"Particle size reference standards have been in continuous development for the past 30 years," said Dr Rideal. "They have responded to advances in particle sizing instrumentation, the most notable of which have been in the field of laser diffraction. Today many different methods of particle sizing are in use, from sieving, one of the oldest, to automated image analysis, one of the newest. Each has its challenges and appropriate reference standards are more essential than ever."

A paper reviewing the development of reference standards over three decades, given at last December's USP Workshop on Particle Size in Rockville MD, received a warm welcome from delegates. Presenter Dr Graham Rideal of Whitehouse Scientific was delighted with the level of interest his talk elicited at the event, which has translated into continuing requests for the paper itself.

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