Oxamyl water

Figure 13.15 Chromatograms obtained by on-line ti ace enrichment of 50 ml of Ebro river water with and without the addition of different volumes of 10% Na2S03 solution for every 100 ml of sample (a) blank with the addition of 1000 p.1 of sulfite (b) spiked with 4 p.g 1 of the analytes and 1000 p.1 of sulfite (c) spiked with 4 p.g 1 of the analytes and 500 p.1 of sulfite (d) spiked with 4 p.g 1 of the analytes without sulfite. Peak identification is as follows 1, oxamyl 2, methomyl 3, phenol 4, 4-niti ophenol 5, 2,4-dinitrophenol 6, 2-chlorophenol 7, bentazone 8, simazine 9, MCPA 10, atrazine. Reprinted from Journal of Chromatography, A 803, N. Masque et ai, New chemically modified polymeric resin for solid-phase extraction of pesticides and phenolic compounds from water , pp. 147-155, copyright 1998, with permission from Elsevier Science.

Fresh oxamyl standards were prepared for each fortification event. Concentrations of 50 and 400 qg mL analytical-grade oxamyl were prepared in a 20% acetonitrile-80% FIPLC-grade water solution. The solutions were tranferred in 1-mL aliquots into uniquely identified vials so that each vial contained the correct volume of oxamyl standard to fortify one quality control sample. The vials were shipped as needed during the course of the study to each field site. 

Six control sample jars of 0.01% Aerosol OT detergent in distilled water solution (200 mL each) were prepared at each site on sampling days 1,14 and 28 by dislodging leaf disks taken from the untreated control area. Triplicate samples were fortified at each of two concentrations. Fortification levels were 50 and 400 qg of oxamyl per sample. 

Crops, food, and feed. The first recommended method is based on the Dutch Multiresidue Method 2 for A-methylcarbamates, which was originally developed by de Kok et The method has recently been validated by DuPont Crop Protection and Batelle, Geneva Research Centres, for the analysis of methomyl and oxamyl in dry, high-water, high-fat, and high-acid content crops and in various grape processed products. The limit of detection for each analyte is 0.003-0.005 mg kg . ... 

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. 

A sensitive and selective method, which is specific for oxamyl and may be applicable to other oxime carbamates and their metabolites in heavily polluted waters, involves the use of HPLC/MS/MS. A 75-mL reservoir is attached on top of a Bond-Elut SAX (l-g/6-mL) (Varian), which is connected to an Oasis HLB (l-g/20-mL)... 

ChemicaPPhysical. The hydrolysis half-lives of oxamyl in a sterile 1% ethanol/water solution at 25 °C and pH values of 4.5, 6.0, 7.0, and 8.0 were 300, 17, 1.6, and 0.20 wk, respectively (Chapman and Cole, 1982). Under alkaline conditions, oxamyl hydrolyzed following first-order kinetics (Bromilow et al., 1980). 

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., , ... 

Oxamyl. Oxamyl Is an oxime carbamate with a 280,000 ppm water solubility (63) and a 2,3 x 10 torr vapor pressure (19). It Is used as an Insectlclde/nematlclde. 

Oxamyl Is entirely stable to hydrolysis for 11 days at pH 4.7 and room temperature, has a half-life of about 6 days at pH 6.9, and an estimated half-life of less than 1 day at pH 9.1 (102). Degradation Is more rapid In river water (102). 

Oxamyl has been found In Long Island, New York ground water at concentrations typically between 5 and 65 ppb (19). 

Sorption. Kqp values have been looked upon as constant for neutral organic chemicals. Independent of soil type (73). The parameter Is valid for comparison of leaching potential of pesticides with widely varying water solubility however. It Is difficult to make quantitative comparisons among polar organics. For example, note the wide range In Kq, for oxamyl described In Table IV. This may be due In part to Interactions with soil mineral fractions which become Important when the soil organic matter content Is low (56,112). Also, use of water solubility... 

Oxamyl, methomyl Reversed-phase-ODS, acetonitrile-water Fluorescence 20 ng/g 24... 

Oxamyl methomyl -Phoxan, 2,4,5 trichlorophenoxy acidic acid 2.4DB, NCPB Removal of pesticides from water on graphitised carbon block 0.003- 0.07pg L1 [140]... 

Hartley, G.S., Graham-Bryce, IJ. (1980) Physical Principles and Pesticide Behavior. Volume 2, Academic Press, New York. Harvey, J., Hun, J.C.Y. (1978) Decomposition of oxamyl in soil and water. J. Agric. Food Chem. 26, 536-451. 

