Herbicides linuron

Compounds that affect activities of hepatic microsomal enzymes can antagonize the effects of methyl parathion, presumably by decreasing metabolism of methyl parathion to methyl paraoxon or enhancing degradation to relatively nontoxic metabolites. For example, pretreatment with phenobarbital protected rats from methyl parathion s cholinergic effects (Murphy 1980) and reduced inhibition of acetylcholinesterase activity in the rat brain (Tvede et al. 1989). Phenobarbital pretreatment prevented lethality from methyl parathion in mice compared to saline-pretreated controls (Sultatos 1987). Pretreatment of rats with two other pesticides, chlordecone or mirex, also reduced inhibition of brain acetylcholinesterase activity in rats dosed with methyl parathion (2.5 mg/kg intraperitoneally), while pretreatment with the herbicide linuron decreased acetylcholine brain levels below those found with methyl parathion treatment alone (Tvede et al. 1989). 

Cessna, A. J., The determination of the herbicide Linuron in Saskatoon berries using HPLC with column switching, /. Liq. Chromatogr., 11, 725, 1988. 

Engelhard , G., Wallnofer, P.R., and Plapp, R. Identification of N, O-dimethylhydroxylamine as a microbial degradation product of the herbicide, linuron, Appl Microbiol, 23 664-666, 1972. 

You are concerned about the longevity of the herbicide, linuron, leaching into a river from some neighboring farmland. Given the structure of this urea derivative, you expect it will be biodegraded via a hydrolysis mechanism. You recall a report of a hydrolase enzyme from a common bacterium that exhibits a half-saturation constant, KMM, for linuron of 2 /tM and a maximum degradation rate, Vmax, for linuron of 2500 /nmol kg-1 protein s l. 

SE Katz. Determination of the substituted urea herbicides linuron, monuron, diuron, neburon and fenuron in surface waters. J Assoc Off Anal Chem 49 452-456, 1966. 

On the other hand, the broad weed control spectrum of chloramben, which was introduced in 1959, brought with it widespread acceptance. As an over-the-row band for control of both broadleaf and grass weeds, cost was minimized. With good crop tolerance, chloramben dominated the early soybean herbicide market. During 1972, 85% of the product was applied as the granular formulation (Table 4.2). However, as application practices changed for the soybean crop, banded applications became an inconvenience. Herbicides such as metribuzin (a triazine herbicide), linuron, and bentazon, which could be applied as an affordable broadcast treatment, soon became products of choice, and the marketing of chloramben was eventually discontinued in 1990. 

Huber, G., Gemes, E. (1981) Decomposition of urea herbicide linuron (3-(3,4-dichlorophenyl)-l-methoxy-l-methylurea) in water of Lake Balaton. Hungar. J. Ind. Chem. 9, 113. 

Urosol, N.J., Hance, RJ. (1974) The effect of temperature and water contents on the rate of decomposition of the herbicide linuron. Weed Sci. 16, 19-21. 

Some responses, such as mortality, are irreversible. However, many sublethal responses may be reversible, such as the impact of the photosynthesis-inhibiting herbicide linuron on macrophytes (Snel et al. 1998). Linuron inhibits photosynthesis by disturbing electron transport in photosystem II. Table 6.2 presents the kinetics of photosynthesis inhibition when shoots of macrophytes are placed in water with 50 pg/L linuron, and subsequent recovery when placed in uncontaminated water. The EC50 values are remarkably similar between macrophytes, and half-life estimates for inhibition and recovery are less than 2 hours (Table 6.2). Except for Potamogeton... 

Cuppen JGM, van den Brink PJ, van der Woude H, Zwaardemaker N, Brock TCM. 1997. Sensitivity of macrophyte-dominated freshwater microcosms to chronic levels of the herbicide linuron. Ecotoxicol Environ Safety 38 25-35. 

Snel JFH, Vos JH, Gylstra R, Brock TCM. 1998. Inhibition of photosystem II (PSII) electron transport as a convenient endpoint to assess stress of the herbicide linuron on freshwater plants. Aquat Ecol 32 113-123. 

Another approach is to combine chemical and microbial herbicides. It was reported that the addition of sublethal rates of the herbicides, linuron [N -(3,4-dichlorophenyl)-N-methoxy-N-methylurea], imazaquin (2-[4,5-dihydro-4-methyl-4(1-methylethyl)-5-oxo-lH-imidazol-2-yl]-3-quinolinecarboxylic acid, and lactofen (+)2-ethoxy-l-methyl-2-oxoethyl-5-[2-chloro-... 

Thus, the reaction has some value for the synthesis of known ureas derived from methoxymethyl amine such as the herbicide Linuron [see scheme 141] (Ref. 196). 

Scheme 141 Preparation of the herbicide Linuron from chloiomethyl-N(4-chloro-phenyl) carbamate.

An array of two electrodes was set up with the first one at a low potential (250 mV) for sample clean up, while the second electrode served for measurements. This array allowed LOD in the ppt range for 5 mL samples of water, after applying an SPE preconcentration step . Simultaneous determination of phenol, 26 substituted phenols and herbicides was carried out by SPE followed by RP-HPLC using a gradient of a solvent modifier and a counter-ion with an array of ELDs. The identity of each chromatographic peak was based on its retention time and the peak height ratio across the electrode array, as compared with those of an authentic standard. The method was applied to determination of phenylurea herbicide residuals, phenol, chlorophenols and nitrophenols in waters of various origins. LOD for the less sensitive analyte, the herbicide Linuron (114), was 0.5 ngL at SNR 3, much lower than the European Community specification . ... 

Synechoccocus herbicides (linurone. amperometric electrode linurone 50-500 pg/l [31]... 

Phenylamides. The phenylamide herbicide diphenamid (Table IX) probably behaves much like the acetanilides in aqueous and soil systems. The compound is moderately soluble, 260 ppm, and leaches much more readily in soils than the phenylurea herbicide linuron 371), Deli and Warren 384) also found that diphenamid was readily leached through several types of soil. Harris 151) found that diphenamid was moderate to high in its mobility in soil, falling between the phenylureas norea and monuron. Diphenamid moved more through course textured soils than... 

Chloroalkyl carbamates, prepared with phosgene (see Section 4.3.2 Carbamates ), react with hard nucleophiles such as methoxymethyl amine to afford known ureas such as the herbicide Linuron [219]. 

Dordevic J, Papp Z, Guzsvany V, Svancara I, Trtic-Petrovic T, Purenovic M, Vytras K (2012) Voltammetric determination of the herbicide linuron using a trioesyl phosphate-based carbon paste electrode. Sensors 12 148-161... 

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