Exploring Weightings for Ophthalmic Suspension Testing

[dwilkerson]

Equipment: Nicomp 380ZLS&S Sub-micron Particle Sizer &
Malvern Mastersizer X

Material: Ophthalmic Suspension, viscous and opaque

When installing these instruments the technician started explaining why the Volume weighting was the most representative measurement for what I'm testing.

For example, if the suspension or emulsion average particle diameter is 500nm the volume weighting will read around 500nm and the intensity weighting will read a little lower - maybe 300-400nm, then the number weighting will read very low - less than 100nm.

Why are these weightings so different? Is it my sample preparation? Can anyone explain why volume should be my representative reading and not intensity or number?

Thanks,
D. Wilkerson

 

[Valerie Park]

The reason why volume weighting should be the most representative measurement of what you are testing is because it takes into account the size and shape of the particles. Intensity and number weightings only take into account the size of the particles and not their shape. Volume weighting provides a more accurate representation of the size distribution of the sample since it accounts for both the size and shape. This is especially important for samples that have a large range of particle sizes, such as suspensions and emulsions. It also allows you to make better comparisons between different samples, since the size and shape of the particles can vary widely.