analysis of pesticides in foof and environmental samples

in The Pesticide Manual, British Crop Protection Council, 2000; http: ==ec.europa.eu=food=plant=protection=evaluation=exist_subs_rep_en.htm; http:==www.epa .gov=opprd001=factsheets=; Hor

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CRC Press is an imprint of the

Boca Raton London New York

Edited by José L Tadeo

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Library of Congress Cataloging-in-Publication Data

Analysis of pesticides in food and environmental samples / editor, Jose L Tadeo.

p cm.

Includes bibliographical references and index.

ISBN 978-0-8493-7552-1 (alk paper)

1 Pesticide residues in food 2 Food Analysis 3 Pesticides I Tadeo, Jose L

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Preface vii

Editor ix

Contributors xi

Chapter 1 Pesticides: Classiﬁcation and Properties 1

José L Tadeo, Consuelo Sánchez-Brunete, and Lorena González Chapter 2 Sample Handling of Pesticides in Food and Environmental Samples 35

Esther Turiel and Antonio Martín-Esteban Chapter 3 Analysis of Pesticides by Chromatographic Techniques Coupled with Mass Spectrometry 59

Simon Hird Chapter 4 Immunoassays and Biosensors 95

Jeanette M Van Emon, Jane C Chuang, Kilian Dill, and Guohua Xiong Chapter 5 Quality Assurance 125

Árpád Ambrus Chapter 6 Determination of Pesticides in Food of Vegetal Origin 151

Frank J Schenck and Jon W Wong Chapter 7 Determination of Pesticides in Food of Animal Origin 177

Antonia Garrido Frenich, Jose Luis Martinez, and Adrian Covaci Chapter 8 Determination of Pesticides in Soil 207

Consuelo Sánchez-Brunete, Beatriz Albero, and José L Tadeo Chapter 9 Determination of Pesticides in Water 231

Jay Gan and Svetlana Bondarenko

v

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Chapter 10 Sampling and Analysis of Pesticides in the Atmosphere 257

Maurice Millet

Chapter 11 Levels of Pesticides in Food and Food Safety Aspects 287

Kit Granby, Annette Petersen, Susan S Herrmann,and Mette Erecius Poulsen

Chapter 12 Monitoring of Pesticides in the Environment 319

Ioannis Konstantinou, Dimitra Hela, Dimitra Lambropoulou,and Triantafyllos Albanis

Index 359

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You should go on learning for as long as your ignorance lasts;

and, if the proverb is to be believed, for the whole of your life

Lucius Annaeus SenecaConsumer concerns on food safety and society awareness of chemical contaminants

in the environment have increased in the past few years As a consequence, morerestrictions in the use of chemical products have been imposed at national andinternational levels

Pesticides are widely used for the control of weeds, diseases, and pests ofcultivated plants all over the world, mainly since after Second World War, withthe discovery of some organic compounds with good insecticide or herbicideactivity At present, around 2.5 million tons of pesticides are used annually and thenumber of registered active substances is higher than 500

However, as pesticides are toxic substances that may have undesirable effects,their use has to be regulated Risk assessment of pesticides requires information onthe toxicological and ecotoxicological properties of these compounds as well as ontheir levels in food and environmental compartments Therefore, reliable analyticalmethods are needed to carry out the monitoring of pesticide residues in thosematrices

Analysis of Pesticides in Food and Environmental Samples focuses on theanalytical methodologies developed for the determination of these compounds and

on their levels in food and in the environment It includes information on the differentpesticides used, sample preparation methods, quality assurance, chromatographictechniques, immunoassays, pesticide determination in food, soil, water, and air, andthe results of their monitoring in food and environmental compartments I think thatthis timely and up-to-date work can signiﬁcantly improve the information in thisresearch area and contribute to a better understanding of the behavior of pesticidesthat will lead to an improvement of their use

My sincere thanks to everyone who has contributed and particularly to all thecontributors of the different chapters of Analysis of Pesticides in Food and Environ-mental Samples

This work is dedicated to Teresa, my wife

José L Tadeo

vii

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In 1977, Dr Tadeo was a research scientist at the Institute for AgriculturalResearch in Valencia where his work focused on the study of the chemical compo-sition of citrus fruits and the behavior of fungicides used during postharvest of fruits.