Edgington and Peterson (4) have subdivided apoplastic xeno-biotics into two classes. Euapoplastic (only transported in the apoplast) and pseudoapoplastic (transport occurs mainly in the xylem but entry into the symplast occurs). Most traditional "apoplastic" chemicals are now known to really be pseudoapoplastic chemicals, e.g., atrazine, diuron, oxamyl, etc. The unresolved question is why don t these pseudoapoplastic chemicals which cross the cell membranes and enter the symplast remain in the symplasm of the phloem There have been numerous studies focusing on the molecular requirements for phloem mobility (1-5), In general, there is not a good correlation between phloem mobility and water solubility, metabolism of the xenobiotic, or the presence of various substitution groups in a molecule. 

Oxamyl. The only new state reporting oxamyl in ground water is Rhode Island (59). It was found in at least four observation wells out of 11 sampled. Typical levels of oxamyl in ground water range from 1 to 60 ppb, with the Rhode Island results closer to 1 ppb. Oxamyl has now been found in the ground water of two states. 

A soil and water monitoring program was carried out throughout the summer of 1980. Initial results looked promising. The compound was not detected in groundwater. The soil sampling results also indicated that oxamyl was decomposing rapidly in the top soil layers and only one site showed a low level of contamination in the 20 inch cores. 

The 1981 report (1 2) concluded, "That under normal use conditions oxamyl does not contaminate well water on Long Island."... 

However, in 1982, the Suffolk County Health Department took over the Union Carbide (manufacturer of aldicarb) sampling program for aldicarb in drinking water and surveyed areas not previously covered. The County also began monitoring for oxamyl. By November, 1982, 27 homeowner wells had been found to contain oxamyl at concentrations less than the New York State Health Department guideline of 50 ug/1. 

The World Health Organization (WHO) (15), in 1981, set a temporary ADI for oxamyl based on a no-effect level from a 2-year dog study. The Committee expressed concern, however, that the dog is somewhat less sensitive to oxamyl than the rat and that a clear no-effect level had not been established in the rat. Additional concern was expressed over the lack of identification of 50% of the tissue residues of oxamyl. The WHO was requiring that by 1983 tissue residues be identified and that the no-effect level in the rat be clarified. Based on the WHO temporary ADI, a drinking water guideline of 70 ug/1 can be calculated. 

The U.S.A., through the National Pesticide Survey, " which was organized by the Environmental Protection Agency (US-EPA), established a fist of compounds based on the amount used (>7000 Tons), water solubility (>30 mg/1), and hydrolysis half-life (>25 weeks). The list includes some carbamate pesticides (e.g., aldicarb, propoxur, carbaryl, carbofuran, methiocarb, methomyl, oxamyl, cycloate, butylate, propham, and swep) and various derivatives (e.g., aldicarb sulphone, aldicarb sulphoxide, and 3-hidroxycarbofiiran). In Europe, a list of priority pollutants including pesticides was established in order to protect the environment from the adverse ecological impact of these compounds. ... 

Newsome et al. [974] studied the chromatography of 11 carbamate pesticides (e.g., aldicaib, aldicarb sulfoxide and sulfone, oxamyl, cathofiiran, 3-hydroxy- and 3-ketocaiboiuran) on a Cg column. A postcolumn o-phthalaldehyde derivatization technique (A = 336 run, ex 440 nm, em) was compared with an atmospheric pressure ionization MS detector. A 20-min 12/78 -> 70/30 acetonitrile/water gradient generated good resolution and peak shapes. Detection limits forall compounds were tabulated and were 0.1 ng for fluorescence and 1 ng for APCl/MS. 

All tests shown in Fig. 5 have been carried out using commercial products, because the treatment must destroy not only active matter, but any other organic contained in the formulation as well. Unfortunately, very little information on the effects of adjutants in photocatalysis degradation is available because pesticides commercial formulations are usually patent protected. Fig. 5 summarizes tests carried out with 4 commercial pesticides. The initial TOC obtained fi-om adding 100 mL of Vydate (24% w/v oxamyl) to 247 L of water produced a TOC of almost 90 mg V of which only 37 mg L come from oxamyl, and the rest come from the formulation. Likewise, with 62 mL of Confidor (20% w/v imidacloprid) the initial TOC obtained is 130 mg V of which 21 mg L of TOC are imidacloprid adding 82 mL of Rufast (15% w/v of acrinathrin), TOC was almost 50 mg/L, of which only 29 mg/L are from acrinathrin a 0.33 mL/L Tamaron 50 (methamidophos 50% w/v)/water solution has a TOC of 100 mg/L (only 28 mg/L are from methamidophos). 

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