Prepare by :

Gerges george mariam safwatManar wagdy

Pesticides: Substances or mixtures of substances used for controlling, preventing, destroying, repelling, or attracting any biological organism deemed to be a pest. Ex: Insecticides, herbicides, fungicides and rodenticides

1- BY CHEMICAL NATURE: Classification of pesticides to two groups: organic and inorganic. - Organic pesticides: Based on chemicals having carbon in their molecular structure. This chemicals are more complex than inorganic pesticides and usually do not dissolve easily inwater. Classification of Pesticides

- Inorganic pesticides: are simpler compounds. They have a crystalline, salt-like appearance, are environmentally stable, and usually dissolve readily in water. The earliest chemical pesticides were inorganic, and included substance such as sulfur, Zinc , Selenium, NickelMercury, Lead , Copper , Chromium , Cadmium, Arsenic and lime. The vast majority of modern pesticides contain an organic chemical often with oxygen, phosphorus, or sulfur in their molecules, in addition to their basic carbon structure.

- Organic pesticides : can be subdivided into two additional groups:The natural organics, and the synthetic organics. - The natural organic pesticides: are derived from naturally sources such as plants. Rotenone and pyrethrum.- Synthetic organic pesticides : are produced by chemical synthesis. This group include DDT, permethrin, glyphosphat.

DDT

2-BY PESTICIDE FUNCTION: Organochlorines: include DDT used for vector control in some areas of the world (particularly where malaria occurs), DDT's uses was suspended by the EPA many years ago, and no longer used in the United States.

Organophosphates: OPS uses are decreased because of greater human health risk for pesticide applicators than other pesticides.

Carbamates: are chemically similar in structure to organophosphates, but OPS are derivatives of phosphoric acid, carbamates are derivatives of carbamic acid.Pyrethrum: is a natural organic insecticide that is derived from plants. Pyrethrins: is an insecticide produced by grinding of the flowers , Insecticides containing pyrethrins are neurotoxic to nearly all insects. They are harmful to fish, but are less toxic to mammals and birds many synthetic insecticides are non-persistent, breaking down easily on exposure to light.

UracilPyrethrincarbamateCarbamic acidTriazine_

Pyrethrins are usually mixed with PBO (piperonyl butoxide), to increase toxicity of insecticides. PBO are not pesticidal by themselves. PBO may have a longer residual life in aquatic systems. Pyrethrins are highly toxic to fish and their direct application to water is restricted.

Pyrethroids:

are synthetically produced similar to pyrethrins. Pyrethroids are not persistent. They break down quickly in sunlight, and are rarely present after just a few days. The mode of action of pyrethroids is the same as that of pyrethrins. Used in the control of adult mosquitoes.

Biorational pesticides: are pesticides that are non-toxic to humans and are also environmentally safe. This pesticides derived from such natural materials as animals, plants and bacteria.Biorationals can be separated into two groups: (1) biochemical (hormones, enzymes )(2) microbial (viruses, bacteria, )

MATERIALS APPLIED TO WATER SURFACES:

- Petroleum oils: are refined from crude oil and are used both as carriers for insecticides . - Alcohols : These materials act by reducing surface tension of the water.

The disadvantage of Oils and alcohols product : kill non-target organisms that either breath at the water surface (e.g., small aquatic beetles), or that depend on surface tension of the water (e.g., beetles).

Formulations with Combinations of PesticidesThe reasons for combining pesticides are:Increase the effectiveness of one of the chemicals. For example addition of piperonyl butoxide (PBO) to pyrethrum, pyrethrins. Without the addition of PBO, flying insects may be knocked down by these insecticides, but will later recover and fly away.To provide better control than pesticide alone . To control different types of pests with a single application at the same time.. It is usually more economical

When two or more pesticides cannot be used in combination, they are said to be incompatible. combination of incompatible pesticides result in :

Effectiveness of one or both compounds may be reduced.Precipitation may occur and clog the nozzles of application equipment.Various types of toxicity may occur.Excessive residues may result..

- In some cases, the combination increases the toxicity of a compound that is normally low toxicity, so result is a compound has highly toxic to people, other animals or plants.- Some pesticide labels indicate known compatibility problems or not.

HERBICIDESIt use in kill plants, or inhibit growth of plants . Herbicides can be separated into organic or inorganic materials. 1- Organic herbicides: have a carbon based molecular structure and usually act by altering the normal growth of the plant. It divided into two major groups: petroleum oils and synthetic organic herbicides.

The petroleum oils, refined from crude oil, can be used as either herbicides or insecticides. It usually is applied without dilution Synthetic organic herbicides are prepare in laboratories, are made up of carbon, hydrogen, often nitrogen, and other elements.

Inorganic herbicides: are often in the form of a salt, or contain a metal that is toxic to plants for example: copper sulfate, sulfuric acid, and sodium chlorate. are extremely persistence and caused soil pollution problems

CHEMICAL GROUPS OF HERBICIDES Phenoxies: Phenoxy herbicides are used in both crop and non-crop areas ex: ( Butoxone or Butyrac).Triazines Ex: atrazine Thiocarbamates Ex: thiocarbamate. Ureas and Uracils These compounds are primarily applied to soil as herbicides. by inhibiting their ability to photosynthesize

Benzoics Benzoic acid herbicides are used in both crop and noncrop.AcetanilidesSulfonylureas Used at extremely low rates as chlorsulfuron , triasulfuronImidazolinones This group acts as biosynthesis inhibitors within the actively growing plant

Environmental effectAir:when pesticides suspended in the air as particles are carried by wind to other areas, potentially contaminating them It canvolatilize, potentially posing a threat to wildlife Weather conditions ,temperature and relative humidity change the spread of the pesticide in the air.