In 1988, he became a senior researcher at the Instituto Nacional de Investigación

y Tecnología Agraria y Alimentaria During his stay at the Plant Protection ment, the main research lines were the analysis of herbicide residues and the study oftheir persistence and mobility in soil

Depart-His current research at the Environment Department of the Instituto Nacional deInvestigación y Tecnología Agraria y Alimentaria is the analysis of pesticidesand other contaminants in food and environmental matrices and the evaluation ofexposure to biocides and existing chemicals He has published numerous scientiﬁcpapers, monographs, and book chapters on these topics He has been a member ofnational and international working groups for the evaluation of chemicals, and he iscurrently involved in the assessment of biocides at the international level

ix

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Instituto Nacional de Investigación y

Tecnología Agraria y Alimentaria

Almeria, Spain

Lorena GonzálezDepartment of EnvironmentInstituto Nacional de Investigación yTecnología Agraria y AlimentariaMadrid, Spain

Kit GranbyThe National Food InstituteTechnical University of DenmarkSøborg, Denmark

Dimitra HelaDepartment of Business Administration

of Agricultural Products and FoodUniversity of Ioannina

Agrinio, Greece

Susan S HerrmannThe National Food InstituteTechnical University of DenmarkSøborg, Denmark

Simon HirdCentral Science LaboratorySand Hutton, York, United Kingdom

Ioannis KonstantinouDepartment of Environmental andNatural Resources ManagementUniversity of Ioannina

Agrinio, Greece

xi

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Madrid, Spain

Jose Luis Martinez

Department of Analytical Chemistry

Centre de Géochimie de la Surface

Université Louis Pasteur

Strasbourg, France

Annette Petersen

The National Food Institute

Technical University of Denmark

Søborg, Denmark

Mette Erecius Poulsen

The National Food Institute

Technical University of Denmark

Søborg, Denmark

Consuelo Sánchez-Brunete

Department of Environment

Madrid, Spain

Frank J SchenckSoutheast Regional LaboratoryU.S Food and Drug Administration

Ofﬁce of Regulatory AffairsAtlanta, Georgia

José L TadeoDepartment of EnvironmentInstituto Nacional de Investigación yTecnología Agraria y AlimentariaMadrid, Spain

Esther TurielDepartment of EnvironmentInstituto Nacional de Investigación yTecnología Agraria y AlimentariaMadrid, Spain

Jeanette M Van EmonNational Exposure Research LaboratoryU.S Environmental Protection AgencyLas Vegas, Nevada

Jon W WongCenter for Food Safety and AppliedNutrition

U.S Food and Drug AdministrationCollege Park, Maryland

Guohua XiongNational Exposure Research LaboratoryU.S Environmental Protection AgencyLas Vegas, Nevada

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1 Pesticides: Classiﬁcation

and Properties

José L Tadeo, Consuelo Sánchez-Brunete, and Lorena González

CONTENTS

1.1 Introduction 2

1.2 Herbicides 4

1.2.1 Amides 5

1.2.2 Benzoic Acids 5

1.2.3 Carbamates 6

1.2.4 Nitriles 7

1.2.5 Nitroanilines 8

1.2.6 Organophosphorus 10

1.2.7 Phenoxy Acids 10

1.2.8 Pyridines and Quaternary Ammonium Compounds 12

1.2.9 Pyridazines and Pyridazinones 13

1.2.10 Triazines 14

1.2.11 Ureas 15

1.2.11.1 Phenylureas 15

1.2.11.2 Sulfonylureas 16

1.3 Insecticides 16

1.3.1 Benzoylureas 16

1.3.2 Carbamates 16

1.3.3 Organochlorines 19

1.3.4 Organophosphorus 20

1.3.5 Pyrethroids 20

1.4 Fungicides 23

1.4.1 Azoles 23

1.4.2 Benzimidazoles 23

1.4.3 Dithiocarbamates 26

1.4.4 Morpholines 26

1.4.5 Miscellaneous 27

1.5 Mode of Action 28

1.5.1 Herbicides 28

1.5.1.1 Amino Acid Synthesis Inhibitors 28

1.5.1.2 Cell Division Inhibitors 30

1

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1.5.1.3 Photosynthesis Inhibitors 30

