Summary of Methods Used in the Study of Pesticide Biotransformation and Disposition - Pesticide Biotransformation and Disposition - page 9

“Reverse phase”
(i.e. hydrophobic)
chromatographic
support
- Highly hydrophobic pesticide
- Moderately hydrophobic pesticide
- Water soluble pesticide
Figure 2.1 Column chromatography. Pesticides that are highly hydrophobic will have a high affinity
for the stationary phase and will be the last to elute from the column, while water-soluble pesticides
will elute first.
with petroleum ether. He called the process chromatography, or “color writing”. The
fundamental principles of chromatography are the same, regardless of whether it is pre-
parative chromatography or analytical chromatography. There is a stationary phase and
a mobile phase, and the separation of sample components is achieved through the dif-
ferential interaction between the two phases. Compounds that have a higher affinity
for the mobile phase will move through the system very quickly, whereas compounds
that have a higher affinity for the stationary phase will move very slowly through the
system ( Figure 2.1 ). This process is the basis for the vast majority of analytical chemis-
try techniques in use today.
Thin-Layer Chromatography
Many toxicants and their metabolites can be separated from interfering substances with
TLC. In this form of chromatography, the adsorbent is spread as a thin layer (250-
2000 µm) on glass or resistant plastic backings. When the extract is placed near the bot-
tom of the plate and the plate is placed in a tank containing a solvent system, the solvent