Herbicide phenylurea

Carbamates and ureas constitute important groups of pesticides that are used as herbicides (phenylureas, sulfonylureas, phenylcarbamates, and alkylthiocarbamates), insecticides (ben-zoylureas, methylcarbamates, and oximemethylcarbamates), or fungicides (dithiocarbamates, alkylenebisdithiocarbamates, and benzimidazolecarbamates) in different crops to control various weeds, pests, and diseases. 

Use of 3(3-azido-4 chlorophenyl)-1,1-dimethylurea (azidomonuron), a photoaffinity labelling analogue of the herbicidal phenylurea 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), has revealed Tyr 237 and Tyr 254 of D1 to be close to the herbicide binding site (1). An interesting property of DCMU is its ability, under certain conditions, to displace a bicarbonate ion which normally binds to PS2 in the region of the non-heme ferrous atom situated between and Qg. 

Grace Davison, Deerfield, USA Aflatoxins, lactoferrin, vitamin B12, testosterone, nortestosterone, ethinyl estradiol, estradiol, estrone, bisphenol A, chlorophenoxy acetic acid herbicides, phenylurea herbicides, organophosphate pesticides, vindozolin... 

An on-line concentration, isolation, and Hquid chromatographic separation method for the analysis of trace organics in natural waters has been described (63). Concentration and isolation are accompHshed with two precolumns connected in series the first acts as a filter for removal of interferences the second actually concentrates target solutes. The technique is appHcable even if no selective sorbent is available for the specific analyte of interest. Detection limits of less than 0.1 ppb were achieved for polar herbicides (qv) in the chlorotriazine and phenylurea classes. A novel method for deterrnination of tetracyclines in animal tissues and fluids was developed with sample extraction and cleanup based on tendency of tetracyclines to chelate with divalent metal ions (64). The metal chelate affinity precolumn was connected on-line to reversed-phase hplc column, and detection limits for several different tetracyclines in a variety of matrices were in the 10—50 ppb range. 

Phenylurea herbicides (urons). Dinocap, Dinoseb, Benomyl, Carbendazim and Metamitron in Waters [e.g. determination of phenylurea herbicides by reverse phase HPLC, phenylurea herbicides by dichloromethane extraction, determination by GC/NPD, phenylurea herbicides by thermospray LC-MS, Dinocap by HPLC, Dinoseb water by HPLC, Carbendazim and Benomyl (as Carbendazim) by HPLC], 1994... 

V. Pichon, F. Chen, M.-C. Hennion, R. Daniel, A. Martel, F. Fe Goffic, J. Abian and D. Barcelo, Preparation and evaluation of immunosoi bents foi selective rtace enrichment of phenylurea and triazine herbicides in environmental waters . Anal. Chem. 67 2451-2460(1995). 

I. Fener, V. Pichon, M-C. Hennion and D. Barcelo, Automated sample preparation with exti action columns by means of anti-isoproturon immunosorbents foi the determination of phenylurea herbicides in water followed by liquid chi omatography-diode aixay detection and liquid cliromatogi aphy-atmospheric pressure chemical ionization mass spectrometiy , 7. Chromatogr. 777 91-98 (1997). 

Pesce S, Fajon C, Bardot C, Bonnemoy F, Portelli C, Bohatier J (2006) Effect of the phenylurea herbicide diuron on natural riverine microbial communities in an experimental study. Aquat Toxicol 78 303... 

El Fantroussi S, L Verschuere, W Verstraete, EM Top (1999) Effect of phenylurea herbicides on soil microbial communities estimated by analysis of 16S rRNA gene fingerprints and community-level physiological profiles. Appl Environ Microbiol 65 982-988. 

Lord and Pawliszyn" developed a related technique called in-tube SPME in which analytes partition into a polymer coated on the inside of a fused-silica capillary. In automated SPME/HPLC the sample is injected directly into the SPME tube and the analyte is selectively eluted with either the mobile phase or a desorption solution of choice. A mixture of six phenylurea pesticides and eight carbamate pesticides was analyzed using this technique. Lee etal. utilized a novel technique of diazomethane gas-phase methylation post-SPE for the determination of acidic herbicides in water, and Nilsson et al. used SPME post-derivatization to extract benzyl ester herbicides. The successful analysis of volatile analytes indicates a potential for the analysis of fumigant pesticides such as formaldehyde, methyl bromide and phosphine. 

Electrospray mass spectrometry has been used to characterise triazine, phenylurea, and other herbicides in estuarine water [391]. 

Analysis of pesticides in water was performed by fully automated online solid-phase extraction-liquid chromatography-tandem mass spectrometry (SPE-LC-MS/ MS) [25, 31]. These pesticides (a total of 22 belonging to the classes of triazines, OP, chloroacetanilides, phenylureas, thiocarbamates, acid herbicides, and anilides) were selected on the basis of previously published studies [20, 25], information gathered from the water authorities, and known use in rice crops. 

Following the earlier work of Kirkland [125] on phenylurea herbicides, Sidwell and Ruzicka [126] applied liquid chromatography to the identification and determination of active ingredient contents of phenylurea herbicide formulations. Smith and Lord [118] have used liquid chromatography for the determination of Chlorotoluron residues in soil, but Diuron and Monuron interfered in their chromatographic system. 

Two of the most commonly used types of pesticides in Britain are herbicides, of the carboxyacid and phenylurea groups, applied to cereal growing land (Table 16.4). 

Propanil (3,4-dichloropropionanilide) is an important arylamide herbicide that is used in rice, barley, oat and wheat fields. The 3,4-dichloroaniline moiety is also found in the TV-substituted phenylureas linuron, diuron and neburon. Hence, exposure to 3,4-dichloroaniline derivatives will be common and has been associated with methemoglobinemia in humans142. 

More than 25 different substituted urea herbicides are currently commercially available [30, 173]. The most important are phenylureas and Cycluron, which has the aromatic nucleus replaced by a saturated hydrocarbon moiety. Benzthiazuron and Methabenzthiazuron are more recent selective herbiddes of the class, with the aromatic moiety replaced by a heterocyclic ring system. With the exception of Fenuron, substituted ureas (i.e., Diuron, Fluometuron, Fig. 10, Table 3) exhibit low water solubilities, which decrease with increasing molecular volume of the compound. The majority of the phenylureas have relatively low vapor pressures and are, therefore, not very volatile. These compounds show electron-donor properties and thus they are able to form charge transfer complexes by interaction with suitable electron acceptor molecules. Hydrolysis, acylation, and alkylation reactions are also possible with these compounds. 

Determination of preservatives (sorbic and benzoic acid, parabens) in food products Determination of phenylurea herbicide residues in vegetables and vegetable processed food Separation of flavonoids from extracts of Adinandra nitida leaves... 

Attaway, H.H., Paynter, M.J.B., and Camper, N.D. Degradation of selected phenylurea herbicides by anaerobic pond sediment, J. Environ. Sci. Elealth, B17 683-700, 1982a. 

Wallington, T.J. and Kurylo, M.J. Flash photolysis resonance fluorescence investigation of the gas-phase reactions of OH radicals with a series of aliphatic ketones over the temperature range 240-440 K, J. Phys. Chem., 91 (9) 5050-5054, 1987. Wallnoefer, P.R., Safe, S., and Hutzinger, 0. Microbial demethylation and debutylation of four phenylurea herbicides, Pestic. Biochem. Physiol., 3 253-258, 1973. 

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