1.5.2 Insecticides 30

1.5.2.1 Signal Interference in the Nervous System 30

1.5.2.2 Inhibitors of Cholinesterase 31

1.5.2.3 Inhibitors of Chitin Synthesis 31

1.5.3 Fungicides 31

1.5.3.1 Sulfhydryl Reagents 31

1.5.3.2 Cell Division Inhibitors 31

1.5.3.3 Inhibitors of Ergosterol Synthesis 32

1.6 Toxicity and Risk Assessment 32

References 34

1.1 INTRODUCTION

A pesticide is any substance or mixture of substances, natural or synthetic, formu-lated to control or repel any pest that competes with humans for food, destroys property, and spreads disease The term pest includes insects, weeds, mammals, and microbes, among others [1]

Pesticides are usually chemical substances, although they can be sometimes biological agents such as virus or bacteria The active portion of a pesticide, known as the active ingredient, is generally formulated by the manufacturer as emulsiﬁable concentrates or in solid particles (dust, granules, soluble powder, or wettable powder) Many commercial formulations have to be diluted with water before use and contain adjuvants to improve pesticide retention and absorption by leaves or shoots

There are different classes of pesticides according to their type of use The main pesticide groups are herbicides, used to kill weeds and other plants growing in places where they are unwanted; insecticides, employed to kill insects and other arthropods; and fungicides, used to kill fungi Other types of pesticides are acaricides, mollusci-cides, nematimollusci-cides, pheromones, plant growth regulators, repellents, and rodenticides Chemical substances have been used by human to control pests from the beginning of agriculture Initially, inorganic compounds such as sulfur, arsenic, mercury, and lead were used The discovery of dichlorodiphenyltrichloroethane (DDT) as an insecticide by Paul Müller in 1939 caused a great impact in the control

of pests and soon became widely used in the world At that time, pesticides had a good reputation mainly due to the control of diseases like malaria transmitted by mosquitoes and the bubonic plague transmitted by ﬂeas, both killing millions of people over time Nevertheless, this opinion changed after knowing the toxic effects

of DDT on birds, particularly after the publication of the book Silent Spring by Rachel Carson in 1962 [2] At present, due to the possible toxic effects of pesticides

on human health and on the environment, there are strict regulations for their registration and use all over the world, especially in developed countries However, although some progress is achieved in the biological control and in the development

of resistance of plants to pests, pesticides are still indispensable for feeding and protecting the world population from diseases It has been estimated that around one-third of the crop production would be lost if pesticides were not applied

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Pesticide use has increased 50-fold since 1950 and around 2.5 million tons ofindustrial pesticides per year are used nowadays Figure 1.1 shows the time course ofpesticide sales during the last years.

According to the European Crop Protection Association (ECPA) Annual Report

2001–2002, the main agricultural areas of pesticide usage are North America,Europe, and Asia with 31.9%, 23.8%, and 22.6%, respectively, in 2001 (Figure 1.2).These percentages of pesticide sales are expressed in millions of euros and, althoughthe mentioned regions are the most important agricultural areas in the global pesticidemarket, their relative position may vary due to changes in the currency exchange rates,climatic conditions, and national policies on agricultural support and regulations

The amount of pesticides applied in a determined geographical area depends onthe climatic conditions and on the outbreak of pests and diseases of a particular year.Nevertheless, herbicides are the main group of pesticides used worldwide, followed

by insecticides and fungicides (Figure 1.3)

20,000 22,000 24,000 26,000 28,000 30,000 32,000

1990 1992 1994 1996 1998 2000 2002 2004 2006

FIGURE 1.1 World market of pesticides since 1990 Values are expressed in millions ofU.S dollars (From European Crop Protection Association (ECPA) Review 2005–2006,http:==www.ecpa.be.)

0 2,000 4,000 6,000 8,000 10,000

North America

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The development of a new chemical as a pesticide takes at present nearly

15 years and around $20 million, and only one compound out of 10,000 compoundsinitially tested might reach, on average,final commercial production The registra-tion of a pesticide for its application on a particular crop requires a complete set ofdata to prove its efficacy and safe use This normally includes data on physicochem-ical properties, analytical methods, efficacy, toxicology, ecotoxicology, and fate andbehavior in the environment Residues left on crops after pesticide application havebeen restricted in developed countries to guaranty a safe food consumption Themaximum residue levels (MRLs) in different foods have been established according togood agricultural practices, the observed toxic effects of the pesticide, and the amount

of food consumed MRLs are normally ﬁxed in relation with the admissible dailyintake (ADI) of pesticides, which is the amount of pesticide that can be ingested dailyduring the whole life without showing an appreciable adverse effect MRLs areproposed by the Joint FAO=WHO Meeting on Pesticide Residues (JMPR) andrecommended for adoption by the Codex Committee on Pesticide Residues [3,4]

