ABSTRACT
Herbicides are chemicals used to control weeds in
several areas such as agriculture, forestry, industry,
and transport. These compounds control weeds in a
variety of ways, showing different modes of action,
selectivity, and application characteristics. Soil-applied
herbicides are absorbed by roots or emerging shoots
and foliage-applied herbicides are absorbed into the
leaves, where they may be translocated to other parts
of the plant. The herbicides can be grouped according
to their chemical structures in different herbicide
classes (1). Table 1 shows the chemical structures of
the major classes of herbicides. The use of herbicides in agriculture has advantages,
such as an increase in the quantity and quality of food
crops. Nevertheless, herbicides are toxic substances
and, as a consequence of the large quantities used, their
residues can be present in foods. To protect consumers’
health, maximum residue limits (MRLs) have been
established at international and national levels. The
physicochemical properties of these compounds and
their MRLs (2-5) are given in Table 2. Residues of herbicides will persist in the plant for
a variable time, depending on their physicochemical
properties and on the environmental conditions.
Herbicides of a wide range of polarities have to be
determined in complex matrices, such as food, at very
low levels. Knowledge of their physicochemical prop-
erties is important to develop analytical procedures
for the determination of herbicide residues. Several