Latices overview

Certified Divinylbenzene (dvb) latex beads from Duke Scientific have long provided a very useful means of checking the performance of all Malvern particle sizing products (except dry powder feeders).

Traceable to the US National Institute of Standards and Technology (NIST), they are available in bottles covering a size range from 20 nm to 1000 µm, although for the purposes of checking the performance of laser diffraction instruments 100µm is the practical upper limit.

The main advantage of using these latices for laser diffraction instruments is that they are generally monodisperse and so the measurements obtained from them will be free from any distribution bias that may be introduced by differences in sample dispersion units. Sample dispersion unit performance can then be checked separately using a material having a broader size distribution which will challenge the correct performance of the sample dispersion unit.

Latex beads also have the advantage of being spherical so that the results obtained can be compared with those obtained using other techniques. The sizes of non-spherical particles can be interpreted quite differently by different particle sizing techniques.

Malvern uses a limited selection of sizes to perform operational qualification of their instruments rather than a complete "scale" of sizes since laser diffraction is a technique which measures light scattered across an instrument's detector array rather than being a counter-based technique where individual size bins need to be calibrated.