Collaboration with Astrazeneca has lead to the development of the Subsieve Autosizer (SAS) solids particle analyser from HEL.
Astrazeneca had been using the Fisher Sub Sieve Sizer (FSSS) for obtaining development and QC data for over 30 years.
This instrument works on the principle of particle sizing by air permeability, which was established in the 1940s for companies to prove the batch-to-batch consistency of products.
John Sherwood, Astrazeneca's associate principle scientist, said: 'The technique gives a measure of the SSA (specific surface area) of a compound.
'With the measurement of particle size, one is interested in a property of the particles not necessarily the particle size distribution itself.
'Hence, when assessing the bio-availability or lubricating properties of a compound, one is interested in the surface properties of the particle size distribution of the compound, such as the "envelope" surface area, which is measured directly by the permeability technique.
'Although the Fisher is an excellently designed instrument, there has always been a desire to update it so that it could be more easily calibrated, reduce the operators involvement and to produce an automated electronic report.' Last year, Sherwood approached the manufacturer to purchase a new FSSS system and found that it had been discontinued.
'This had wide implications for Astrazeneca, as the SSA has become one of the key batch release parameters for over 50 per cent of our compounds,' added Sherwood.
'Alternative particle sizing techniques were considered.
'However, to change to another type of technique, such as light scattering, would be both expensive in capital costs and resources, and would need significantly more work to validate.' It was then that a colleague recommended HEL to Sherwood.
After initial discussions it became clear that HEL had the internal capabilities to take on this development.
Having in-house software, mechanical and electrical development engineers, Sherwood was confident that the company was able to take this product from initial design through to manufacture.
The Subsieve Autosizer (SAS) is the basis of a new generation of measurement of particle sizing by air permeability.
It improves on the FSSS's performance and offers automated functions together with electronically recorded data.
It reports particle sizes in the range 0.2 to 75um and calculates the resulting SSA and does this based on the pressure drop across a packed bed of powder.
By varying the sample height and the porosity of the bed, average surface area and particle size can be determined as a function of pressure drop in accordance with the Carmen equation.
'The SAS is operated by HEL's automation software with touch-screen interface, which makes operation and report generation simple and intuitive,' said John Lee, project manager at HEL.
