Diazinon hydrolysis

The main purpose of this work is development of small-scale and mobile dsMmposition system of these chemicals. A number of studies on decomposition of organophosphorus insecticides have been conducted [1-3]. It is well known that or nophosphorus insecticides are decomposed by hydrolysis under alkaline condition, and its meciianisms have been studied [4], Even so, relatively few papers have address the devdopment of kinetic equations for reactor desipi. In this study, we aim to get kinetic equaticms for their decomposition under alkaline condition. As organophosphtous, we used parathion, fenitrothion, diazinon, malathion and phenthoate. 

Although the inhibition-based biosensors are sensitive, they are poor in selectivity and are rather slow and tedious since the analysis involves multiple steps of reaction such as measuring initial enzyme activity, incubation with inhibitor, measurement of residual activity, and regeneration and washing. Biosensors based on direct pesticide hydrolysis are more straightforward. The OPH hydrolyzes ester in a number of organophospho-rus pesticides (OPPs) and insecticides (e.g. paraoxon, parathion, coumaphos, diazinon) and chemical warfare agents (e.g. sarin) [53], For example, OP parathion hydrolyzes by the OPH to form p-nitrophenol, which can be measured by anodic oxidation. Rainina... 

Bank, S. and D.M. Munnecke. 1982. Enzymatic hydrolysis of concentrated diazinon in soil. Bull. Environ. Contam. Toxicol. 29 235-239. 

Meier, E.R, M.C. Warner, W.H. Dennis, W.F. Randall, and T.A. Miller. 1976. Chemical Degradation of Military Standard Formulations of Organophosphate and Carbamate Pesticides. I. Chemical Hydrolysis of Diazinon. U.S. Army Med. Bioengin. Res. Dev. Lab., Fort Detrick, Frederick, MD. Tech. Rep. 7611. 32 pp. 

Plant Diaziuou was rapidly absorbed by and translocated in rice plants. Metabolites identified in both rice plants and a paddy soil were 2-isopropyl-4-methyl-6-hydroxypyrimidine (hydrolysis product), 2-(l -hydroxy-l -methyl)ethyl-4-methyl-6-hydroxypyrimidine, and other polar compounds (Laanio et al, 1972). Oxidizes in plants to diazoxon (Laanio et al., 1972 Ralls et al, 1966 Wolfe et al., 1976) although 2-isopropyl-4-methylpyrimidin-6-ol was identified in bean plants (Kansouh and Hopkins, 1968) and as a hydrolysis product in soil (Somasundaram et al., 1991) and water (Suffet et al., 1967). Five d after spraying, pyrimidine ring-labeled C-diazinon was oxidized to oxodiazinon which then hydrolyzed to 2-isopropyl-4-methylpyrimidin-6-ol which, in turn, was further metabolized to carbon dioxide (Ralls et al, 1966). Diazinon was transformed in field-sprayed kale plants to hydroxydiazinon 0,0-diethyl-0-[2-(2 -hydroxy-2 -propyl)-4-methyl-6-pyrimidinyl] phosphorothioate which was not previously reported (Pardue et al., 1970). 

Sethunathan, N. and Pathak, M.D. Increased biological hydrolysis of diazinon after repeated application in rice paddies, J. 

Sethunathan. N. and Yoshida. T. Fate of diazinon in submerged soil. Accumulation of hydrolysis product. J. Agric. Food Chem., 17(6) 1192-1195. 1969. 

Neutral Hydrolysis Studies. Investigations of neutral (pH-independent) hydrolysis kinetics in sediment/water systems were conducted for three organophosphorothioate insecticides (chlorpyrifos, diazinon and Ronnel), 4-(p-chlorophenoxy)butyl bromide, benzyl chloride, and hexachlorocyclopentadiene. 

Diazinon and Ronnel. The conclusion that neutral hydrolysis of sorbed chlorpyrifos is characterized by a first-order rate constant similar to the aqueous phase value is strengthened and made more general by the results for diazinon, 0,0-diethyl 0-(2-iso-propyl-4-methyl-6-pyrimidyl) phosphorothioate, and Ronnel, 0,0-dimethyl 0-(2,4,5-trichlorophenyl) phosphorothioate (10). The results for the pH independent hydrolysis at 35°C for these compounds in an EPA-26 sediment/water system (p=0.040) are summarized in Table IV. Because the aqueous (distilled) values of k for diazinon and Ronnel are similar in magnitude to the value for chlorpyrifos, and because these values were shown by the chlorpyrifos study to be slow compared to sorption/desorption kinetics, computer calculations of were not deemed necessary and were not made for these data. 

Thus, for chlorpyrifos, diazinon, Ronnel (and by extension, other organophosphorothioate pesticides), neutral hydrolysis proceeds at similar rates in both the aqueous and sediment phases of sediment/water systems. 

The relative importance of the two processes in a model evaporation pond, along with the time lor 97% loss of the applied pesticide (system purification time), were calculated (Table V). This calculation confirmed that mevinphos and malathion dissipated primarily by hydrolysis, with malathion the more rapid of these two chemicals. For methyl and ethyl parathion, both processes were significant, although volatilization was the dominant dissipation route. However, since both processes were relatively slow for these pesticides, the purification time was fairly long. Diazinon was predicted to be lost primarily via volatilization, and the purification time was relatively short. 

Dennis, W., A. Rosencrance, W. Randall, E. Meier. "Acid Hydrolysis of Military Standard Formulation of Diazinon." J. of Env. Sci. Health, Part B, Pesticides, Food Contam. Ag Wastes, 1315(1), 47-60 (1980). 

