Pesticide Analysis: An Overview of Methods.

This article will examine some of the more common procedures used to analyze pesticides. In broad terms, a pesticide is any agent used to kill or control undesired insects, weeds, rodents, fungi, bacteria, or other organisms. Thus, the term comprises insecticides, herbicides, rodenticides, fungicides, nematicides, disinfectants, fumigants, wood preservatives, and plant growth regulators.

In the U.S. alone, approximately 4.5 billion pounds of chemicals are used as pesticides per year. That figure includes 20,700 pesticide products and about 890 active ingredients registered as pesticides. Agricultural use accounts for more than three-fourths of the volume of pesticides used, with the remainder used for industrial and home or garden applications. Herbicides are the most widely used type of pesticide: The herbicide atrazine is the pesticide most commonly used in U.S. agricultural crop production, and the herbicide 2,4-D is the pesticide most commonly used for home/garden and industrial applications.

Because of their toxicity and widespread usage, pesticides present a risk to human health and the environment. As a result, pesticide analyses are an important part of environmental monitoring and testing. The three sections below describe the most common methods of analysis and provide tables detailing some of the pesticides covered by those methods.

Method 8081A/608--Organochlorine Pesticides

Methods 8081A and 608 determine the concentrations of various organochlorine pesticides in extracts from solid and liquid matrices, using fused-silica, open-tubular, capillary columns with electron capture detectors (ECDs). Table 1 identifies some (but not all) of the pesticides analyzed by this method. Many of the organochlorine pesticides listed in Table 1 have been discontinued in the United States, but most will persist in soil for many years.

Method 8151A--Organochlorine Herbicides

Method 8151A is a capillary gas chromatographic (GC) method for determining the presence of certain chlorinated acid herbicides and related compounds in aqueous, soil, and waste matrices. Table 2 gives some (not all) of the compounds analyzed by this method.

Method 8141--Organophosphate Pesticides

Method 8141 is a capillary gas chromatographic (GC) method that uses nitrogen-phosphorous or flame photometric detectors to determine the presence of certain organophosphate pesticides and related compounds in aqueous, soil, and waste matrices. Table 3 gives some (not all) of the compounds analyzed by this method.

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                             Method 8081A/608
Pesticide           Properties and Uses
4,4 -DDD            Miticide formerly use on vegetables and
                    tobacco. Discontinued in U.S. since 1970s.
4,4 -DDE            Degradation product of DDT. Insecticide, no
                    longer used in U.S.
4,4 -DDT            Insecticide extensively used from 1944 until
                    severely restricted in 1973 because of
                    adverse effects on wildlife.
Aldrin              Insecticide introduced in 1959, primarily
                    for soil insects including termites.
                    Discontinued in U.S. Degrades to dieldrin.
Alpha-BHC           Insecticide introduced in 1942, no longer
                    used in U.S.
Beta-BHC            Insecticide introduced in 1942, no longer
                    used in U.S.
Chlordane           Insecticide used since 1945 for termite
                    control & wood treatment. Technical product
                    includes 2 isomers & heptachlor.
Delta-BHC           Insecticide introduced in 1942, no longer
                    used in U.S.
Dieldrin            Insecticide introduced in 1949, formerly
                    used on corn and for termite control.
                    Restricted in the U.S. after 1974.
Endosulfan I        Insecticide introduced in 1956, used on
                    citrus, fruits, cotton, vegetables. Exists
                    as two isomers, I and II.
Endosulfan II       Insecticide introduced in 1956, used on
                    citrus, fruits, fiber crops, vegetables.
                    Exists as two isomers, I and II.
Endosulfan sulfate  Oxidation product of endosulfan. Found in
                    the environment as a result of endosulfan
                    use.
Endrin              Insecticide introduced 1951 and discontinued
                    1987. Formerly used on cotton, grains.
Endrin aldehyde     Oxidation product of endrin.
Gamma-BHC (lindane) Insecticide introduced in 1942, no longer
                    used in U.S. More toxic than DDT. Formerly
                    used on wheat, corn, & pastures.
Heptachlor          Insecticide introduced in 1951, now
                    restricted. Used for termite control & wood
                    treatment.
Heptachlor epoxide  Oxidation product of heptachlor, occurs in
                    soil after treatment with heptachlor.
Methoxychlor        Insecticide introduced in 1944. Used on
                    fruit trees, vegetables, cattle, home
                    gardens.
Toxaphene           Insecticide and miticide introduced 1948.
                    Used on cotton, vegetables, livestock,
                    poultry, soybeans, alfalfa, wheat.
                               Method 8151A
Herbicide Properties and Uses
2,4,5-T   Herbicide used after 1944 in industry,
          range lands, & lawns. U.S. has cancelled
          use since 1985.
2,4,5-TP  Herbicide introduced in 1953 for industrial uses,
(Silvex)  on pastures & range land, and along floodways &
          canals, U.S. cancelled use in 1985.
2,4-D     The herbicide most commonly used for
          nonagricultural applications, eighth
          most common herbicide for agricultural use.
2,4-DB    Herbicide introduced in 1957.
Dicamba   Selective postemergent herbicide for use on
          corn & wheat, and on landscapes & grains.
Dinoseb   An herbicide & insecticide introduced in
          1945, now discontinued in U.S. Used on
          soybean, vegatables, fruits, & citrus.
                                Method 8141
Pesticide               Properties and Uses
Chlorpyrifos (Dursban & One of the most widely used organophosphates,
Lorsban)                found in many home & garden products for
                        controlling insects. Residential uses include
                        treatment of lawns, ornamentals, & interiors of
                        homes & buildings. Also used as a termiticide
                        & in pet collars. Widely used on more than
                        40 different agricultural crops/sites. Because
                        of health risks to children, U.S. EPA recently
                        banned chlorpyrifos from use in gardens
                        & homes, and curtailed its use in
                        agricultural applications.
Demeton (Systox)        Systemic insecticide-acaricide, introduced
                        in 1954 and discontinued in 1989.
Diazinon                Insecticide, acaricide, nematicide used widley
                        since 1952 on fruits, vegetables, field crops,
                        range, grasslands & household insects.
Disulfoton              Systemic insecticide-acaricide introducted
                        in 1956.
Ethion                  Insecticide-acaricide introduced in 1955
                        for control of aphids, mites, & leafhoppers
                        on crops & ornamentals. Slowly oxidized
                        in air.
Malathion               Insecticide, algaecide, miticide introduced
                        in 1950. Used on fruits, vegatables, &
                        ornamentals.
Methyl parathion        Insecticide used on crops. Introduced in
                        1949, more rapidly hydrolyzed than parathion.
Parathion               Insecticide, miticide, avicide developed
                        in 1944. Very toxic to mammals as well as
                        insects. Metabolized to p-nitrophenol.