Diazinon mixtures

Fig. 1 chromatogram of the thiophosphate insecticides (each ca. SOO ng) after treatment with dipping solutions I and II (A) before and (B) after complete drying of the TLC plate. TVacks 1 and S mixture Track 2 azinphos ethyl Track 3 malathion Track 4 diazinone. 

Diazinon SOW was applied by air blast sprayers in accordance with typical application practices for orchards. Application began in March and continued until early-to mid-July. Dormant sprays typically contained diazinon in an oil mixture. Aqueous emulsions were applied as foliar sprays thereafter. Eqmpment was calibrated to provide an application rate of 3.4 kg active ingredient (a.i.)ha At least five applications were made at approximately 2-week intervals. During these applications, 233 samples were taken from spray tanks across the four treatment fields to estimate the application rate in PA, and 244 samples were collected in WA. 

In many applications nowadays it is essential to link a mass spectrometer to the gas chromatography in order to achieve positive identification and sensitivity of analysis. Some 12 types of compounds are listed in Table 1.11(a) which are based on the application of this technique, viz. polyaromatic hydrocarbons, polychlorobenphenyls, dioxins, chloro, carbamate and triazine types of herbicides and pesticides, Diazinon, Dicamba, Imidazoline and Cyperquat herbicides and herbicide pesticide mixtures. 

Fig. 28.3. Reproduced from Fig. 3 of Ref. [45], with permission from Elsevier. Detection of organo-phosphates extracted from wool, (a) Extracts containing either chlorfenvinphos (C) or diazinon (D) numbers are X in 10-XM. (b) Extracts containing mixtures of the two total concentration of organo-phosphates was 10-5M. Electrodes were exposed to the extracts, dried overnight and the currents generated in the presence of butyrylthiocholine measured. White columns, electric eel acetylcholinesterase grey, bovine erythrocyte acetylcholinesterase and black, horse serum butyryl cholinesterase.

Gas chromatography has been used [183] to determine the following at organophosphorus insecticides at the microgram per litre level in water and waste water samples Azinphos-methyl, Demeton-O, Demeton-S, Diazinon, Disulfoton, Malathion, Parathion-methyl and Parathion-ethyl. This method is claimed to offer several analytical alternatives, dependent on the analyst s assessment of the nature and extent of interferences and the complexity of the pesticide mixtures found. Specifically, the procedure uses a mixture of 15% v/v methylene chloride in hexane to extract... 

FIGURE 4.2 Mortality of fathead minnows in relation to acetylcholinesterase activity.3 a As measured in the brain tissue following (A) a 14-day exposure to a ternary mixture of azinphos-methyl, diazinon, and chlorpyrifos in a concentration-response study and (B) a 7-day exposure to a ternary mixture of azinphos-methyl, diazinon, and chlorpyrifos applied as equipotent (toxic equivalent [TE]) mixtures. Note Dashed lines correspond to 50% reduction in AChE activity the dashed-dotted line corresponds to 50% mortality. Source Redrawn from Sibley et al. (2000). 

Amsterdam (The Netherlands) University of Amsterdam, 152 p. van der Geest HG, Greve GD, Boivin ME, Kraak MHS, van Gestel CAM. 2000. Mixture toxicity of copper and diazinon to larvae of the mayfly (Ephoron virgo) judging additivity at different effect levels. Environ Toxicol Chem 19 2900-2905. van der Hoeven N, Gerritsen AAM. 1997. Effects of chlorpyrifos on individuals and populations of Daphnia pulex in the laboratory and field. Environ Toxicol Chem 16 2438-2447. 

A recent publication on PBTK/TD modeling to determine dosimetry and cholinesterase inhibition for a chemical mixture of 2 organophosphorus insecticides, chlo-rpyrifos and diazinon (Timchalk and Poet 2008), deserves some special discussion here. Based on the individual PBTK/TD models developed earlier by the same laboratory, Timchalk and Poet (2008) reported their development of a binary interaction PBTK/TD model for chlorpyrifos and diazinon. In their development of the model, Timchalk and Poet (2008) took into consideration a number of important metabolic steps (CYP450 mediated activation and detoxification of a number of esterases—B-... 

Timchalk C, Poet TS. 2008. Development of a physiologically based pharmacokinetic and pharmacodynamic model to determine dosimetry and cholinesterase inhibition for a binary mixture of chlorpyrifos and diazinon in the rat. Neurotoxicology 29 428 443. 

