Symptoms Of Poor Sample Preparation - Malvern Mastersizer 3000 User Manual

Chapter 6

Symptoms of poor sample preparation

Use this table to identify sample dispersion problems:
Page 6-10
Problem
Sample dissolving
Dispersant contains
impurities
Bubbles within the dis-
persant
Sample floating on the
surface of the dispersant
Sample clumps together
Sample sinks to the bot-
tom
Sample swells in disper-
sant
Particles sticks to the
windows
Condensation on the cell
windows
Bubbles sticking to win-
dows
Sample preparation guidance
Symptom
Obscuration decreases.
Poor background read-
ings.
Bubbles typically show
as a secondary peak at
100 microns.
Sample seen on the sur-
face of the dispersant in
the tank.
Obscuration decreases.
Obscuration decreases
as the larger particles
settle out.
Obscuration decreases.
Rapidly increasing 
obscuration.
Rapidly increasing 
obscuration.
Difficulty in obtaining low
background despite
many rinses.
Action
Try another dispersant.
Filter the dispersant
before use.
Degas the system.
Add surfactant or 
admixture.
Add surfactant or admix-
ture, or use ultrasonic
action.
Increase the pump/stir-
rer speed.
Try another dispersant.
Use an admixture or sur-
factant.
If (and only if) the disper-
sant is water, add a
quantity of hot (not boil-
ing) water to the tank. If
the obscuration falls,
condensation is the
problem.
Drain the sampling tank.
The bubbles will burst.
Fill the system carefully
with degassed disper-
sant. In a new system,
adding Decon 90 to the
tank overnight and rins-
ing 7 or 8 times will wet
out the cell surface and
reduce bubble formation.
MAN 0474