Diazinon techniques

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. 

Lopez-Avila et al. [36] used a stable isotope dilution gas chromatography-mass spectrometric technique to determine down to O.lppb of pentachlorophenol (also Atrazine, Diazinon and lindane) in soil. Soil samples are extracted with acetone and hexane. Analysis is performed by high-resolution gas chromatography-mass spectrometry with mass spectrometer operated in the selected ion monitoring mode. Accuracy greater than 86% and a precision better than 8% were demonstrated by use of spiked samples. 

One important aspect of any cleanup technique, is the type of degradation products that are produced. These products must be known in order to assess their potential environmental impact and toxicological hazards. One of the major degradation products of diazinon, oxypyrimidine was measured in soil after treatment with parathion hydrolase. Figure 6 shows that oxypyrimidine increases in soil as the diazinon is degraded by the enzyme. 

Section 104(I)(5) of CERCLA, as amended, directs the Administrator of ATSDR (in consultation with the Administrator of EPA and agencies and programs of the Public Health Service) to assess whether adequate information on the health effects of diazinon is available. Where adequate information is not available, ATSDR, in conjunction with the National Toxicology Program (NTP), is required to assure the initiation of a program of research designed to determine the health effects (and techniques for developing methods to determine such health effects) of diazinon. 

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. 

Recently SuflFet (25) and Faust and Suffet (26) reported an intensive study on the separation and identification of the phosphate ester pesticides parathion, diazinon, and fenthion and their degradation products. A summary of a microspectrophotometric ultraviolet technique that was utilized as an aid in identifying these compounds is presented here. 

The success of this technique has hinged upon the knowledge that many xenobiotic-degrading genes are resident on extrachromosomal pieces of DNA called plasmids (23). Pesticide degradation plasmids were first described for 2,4-D and MCPA (29-311. Plasmids are also known to code for enzymes degrading 2,4,5-T (12.) and the OP insecticide diazinon (2Z) Several copies of a specific plasmid occur within an individual cell, and plasmids can be transferred from a donor cell to a recipient cell. 

In one studyOPPs were extracted with SPME (85 /rm of polyacrylate coating) by the immersion technique at 75°C for 60 min. Desorption was done in a desorption device by supercritical fluid carbon dioxide (temperature 50°C pressure 306 atm) prior to online introduction into LC. The detection limits were 300 /rg/l for diazinon, 40 /rg/l for EPN, and 60 /rg/1 for chlorpyrifos, with recoveries ranging from 62 to 64%. 

Earlier reports show that microorganisms metabolize diazinon either in the presence of additional carbon source (2, 17, 23, 27, 28) or syner-gistically by the action of two microorganisms (24). Bacteria capable of degrading diazinon are listed in Table V. These studies show clearly that attempts to isolate a bacterium utilizing diazinon as sole carbon source have been unsuccessful. In this report, using a maximum dilution-frequency technique, we have succeeded in isolating a Flavobacterium sp. from paddy water of diazinon-treated fields that could metabolize diazinon as sole carbon source. 

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. 

As methods of exposure estimation, neither the fluorescent tracer technique nor the patch technique have been validated. Nevertheless, it would be encouraging if a comparison of estimates by the two methods yielded roughly equivalent results. The only body region which can be reasonably compared is the head, as the patch method assumes no clothing penetration, and no hand wash was conducted in this study. Furthermore, four of the six workers must be excluded, as they wore face shields. Thus, the only comparison available is the head and neck exposure of workers 1 and 2. These data are presented in Table IX. Following the protocol outlined by Durham and Wolfe ( ) and Davis ( ), the amount of diazinon recovered from the dermal monitor on the chests of the two workers is employed to calculate exposure to the face and front of neck. A similar patch on the back allows calculation of exposure to the back of the neck. 

Recently this technique was applied to the evolution of OPH for increased methyl parathion hydrolysis. After two rounds of DNA shuffling, a variant that could hydrolyze methyl parathion 25-foId faster than wild type was isolated. The mutations were not directly located in the active site and could not be otherwise predicted a priori (55), This technique could be used to target other slow degrading pesticides such as chlorpyrifos and diazinon and against chemical warfare agents VX and sarin. 

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