Insecticides methoxychlor

A need has arisen for a sensitive and specific method of estimating microgram quantities of the insecticide methoxychlor in plant and animal products.. Methoxychlor, l,l,l-trichloro-2,2-bis(p-methoxyphenyl)-ethane, is an analog of DDT and therefore procedures for the determination of DDT should be applicable to methoxychlor as well. Such has actually been found to be the case. 

Tullner WW Uterotrophic action of the insecticide methoxychlor. Science 133 647-648, 1961... 

Estimate the Ki0Vi values at 25°C of the following compounds based on the experimental Ki0Vi values of the indicated structurally related compounds (a) benzoic acid dimethylaminoethyl ester from benzoic acid ethyl ester (log Kiaw = 2.64), (b) the insecticide methoxychlor from DDT (log Ki0Vi = 6.20), (c) the insecticide fenthion from parathion [log Kiow = 3.83, see 111. Ex. 7.2, Answer (d)], and (d) the hormone estradiol from testosterone [log Ki0Vi = 3.32, see 111. Ex. 7.2, Answer (e)]. 

The following are examples of priority pollutants arsenic, selenium, barium, cadmium, chromium, lead, mercury, silver, benzene, ethylbenzene, chlorobenzene, chloroethene, dichloromethane, and tetrachloroethene. The priority pollutants also include the pesticide and fumigant eldrin, the pesticide lindane, the insecticide methoxychlor, the insecticide and fumigant toxaphene, and the herbicide and plant growth regulator silvex. There are a total of 65 priority pollutants. 

Many pesticides or their degradation products tend to be adsorbed by or incorporated into soil organic matter, particularly humus. For example, Ma-thur and Morley (1975, 1978) showed that even the relatively unreactive insecticide methoxychlor was unextractably retained in model chemical and fungal humic acids to levels of 263 and 50 ppm, respectively. 

An individual method was described for the determination of 2,2-bis(p-methoxyphenyl)-1,1,1-trichloroethane isomer in the insecticide methoxychlor by TLC. The presence of this isomer in technical grade and emulsifiable concentrate of the methoxychlor could be established by this method, in which silica gel plates were developed with n-pentane-ether (9 1) (53a). 

Methoxychlor 0.04 0.04 Reproductive difficulties Runoff/leaching from insecticide used on fruits, vegetables, alfalfa, livestock... 

Recently a colorimetric test for methoxychlor residues was proposed by Fairing (27). The methoxychlor sample is treated with alcoholic potassium hydroxide, the reaction product is extracted with ether, the ether is removed, and the residue is treated with concentrated sulfuric acid. An intense cherry-red color is developed. No other insecticide has been found to interfere, and the reaction is sensitive to about 5 micrograms of methoxychlor. 

For some important insect pests there are still no satisfactory chemical controls. Such problems should be given due consideration in the development program. Many of these problems appeared to be solved with the discovery of DDT, benzene hexachlo-ride (hexachlorocyclohexane), and some of the more recent insecticides. Further studies of the toxicity of some of these products to warm-blooded animals have raised the important question of the advisability of continuing their use where food and feed products are concerned. Considerable attention is being centered on finding safer analogs, such as TDE and methoxychlor, and new and better insecticides. 

The dehydrohalogenated product reacts with 85% sulfuric acid to produce a red complex of unknown composition with an absorption maximum at 555 mfi (Figure 1). No other organic insecticide now in use produces any color under similar conditions. Therefore, the method is specific for methoxychlor. Fats and waxes, however, yield strong brown colors which will completely mask the methoxychlor reaction. In the method described this interference has been reduced to a point where it introduces an error of less than 1% when the methoxychlor concentration is between 5 and 50 micrograms. Quantities of methoxychlor of less than 1 microgram may be determined by this method. 

A procedure for the determination of 7-benzene hexa-chloride and DDT in benzene hexachloride-DDT-sul-fur formulations, employing partition chromatography, is described. The procedure has also been applied to the assay of 1,1,1 -trichloro-2,2-bis(p-methoxyphenyl)-ethane in technical methoxychlor. Results of separation of other insecticidal ingredients are discussed. 

Methoxychlor [1,1,l-trichloro-2,2-bis(p-methoxyphenyl)-ethane], benzene hexachloride (BHC), chlordan, and toxaphene are chlorinated compounds of recognized importance in the insecticide field. Other chlorinated compounds now undergoing-field testing experiments will, no doubt, soon be added to the list. The need for specific analytical methods is familiar to those concerned with the analysis of formulations containing one or more of the above insecticides. 

