Malvern Instruments Mastersizer X, Manual

Page: 63 / 102

Introduction
This chapter, in conjunction with chapter 9 of the Getting Started manual,
provides you with information on one of the most important stages in making a
measurement.
Read very carefully chapter 9 of the Getting Started manual, particularly the
advice given on wet measurements. This chapter provides you with specific
sample preparation information when using this Accessory.
Trapped air/bubbles
To the Mastersizer, trapped air or bubbles are seen as particles and are therefore
measured. Bubbles will vary in size but will typically be in the region of 100
microns in size. In many cases these bubbles can be seen clearly as a second and
separate peak when the measurement data is analysed.
You should always be wary of bubbles within your system.
When dispersant has been added to the Dispersion Unit and circulated, it is
advisable to switch off the Dispersion Unit for a period to allow trapped air to rise
out of the system. During installation you should ensure there are no twists or
loops in the connected sample tubing.
When you are adjusting the speed control for a particular sample, ensure the
speed is not so fast as to introduce air into the system, particularly when using a
viscous dispersant.
If your dispersant is stored under pressure or low temperature, you must consider
de-gassing before use. The pressure release, or temperature rise will reduce the
solubility of gasses resulting in the formation of bubbles in the pipes and tank etc.
This is particularly a problem with some mains water supplies. The simple
answer is to store sufficient dispersant at room temperature and pressure for
several hours before use to allow the de-gassing to occur.
If you add a surfactant to your sample, excessive speed of the stirrer/pump may
cause frothing. This will force bubbles into the system.
C H A P T E R 8
Q S S M A L L V O L U M E S A M P L E D I S P E R S I O N U N I T
P a g e 8 . 1