Water

Pesticide residues have also been found in rain and groundwater - Factors that affect a pesticide's ability to contaminate water include its watersolubility , the distance from an application site to a body of water, weather, soil type, presence of a growing crop, and the method used to apply the chemical .

Soil Many of the chemicals used in pesticides are persistentsoil contamination .Degradation and sorption are both factors which effect the persistence of pesticides in soil. Depending on the chemical nature of the pesticide, it transport from soil to water, and in turn to air and our food

Effect on plants pesticides have some direct harmful effect on plant including poor root hair development, shoot yellowing and reduced plant growth

Effect on animals Animals including humans may be poisoned by pesticide residues that remain on food

Aquatic life Fish may be harmed by pesticide-contaminated water.Pesticidesurface runoffinto rivers and streamsApplication of herbicides to bodies of water can cause fish killswhen the dead plants decay and consume the water's oxygen,Herbicides such ascopper sulfitethat are applied to water to kill plants are toxic to fish and other water animals

Humans Pesticides can enter the body through inhalation ofaerosols, dust andvaporthat contain pesticides; through oral exposure by consuming food/water; and through skin exposure by direct contact and pesticide spray can drift and pollute the air its effect depend on the toxicity of the chemical and the length and magnitude of exposure Exposure effects can range from mild skin irritation tobirth defects, tumors, genetic changes, blood and nerve disorders,comaor death

Uses used to control organisms that are considered to be harmful .Prevent sickness in humans that could be caused bymoldy food or diseased produce. save farmers money by preventing crop losses to insec save farmers ts and other pests Ex : DDT, sprayed on the walls of houses, is an organochloride that has been used to fight malaria

Determination of specific organochlorine, organophosphorus and pyrethroid insecticide residuesPreparation of samplePreparation of sample Extraction To 10 g of the substance being examined, coarsely powdered, add 100 ml of acetone and allow to stand for 20 min Add 1 ml of a solution containing 1.8 g /ml of carbophenothion R in toluene. Homogenize using a high-speed blender for 3 min. Filter and wash the filter cake with two quantities, each of 25 ml, of acetone Combine the filtrate and the washings and heat using a rotary evaporator at a temperature not exceeding 40 C until the solvent has almost completely evaporated. To the residue add a few milliliters of toluene and heat again until the acetone is completely removed. Dissolve the residue in 8 ml of toluene Filter through a membrane filter (45 m), rinse the flask and the filter with toluene and dilute to 10.0 ml with the same solvent (solution A).

The colum chromatographic procedure may be carried out using:

glass tube column packed with styrene-di vinylbenzene copolymer R (5 m) As mobile phase toluene R at a flow rate of 1 ml/min. . Inject 100 l of a solution containing 0.5 g/l of methyl red R and 0.5 g/l of oracet blue 2R in toluene R and proceed with the chromatography. The column is not suitable unless the color of the eluate changes from orange to blue at an elution volume of about 10.3 ml. If necessary calibrate the column using a solution containing toluene. At a suitable concentration, the insecticide to be analyzed with the lowest molecular mass (ex: dichlorvos) and that with the highest molecular mass (ex:, deltamethrin).

Purification of the test solutionheat silica gel for chromatography R in an oven at 150 C for at least 4 h. Allow to cool and add drop wise a quantity of water R corresponding to 1.5% of the mass of silica gel used Shake vigorously until agglomerates have disappeared and continue shaking for 2 h using a mechanical shaker. Condition the column using 1.5 ml of hexane. Pre packed columns containing about 0.5 g of a suitable silica gel may also be used provided they have been validated before hand.quantitatively on to the column and proceed with the chromatography using 1.8 ml of toluene R as the mobile phase. Collect the eluate (solution C)..

Gas Chromatography (GC)This method depends upon the solubility and boiling points of organic liquids in order to separate them from a mixture. It is both a qualitative (identity) and quantitative (how much of each) tool.

GC Instrumentation

GC TheoryTo detectorAnalyteColumn + packingTime

SeparationsTo detector

Chromatographic procedure for determine Organo chlorine and pyrethroid insecticidesinternal standard is Carbo phenothion Test solution: Concentrate solution C in a current of helium for chromatography Reference solution. Prepare at least 3 solutions in toluene R containing the insecticides to be determined and carbo phenothion at concentrations suitable for plotting a calibration curve.a fused-silica column 30 m long and 0.32 mm in internal diameter, the internal wall of which is covered with a layer 0.25 m thick of poly(dimethyl) siloxane Rcarrier gas : Hydrogen a phosphorus-nitrogen flame-ionization detector or an atomic emission spectrometry detector,

maintaining the temperature of the column at 80 C for 1 min, then raising it at a rate of 30 C/min to 150 C, maintaining it at 150 C for 3 min, then raising the temperature at a rate of 4 C/min to 280 C and maintaining at this temperature for 1 min, and maintaining the temperature of the injector port at 250 C and that of the detector at 275 C. Inject the chosen volume of each solution. Calculate the content of each insecticide from the peak areas and the concentrations of the solution.

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