In the following sections of this chapter, the main classes of pesticides cides, insecticides, and fungicides) will be described together with their mainphysicochemical properties and principal uses These data have been gatheredmainly from The Pesticide Manual [5] as well as from the primary manufacturesources [6,7] and other available publications [8,9]

(herbi-1.2 HERBICIDES

The implementation of mechanization in agriculture has increased the ability ofhuman to control weeds and cultivate crops; herbicides have played a main part inthis development; and a higher proportion of farmers would be needed if herbicideswere not used

Herbicides can be classiﬁed as soil- or foliage-applied compounds, which arenormally absorbed by roots or leaf tissues, respectively These compounds can be

0 10 20 30 40 50 60 70

Herbicides Insecticides Fungicides

FIGURE 1.3 Distribution of the market (%) per pesticide type (From Environmental tion Agency (USEPA), pesticides industry sales and usage, 2001, http:==www.epa.gov=oppbead1=pestsales= and ECPA Annual Report 2001–2002, http:==www.ecpa.be.)

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Protec-total or selective herbicides Total herbicides can kill all vegetation, whereas ive herbicides can control weeds without affecting the crop These chemical sub-stances may be applied at different crop stages, such as presowing and pre- orpostemergence, and these different treatments will be used depending on the weedneeded to be controlled in a particular crop The selectivity of a herbicide maydepend on a differential plant uptake, translocation, or metabolism, as well as ondifferences at the site of action A knowledge of physicochemical properties, that is,vapor pressure (V.p.), octanol=water partition coefﬁcient (Kow, expressed in thelogarithmic form log P), and solubility in water allows the fate and behavior ofsuch chemicals in the environment to be predicted.

select-In addition, herbicides can be classiﬁed according to their chemical composition.The principal physicochemical properties, together with the ﬁeld persistence andmajor uses of representative herbicides, grouped in their main chemical classes, aredescribed later

1.2.2 BENZOICACIDS

This group is mainly formed by chlorinated derivatives of substituted benzoic acids

Cl

CO2H OCH3

Cl Dicamba

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The benzoic acid herbicides are known to have growth regulating and auxin activityproperties These compounds are especially used to control deep-rooted perennialweeds and applied as salts or esters (Table 1.2).

1.2.3 CARBAMATES

Carbamates are esters of the carbamic acid (R1–O–CO–NR2R3) and together withthiocarbamates (R1–S–CO–NR2R3) represent a broad group of herbicides, frequentlyapplied to soil in preemergence

Water Solubility mg=L (258C)

Half-Life

in Soil (Days) Acetochlor

Butachlor

C 17 H 26 ClNO 2

N-Butoxymethyl-2-chloro-20,60 diethylacetanilide

Metolachlor

C 15 H 22 ClNO 2

(2-methoxy-1-methylethyl) acet-o-toluidide

a 208C.

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These compounds are root or shoot absorbed and are frequently used to controlannual grasses and broad-leaved weeds in peas, beet, and other horticultural crops.These herbicides are normally decomposed by soil microorganisms in 3–5 weeks.Their main physicochemical properties are summarized in Table 1.3.

CN

I OH I

They are formulated as salts or octanoate esters and foliage applied to control leaved weeds in cereals and horticultural crops These compounds are used inpostemergence and frequently applied in combination with other herbicides toextend the spectrum of weed species to be controlled They have a low persistence

Water Solubility g=L (258C)

Half-Life

in Soil (Days) Chloramben

C 7 H 5 Cl 2 NO 2

dichlorobenzoic acid

Chlorthal-dimethyl

C 10 H 6 Cl 4 O 4

Dimethyl tetrachloroterephthalate

Dicamba

C 8 H 6 Cl 2 O 3

methoxybenzoic acid

Sources: Data from Tomlin, C (Ed.) in The Pesticide Manual, British Crop Protection Council, 2000;

http: ==ec.europa.eu=food=plant=protection=evaluation=exist_subs_rep_en.htm; http:==www.epa gov=opprd001=factsheets=; Hornsby, A.G., Wauchope, R.D., and Herner, A.E in Pesticide Properties in the Environment, Springer-Verlag, New York, 1996; De Liñan, C in Farmacología Vegetal, Ediciones Agrotecnicas S.L., 1997.

