Dionex ASE 150, Operator'S Manual

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ASE 150 Operator’s Manual
154
Doc. 065207-02 9/08
from fish tissue using ASE. They reported that, as the temperature of the
extraction rises or as the polarity of the solvent increases, the capacity of the
alumina to retain lipids decreases. For example, if hexane or heptane is the
extraction solvent, heat-activated alumina will retain about 70 mg of lipid per
gram of alumina. If DCM is used, then the capacity is only about 35 mg of lipid
per gram of alumina. If the correct amount of sorbent is used, then extracts can be
produced using ASE that require no additional post-extraction treatment other
than volume adjustment.
The most common use of adsorbents in ASE has been for the extraction and
determination of nonpolar compounds such as PCBs, OCPs, PCDDs, and PCDFs
in high lipid content matrices such as food or animal tissue. Other adsorbents that
have been used include copper, C18 resin, Florisil, silica gel, acid-impregnated
silica gel, and ion-exchange resins.
Table E-2 shows a summary with related
references.
There are a few interesting things to note from this table. Acid-impregnated silica
gel has the highest capacity for lipid retention of all the adsorbents that have been
reported. It has roughly double the capacity of alumina. The sulfuric acid is
typically present on the silica at 40% (wt/wt). Copper powder (cleaned with HCl
first) can be used to retain sulfur when extracting sediment samples.
An interesting use of a C18 adsorbent was reported by Gentili and colleagues
(21). In this case, they were extracting polar antibiotics (sulfonamides) from
animal tissues. They put C18 material in the outlet of the cell to retain some of the
Adsorbent Uses Reference
Silica Removes nonpolar lipids 4
Florisil Removes nonpolar lipids 15, 16
Alumina Removes nonpolar lipids
and colored compounds 13, 17, 18
C18 resin Removes nonpolar lipids 19, 20
I
on-exchange resins Removes ionic
interferences 22
Copper powder Removes sulfur 11, 23
Carbon Assists with purification of
PCDDs, PCDFs, and
coplanar PCBs 24, 25
Table E-2. List of Adsorbents Used in ASE