they were doing in the 1990s. In the early 1990s (1992 -1994) I was a Ph.D. student investigating the properties of emulsions stabilized by protein/polysaccharide complexes. My main techniques were particle sizing by laser diffraction (on a DOS-based Mastersizer 1000 in another department), zeta potential (using a microscope and a stopwatch-based system), an image analysis technique for surface tension, and a lot of rheological experiments. Looking back at this time now, I can be critical of many things. Such as my fashion sense (I do not “rock” a trench coat / dangly earring/hat combo) and some of my science (having just picked up my thesis for the first time in years).

Not everything was better in the past

It was a different time. Whilst the internet was a thing, it was mainly USENET discussion groups (think a text based version of Facebook). Websites and browsers were just appearing but any kind of support and help was pretty much non-existent. Any training in equipment use (if you were lucky) was pretty much from someone who had occasionally used the instrument before and knew a little. And any mistakes you made were ones you quickly learned from. Like accidentally wiring the zeta potential device so it was live electrically for instance…

Discussion and advice on the most appropriate size parameters to use, what a good background was, and what analysis was the best to use, were simply not available. Looking at my data, I was doing mathematical analysis of the data myself (by hand typing results into a program) where the Mastersizer itself could have provided that information had I been told it could. It would have saved hours!

Profit from progess

Things are better now. Here at Malvern Panalytical, we have a host of expertise in applications, technical and customer support here to help you. We also contribute to organizations such as ISO who write standards in the technologies we provide. An ISO standard for a technology is a great briefing document. If you understand what it contains, you won’t be treating your technique as a black box. You’ll have a good understanding of what it can give you and how to get the best out of a system.

What I wish I’d known about particle characterization before doing my PhD

If I could go back in time and scientifically provide advice to my former self what would I say?

  1. Get a better understanding of all the parameters the machine provides by default. These are likely in most cases to be better than you, processing your results in ways that you don’t really understand, because someone else did it that way before you.
  2. Understand the optical properties and analysis you are choosing and what effect that has on your distribution.
  3. Know what a good alignment and background look like and how much sample to add to get the best quality data from the system.
  4. Understand how to export data from the system for easier manipulation later (don’t type in printouts).
  5. Get a better appreciation for the technique itself and its principles. Whilst I don’t think I ever treated the machines I used as black boxes, there were big gaps in my understanding that if I’d known, I could have got more out of my data.

Get more from your Mastersizer

In a forthcoming webinar on the 3rd of June, which I’m co-presenting with one of my colleagues, John Ddungu, we will pass on this advice to you. Hopefully, this will allow you to get more from your Mastersizer and be more confident in the results you are using in your papers and theses.

That’s the kind of thing that will never go out of fashion. Unlike tartan flannel shirts (yes, I admit to owning some, don’t hold that against me!) …

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