Discussion Category:  Particle Size Analyzers

difference in size with intensity and number

dear Mr/Mrs

 I analysed 4 samples with zetasizer to earn size of nano capsules but there are a big difference between obtained size by number and intensity. for example, for a sample:

Z-average (d.nm) by intensity= 175.4

mean size by nmber= 32.2

which of them is correct?

 

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Asked by

zeinab
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avatar placemarkReply by
Malvern Panalytical

The instrument measures/calculates the distribution by intensity from the raw data, so the intensity distribution is the primary result. The number (and volume) distributions are based on calculations, taking into account the optical properties of the particles measured. In addition, when considering the scattering intensity, a single large particle is contributing a lot more scattering (intensity) than it is contributing to the count (number) - number distributions tend to skew towards the smaller sizes for polydisperse samples for this reason.

If you would like to discuss this further, please contact the Helpdesk. http://www.malvern.com/en/about-us/contact-us/

The Malvern team

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avatar placemarkReply by
zetasizer

Both answers are correct. They describe different aspects of your sample. 

Please take a look at the blog Intensity Volume Number : Which size is correct?

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