Calculating The Result - Malvern Mastersizer Series Getting Started

(imaginary refractive index) and the refractive index of the medium that the
particle is suspended in (dispersant).
Once the Malvern software knows this information it can calculate the expected
scattering pattern from these particles. This scattering pattern is known as the
"presentation". The presentation is identified by a label of the form "3OHD".
The details of how these codes are made up will be discussed later.
There are three ways of selecting a presentation.
. The easiest way is to use one of the four "default" or "system" presenta-
tions. These are;
Fraunhofer (3$$D). This is the presentation that is used when you wish
to use the simpler Fraunhofer model.
Standard - Wet (3OHD). This is a presentation that takes a "middle of
the road" value for the refractive index and adsorption of the sample and
assumes that the particle is suspended in water.
Standard - Dry (3RHA). This presentation is the same as standard-wet
except assumes that the particle is suspended in air.
Reference Reticle (3$$1). This is the presentation that is used when the
Diffraction Reference Reticle accessory is used to validate the system.
Obviously this will only be used if you have the accessory. Read the
Diffraction Reference Reticle accessory manual for further details.
. For a more accurate choice you can enter the refractive index of the particle
etc. and the software can then find the nearest match from the many pre-
calculated presentations stored on the computer.
. Thirdly, if you require an exact presentation you can again enter the particle
details and then ask the software to generate the exact presentation.
You may ask yourself "If I can generate the exact presentation why bother with a
default or near-match choice". Firstly, generating the exact presentation takes
time. Secondly, for most samples using either the standard-wet or standard-dry
presentations are more than sufficient. Choosing another presentation is only
required in specific circumstances, such as the majority of particles being under
10 microns in size. Details of choosing the correct presentation are given in
chapter 5. Until you know more about choosing a presentation it is
recommended that you use one of the two standard presentations.

Calculating the result

Once the analysis and presentation have been selected, the result is calculated by
simply pressing the calculate button. The progress of the calculation of the result
G E T T I N G S T A R T E D
C H A P T E R 3
P a g e 3 . 7