Aldicarb metabolites

Aldicarb, metabolites Hydrolysis, partition, column (silica gel) Sugarbeets GC 14... 

Aldicarb is readily absorbed from all routes of exposure. Oxidation reactions rapidly convert aldicarb to aldicarb sulfoxide, of which a small portion may then be slowly oxidized to aldicarb sulfone. Both the parent compound and its oxidized metabolites can be converted to their respective oximes and nitriles, which may ultimately be converted to aldehydes, acids, and alcohols. Animal studies have indicated aldicarb and its metabolites are distributed to many different tissues but no evidence of accumulation has been found. In the various tissues examined, aldicarb residues were not detected more than 5 days after exposure. The presence of aldicarb in fetal tissue indicates placental transfer in pregnant rats. Various aldicarb metabolites have been found in the milk of cows acutely treated with aldicarb. 

Experiments 1-2, 3-4, and 5-6 represent paired cases of investigation of A, A-SO and A-S02 in Palmyra soil. Sterilized soil was used in these cases to isolate chemical oxidation and hydrolysis from biological conversion processes, and to determine whether the curve-fitted values of K and k depend on water velocity. The only difference within a pair of experiments was in the flow velocity (v). Between pairs, the difference was the aldicarb metabolite applied. 

Oxime carbamates are not directly amenable to gas chromatography (GC) because of their high thermal instability, which often leads to their breakdown at the injection port or in the column during analysis. Analysis of oxime carbamates by GC with sulfur detection or flame photometric detection involves oxidation of the intact insecticides or alkaline hydrolysis to form the more volatile but stable oxime compound. Enzymatic techniques have been reported for the analysis of these compounds. Enzyme-linked immunosorbent assay (ELISA) has been used to determine aldicarb and its sulfone and sulfoxide metabolites and methomyl in water, soil, and sediment samples. 

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. ... 

In aerobic soils, aldicarb degraded rapidly (half-life = 7 d) releasing carbon dioxide. Mineralization half-lives for the incubation of aldicarb in aerobic and anaerobic soils were 20-361 and 223-1,130 d, respectively. At an application rate of 20 ppm, the half-lives for aldicarb in clay, silty clay loam, and fine sandy loam were 9, 7, and 12 d, respectively (Coppedge et al, 1967). Other soil metabolites may include acids, amides, and alcohols (Hartley and Kidd, 1987). 

Groundwater. In Florida groundwater, aldicarb was converted to aldicarb sulfoxide under aerobic conditions. Conversely, under anaerobic conditions (pH 7.7), oxidative metabolites (aldicarb sulfoxide and aldicarb sulfone) reverted back to the parent compound (aldicarb). Half-lives in unfiltered and filtered groundwater were 635 and 62 d, respectively (Miles and Delfino, 1985). In sterile anaerobic groundwater at pH 8.2, aldicarb slowly hydrolyzed to the aldicarb oxime. In a microorganism-enriched groundwater at pH 6.8, aldicarb rapidly degraded to... 

The first objective has been accomplished by the development of an HPLC procedure as reported by Spalik et al. ( 5) and GC/NPD procedures developed by Lemley and Zhong ( ). The second and third objectives are being accomplished by fundamental solution studies and reactive ion exchange experiments conducted in parallel. Lemley and Zhong (7) determined recently the solution kinetics data for base hydrolysis of aldicarb and its oxidative metabolites at ppm concentrations and for acid hydrolysis of aldicarb sulfone. They have since ( ) reported similar results for ppb solutions of aldicarb and its metabolites. In addition, the effect on base hydrolysis of temperature and chlorination was studied and the effect of using actual well water as compared to distilled water was determined. Similar base hydrolysis data for carbofuran, methomyl and oxamyl will be presented in this work. 

Aldicarb, ethiofencarb, methiocarb, and metabolites Sep-Pack aminopropyl cartridges Fruits and vegetables HPLC 53... 

Y Tsumura, K Ujita, Y Nakamura, Y Tonogai, Y Ito. Simultaneous determination of aldicarb, ethio-fencarb, methiocarb and their oxidized metabolites in grains, fruits and vegetables by high performance liquid chromatography. J Food Protection 57 1001-1007, 1994. 

Acetonitrile-silver nitrate extracts of soil, partitioned with methylene chloride and cleaned up on silica gel, have been used in the high-performance liquid chromatographic determination of benfuracarb and carbofuran herbicides [204], McGarevy et al. [336] and Lin and Cooper [336] used optimised isocratic high-performance liquid chromatography with UV detection to determine Aldicarb and its metabolites in soil. 

Aldicarb and oxidative metabolites Open tubular column Nitrogen- Recoveries phosphorus 95% to 105% type lligL [431]... 

