Pesticides paraquat

Many aryl- and heteroaryl-substituted derivatives of the ir-deficient heterocyclic compounds have been prepared and some of them are of considerable commercial importance, for example as pesticides (paraquat and diquat) and as pharmaceuticals. 

To assess the combined effect of l-methyl-4-phenyl-l,2,3,6-tetrahy-drdopyridine (MPTP, Kow = 2.71), which is known to induce PDj32l and the organophosphate pesticide paraquat (KQW = -2.71), mice were treated... 

The effects of various additives on the sensitivity and selectivity ofTSP-LC-MS of thiocyanates and anilines were studied to optimize ionisation conditions. Trialky-lammonium formates were found to increase the selectivity and sensitivity of the TSP process [242]. TSP-LC-MS was also used for the characterization of the quaternary amine pesticides paraquat, difenzoquat, diquat, mepiquat and chlorme-quat from water and soil samples. Base peaks were [M-i-H] and [M-CH3-i-H] [243]. Difenzoquat, a difficult-to-determine quaternary ammonium pesticide was analysed using a post-column ion-pair extraction system [244]. 

The quaternary ammonium herbicides paraquat and diquat were first separated by CZE and then detected by ESI on a laboratory-built TOP instrument by means of volatile buffers. Depending on the buffer the ESI-TOF mass spectra of paraquat and diquat under these conditions showed singly and doubly charged molecular ions [489]. Moyano et al. also applied ESI-CZE-MS(-t) to the determination of the herbicides mepiquat, chlormequat, diquat, paraquat and difenzoquat in water. MS/MS provided the structural information essential for the confirmation of identity [490]. For product quality check-up of formulations of the herbicide chlormequat ESI-CZE-MS was used, allowing the determination of contaminants contained in the formulation [491]. The quaternary ammonium pesticides paraquat diquat, difenzoquat, chlormequat and mepiquat were analysed by ESI-LC-MS(-t). Prior to analysis ion-pairing extraction was applied to concentrate compounds prior to analysis on different SPE materials (e.g. Cg, Cjg, and PS-VDB)... 

The polarographic and voltammetric determination of chlorinated compounds, S-triazines, 2,4-AD-herbicides, nitro-containing pesticides, paraquat, diquat, carbamate pesti-... 

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

Paraquat Pesticides (includes acaricides, avicides, bactericides, insecticides, molluskicides, nematocides, piscicides, rodenticides) L S Chlorinated hydrocarbons (q.v.) Carbamates (q.v.) Organophosphorus compounds (q.v.) Herbicide... 

For aerosols of nonvolatile pesticides (e.g., paraquat) and aerosols containing pesticides, sampling methods consisting of filtration and employing inertial samplers... 

Asztalos, B., J. Nemcsok, I. Benedeczky, R. Gabriel, and A. Szabo. 1988. Comparison of effects of paraquat and methidation on enzyme activity and tissue necrosis of carp, following exposure to the pesticides singly or in combination. Environ. Pollut. 55 123-135. 

Asztalos, B., J. Nemcsok, I. Benedeczky, R. Gabriel, A. Szabo, and OJ. Refaie. 1990. The effects of pesticides on some biochemical parameters of carp (Cyprinus carpio L). Arch. Environ. Contam. Toxicol. 19 275-283. Autor, A.P. (ed.). 1977. Biochemical Mechanisms of Paraquat Toxicity. Academic Press, New York. 240 pp. Babich, H., M.R. Palace, and A. Stern. 1993. Oxidative stress in fish cells in vitro studies. Arch. Environ. Contam. Toxicol. 24 173-178. 

Holmstedt (1959) and Brown and Muir (1971) have reviewed perocular absorption of pesticides. More recently, Sinow and Wei (1973) have shown that the quartemary herbicide paraquat can be lethal to rabbits if applied directly to the surface of the eyes. Parathion, in particular, is exceedingly toxic when administered via the eye, a concern that must be kept in mind for the protection of pesticide applicators. 

Fig. 8.48 Summary data of pesticide residues in the soil environment, sho wing the distribution between mineralization and extractabihty (A) atrazine, (B) dicamba, (C) isoproturon, (D) hndane, (E) paraquat and (F) tiifluralin. Reprinted from Mordaunt CJ, Gevao B, Jones KC, Semple KT (2005) Formation of non-extractable pesticide residues observations on compound differences, measurement and regulatory issues. Entiron Pollution 133 25-34. Copyright 2005 with permission of Elsevier...

Fig. 12.18A shows the results of an experiment using " C-labeled paraquat adsorbed on a clay mineral (Li-montmorillonite) suspension through a soil column. When the suspension medium was distilled water, 50% of the pesticides penetrated beyond 12 cm. Under these conditions, clay remains dispersed and pestieide is readily transported through the soil. However, for a suspension medium with an electrolyte concentration of 1 mM CaCl, paraquat remains in the upper 1 cm layer. The high calcium concentration results in rapid immobilization of the clay in the soil through flocculation, and consequently little pesticide transport occurs. 

Fig. 12.18 Vertical transport of paraquat and DDT adsorbed on suspended particles (in percentage of total applied). (A) C-labeled paraquat adsorbed on Li-montmorillonite, (B) C-labeled DDT adsorbed on suspended solids in sewage effluent. Reprinted with permission from Vinten AJ, Yaron B, Nye PH (1983a) Vertical transport of pesticides into soil when adsorbed on suspended particles. J Agri Food Chem 31 661-664. Copyright 1983 American Chemical Society...

Extracts of samples from the Horticulture pit were also analyzed for alachlor, carbaryl, glyphosate, dicofol, MCPP, paraquat, penoxalin and 2,4,5-T. They were either not detected or, if detected, concentrations were <1 ppm. No plots of these results are included in this report. In addition, plots are not included for several pesticides where only results from 1979 were available. These pesticides, with their average ppm concentrations in parentheses, were 2,4-D (40), dicamba (3), metribuzin (25), naptalam (60) and tetrachloroterephthalic acid (30). 

Decomposition of farm-generated pesticide wastewater was demonstrated with a mobile 66-lamp ultraviolet (UV) unit and ozone. Aqueous solutions of 2,4-D (1086 ppm) and atrazine (4480 ppm) were degraded more than 80% in about 2-3 h, while paraquat (1500 ppm) was degraded more slowly. 

Dwell time, or the time the molecule was actually in the lamp unit, and concentration were two parameters that affected the rate of degradation. Mass spectra of the trimethylsilyl (TMS) derivatives of atrazine subjected to UV-ozonation revealed a number of dehalogenated, dealkylated s -triazines, paraquat yielded the 4-picolinic acid, and 2,4-D gave oxalic acid, glycolic acid and several four-carbon oxidation products. The economics of UV-ozonation as a pretreatment for land disposal compares favorably with incineration and other options open to the small pesticide user. 

Chemicals processed. Waste pesticide solutions were collected after spray operations during late May, June, and July of 1983, and consisted primarily of three compounds 2,4-D [(2,4-dichloro-phenoxy)acetic acid], atrazine (2-chloro-4-(ethylamino)-6-(isopropylamino)- -triazine) and paraquat (1,1 -dimethyl-4,4 -bipyridinium dichloride). Our efforts were primarily directed at these pesticides, which are shown in Table I together with their formulations and concentrations. 

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