Introduction to Soil Chemistry

Liquid CO 2
Additives
extract cleanup 139
Pumps
Extraction cell
Figure 7.6. Setup for supercritical extraction of soil.
of interest from the soil that are later desorbed or extracted from the adsorbant
and analyzed by chromatographic and spectrophotometric methods.
There are two issues with this type of analysis: (1) whether there is significant
contact between soil and the adsorbant such that a representative sample of
the compound of interest is obtained and (2) whether it can be ensured that
the adsorbant is not completely saturated such that some of the compound of
interest is not adsorbed, resulting in an inaccurate analytical result. If these
two conditions can be adequately addressed, then this procedure can be used
successfully [1–5,7–9].
7.5. EXTRACT CLEANUP
Although extraction methods are designed to extract a specific component of
interest, it is rare that the extract will be clean enough for direct analysis.
During extraction many compounds and water will be dissolved in the extracting
solution. Some of these components will be innocuous, but some will interfere
with further analysis or decrease either the accuracy or precision of the
analysis, and some may prevent successful completion of the analytical
process. Interfering or potentially interfering components thus must be
removed before further analysis is undertaken.
7.5.1. Suspended Particle Removal
Product
collection
Soil contains many very small and colloidal organic and inorganic particles.
These particles are hard to separate or remove from extractants and can cause