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Nitroanilines are a group of herbicides with similar physicochemical properties, such

as low water solubility and high octanol–water partition coefﬁcient These compoundsare soil-applied herbicides used to control annual grasses and many broad-leaved

Half-Life

in Soil (Days) Chlorpropham

C 10 H 12 ClNO 2

chlorocarbanilate

Desmedipham

C 16 H 16 N 2 O 4

Ethyl-3-phenylcarbamoyloxy phenylcarbamate

EPTC

C 9 H 19 NOS

S-Ethyl dipropylthiocarbamate

Molinate

C 9 H 17 NOS

S-Ethyl carbothioate

Phenmedipham

C 16 H 16 N 2 O 4

(3-methylcarbaniloyloxy) carbanilate

Propham

C 10 H 13 NO 2

Isopropyl phenylcarbamate

Sublimes slowly

Thiobencarb

C 12 H 16 ClNOS

S-4-Chlorobenzyl diethylthiocarbamate

Triallate

C 10 H 16 Cl 3 NOS

S-2,3,3-Trichloroallyl diisopropyl(thiocarbamate)

http: ==ec.europa.eu=food=plant=protection=evaluation=exist_subs_rep_en.htm; http:==www.epa gov =opprd001=factsheets=; Hornsby, A.G., Wauchope, R.D., and Herner, A.E in Pesticide Properties in the Environment, Springer-Verlag, New York, 1996; De Liñan, C in Farmacología Vegetal, Ediciones Agrotecnicas S.L., 1997.

a

208C.

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weeds in a wide variety of crops The 2,6-dinitroanilines possess a marked generalherbicide activity Substitution at the third and=or fourth position of the ring or on theamino group modiﬁes the degree of herbicidal activity In general, they have acertain persistence in soil and are normally soil incorporated due to their signiﬁcantvapor pressure (Table 1.5).

Half-Life

in Soil (Days) Bromoxynil

C 7 H 3 Br 2 NO

hydroxybenzonitrile

Ioxynil

C 7 H 3 I 2 NO

diiodobenzonitrile

Half-Life

in Soil (Days) Butralin

C 14 H 21 N 3 O 4

N-sec-Butyl-4-tert-butyl-2, 6-dinitroaniline

Ethalﬂuralin

C 13 H 14 F 3 N 3 O 4

(2-methylallyl)-2,6-dinitro- p-toluidine

Pendimethalin

C 13 H 19 N 3 O 4

dinitro-3,4-xylidine

Tri ﬂuralin

C 13 H 16 F 3 N 3 O 4

N,N-dipropyl-p-toluidine

http:==ec.europa.eu=food=plant=protection=evaluation=exist_subs_rep_en.htm; http:==www.epa gov =opprd001=factsheets=; Hornsby, A.G., Wauchope, R.D., and Herner, A.E in Pesticide Properties in the Environment, Springer-Verlag, New York, 1996; De Liñan, C in Farmacología Vegetal, Ediciones Agrotecnicas S.L., 1997.

a

208C.

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1.2.6 ORGANOPHOSPHORUS

HO2CCH2NHCH2P(OH)2

O

Glufosinate Glyphosate

CH3PCH2CH2CHCO2H O

OH NH2

Glyphosate and glufosinate are broad spectrum, nonselective, postemergence contactherbicides active only for foliar application They are extensively used in variousapplications for weed control in aquatic systems and vegetation control in noncropareas Aminomethylphosphonic acid (AMPA) is the major degradation product ofglyphosate found in plants, water, and soil The main properties of these compoundsare shown in Table 1.6

1.2.7 PHENOXYACIDS

Phenoxy acids are a common name given to a group of compounds formed by aphenoxy radical linked to a low carbon number alkanoic acid, such as 2,4-dichlorophe-noxyacetic acid (2,4-D, acetic acid) or mecoprop (propionic acid) Some herbicides

of this group are formed by stereoisomers, which are commercialized as singleenanthiomers or racemic mixtures

Half-Life

in Soil (Days) Glyphosate

C 3 H 8 NO 5 P

N-(Phosphonomethyl) glycine

Glufosinate-ammonium

C 5 H 15 N 2 O 4 P

Ammonium 4-[hydroxy(methyl) phosphinoyl]- DL - homoalaninate

Sources: Data from Tomlin, C (Ed.) in The Pesticide Manual, British Crop Protection Council,

2000; http: ==ec.europa.eu=food=plant=protection=evaluation=exist_subs_rep_en.htm; http:==www epa.gov =opprd001=factsheets=; Hornsby, A.G., Wauchope, R.D., and Herner, A.E in Pesticide Properties in the Environment, Springer-Verlag, New York, 1996; De Liñan, C in Farmacología Vegetal, Ediciones Agrotecnicas S.L., 1997.

a

208C.