Munnecke, D. "Enzyme Hydrolysis of Organophosphate Insecticides, a Possible Disposal Method." J. App. Environ. Microbiol., Series 32, Issue 1, 7-13 (1976). Munnecke, D. and S. Bank. "Enzymatic Hydrolysis of Diazinon in Soil." Dept, of Bot. Micro., Univ. of Oklahoma, May 26, 1981. 

Thus, exposure to any of these enzyme inducers concurrent with or after exposure to diazinon may result in accelerated bioactivation to the more potent anticholinesterase diazoxon. The extent of toxicity mediated by this phenomenon is dependent on how fast diazoxon is hydrolyzed to less toxic metabolites, a process that is also accelerated by the enzyme induction. Similarly, concurrent exposure to diazinon and MFO enzyme-inhibiting substances (e.g., carbon monoxide ethylisocyanide SKF 525A, halogenated alkanes, such as CC14 alkenes, such as vinyl chloride and allelic and acetylenic derivatives) may increase the toxicity of diazinon by decreasing the rate of the hydrolytic dealkylation and hydrolysis of both parent diazinon and activated diazinon (diazoxon) (Williams and Burson 1985). The balance between activation and detoxification determines the biological significance of these chemical interactions with diazinon. 

Diazinon exposure may interfere with the short-acting muscle relaxant, succinylcholine, used concurrently with anesthetics. The action of succinylcholine is terminated by means of its hydrolysis by serum cholinesterase (Klaassen et al. 1986). Since serum cholinesterase is strongly inhibited by diazinon (Davies and Holub 1980b Edson and Noakes 1960 Klemmer et al. 1978 Williams et al. 1959), it is possible that concurrent exposure to diazinon may result in the prolongation of the action of succinylcholine leading to prolonged muscular paralysis. 

Diazinon released to water may be subject to both abiotic degradation (i.e., hydrolysis and photolysis) and biotic degradation by microorganisms. The rate of abiotic degradation is influenced strongly by pH and temperature. In a laboratory study, Chapman and Cole (1982) reported that pH alone influenced the half-life of diazinon maintained in sterile water-ethanol (99 1) phosphate buffer solutions at 25 °C. 

Although diazinon has been detected in groundwater samples in both the United States and Canada (Cohen 1986 EPA 1989a Frank et al. 1987, 1990b HazDat 1996), no studies were identified concerning diazinon transformation and degradation processes within aquifers. Based on theoretical considerations, abiotic hydrolysis mechanisms would be expected to degrade diazinon within a few months (Chapman and Cole 1982 Cowart etal. 1971). 

Dr. P. Jeffers at the State University of New York at Cortland is gathering information to determine the persistence of organophosphorus compounds in groundwater and the effects of various soils on the degradation and transport of these compounds. Both neutral and base hydrolysis processes will be evaluated. Transport studies in soil columns will be conducted to determine the mobility of diazinon in soils. 

There are also methods for the analysis of diazinon degradation products in air, water, and soil. Williams et al. (1987) published a method for diazinon and its oxon (diazoxon) in air. Other methods have been reported for diazinon, its oxon, and hydrolysis products in water (Suffet et al. 1967), soils and water (Lichenstein et al. 1968), and soil (Burkhard and Guth 1979). The hydrolysis product 2-isopropyl-6-methyl-4-hydroxypyrimidine was studied along with diazoxon in submerged soil (Sethunathan and Yoshida 1969). Suffet et al. (1967) demonstrated the ability of GC to separate diazinon, diazoxon, and 2-isopropyl-6-methyl-4-hydroxypyrimidine. However, no validated methods for the determination of... 

As can also be seen from Table 13.12, acid-catalyzed hydrolysis is unimportant for many phosphoric and thiophosphoric acid triesters. Among the exceptions are diax-onon and diazinon (/AN = 6.4 and 5.7, respectively). Try to explain why. 

Diazinon, Parathion, Malathion, Fenthion and oxygen analyses and hydrolysis products Reoplex- 400 Electron capture flame ionisation [450]... 

It has been proposed that parathion hydrolase, also known as organophosphorous phosphotriesterase, be used for pesticide detoxification as an alternative to more common treatment methods. Parathion hydrolase is produced by a number of bacteria including Pseudomonas sp., Flavobacte-rium sp. and a recombinant Streptomyces [17,54]. It has been shown to hydrolyze some of the most widely used organophosphate pesticides such as methyl and ethyl parathion, diazinon, fensulfothion, dursban, and couma-phos [18,19]. It should be noted that organophosphate pesticides constitute the major proportion of agricultural pesticides used at present and are implicated in an estimated 800,000 pesticide poisoning cases every year [18]. Hydrolysis accomplishes the detoxification of the pesticide and makes the products amenable to biological treatment. 

Organophosphate hydrolysis is frequently observed as the initial reaction for pesticides having organophosphate bonds, such as methyl parathion, chlorpyrifos (9) (eq. 13), diazinon, and coumaphos (19). Several genera of organophosphate-hydrolyzing bacteria have been identified, including... 

The dependence of transformation rate on pH is not always consistent among pesticides within the same chemical class. For example, while the hydrolysis reactions of most OP (Konrad and Chesters, 1969 Konrad et al., 1969 Mabey and Mill, 1978) and carbamate insecticides (Wolfe et al., 1978) are primarily base-catalyzed, both diazinon (Konrad et al., 1967) and carbosulfan (Wei et al., 2000) are also subject to the acid-catalyzed reaction. Summaries of the pH dependence of hydrolysis rates for a variety of pesticides have been provided by Mabey and Mill (1978), Bollag (1982), Schwarzenbach et al. (1993), and Barb ash and Resek (1996). 

---