Chlorinated acid pesticides

SFE/derivatization of several chlorinated acid pesticides (those listed in EPA method 515.1) have been performed using conditions similar to those used for the bacterial phospholipids. The derivatized products from the SFE procedure for several representative organics are shown in Figure 6. As would be expected using the TMPA/methanol reagent, the carboxylic acids form the methyl esters (2,4-D and dicamba) while the phenols form the methyl ethers (pentachlorophenol). Esters of the carboxylic acids (e.g., the di-isopropyl amine ester of 2,4-D) also form the methyl esters. For ethers, two derivatized products resulted since the ether linkage could be cleaved on either side of the oxygen and methylated as shown by acifluorfen. 

Both underivatised and methylated samples are examined because uracil herbicides give a mixture of products on methylation and should be chromatographed in their underivatised forms, whereas carboxylic acid pesticides, e.g. chlorinated phenoxy acid herbicides, are best examined as methyl derivatives. 

PAHs can be eluted as a separate band although they may still coelute with chlorinated aromatics, pesticides, and nitroaromatics, thus necessitating another cleanup step prior to analysis. Another strategy is to separate the organic acids and phenols from soil/sediment extracts by performing a liquid-liquid extraction with 10 N NaOH. ° The solvent extract is shaken in a separatory funnel with three aliquots of concentrated NaOH. The combined extracts containing the acids and phenols is discarded while the extract, in DCM, is dried and concentrated for GC analysis or solvent exchanged for another analysis method. 

In many contributions reporting on acidic pesticides in environmental samples ESI applied as ion spray was predominantly performed to analyse these pollutants. APCl, however, was not as effective as ESI as studies with standard solutions of the pesticide mixtures made obvious [325] when phenoxy acid compounds were determined using both types of interface. MSn quantitative results were used for confirmation. Mass detection after CZE-MS interfaced by ESI was successfully apphed to analyse drinking water spiked with chlorinated acid herbicides. Selected-ion elec-... 

Chlorine s most important use is as bleach in the manufacture of paper and cloth. It is also used widely as a chemical reagent in the synthesis and manufacture of metallic chlorides, chlorinated solvents, pesticides, polymers, synthetic rubbers, and refrigerants. Sodium hypochlorite which is a component of commercial bleaches, cleaning solutions, and disinfectants for drinking water, wastewater purification systems, and swimming pools—releases chlorine gas when it comes in contact with acids. 

Examples of the application of HPLC to the analysis of (a) acetaminophen, salicylic acid, and caffeine (b) chlorinated pesticides (c) tricyclic antidepressants and (d) peptides. (Chromatograms courtesy of Alltech Associates, Inc. Deerfield, IL). 

Only particular solvents are suitable for certain purposes. The choice depending, for instance, on their residual water content or their acid-base nature if Rf values are to be reproduced [1, 2]. Halogen-containing solvents may not be employed for the determination of chlorinated pesticides. Similar considerations apply to PAH analyses. Pro analyst grades are no longer adequate for these purposes. It is true that it would be possible to manufacture universally pure solvents that were adequate for all analytical purposes, but they would then be too expensive for the final user [3, 4]. 

Haloacetyl groups have also a synthetic potential. Thus, pesticidal (alkylthio)-vinyl esters of phosphorus acid derivatives have been prepared by the introduction and subsequent displacement of two chlorine atoms in the acetyl moiety attached to the furazan ring (Scheme 69) [73GEP(0)2144393]. 

Attempts have been made to apply the structure-activity concept (Hansch and Leo 1995) to environmental problems, and this has been successfully applied to the rates of hydrolysis of carbamate pesticides (Wolfe et al. 1978), and of esters of chlorinated carboxylic acids (Paris et al. 1984). This has been extended to correlating rates of biotransformation with the structure of the substrates and has been illustrated with a number of single-stage reactions. Clearly, this approach can be refined with the increased understanding of the structure and function of the relevant degradative enzymes. Some examples illustrate the application of this procedure ... 

A limited number of pure substances are available from NIST, primarily clini-cally-relevant compounds such as cholesterol, urea, uric acid, creatinine, glucose, cortisol, tripalmitin, and bilirubin (NIST SRM website). These compounds are certified for purity (greater than 99 %) and are used as primary calibrants in definitive methods for these clinical analytes (see below). Several additional pure substances are available for specific applications such as microchemistry, i.e. elemental composition (acetanilide, anisic acid, cystine nicotinic acid, o-bromobenzoic acid, p-fluoro-benzoic acid, m-chlorobenzoic acid), polarimetric standards (sucrose and dextrose), acidimetric standard (benzoic acid and boric acid). Only three pure substance NIST RMs are available for environmental contaminants, namely the chlorinated pesticides, lindane, 4,4 -DDT, and 4,4 -DDE. 

Residue analytical chemistry has extended its scope in recent decades from the simple analysis of chlorinated, lipophilic, nonpolar, persistent insecticides - analyzed in the first Si02 fraction after the all-destroying sulfuric acid cleanup by a gas chro-matography/electron capture detection (GC/ECD) method that was sometimes too sensitive to provide linearity beyond the required final concentration - to the monitoring of polar, even ionic, hydrophilic pesticides with structures giving the chemist no useful feature other than the molecule itself, hopefully to be ionized and fragmented for MS or MS" detection. 

Japenga et al. [56] determined polychlorinated biphenyls and chlorinated insecticides in River Elbe estuary sediments by a procedure in which the sediments were pretreated with acetic acid, mixed with silica and Soxhlet-extracted with benzene/hexane. Humic material and elemental sulphur were removed by passing the extract through a chromatographic column containing basic alumina, on which sodium sulphite and sodium hydroxide were adsorbed. Silica fractionation was followed by gas chromatography to analyse chlorinated pesticides, polychlorinated biphenyls and polyaromatic hydrocarbons. Recovery experiments with standard solutions gave recoveries of 90-102%. 

This group of pesticides comprises different families of chemicals with her-bicidal action including substituted phenols, chlorinated aliphatic acids, chloro-phenoxy alkanoic acids, and substituted benzoic acids, which possess carboxyl or phenolic functional groups capable of ionization in aqueous media to yield anionic species [47,151,168-170]. 

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