Oximes pesticides

Miles, C.J., Trehy, M.L., and Yost, R.A. Degradation of A-methylcarbamate and carbamoyl oxime pesticides in chlorinated water. Bull. Environ. Contam. Toxicol, 41(6) 838-843, 1988. 

Carbamate, methyl urea and oxime pesticides and herbicides Ag 0.1M nh4o cch3 Large dynamic range of 10z Thermo spray HPLC-MS [ Ippb [25]... 

The recommended technique for the determination of oxime carbamates and their metabolites by HPLC/MS and HPLC/MS/MS is positive ESI. Electrospray is a soft ionization technique and is suitable for thermally labile compounds. Ions are produced in the liquid phase at quasi-ambient temperature and atmospheric pressure, thus leaving the fragile pesticides intact. For oxime carbamates, the molecular adducts that can be monitored during HPLC/MS analysis with electrospray in positive mode are [M- -H]+, [M- -Na]+, or [M- -NH4]+, depending on the nature of mobile phase used. ... 

Oxime carbamates are generally applied either directly to the tilled soil or sprayed on crops. One of the advantages of oxime carbamates is their short persistence on plants. They are readily degraded into their metabolites shortly after application. However, some of these metabolites have insecticidal properties even more potent than those of the parent compound. For example, the oxidative product of aldicarb is aldicarb sulfoxide, which is observed to be 10-20 times more active as a cholinesterase inhibitor than aldicarb. Other oxime carbamates (e.g., methomyl) have degradates which show no insecticidal activity, have low to negligible ecotoxicity and mammalian toxicity relative to the parent, and are normally nondetectable in crops. Therefore, the residue definition may include the parent oxime carbamate (e.g., methomyl) or parent and metabolites (e.g., aldicarb and its sulfoxide and sulfone metabolites). The tolerance or maximum residue limit (MRL) of pesticides on any food commodity is based on the highest residue concentration detected on mature crops at harvest or the LOQ of the method submitted for enforcement purposes if no detectable residues are found. For example, the tolerances of methomyl in US food commodities range from 0.1 to 6 mg kg for food items and up to 40 mg kg for feed items. ... 

The European drinking water guidelines set a maximum admissible concentration of 0.10 pgL for individual pesticides and their related compounds in drinking water. The recommended methods for oxime carbamates and their metabolites in groundwater and surface water are suitable for detection limits below 0.10 pgL. The first method is the HPLC/lluorescence multiresidue method of de Kok et al The second method is an HPLC/MS/MS method of DuPont Crop Protection which is specific for oxamyl and may be applicable for the analysis of other oxime carbamates in heavily polluted waters. 

Vacuum distillation of the product at 61°C/27 mbar must be interrupted when a solid separates from the residue, to avoid an explosion [1], A serious explosion occurred in a cooling loop containing the oxime and hydrochloric acid, dining shutdown to clear a blockage elsewhere in a pesticide plant [2],... 

Andrawes, N.R., Bagley, W.P., and Herrett, R.A. Fate and carryover properties of Temik aldicarb pesticide [2-methyl-2-(methylthio)propionaldehyde 0-(methylcarbamoyl)oxime] in soil, J. Agric. Food Chem., 19(4) 727-730, 1971. Andrawes, N.R., Romine, R.R., and Bagley, W.P. Metabolism and residues of Temik aldicarb pesticide in cotton foliage and under field conditions, J. Agric. Food Chem., 21(3) 379-386, 1973. 

Base hydrolysis kinetic data are reported for ppb solutions of carbofuran,3-OH carbofuran, methomyl and oxamyl. The results are compared with those reported previously for aldicarb, aldlcarb sulfoxide, and aldicarb sulfone. Second order reaction rate constants, k, have been calculated and range from 169 liter mln mole for oxamyl to 1.15 liter mln mole for aldicarb. The order for rate of base hydrolysis is as follows oxamyl >3-hydroxycarbofuran >aldicarb sulfone v- carbofuran >aldicarb sulfoxide > methomyl -v aldicarb. The activation energy for the base hydrolysis of carbofuran was measured to be 15.1 +0.1 kcal mole , and is similar to the value previously reported for aldicarb sulfone. Rapid detoxification of aldicarb, a representative oxime carbamate pesticide, by in situ hydrolysis on reactive ion exchange beds is reported. 

Fig. 5 gives examples of many of the types of sulfur-containing pesticides which are currently in use or have been used. It is clear that the types of functionalities present, e.g. organophosphate derivatives, chlorocarbons, sulfanamides, dithiocarbamates, oxime derivatives, and cyclic sulfite esters are "unnatural" (or at least presently "unnatural") groupings... 

