Chlorophenoxy acid pesticides

Chlorophenoxy acids are relatively polar pesticides which are usually determined by LC because volatile derivatives have to be prepared for GC analysis. This group of herbicides can be detected by multiresidue methods combined with automated procedures for sample clean-up, although selectivity and sensitivity can be enhanced by coupled-column chromatographic techniques (52). The experimental conditions for Such analyses are shown in Table 13.1. 

Methods for Organochlorine Pesticides and Chlorophenoxy Acid Herbicides in Drinking Water and Raw Source Water Environmental Monitoring and Support Laboratory. U.S. Environmental Protection Agency Cincinnati, OH EPA 600/4-81-053. 

In both these areas, chemical derivatisation has traditionally played a role and with the advent of gas chromatography an even more important role. The reasons for preparing a derivative suitable for GC analysis are many and varied and have been discussed thoroughly in a number of books and reviews (l- >). For convenience they are summarised in Table I. As can be seen, two different types of chemical derivatisation techniques are mentioned under Item 4 of Criteria, There is the chemical derivatisation of a pesticide as a pre-requisite of the method of analysis, e.g. esterification of the chlorophenoxy acids, as well as derivatisation as a method for confirmation of identity. The former must meet all the requirements associated with a practical, viable analytical procedure while for the latter the emphasis is on speed, ease of operation and reproducibility. 

As Table I illustrates, the chemical classes represented by the pesticides studied include thiophosphates [0,0-diethyl-o-p-nitrophenyl phos-phorothioate], carbamates [1-naphthyI-N-methylcarbamate], dinitrophe-nols [2,4-dinitro-o-sec-butylphenol and 2,4-dinitro-o-cyclohexylphenol], and chlorophenoxy acids [2,4-dichlorophenoxyacetic acid, 2,4,5-trichloro-phenoxyacetic acid, and 2-(2,4,5-trichlorophenoxy)propionic acid]. In addition, a number of molecularly related nitrophenols have been studied to establish the effects of molecular geometry and substituent groups on adsorption of pesticide-type materials. 

See also Chlorophenoxy Herbicides 2,4-D (2,4-Dichioro-phenoxy Acetic Acid) Pesticides Poiiution, Water. 

The first section of this book describes the application of LC/MS to the analysis of agricultural chemicals and their metabolites. Using LC/MS for residue analysis in agricultural chemistry has become routine in many laboratories. Many pesticides, such as the chlorophenoxy acid and sulfonyl urea herbicides or organophosphorus and methyl carbamate insecticides, are too polar or thermally labile for analysis via GC. The use of LC/MS for the identification of polar pesticide metabolites and conjugates, an area traditionally dominated by radiolabeled compounds, stands out as a particularly dramatic demonstration of the power of this technique. 

These phenoxy herbicides are very popular in W. Europe and Japan. Total Western European capacity for p-chloro-o-cresol exceeds 21-22,000 tpa. Major producers of PCOC include Coalite Chemicals, UK (9000 tpa) and Rhone-Poulenc (5000 tpa), UK, and BASF (7000 tpa) in Germany. These companies along with Bayer and Chemie Linz, which also produce PCOC in plants with flexible operations are the major producers of the chlorophenoxy carboxylic acid pesticides. 

In addition to those listed above, many other classes of compounds are also used in several pesticide formulations dithiocar-bamates, chlorophenols, nitrophenols, and various phthalimides. While the former three classes of substances—organochlorine pesticides, organophosphates, and carbamates— are among the best known pesticides (e.g., insecticides, rodenticides), triazines, chlorophenoxy acids, and bipyridyls are used in making herbicides. There are also many pesticides that do not fall under any specific class of structures. These are discussed separately. 

Liquid chromatography-mass spectrometry The initial attempts to couple LC with MS lacked important attributes for trace analysis sensitivity, robustness, and reliable quantitation. Moreover, the cost of the early LC-MS instruments was prohibitive for most laboratories. The revolutionary introduction of atmospheric pressure ionization (API) techniques, mainly electrospray (ESI) and atmospheric pressure chemical ionization (APCI), resulted in greater applicability of LC-MS and manufacture of more reliable, affordable, and user-friendly instruments. Thus, LC-MS is now becoming an indispensable part of the analytical strategy in many routine laboratories, enabling direct, selective, and sensitive multiclass, multiresidue analysis of more polar, low volatile, and/or thermolabile pesticides, such as carbamates, phenylureas, sulfonylureas, imidazoles, triazoles, imidazolinones, chlorophenoxy acids, and many others. 

Some synthetic pesticides and drugs have a phenyl or a naphthyl ring attached to the principal chain of fatty acids. The phenoxy acid pesticides, which are derivatives of formic, acetic, propionic, or butyric acids, belong to the synthetic fatty acids (SFAs) family. These acids are usually referred to as phenoxy acids and not as fatty acids, although they should be included in the fatty acids family, because they are derivatives of fatty acids. One such example is (2-methyl-4-chlorophenoxy)acetic acid (Figure 16). 

