Malvern Mastersizer 2000, User Manual

Page: 106 / 154

Chapter 8 Sample preparation
Page 8-10 MAN 0384
Symptoms of poor sample preparation
Use this table to identify sample dispersion problems:
Problem Symptom Action
Sample dissolving Obscuration decreases. Try another dispersant.
Dispersant contains
impurities Poor background readings. Filter the dispersant
before use.
Bubbles within the
dispersant Bubbles typically show as a
secondary peak at 100
microns. Degas the system.
Sample floating on
the surface of the
dispersant Sample seen on the surface
of the dispersant in the tank. Add surfactant or
admixture.
Sample clumps
together Obscuration decreases. Add surfactant or admix-
ture or use ultrasonic
action.
Sample sinks to the
bottom Obscuration decreases as
the larger particles settle out. Increase the pump/stirrer
speed.
Sample swells in
dispersant Obscuration decreases. Try another dispersant.
Particles sticks to
the windows Rapidly increasing
obscuration. Use an admixture.
Condensation on
the cell windows Rapidly increasing
obscuration. If (and only if) the disper-
sant is water, add a quan-
tity of hot (not boiling)
water to the tank. If the
obscuration falls, conden-
sation is the problem.
Bubbles sticking to
windows Difficulty in obtaining low
background despite many
rinses. Drain the sampling tank.
The bubbles will burst. Fill
the system carefully with
degassed dispersant. In a
new system, adding
Decon 90 to the tank
overnight and rinsing 7 or
8 times will wet out the
cell surface and reduce
bubble formation.
MAN0384-1.0 Mastersizer 2000.book Page 10 Tuesday, March 20, 2007 8:56 AM