Alachlor, benzene hexachloride, cycloodines, aldrin, chlordane, dieldrin, endrin, endosulfan, heptachlor, isodrin, telodrin and toxaphene, DDT and metabolites, dicofol, dimethoate, lindane, methoxychlor, mirex, pentachlorophenol, perthane Azinphosmethyl, bromophos ethyl, chlorpyrifos, crotoxyphos, demeton, diazinon, dichlorvos, ethion, fenitrothion, fensulfothin, fenthion, flusulfothin, methamidophos, mevinphos monocrotophos and dichrotophos, oxamyl, phorate, parathion (ethyl), parathion (methyl), phosphomidon, quinolphos temephos Aldicarb, benomyl, carbaryl, chlorpropham, fenvalerate, methomyl... 

In APCI mass spectra of carbamates, fragment ions are observed, which are most likely due to thermal decomposition in the heated nebulizer interface and snbseqnent ionization of the thermal decomposition products [11, 14, 20-23]. For example, base peaks were observed at m/z 163 for oxamyl, due to the loss of methyl isocyanate, at m/z 168 for propoxur, dne to the loss of propylene, and at m/z 157 for aldicarb, due to the loss of HjS. The APCI mass spectra of aldicaib and two of its metabolites, aldicarb sulfoxide and aldicarb snlfone, showed significant fragmentation. Major fragments for aldicarb were dne to the loss of carbamic acid (to m/z 116) and due to charge retention at [CH3-S-C(CH3)2]. For aldicarb sulfoxide and aldicarb sulfone, the loss of carbamic acid resnlted in the base peaks of the spectra (at m/z 132 and 148, respectively). 

Animal studies have indicated the major route of excretion to be urinary with at least 80% of the original dose generally eliminated within 24 h. Aldicarb is excreted primarily as aldicarb sulfoxide and sulfoxide oxime the parent compound is excreted only in trace amounts. Biliary metabolites have been shown to undergo resorption and urinary excretion. 

Aldicarb is highly water soluble and soil application of this insecticide has the potential to result in runoff or leaching of the insecticide or active metabolites and contamination of surface or groundwater. Aldicarb is acutely toxic to bees, birds, and fish. Species-specific rates of bioactivation may influence the sensitivity of a particular organism to this insecticide. 

Toxicity of organophosphates can be potentiated 15-20-fold in rats and mice by pretreatment with a metabolite of tri-O-cresylphosphate, CBDP (2-0-cresyl)-4H-l,3,2-benzodioxa-phosphorin-2-oxide), which is an irreversible inhibitor of CarbEs. In similar studies, tetraisopropylpyrophosphoramide (iso-OMPA), or mipafox, an organophosphate-irreversible inhibitor of CarbEs, potentiates three-to fivefold the toxicity of several OPs (soman, DFP, and methylparathion) and carbamates (carbofuran, aldicarb, propoxur, and carbaryl). Inhibition of CarbEs by CBDP, iso-OMPA, or mipafox pretreatment, particularly in plasma, liver, heart, brain, and skeletal muscles, is a major contributory factor in the potentiation of toxicity of organophosphates and carbamates. Thus, the toxicity of any drug, pesticide, or other type of agent that is normally detoxified by CarbEs, could be potentiated by pre-exposure to an organophosphorus or other carboxylesterase inhibitor. 

Table V. Degradation Rates for Aldicarb and its Metabolites Measured...

Aldicarb [2-methyl-2-(methylthio) propionaldehyde 0-(methylcarbamoyl) oxime] is a noncorrosive, nonflammable insecticide incorporated into the seeded furrow during planting to control several species of insects, mites, and nematodes. Aldicarb is extremely toxic to mammals, and its oxidation produces two toxic metabolites, aldicarb sulfoxide and aldicarb sulfone. Both aldicarb and its toxic derivatives are very soluble in water. 

Enhanced microbial activity was present for carbofuran, chlorethoxyphos, DOHCO 429X, isofenphos, fensulfothion and trimethacarb and the sulfoxide/sulfone metabolites of aldicarb, disulfoton, fensulfothion and terbufos within 6 weeks of the initial application. E-factors ranged from 2 to 31. Chlorpyrifos and... 

Toxicokinetic and enzyme inhibition studies have established that aldicarb can readily bioactivate in most organisms into aldicarb sulfoxide and sulfone, which are more potent inhibitors of acetylcholinesterase. These metabolites may further convert into oximes and nitriles, all of which may be excreted out mostly in the urine. Studies in cows have shown that about 90% of aldicarb eliminated out within 24 -honrs through urine, exhaled air and milk. Stndies in fish indicate that both the cytochrome P450 and flavin monooxygenase systems are involved in bioactivation of aldicarb to its snlfoxide (Perkins, Jr. and Schlenk 2000). 

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