Aldicarb water

Determination of Aldicarb and other N-methyl carbamates in Waters (by HPLC or Confirmation of total Aldicarb residues and other N-methyl carbamates in waters by GC), 1994... 

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. 

Phenylcarbamates, or carbanilates, generally exhibit low water solubilities, and thus they are almost immobile in soil systems. Chlorpropham and Propham are readily volatilized from soil systems, but Terbutol and Carbaryl (Fig. 10, Table 3) are not. Ester- and amide-hydrolysis, N-dealkylation and hydroxylation are among the chemical reactions that carbamates undergo. The N-methylcar-bamate insecticides (Fig. 10, Table 3) commonly used in soils are Carbaryl, Methiocarb,Aldicarb,and Carbofuran [74,173]. 

Rajagopal et al. (1984) used numerous compounds to develop a proposed pathway of degradation of aldicarb in soil. These compounds included aldicarb oxime, A-hydroxymethyl aldicarb, A-hydroxymethyl aldicarb sulfoxide, A-demethyl aldicarb sulfoxide, A-demethyl aldicarb sulfone, aldicarb sulfoxide, aldicarb sulfone, A-hydroxymethyl aldicarb sulfone, aldicarb oxime sulfone, aldicarb sulfone aldehyde, aldicarb sulfone alcohol, aldicarb nitrile sulfone, aldicarb sulfone amide, aldicarb sulfone acid, aldicarb oxime sulfoxide, aldicarb sulfoxide aldehyde, aldicarb sulfoxide alcohol, aldicarb nitrile sulfoxide, aldicarb sulfoxide amide, aldicarb sulfoxide acid, elemental sulfur, carbon dioxide, and water. Mineralization was more rapid in aerobic surface soils than in either aerobic or anaerobic subsurface soils. In surface soils (30 cm depth) under aerobic conditions, half-lives ranged from 20 to 361 d. In subsurface soils (20 and 183 cm depths), half-lives under aerobic and anaerobic conditions were 131-233 and 223-1,130 d, respectively (Ou et al, 1985). The reported half-lives in soil ranged from approximately 70 d (Jury et ah, 1987) to several months (Jones et al, 1986). Bromilow et al. (1980) reported the half-life for aldicarb in soil to be 9.9 d at 15 °C and pH 6.34-7.0. 

Aldicarb degrades rapidly in the chlorination of drinking water forming aldicarb sulfoxide which subsequently degrades to aldicarb sulfone, (chloromethyl)sulfonyl species and A-chloro-aldicarb sulfoxide (Miles, 1991). 

Miles, C.J. Degradation of aldicarb, aldicarb sulfoxide, and aldicarb sulfone in chlorinated water, Environ. Sci Technol, 25(10) 1774-1779, 1991. 

Trehy, M.L., Yost, R.A., and McCreary, J.J. Determination of aldicarb, aldicarb oxime, and aldicarb nitrile in water by gas chromatography/mass spectrometry. Anal. Cbem., 56(8) 1281-1285, 1984. 

An example of a redox transformation in natural water (oxidation) and sediments (reduction) of an organochlorinated contaminant (aldicarb insecticide) is given in Fig. 13.6. 

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. 

Materials. Aldicarb standards were obtained from the United States Environmental Protection Agency (USEPA), Quality Assurance Section and from Union Carbide Corporation. Crystalline samples of carbofuran and 3-hydroxycarbofuran were supplied by the Agricultural Chemical Group of FMC Corporation. Reference standards of methomyl (99% pure) and oxamyl (99% pure) were obtained from USEPA. HPLC grade methanol was purchased from Burdick and Jackson, Inc. Methylene chloride used for bulk extractions of the carbamate pesticides in solution was recovered, distilled and reused. Analytical reagent grade chemicals and solvents were used in all experiments. Doubly distilled deionized water was used for solution rate studies. Deionized distilled water (DDW) was used for dilutions in reactive ion exchange experim ts., , ... 

Aldicarb residues leached deeper than one meter 6-9 months after application to a sandy Long Island soil (39) Based on a comparison of computer simulation modeling and ground water data, at least several percent of the aldicarh applied to certain Long Island fields leached to ground water (37). 

These data were measured at or extrapolated to ambient temperature and pH values. The data are discussed in the text. NA = not available. b/ Kq = soil water distribution coefficient (K ) divided by the organic carbon content of the soil, cj Whenever possible, half-life for soil dissipation is derived from the field data half-lives described in the text rather than lab data. As such, it may not represent a true first-order process. Value has been estimated from the equation in ref. 20. e/ Hydrolysis of total residues (aldicarb + sulfoxide + sulfone). pK for p -phthalic acid is 3.5. The chlorine atoms of DCPA should lower the pK to about 2. Conditions optimized for soil metabolism. 

A third important carbamate is aldicarb or Temik , an insecticide and nematocide for potato and vegetable crops. This chemical has been foimd in water wells in 11 states above the 1 ppm EPA safety threshold, barring use in some locales in 1982. According to Union Carbide, one manufacturer, humans can safely ingest 500 ppb. But it is one of the most acutely toxic pesticides registered by the EPA. A fourth carbamate insecticide is methomyl. 

Figure 10. Reaction chromatograms for A, Amstel river water and B, Amstel river water fortified with 3 ng of aldicarb (peak 1) 3 ng of methomyl (peak 2) 5 ng of propoxur (peak 3) 5 ng of carbaryl (peak 4) and 10 ng of methiocarb (peak 5). Conditions 150-mm X 4.6-mm i.d. column packed with Spherisorb ODS mobile phase of 50% water and 50% methanol (v/v) at a flow rate of 1.0 mL/min 60-mm X 4.6-mm i.d. reactor column packed with Aminex A-28 reaction temperature of 100 °C OF A reagent flow rate of 30 pL/min detection with Perkin-Elmer Model 204A fluorescence spectrometer excitation wavelength of 340 nm emission wavelength of 455 nm. (Reproduced with permission from reference 46. Copyright 1983 Elsevier Scientific Publishers.)...

Wear eye protection and gloves. To each 1 g of aldicarb, add 100 mL of 3 M sulfuric acid (17 mL of concentrated sulfuric acid added to 83 mL of cold water) and 4.7 g of potassium permanganate. The mixture is stirred at room temperature for 30 minutes. Add a saturated solution of sodium bisulfite until the solution is colorless. The solution is neutralized by the careful addition of soda ash (foaming may occur) or 5% aqueous sodium hydroxide. Wash the clear solution into the drain with water.4... 

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