Organophosphate pesticides spraying

The use of ligand exchange has been examined for the analysis of PTH (phenylthio-hydantoin) amino acids separated on silica gel plates [92]. The method is an extension of the procedure developed for organophosphate pesticides [84]. The chromatoplate is sprayed with a solution of palladium(II) chloride and calcein. Palladium complexes with calcein to form a non-fluorescent chelate. However, in the presence of many sulfur-containing compounds, such as PTH-amino acids, the palladium is displaced from the complex liberating free calcein which gives an intense fluorescence. This method is capable of determining 0.1-nmole amounts of PTH-amino acids. 

Techniques. In 1962, McKinley and Read (42) developed an esterase-inhibition technique for the detection of organophosphate pesticide residues on paper chromatograms. The procedure involved conversion of the thiophosphates with bromine to yield active esterase inhibitors, the inhibition by the pesticide of the esterases from a beef liver homogenate sprayed onto the chromatogram, the hydrolysis of the substrate (a-naph-thyl acetate) which was sprayed onto the paper after the liver homogenate had dried, and the development of a background color between Fast Blue RR and the hydrolysis product, a-naphthol. 

In a 1991 study, every surveyed pesticide spray applicator working regularly with dimethoate reported suffering often from nausea, sore eyes and headaches, the symptoms of organophosphate poisoning. Other studies have indicated that this insecticide can cause anxiety and depression in people who have been regularly exposed. 

The feasibility of employing fluorescent tracers and video imaging analysis to quantify dermal exposure to pesticide applicators has been demonstrated under realistic field conditions. Six workers loaded a tracer with the organophosphate pesticide, diazinon, into air blast sprayers, and conducted normal dormant spraying in pear orchards. They were examined prior to and immediately after the application. UV-A illumination produced fluorescence on the skin surface, and the pattern of exposure was digitized with a video imaging system. Quantifiable levels of tracer were detected beneath cotton coveralls on five workers. The distribution of exposure over the body surface varied widely due to differences in protective clothing use, work practices and environmental conditions. This assessment method produced exposure values at variance with those calculated by the traditional patch technique. 

Zheng YZ, Lan WS, Qiao CL, Mulchandani A, Chen W (2007) Decontamination of vegetables sprayed with organophosphate pesticides by organophosphorus hydrolase and carboxylesterase (Bl). Appl Biochem Biotechnol 136 233-241... 

Method 1 (cellulose layers). The cellulose powder is washed twice with isopropanol-ammonium hydroxide-water (6 3 1), washed once in isopropanol and dried at 10S °C for 8 h. The plates (thickness, 0.25 mm) are prepared with a commercial TLC applicator. The slurry consists of 15 g of prepared cellulose in 85 ml of water which has been homogenized in a blender. The plates are dried at room temperature, and then eluted with diethyl ether in order to remove organic impurities. The plates are dried in air immediately before use. The pesticides are spotted and developed with appropriate solvent systems. The chromatoplate is dried in air and sprayed lightly with a 0.05% solution of fisetin in isopropanol. The separated spots are observed visually under a UV light at 365 nm (excitation, 370 nm emission, 533 nm). This method has been examined for several types of pesticides including carbamates, organophosphates, triazines and chlorinated hydrocarbons. 

The widely used organophosphate Insecticide methyl parathlon was the first material to be formulated as a microencapsulated pesticide. This formulation, sold under the tradename PENNCAP-M Insecticide (a registered trademark of Pennwalt Corporation), consists of nylon-type microcapsules which contain the active Ingredient. The capsules are suspended In water and typically have an average particle size of approximately 25 microns (fifty percent by weight of the capsules have a particle size of 25 microns or more). Upon application by conventional spray equipment the water evaporates, and the active Ingredient Is slowly released over an extended period of time. 

As with drugs, an important factor in the toxicity of OPs can be the effect of simultaneous exposure to other chemicals, including other pesticides and contaminants. The effects may be difficult to predict as some chemicals can increase while others inhibit detoxication, and with some organophosphates there are multiple metabolic pathways. If two or more pesticides are sprayed by the same operator within a short time there could be dangerous and unexpected interactions. The same may apply to wildlife in the vicinity of the spraying. A poisoning incident in Pakistan illustrates this problem and the difficulty of predicting such events. 

The Ohio farmer does exhibit respect for pesticides of different toxicity levels. An example can be seen in Table IX relative to the use of organophosphates of different toxlcltles on alfalfa. Noticeable contrasts can be seen in the wearing of rubber gloves, spray suits, eye or face protection and respirators in the handling and applying of parathlon, dlmethoate, and malathlon which are represent-... 

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