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Half-Life

in Soil (Days) 2,4-D

C 8 H 6 Cl 2 O 3

2,4-Dichlorophenoxy acetic acid

Diclofop

C 15 H 12 Cl 2 O 4

(RS)-2-[4-(2,4-Dichlorophenoxy) phenoxy]propionic acid

Fenoxaprop-P

C 16 H 12 ClNO 5

(R)-2-[4-(6-Chloro-1,3-benzoxazol -2-yloxy)phenoxy]propionic acid

Fluazifop-P

C 15 H 12 F 3 NO 4

(R)-2-[4-(5-Tri pyridyloxy)phenoxy]propionic acid

MCPA

C 9 H 9 ClO 3

4-Chloro-(2-methylphenoxy)acetic acid

Mecoprop-P

C 10 H 11 ClO 3

(R)-2-(4-Chloro-o-tolyloxy) propionic acid

Triclopyr

C 7 H 4 Cl 3 NO 3

3,5,6-Trichloro-2-pyridyloxyacetic acid

a 208C.

b

258C.

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1.2.8 PYRIDINES ANDQUATERNARYAMMONIUMCOMPOUNDS

The herbicide group of pyridines, also named bipyridylium, is formed by paraquatand diquat These compounds were developed as the result of observations thatquaternary ammonium germicides, such as cetyl trimethylammonium bromide,desiccated young plants Other quaternary ammonium compounds, like chlormequatand mepiquat, have been developed and used as plant growth regulators to increaseyields in cereals, promoteﬂowering in ornamental plants, and improve fruit setting inhorticultural plants and trees

Half-Life

in Soil (Days) Diquat dibromide

C 12 H 12 Br 2 N 2

1,10-Ethylene-2,20 bipyridyldiylium dibromide

Paraquat dichloride

C 12 H 14 Cl 2 N 2

1,10-Dimethyl-4,40 bipyridinium dichloride

Mepiquat chloride

C 7 H 16 ClN

1,10-Dimethyl-piperidinium chloride

a 258C.

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dibromide or dichloride salts These herbicides are strongly adsorbed in soil, ing acid digestion for several hours for their desorption.

requir-1.2.9 PYRIDAZINES ANDPYRIDAZINONES

Pyridate and pyridazinones, like norﬂurazon and chloridazon, are included in thisgroup

K ow

log P (258C)

Half-Life

in Soil (Days) Chloridazon

C 10 H 8 ClN 3 O

phenylpyridazin-3(2H)-one

Pyridate

C 19 H 23 ClN 2 O 2 S

4-yl-S-octylthiocarbonate

http:==ec.europa.eu=food=plant=protection=evaluation=exist_subs_rep_en.htm; http:==www.epa gov =opprd001=factsheets=; Hornsby, A.G., Wauchope, R.D., and Herner, A.E in Pesticide Properties in the Environment, Springer-Verlag, New York, 1996; De Liñan, C in Farmacología Vegetal, Ediciones Agrotecnicas S.L., 1997.

a

208C.

b

258C.

Trang 27

broad-in high dosages as soil sterilants In general, these herbicides are applied broad-in pre- orpostemergence and they are absorbed by the roots or by the foliage, respectively Insome cases, they are used in combination with other herbicides to broaden the spectrum

of activity These compounds have an appreciable persistence in soil (Table 1.10)

K ow

log P (258C)

Water Solubility mg=L (258C) Half-Life inSoil (Days) Atrazine

C 8 H 14 ClN 5

6-Chloro-N2-ethyl-N4 isopropyl-1,3,5-triazine- 2,4-diamine

Cyanazine

C 9 H 13 ClN 6

1,3,5-triazin-2-ylamino)- 2-methylpropionitrile

Metribuzin

C 8 H 14 N 4 OS

4,5-dihydro-3-methylthio- 1,2,4-triazin-5-one

Prometryn

C 10 H 19 N 5 S

N2,N4 methylthio-1,3,5- triazine-2,4-diamine

Simazine

C 7 H 12 ClN 5

6-Chloro-N2,N4 1,3,5-triazine-2,4-diamine

Terbutryn

C 10 H 19 N 5 S

N2-tert-Butyl-N4 6-methylthio-1,3,5- triazine-2,4-diamine

a

208C.