Aspila et al. [338] reported the results of an interlaboratory quality control study in five laboratories on the electron capture gas chromatographic determination of ten chlorinated insecticides in standards and spiked and unspiked seawater samples (lindane, heptachlor, aldrin, 5-chlordane, a-chlordane, dield-rin, endrin, p, p -DDT, methoxychlor, and mirex). The methods of analyses used by these workers were not discussed, although it is mentioned that the methods were quite similar to those described in the water quality Branch Analytical Methods Manual [339]. Both hexane and benzene were used for the initial extraction of the water samples. 

Chlordane interacts with other chemicals to produce additive or more-than-additive toxicity. For example, chlordane increased hepatotoxic effects of carbon tetrachloride in the rat (USEPA 1980 WHO 1984), and in combination with dimethylnitrosamine acts more than additively in producing liver neoplasms in mice (Williams and Numoto 1984). Chlordane in combination with either endrin, methoxychlor, or aldrin is additive or more-than-additive in toxicity to mice (Klaassen et al. 1986). Protein deficiency doubles the acute toxicity of chlordane to rats (WHO 1984). In contrast, chlordane exerts a protective effect against several organophosphorus and carbamate insecticides (WHO 1984), protects mouse embryos against influenza virus infection, and mouse newborns against oxazolone delayed hypersensitivity response (Barnett et al. 1985). More research seems warranted on interactions of chlordane with other agricultural chemicals. 

In general, the control of insect pests of cacao has been neglected. Also, little is known regarding the effect of insecticides on cacao. Cardona (9) in Colombia has studied the influence of some insecticides on the pollination and fruit setting. He used various preparations of BHC Agrocide, chlordan, DDT, dieldrin, dieldrex, methoxychlor [l,l,l-trichloro-2,2-bis(p-methoxyphenyl) ethane], and toxaphene. 

Insecticidal activity of DDT and related compounds is due to their neuroexcitatory effect, the mechanism of which is very similar to that of pyrethroids 75). Using a number of analogs of DDT (34), DDD (35), and prolan (36), p,p -substituents of which are modified variously as well as those of methoxychlor (37), the trichloro-... 

Wolfe et al. (1977) have determined the rate constants for the neutral and base-catalyzed transformation of the two classical insecticides DDT and methoxychlor in water at 27°C ... 

A few OC insecticides that are in use currently—methoxychlor, dicofol, endosulfan, and lindane (y-IICII)—are being reassessed by the U.S. Environmental Protection Agency (USEPA). For instance, approximately 45% of the 350 tons of dicofol was used in the USA in 1997 for the control of pests in... 

The apparent rate of hydrolysis and the relative abundance of reaction products is often a function of pH because alternative reaction pathways are preferred at different pH. In the case of halogenated hydrocarbons, base-catalyzed hydrolysis will result in elimination reactions while neutral hydrolysis will take place via nucleophilic displacement reactions. An example of the pH dependence of hydrolysis is illustrated by the base-catalyzed hydrolysis of the structurally similar insecticides DDT and methoxy-chlor. Under a common range of natural pH (5 to 8) the hydrolysis rate of methoxychlor is invariant while the hydrolysis of DDT is about 15-fold faster at pH 8 compared to pH 5. Only at higher pH (>8) does the hydrolysis rate of methoxychlor increase. In addition the major product of DDT hydrolysis throughout this pH range is the same (DDE), while the methoxychlor hydrolysis product shifts from the alcohol at pH 5-8 (nucleophilic substitution) to the dehydrochlorinated DMDE at pH > 8 (elimination). This illustrates the necessity to conduct detailed mechanistic experiments as a function of pH for hydrolytic reactions. 

The phenomenal success of DDT stimulated further research, and by 1946 the two DDT analogs, DDD and methoxychlor (Table 1,A) had been produced (Tables are at the end of the chapter). The observation of greater insecticidal activity in those organochlorine compounds that lose their HC1 more easily led to yet another group of chlorinated derivatives, the condensed ring chlorocyclodienes (Table 1,B). Thus, nearly all of the chlorinated pesticides currently in use had been... 

Methoxychlor is degraded in vivo by 0-dealkylation and excreted as mono-and bis-phenols. It is much less environmentally persistent also much less toxic to rats (oral LD q> 6000 mg/Kg compared with LD q 118 mg/Kg for DDT Metcalf, ref. 16). However, methoxychlor toxicity in fish approaches that of DDT, and in cold water fish, e.g., Atlantic salmon, it can accumulate to excessive levels. Although much less toxic in mammals than DDT it is similar in its estrogenic action. Methylchlor is less toxic to fish than methoxychlor, but also rather ineffectual as an insecticide. Comparison of the persistence characteristics of the methyl and methoxy analogs of DDT shows the microsomal side chain oxidation of the alkyl group to be more efficient than microsomal 0-dealkylation. 

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