Figure 22 GC chromatogram of TMAH intrainjector derivatized phenoxy acids. Peaks 1 =2-phenoxypropionic acid 2=p-fluor-ophenoxyacetic acid 3=2-methylphenoxyacelic acid 4=3-me-thylphenoxyacetic acid 5=4-melhylphenoxyacetic acid 6= 2-formylphenoxyacetic acid 7=2,5-dimethylphenoxyacetic acid 8=2-(4-chlorophenoxy)propionic acid 9=2,4-dimethylphenoxy-acetic acid 10=2-methoxyphenoxyace1ic acid 11=4-phenox-ybutyric acid 12=3-melhoxyphenoxyacetic acid 13= 4-methoxyphenoxyacetic acid 14=2-(4-chloro-2-methyl-phenoxy)propionic acid 15 = 4-chloro-2-methylphenoxyacetic acid 16 = 2,4-dichlorophenoxypropionic acid 17 = iodophenoxy-xyacetic acid 18 = a-(2,4,5-trichlorophenoxy)propionic acid 19 = 2,4,5- trichlorophenoxyacetic acid. (Reproduced with permission from Brondz I and Olsen I (1992) Intra-injector formation of methyl esters from phenoxy acid pesticides. Journal of Chro-matogreiphy 598 309-312.)...

Herbicides are the most widely used type of pesticides, and triazines, N-arylcarbamates, and chlorophenoxy acids are among the most important classes of herbicides. Herbicides are used to control unwanted grasses and weeds in a variety of crops, such as cotton, alfalfa, sunflower, sorghum, rice, and a variety of fruits and vegetables. The following experiment involves the analysis of atra-zine as an example of the triazines, 2,4-D for the chlorophenoxy acid herbicides, and chlorpropham for the carbamates. 

Oxamyl methomyl Phoxan, 2,4,5 tri-chlorophenoxy acidic acid 2.4DB, NCPB 52 pesticides Paraquat diquat... 

Chlorophenoxy carboxylic acid type Cereal, berries Pesticide methylated, then GC-MS [136]... 

Low levels of an applied herbicide-pesticide-solvent mix were drawn into the uptake air of a commercial building following the application of a pesticide mix to the lawn in front of that building. Several employees immediately reported CNS and respiratory symptoms, with one sustaining a permanent respiratory injury. The pesticide mix applied to the lawn was composed of 2,4-D (2.82), 2-(2-methyl-4-chlorophenoxy) propionic acid (MCPP 2.48), and dicamba (2.21). The mixture also contained solvent naphtha (a mixture of aliphatic solvents, Kqw = 3.5-5.0) with 14% naphthalene (2.48) and dinitroaniline (3.30). The concentrations of all pesticides and solvents were far below the TLVs both outside and inside the building. The toxic effects observed were ascribed to the mixture of lipophilic and hydrophilic pesticides. 441... 

Acidic compounds This group of pesticides comprises different families of compounds with herbicidal action, including substituted phenols, chlorinated aliphatic acids, chlorophenoxy alkanoic acids, and substituted benzoic acids, which all possess carboxyl or phenolic functional groups capable of ionization in aqueous media to yield anionic species [90,96-99]. The following is a summary ... 

CE has been used for the analysis of chiral pollutants, e.g., pesticides, polynuclear aromatic hydrocarbons, amines, carbonyl compounds, surfactants, dyes, and other toxic compounds. Moreover, CE has also been utilized to separate the structural isomers of various toxic pollutants such as phenols, polyaromatic hydrocarbons, and so on. Sarac, Chankvetadze, and Blaschke " resolved the enantiomers of 2-hydrazino-2-methyl-3-(3,4-dihydroxyphenyl)propanoic acid using CD as the BGE additive. The CDs used were native, neutral, and ionic in nature with phosphate buffer as BGE. Welseloh, Wolf, and Konig investigated the CE method for the separation of biphenyls, using a phosphate buffer as BGE with CD as the chiral additive. Miura et al., used CE for the chiral resolution of seven phenoxy acid herbicides using methylated CDs as the BGE additives. Furthermore, the same group resolved 2-(4-chlorophenoxy) propionic acid (MCPP), 2-(2,4-dichlorophenoxy) propionic acid (DCPP), (2,4-dichlorophenoxy) acetic acid (2,4-D), 2-(4-chlorophenoxy) propionic acid (2,4-CPPA), [(2,4,5-... 

Grace Davison, Deerfield, USA Aflatoxins, lactoferrin, vitamin B12, testosterone, nortestosterone, ethinyl estradiol, estradiol, estrone, bisphenol A, chlorophenoxy acetic acid herbicides, phenylurea herbicides, organophosphate pesticides, vindozolin... 

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