Trang 28

Phenylureas belong to a numerous group of substituted ureas directly applied to soil

in preemergence to control annual grasses in various crops These compounds have arange of speciﬁc selectivity as well as variable persistence in soil according to theirchemical composition (Table 1.11)

K ow

log P (258C)

Half-Life

in Soil (Days) Chlorotoluron

C 10 H 13 ClN 2 O

1,1-dimethylurea

Diuron

C 9 H 10 Cl 2 N 2 O

1,1-dimethylurea

Linuron

C 9 H 10 Cl 2 N 2 O 2

1-methoxy-1-methylurea

a 608C.

b

208C.

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1.2.11.2 Sulfonylureas

Cl

N N N

CH3OCH2CH2Cl

This group of substituted ureas has been developed more recently and they have, ingeneral, a herbicidal activity higher than the phenylurea herbicides, with applicationrates in the range of gram=hectare instead of kilogram=hectare They can be absorbed

by foliage and roots They are normally applied in postemergence and in some casesmay have a noticeableﬁeld persistence (Table 1.12)

1.3 INSECTICIDES

Horticultural crops may be affected by various pests causing serious damages toplants and consequently important yield reductions Therefore, insecticides arewidely used to control pests in crops These compounds may be applied to the soil

to kill soilborne pests or to the aerial part of the plant

A major part of the applied insecticides reaches the soil, either by directapplications to the soil or indirectly by runoff from leaves and stems

A new insecticide activity acting on the moulting process of insects was discovered

in the study of biological activity of some benzoylurea derivatives Benzoylureas act

as insect growth regulators, interfering with the chitin formation in the vital insectexoskeleton Most benzoylureas used as insecticides containﬂuorine atoms and havehigh molecular weights Table 1.13 summarizes the physicochemical properties ofthese compounds

1.3.2 CARBAMATES

The N-methyl and N,N-dimethyl carbamic esters of a variety of phenols possessuseful insecticidal properties Aromatic N-methylcarbamates are derivatives of

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phenyl N-methylcarbamate with a great variety of chloride, alkyl, alkylthio, alkoxy,and dialkylamino side chains Some carbamate insecticides contain a sulfur atom intheir molecule.

Half-Life

in Soil (Days)

Di ﬂubenzuron

C 14 H 9 ClF 2 N 2 O 2

3-(2,6-di ﬂuorobenzoyl)urea

Hexaﬂumuron

C 16 H 8 Cl 2 F 6 N 2 O 3

1-[3,5-Dichloro-4-(1,1,2, 2-tetra ﬂuoroethoxy) phenyl]-3-(2,6-

Tri ﬂumuron

C 15 H 10 ClF 3 N 2 O 3

tri ﬂuoromethoxyphenyl) urea

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O SO

Half-Life

in Soil (Days) Aldicarb

C 7 H 14 N 2 O 2 S

2-Methyl-2-(methylthio) propionaldehyde O-methylcarbamoyloxime

Carbosulfan

C 20 H 32 N 2 O 3 S

2,3-Dihydro-2,2-dimethyl benzofuran-

7-yl(dibutylaminothio) methylcarbamate

Fenoxycarb

C 17 H 19 NO 4

Ethyl-2-(4-phenoxyphenoxy) ethylcarbamate

Methomyl

C 5 H 10 N 2 O 2 S

S-Methyl moyloxy) thioacetamidate

Oxamyl

C 7 H 13 N 3 O 3 S

N,N0-Dimethyl-2-methyl carbamoyloxyimino- 2-(methylthio)acetamide

Pirimicarb

C 11 H 18 N 4 O 2

2-Dimethylamino-5, 6-dimethyl pyrimidin- 4-yl dimethylcarbamate

a 258C.

