principles of extraction and the extraction of semivolatile organics ...

74 principles of extraction
Extraction plate
Collection plate
Organic solvent: methyl ethyl ketone
Diatomaceous earth particle
Aqueous plasma layer
Solid
Support
chloroform within 45 seconds when the flow was very slow or stopped, corresponding
with molecular di¤usion time. The extraction system required no
mechanical stirring, mixing, or shaking.
Solid-supported LLE is a new approach reported by Peng et al. [49,50].
They exploited the e‰ciency of 96-channel, programmable, robotic liquidhandling
workstation technology to automate methodology for this LLE
variation. A LLE plate was prepared by adding inert diatomaceous earth
particles to a 96-well plate with hydrophobic GF/C glass fiber bottom filters.
Samples and solvents were added to the plate sequentially. LLE occurred in
the interface between the two liquid phases and on the surface of individual
particles in each well (Figure 2.18). The organic phase extracts were eluted
under gentle vacuum into a 96-well collection plate. The approach was used
for initial purification of combinatorial library samples and for quantitative
analysis of carboxylic acid–based matrix metalloprotease inhibitor compounds
in rat plasma.
2.3. LIQUID–SOLID EXTRACTION
When a liquid is extracted by a solid, phase A of the Nernst distribution law
[equation (2.2)] refers to the liquid sample, and phase B, the extracting
phase, represents the solid (or solid-supported liquid) phase:
KD ¼ ½XŠ B
½XŠ A
Analyte
Plasma
Layer
Analyte
Organic
Solvent
Organic
Solvent
Figure 2.18. Schematic representation of automated liquid–liquid extraction. (Reprinted with
permission from Ref. 50. Copyright 6 2001 American Chemical Society.)
ð2:2Þ
Classically, batch-mode liquid–solid extractions (LSEs), were used to con-