Malvern Hydro 2000uP User Manual page 35

Making a measurement
Sample loss during sample preparation
Choose a sample preparation method that ensures that all particles are transferred
to the well. A recommended method is to prepare a slurry in a small container and
add this to the well using a pipette. Add as a maximum 2ml of sample volume, but
1ml is preferred.
Material will usually be seen collecting in the bottom of the container.
To take a representative sample of the material:
1.
2.
3.
4.
5.
Cleanliness
Cleanliness is essential; since only 10-50mg of sample is added, it only takes a small
amount of cross-contamination from a previous measurement to bias results signif-
icantly. Consider the following points when making measurements:
Hydro 2000µP
Make the slurry more dilute than is normal for larger volume sample disper-
sion units. This will ensure that adding slurry does not lead to an excessive
concentration.
Tilt the container at an angle.
Agitate the dispersant by continually filling and discharging the pipette to
ensure the material is suspended in the dispersant (rather than sinking to the
bottom).
Once dispersed, finally fill the pipette with as much of the dispersant as possi-
ble and transfer it to the well drop by drop, pausing between drops to allow the
sample to fully disperse i.e. monitor the obscuration value until it stabilises.
When adding the sample, ensure that it is added directly to the dispersant
rather than trickling it down the sides of the well walls. This prevents sample
loss through adhesion.
When cleaning, rinse the system three or four times. It doesn't use much dis-
persant, and gives better performance for the next sample.
The first rinse of a clean is sometimes best done by injecting 5-10ml bursts of
dispersant into the well while the pump is running and the drain valve open.
This tends to rinse larger particles through the system.
When changing dispersants, blow each dispersant out of the fill tube with a
syringe full of air (with the drain open) to reduce cross contamination.
When changing over from an oily organic solvent (vegetable oil, etc.) to water,
use a biological drain cleaner (containing food enzymes) to clean out the last
traces of oil.
Chapter 4
Page 4-3