Dionex ASE 150, Operator'S Manual

Page: 39 / 176

3 • Operation and Maintenance
Doc. 065207-02 9/08
31
3.1.3 Preparing the Sample
If you have successfully followed a particular sample pretreatment
procedure for another extraction method, continue using this procedure
with the ASE 150. If you have never run an extraction—or if you are
preparing a new sample—follow the guidelines here. This section
discusses two sample pretreatment procedures:
•
Samples that are dry, wet, or liquid should be mixed with a drying or
dispersing agent before being loaded into the cells.
•
Samples with large particle sizes should be ground before being
loaded into the cells.
NOTE: Most problems with the ASE (accelerated solvent extraction)
process are caused by errors made during sample preparation. To obtain
high quality analytical results, pay careful attention to the sample
preparation phase of the method. For more details, see
Appendix E .
Guidelines for Selecting a Drying or Dispersing Agent
•
Although sodium sulfate is readily available, it should not be used in
ASE 150 cells. The use of sodium sulfate with very wet samples
(30% moisture) will result in clogging of system components (such as
the solvent line or needles) with recrystallized sodium sulfate. This
occurs particularly if a mixed solvent with a polar component such as
methanol or acetone is used. In these cases, use pelletized
diatomaceous earth (DE) (P/N 062819) as a drying agent and mix it
with the sample before loading into the sample cell (see the sample
preparation guidelines on
page 32 ). (Alternatively, DE can be used as
a drying agent in the cell in place of sodium sulfate for all levels of
moisture.)
•
For very wet samples, regardless of which drying agent is used, you
may add sodium sulfate to the collection vessels after collection and
then pass the extracts through either a drying column or drying
cartridge to dry the extract completely. At the temperatures used
during ASE 150 extractions, more water is co-extracted than with
other extraction procedures. To ensure good analyte recovery,
thoroughly rinse the sodium sulfate out of the collection vessel and
the cleanup column.