Measurement Guidelines - Malvern Hydro 2000uP User Manual

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Chapter 4
Page 4-2

Measurement guidelines

The Hydro 2000µP uses very low volumes (approximately 20ml) of dispersant and
sample. When using such small quantities, take the following precautions when
making a measurement:
Minimise the amount of sample lost during sample preparation, or through
sample adhering to the sides of the well.
Cleanliness of the system is critical: very small amounts of cross-contamination
can bias the results.
Manage the pump speed to prevent the introduction of bubbles, while also
ensuring that the sample is kept in suspension. This is true for all wet sample
dispersion units but particularly important with the small dispersant volumes
of the Hydro 2000µP.
The basic procedure
Add dispersant to the well by injecting the requested dispersant through the inlet
port. Inject the dispersant slowly until the level of the dispersant is within 1 to
2mm of the internal rim of the well.
Because the stirring and the circulation of the sample is carried out in the chamber
below the well cone, keep the level of dispersant in the well low. If sample is seen
adhering to the sides of the well cone, use a pipette to withdraw some of the disper-
sant from the well to rinse the sides of the well. Once the sample has been added, it
is important to replace the well lid and lock it in place using the locking lever.
Minimising sample loss
Sample loss by adhesion
To prevent sample adhering to the side of the sample well during sample addition,
it is typical to have the dispersant at a level a quarter of the way up the well. This
allows the sample to be taken into the well cavity by the dispersant.
A typical procedure is:
Fill the well to 1-2mm below the top of the well.
1.
Run an anaerobic fill sequence (press the Anaerobic fill button on the acces-
2.
sory control dialogue).
Once complete, use a pipette to remove dispersant so that the well is about a
3.
quarter full.
Making a measurement
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