Carbamates are substituted esters of carbamic acid (NH2COOH) with aliphatic or aromatic substituents on the oxygen and nitrogen atoms. Carbamate insecticides have an aryl or oxime N-methylcarbamate structure, and their mode of action is based on the inhibition of the enzyme acethylcholine esterase (1). However, this inhibition is reversible, and recovery from sublethal doses occurs rapidly. Some carbamate fungicides have a dithio, bisdithio, or benzimidazole carbamate basic structure, and dithiocarbamate fungicides inhibit the enzyme aldehyde deshydro-genase (2). The herbicides have an /V-alkylthiocarbamate or A-phenylcarbamate structure and interfere with photosynthetic activity or affect meristematic activity or lipid metabolism (3). Representative structures of carbamate pesticides are shown in Fig. 1. 

Polarographic, thin-layer chromatographic, and spectrometric techniques have been reported for the determination of carbamate pesticides (131-135). These compounds are thermally labile and thus tend to degrade at the elevated temperature of a GC column. Nevertheless, some carbamate insecticides can be determined, directly or indirectly, by GC (44,136-138). The obtaining of thermally stable derivatives has generally been limited to the aryl-V-methylcarbamates. The most difficult carbamate insecticides to chromatograph by GC are the oxime /V-methylcarbamates (139-141). 

Miles and Moye [171] have shown that several classes of nitrogen containing pesticides responded to a high performance liquid chromatography post-column reaction detector that employed ultraviolet photolysis with optional reaction with o-phthalicdicarboxaldehyde-2-mercaptoethanol followed by fluorescence detection. It was applied to the determination of jV-methylcarbamates, carbamoyl oximes, carbamethoic acids, dithiocarbamates and phenyl ureas, phenyl amides and phenyl carbamates in groundwater. See also Table 4.3. 

Similarly, on-column methylation has been applied to carbamate pesticides containing an active N-H group. Wien and Tanaka (41) showed that N-aryl carbamates are methylated on-column with tri-methylanilinium hydroxide-methanol to give the intact N-methyl and N-aryl derivatives. On the other hand N-methyl, 0-aryl carbamates such as carbaryl or carbofuran yielded only the methyl ethers of their respective phenols. This work has now been extended to sulfur-containing carbamates such as methomyl, methio-carb, aldicarb, etc. (42-43). Here the oxime hydrolysis products of these carbamates are chromatographed as the 0-methyl oximes. 

The remainder of this paper will describe specific applications of FTIR in support of one of Diamond Shamrock s pesticide programs. All the results described here were obtained from studies of a single compound, thiofanox (P), 3,3-dimethy1-1-methylthio-2-butanone 0-[(methylamino)carbonyl]oxime. Thiofanox is a potent systemic and contact carbamate insecticide. The infrared spectrum of thiofanox is shown in Figure 4. The major peaks in the spectrum are the N-H stretch at 3380 cm-1,... 

Many oxime amide pesticides have a common structure... 

As discussed earlier, nuclear accidents liave not been die only accidents to occur in recent times. Other disasters at chemical plants have been responsible for a much greater loss of life. Tlie worst disaster in the recent history of the chemical industry occurred in Bhopal, in central India, on December 3, 1984. A leak of methyl isocyanate (MIC) from a chemical pkint, where it was used as an intermediate in the manufacture of a pesticide, spread into tlie adjacent city and caused the poisoning dcatli of more tlian 2500 people apja-oximately 20,000 others were injured. 

Buckley, N.A., Eddleston, M., Szinicz, L. (2005). Oximes for acute organophosphate pesticide poisoning. Cochrane Database Syst. Rev. 1 CD005085... 

ChE by various oximes (Table 62.1). More recently, Worek et al. (2004) determined the kinetic rate constants of inhibition, reactivation, and aging for different NA, pesticides, and oximes with human erythrocyte AChE (see Table 62.2), described by the reactions listed below ... 

Eyer, P. (2003). The role of oximes in the management of organophosphorus pesticide poisoning. Toxicol. Rev. 22 165-90. 

VI. EFFICACY OF PYRIDINIUM OXIMES IN POISONING WITH OP PESTICIDES... 

Kusic et al. (1991) have tested the oxime HI-6 in OP pesticide poisoning in 60 patients. HI-6 was administered four times a day as a single i.m. injection of 500 mg with atropine and diazepam treatment. Oxime therapy was started on admission and continued for 2 to 7 days. Most patients were treated with HI-6 and nine patients severely poisoned with quinalphos were treated 2-PAM Cl (1,000 mg four times per day). HI-6 rapidly reactivated human red blood cell AChE inhibited by diethoxy OPs (phorate, pyr-idaphenthion, quinalphos) as well as that inhibited by dichlorvos (a dimethoxy OP). AChE inhibited with other dimethoxy OPs (dimethoate and phosphamidon) was reported to be resistant to HI-6 treatment, whereas reactivation with malathion was slow (reactivation half-time 10 h). Both HI-6 and 2-PAM successfully reactivated AChE in quinalphos-poisoned patients, with HI-6 acting as a faster AChE reactivator than 2-PAM. 

Balali-Mood, M., Shariat, M. (1998). Treatment of organophos-phate poisoning. Experience of nerve agents and acute pesticide poisoning on the effects of oximes. J. Physiol. (Paris) 92 375-8. 

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