ABSTRACT
The term ‘‘urea pesticide’’ includes many compounds
with important herbicide and insecticide activities.
Chemically, only the presence of a urea moiety is
common to all them. Urea pesticides can be classified
according to their chemical structures into: substituted
ureas, sulfonylureas (SUHs), and benzoylureas (BUIs).
Most of the substituted ureas are phenylureas (PUHs)
and the rest contain heterocyclic groups. Figure 1
shows the chemical pattern for classification of urea
pesticides and some examples. PUHs and ureas with
heterocyclic groups are herbicides inhibiting photo-
synthesis by blocking the electron transfer in Photo-
system II within the chloroplasts of plants. SUHs are
herbicides that interfere with the acetolactate synthase
(acetohydroxyacid synthase) activity that is related to
the biosynthesis of three essential branch-chain ami-
noacids. BUIs act as insect growth regulators, inter-
fering with the chitin formation in the vital insect
exoskeleton. The physical and chemical properties of the urea
pesticides determine the efficacy of the extraction, clean-
up, and detection processes. Tables 1-3 show interesting
properties having influence on the analytical proce-
dures. Urea pesticides are colorless and odorless. Most
substituted urea herbicides are chlorinated, and most
BUIs contain fluorine atoms. Substituted urea herbi-
cides have low molecular weights (usually less than
300), those of the SUHs and BUIs are higher, reaching
540 for the BUI chlorfluazuron. Substituted urea
