Quality control methods for

16. Determination of pesticide residues 
Medicinal plant materials are liable to contain pesticide residues which 
accumulate from agricultural practices, such as spraying, treatment of soils 
during cultivation, and administration of fumigants during storage. It is 
therefore recommended that every country producing medicinal plant materials 
(naturally grown or cultivated) should have at least one control laboratory 
capable of performing the determination of pesticides in accordance with the 
procedure outlined below. 
Since many medicinal preparations of plant origin are taken over long periods of 
time, limits for pesticide residues should be established following the 
recommendations of the Food and Agriculture Organization of the United 
Nations (FAO) and the World Health Organization (WHO) which have already 
been established for food and animal feed (9). These recommendations include 
the analytical methodology for the assessment of specific pesticide residues. 
Classification of pesticides 
Different classifications of pesticides exist (10, 11). A classification based on the 
chemical composition or structure of the pesticide is most useful for analytical 
chemists, for example: 
• chlorinated hydrocarbons and related pesticides: aldrin, HCH 
(hexachlorocy-clohexane or benzene hexachloride, BHC), 
hexachlorobenzene (HCB), chlordane, DDT (clofenotane), dieldrin, 
endrin, heptachlor, lindane, methoxychlor, camphechlor (toxaphene); 
• chlorinated phenoxyalkanoic acid herbicides: 2,4-D; 2,4,5-T;
• organophosphorus pesticides: carbophenothion (carbofenotion), 
coumaphos (coumafos), demeton, dichlorvos, dimethoate, ethion, 
fenchlorphos (fenclofos), malathion, methyl parathion, parathion; 
• carbamate insecticides: carbaryl (carbaril); 
• dithiocarbamate fungicides: ferbam, maneb, nabam, thiram, zineb, ziram;
• inorganic pesticides: aluminium phosphide, calcium arsenate, lead 
arsenate;
• miscellaneous: bromopropylate, chloropicrin, ethylene dibromide, 
ethylene oxide, methyl bromide; 
• pesticides of plant origin: tobacco leaf and nicotine; pyrethrum flower, 
pyrethrum extract and pyrethroids; derris root and rotenoids. 
Only the chlorinated hydrocarbons and related pesticides (e.g. aldrin, chlordane, DDT, 
dieldrin, HCH) and a few organophosphorus pesticides (e.g. carbophenothion) have a 
long residual action. Most other pesticides have very short residual actions. Therefore it 
is suggested that, where the length of exposure to pesticides is unknown, 
the medicinal 
plant material should be tested for the presence of organically bound chlorine 
and phosphorus, or the content of these two substances should be determined. 
Alternative classifications of pesticides may be based on their intended use, for 
example: 
- insecticides; 
- fungicides and nematocides; 

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Quality control methods for medicinal plant materials 
- herbicides; 
- other pesticides (e.g. acaricides, molluscicides, rodenticides); 
- fumigants (e.g. ethylene oxide, ethylene chlorohydrin, methyl bromide).