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These insecticides are characterized by three kinds of chemicals: DDT analogs, zene hexachloride (BHC) isomers, and cyclodiene compounds DDT is one of the mostpersistent and durable of all contact insecticides because of its insolubility in water andvery low vapor pressure DDT has a wide spectrum of activity on different families ofinsects and related organisms BHC isomers are active against a great variety of pests.Cyclodiene compounds are effective where contact action and long persistence arerequired These compounds have a broad spectrum insecticide and have been used forthe control of insect pests of fruits, vegetables, and cotton as soil insecticides and forseed treatment Due to their persistence and toxicity, most of these organochlorinecompounds have been banned or their use as pesticide has been restricted (Table 1.15).

ben-1.3.4 ORGANOPHOSPHORUS

Organophosphorus insecticides are hydrocarbon compounds which contain one ormore phosphorus atoms in their molecule They are relatively short lived in bio-logical systems

The diversity of organophosphorus insecticide types makes them to form the mostversatile group There are compounds with nonresidual action and prolongedresidual action, and compounds with a broad spectrum and very speciﬁc actionthat can have activity as systemic insecticides for plants, seed, and soil treatments,

as well as for animals In general, they are soluble in water and readily hydrolyzedand they dissipate from soil within a few weeks after application Because of theirlow persistence and high effectiveness, these compounds are widely used as systemicinsecticides for plants, animals, and soil treatments (Table 1.16)

Permethrin

Pyrethrins are natural insecticides obtained from pyrethrum, extracted from theflowers of certain species of chrysanthemum The insecticide properties are due tofive esters that are mostly present in the flowers These esters have asymmetric carbonatoms and double bonds in both alcohol and acid moieties The naturally occurringforms are esters from (þ)-trans acids and (þ)-cis alcohols Synthetic pyrethrins, called

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pyrethroids, present better activity for a larger spectrum of pests than natural ones.They show selective activity against insects and present low toxicity to mammals andbirds Pyrethroids are considered as contact poisons, affecting the insect nervoussystem and depolarizing the neuronal membranes These compounds are degraded

in soil and have no detectable effects on soil microﬂora They have also been used inhousehold to controlﬂies and mosquitoes Piperonyl butoxide (C19H30O5) is used as asynergist for pyrethrins and related insecticides (Table 1.17)

1.4 FUNGICIDES

Fungicides used in agriculture to control plant diseases belong to various chemicalclasses A wide variation of physicochemical properties of these substances can beobserved, according to the different chemical structures of fungicides Some fungi-cides are stereoisomers and they are normally commercialized as mixtures of theseisomers Fungicides can be applied pre- or postharvest for the protection of cereals,fruits, and vegetables from fungal diseases

1.4.1 AZOLES

OH CH

CH3

CH2

N N N

CyproconazoleThe imidazole ring is present in several biologically active compounds, while othershave a triazole ring These compounds are fungicides with systemic action, effectiveagainst several phytopathogenous fungi and recommended for seed dressing, as well

as foliage fungicide and postharvest application in fruits They are scarcely soluble inwater, although their salts are soluble in water (Table 1.18)

1.4.2 BENZIMIDAZOLES

N

H N

N S

Thiabendazole

Fungicides of the benzimidazole type have a systemic action Generally, they aretaken up by the roots of the plants, and the active substances are then acropetallytranslocated through the xylem to the leaves These compounds have been used inplant protection in the form of their insoluble salts They are foliage and soil

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fungicides with a speciﬁc and broad spectrum of action, also used for seed treatmentand in postharvest (Table 1.19).

1.4.4 MORPHOLINES

CH2CHCH2(H3C)3C

CH3

FenpropimorphMorpholines are speciﬁc systemic fungicides against powdery mildew fungi andare used to control the disease in cereals, cucumbers, apples, and so on These

Half-Life

in Soil (Days) Benomyl

a 208C.

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compounds are distributed in the plants by translocation from the root and foliageand protect the plants against infection by phytopathogenic fungi They have acertain persistence in soil (Table 1.21).

1.4.5 MISCELLANEOUS

N O

O SCCl3

CN Cl

Cl Cl

Half-Life

in Soil (Days) Mancozeb

(C 4 H 6 MnN 2 S 4 ) x (Zn) y

Manganese ethylenebis (dithiocarbamate) (polymeric) complex with zinc salt

Maneb

C 4 H 6 MnN 2 S 4

Manganese ethylenebis (dithiocarbamate)

Metiram

(C 16 H 33 N 11 S 16 Zn 3 ) x

Zinc ammoniate ethylenebis (dithiocarbamate)- poly(ethylenethiuram disul ﬁde)

Nabam

C 4 H 6 N 2 Na 2 S 4

Disodium ethylenebis (dithiocarbamate)

Zineb

(C 4 H 6 N 2 S 4 Zn) x

Zinc ethylenebis (dithiocarbamate) (polymeric)

Ziram

C 6 H 12 N 2 S 4 Zn

Zinc bis (dimethyldithiocarbamate)

2

a

208C.

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