Organophosphorus pesticides diazinon

PoetTS, KousbaAA, Dennison SL, TimchalkC. 2004. Physiologically based pharmacokinetic/ pharmacodynamic model for the organophosphorus pesticide diazinon. Neurotoxicology 25 1013-1030. 

A recent review has highlighted the stability of chemical species (in speciation studies) with respect to environmental matrices [1], These results are summarized in Table 4.2. It should be noted that samples must be analysed as quickly as possible after collection. The times given in this table are the maximum times that samples should be stored before analysis. It should also be noted that the guidelines given are general in nature. For example, many organophosphorus pesticides (not shown in Table 4.2) can be preserved by the addition of hydrochloric acid. However, as an exception to this, the (organophosphorus) pesticide diazinon breaks down when acidified. 

Poet, T. S, Kousha, A. A., Dennison, S. L, and Timchalk, C. (2004). Physiologically based pharmacokinetic/phannacodyiianiic model for the organophosphorus pesticide diazinon. NeuroToxicology 2S 6), 1013-1030-... 

Five organophosphorus pesticides were chosen that could be iso-thermally and simultaneously analyzed by gas chromatography using an N-P TSD detector. They are all currently commercially used and exhibit a wide range of physicochemical properties (Table I). Also influencing the choice of these pesticides was the fact that volatilization data measured from soil and water under controlled laboratory conditions are scarce for methyl parathion, parathion, and diazinon (14-17), and are not available for malathion and mevinphos. Technical mevinphos (60% E-isomer, Shell Development Co.), diazinon (87.2%, Ciba-Geigy Corp.), and malathion (93.3%, American Cyanamld), and analytical grade methyl parathion (99%, Monsanto) and parathion (98%, Stauffer Chemical Co.) were used. 

The mode of injection in GC-based methods can affect the recoveries of diazinon. In a study of the determination of organophosphorus pesticides in milk and butterfat, it was found that the recoveries of diazinon from butterfat, calculated relative to organic solutions of standard compounds, were 125% and 84% for splitless and hot on-column injections, respectively (Emey et al. 1993). Recoveries from milk were not dependent on the mode of injection. It was concluded that the sample matrix served to increase diazinon transfer to the GC column by reducing thermal stress imposed on the analytes and by blocking active sites within the injector. Therefore, on-column injection should be used in order to prevent bias when organic solutions of standard compounds are used for quantitation if this is not possible, the matrix must be present at low concentrations or the calibration standards must be prepared in residue-free samples to avoid unknown bias. 

SFE also would appear to have utility in sample preparation methods. Lopez-Avila et al. (1992) applied SFE to the recovery of a variety of analytes, including organophosphorus pesticides, from solid matrices. The unoptimized extraction from sand gave a recovery of 54% for diazinon. Supercritical trifluoromethane has been shown to extract diazinon from glass beads with a recovery of 86% (Hillmann and Bachmann 1995). Organophosphorus pesticides have also been recovered from Tenax-GC, an adsorbent used to collect diazinon during air sampling, and analyzed directly by GC (Raymer and Velez... 

Sovocool GW, Harless RL, Bradway DE, et al. 1981. The recognition of diazinon, an organophosphorus pesticide, when found in samples in the form of decomposition products. Analy Toxicol 5 73-80. 

The technique was used to determine several organophosphorus pesticides (E)- and (Z)-Mevinphos, Dichlorvos, Azinphos-methyl, Azinphosethyl, Parathion-methyl, Parathion-ethyl, Malathion, Fenitrothion, Fenthion, Chlorfenvinphos and Diazinon, in groundwater. 

Organophosphorus pesticides are another example of nonionic, moderately polar compounds (Fig. 7.13). These pesticides are commonly used today and include compounds such as methyl parathion, parathion, diazinon, and dimethoate. They are used as insecticides on crops such as cotton, as fungicides on fruits, and as nematocides on soil. They are moderately polar... 

Organophosphorus pesticides Acephate , Azinphos-methyl , Chlorpyrifos , Chlorpyriphos-methyl , Diazinon , Dichlorvos (DDVP), Dicrotophos , Dimethoate , Disulfoton , Ethoprop , Eenamiphos , Eenitrothion , Fenthion , Fosthiazate , Malathion , Methamidophos , Methidathion , Methyl-parathion , Mevinphos , Naled , Oxydemeton-methyl , Para-thion , Phorate , Phosalone , Phosmet , Pirimiphos-methyl , Profenofos , Terbufos , Tetrachlorvinphos , Trichlorfon . 

P-, and y-CyDs on the degradation of eight organophosphorus pesticides in neutral aqueous media. Pesticide degradations were particularly accelerated in diazinon-a-CyD and chloropyrifos- 8-CyD. 

Diazinon, an organophosphoras compound with an anticholinesterase mode of action, was released for experimental evaluation in the early 1950s. Diazinon is now used extensively hy commercial and home applicators in a variety of formulations to control flies, cockroaches, lice on sheep, insect pests of ornamental plants and food crops (especially com, rice, onions, and sweet potatoes), forage crops such as alfalfa, and nematodes and soil insects in turf, lawns, and croplands. Diazinon is the most widely used organophosphorus pesticide in Pakistan to control cabbage root fly and carrot fly. In 1992, more than 612,000 kg of diazinon were used in California on alfalfa, nuts, stone fmits, vegetables, and other crops. 

Organophosphorus pesticides = Most organo-phosphorus pesticides are vinyl ester derivatives of phosphates. Four classes of organophosphorus pesticides are in use phosphates (Rl, R2 = 0), (R1=S, R2 = 0), phosphorothioates (R1 = S, R2 = 0), phosphorothiolothionates (Rl, R2 = S), and phosphonates (with a P-C bond). Examples are Parathion, Diazinon, etc. 

Both of the above organophosphorus pesticides should have similar gas-phase tropospheric lifetimes based on stroctural activity relationship model predictions (2/). OH rate measurements for the two OPs when conducted at 5° C increments between 60 and 85° C, however, showed a significant difference in reactivity. The rate of OH oxidation for diazinon was found to be ca. three to four times more rapid than for chlorpyrifos widi observed tropospheric lifetimes of ca. 1 and 4 hours, respectively. Tlie difference in observed reactivity was not due to wall sorption since both conqxtunds behaved similarly in the gas-phase. 

Ellison, C.A., Tian, Y., Knaak, J.B., et al., 2012. Human hepatic cytochrome P450-specific metabolism of organophosphorus pesticides methyl parathion and diazinon. Drug Metab. Dispos. 40,1-5. 

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... 

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