Eight gallons of each spray solution were applied per application. The calculated amount of DDT sprayed was 5.6 pounds per acre over the test area. Because of analytical difficulties, the calculated amount of diazinon could not be determined. During the 1964 season, when one application of insecticide mixture was made, the spray solution was found to contain 0.25 pound of DDT and 0.125 pound of ethion per gallon. Eight gallons of the spray solution were applied 2 pounds of DDT and 1 pound of ethion per acre. 

The toxic effects of some pesticide mixtures are additive, particularly when their toxic mechanisms are identical. The additive effects of the organophosphates chlorpyrifos and diazanon were demonstrated in one study. T Another study found the s-triazine herbicides atrazine and cyanazine to show additive toxic effects. Not all mixtures of similar pesticides produce additive effects, however. In one study, mixtures of five organophos-phate pesticides (chlorpyrifos, diazinon, dimethoate, acephate, and malathion) were shown to produce greater than additive effects when administered to laboratory animals. Another article discusses nonsimple additive effects of pyrethroid mixtures. Despite the similarities in their chemical structure, pyrethroids act on multiple sites, and mixtures of these produce different toxic effects. 10 ... 

ALDOXIME (107-29-9) C RgNO Flammable liquid. Forms explosive mixture with air [flash point 72 to 96°F/22 to 36°C]. Reacts violently with oxidizers. Capable of reacting as both a weak base and a weak acid. Decomposes on contact with acids, forming hydroxylamine and acetaldehyde. Forms explosive peroxides on contact with air, acids. Attacks various alkali metals (i.e., lithium, sodium, potassium, rubidium, cesium, francium). When exposed to air forms unstable peroxides may explode or decompose violently during distillation. ALFA-TOX (333-41-5) see diazinon. ALFLOC 7020 or ALFLOC 7046 (2425-06-1) see captafol. 

A recent study of Moser eoworkers (2005) Mo,ser et uL (2005), using a do.se-additive design with mixtures of five commonly used OP pesticides (chlorpyrifos, diazinon, dimeihoate, acephaic, and malathion), showed a more-than-additive interaction on multiple end points blood and brain cholinesterase inhibition, motor activity, and gait score (tail-pinch response did not. show a more-than-additive interaction). This study is noteworthy because (i) relatively sensitive end points were used to test the toxic interaction of the OP pesticides, such as cholinesterase inhibition or depression of motor activity (ii) more than two OP compounds were used in the mixture and (iii) comprehensive statistical analyses of the data were performed. The pharmacokinetic interaction of two of the aimpounds in the mixture, chlorpyrifos and diazinon, has been studied in rats (Timchalk et a ., 2004). The authors found that one compound did not affect the pharmacokinetics of the other unless high doses were given, concluding that a more-than-additive interaction is unlikely at environmentally relevant concentrations. 

The pH of the incubation mixture (paddy water or soil plus diazinon solution) ranged from 7.1-7.8 (17) at which diazinon is known to be chemically stable (13, 14). 

When radioactively labelled diazinon was incubated with water from a diazinon-treated field, more than 66% of the added was liberated as C02 in five days (Figure 1). Adding streptomycin to this incubation mixture, however, prevented the breakdown of the diazinon molecule and the formation of C02. No appreciable degradation of diazinon was evident on its incubation with water from untreated field. 

In attempts to characterize the factor that developed in the rice fields of the Institute farm, we enriched paddy water from treated fields with specific diazinon-degrading microorganisms (17). The insecticide in aqueous solution was incubated with paddy water from a treated field at a one to one ratio. When the insecticide disappeared from this mixture, 5 ml of this incubation mixture was incubated again with 5 ml of aqueous diazinon solution. During a 10 day incubation period, five transfers were made. Following the first transfer, the insecticide disappeared from the incubation mixture between 96-120 hours, but in less than 6 hours after the fifth transfer (17, 22). Evidently, the factor originally... 

This study indicated also that within three days of incubation with water from treated field, diazinon was converted to a metabolite (s) which was mineralized to CO2 within the next two days. To study the nature of the metabolite (s), the residue in the incubation mixture (paddy water from treated field plus C-diazinon) were extracted with chloroform-diethyl ether (one to one) and analyzed by cochromatography and radioautography (12), Detailed procedures and results of this study will be published (79). In summary, these studies indicate that diazinon is rapidly hydrolyzed by a biological action in paddy water of treated fields. The hydrolysis product, 2-isopropyl-6-methyl-4-hydroxypyrimidine increased with a corresponding decrease in diazinon levels in the incubation mixture until 75 hours and thereafter declined (Figure 2). No other radioactive metabolite was detected in the autoradiograph of the incubation mixture. Addition of streptomycin to this incubation mixture... 

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