Phenylureas diuron

The appearance of weeds that showed considerable resistance to the triazine herbicides eventually led to detailed biochemical studies that identified resistance mechanisms at the level of a D1 protein amino acid change. Hirschberg and Mclntosh showed that in Amaranthus hybridus this was due to a replacement of serine 264 by glycine. Remarkably, this particular amino acid change did not greatly affect the inhibitory properties of the phenylurea diuron. Subsequent work has shown, however, that changes at amino acids 219 and 275 will give resistance to diuron but have... 

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... 

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. 

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. 

Pesticides containing methyl or other alkyl substituents maybe linked to N or 0 (i.e., N- or O-alkyl substitution). An N- or O-dealkylation catalyzed by microorganisms frequently results in loss of the pesticide activity. Phenylurea (see Chap. 1) becomes less active when microorganisms AT-demethylate the molecules (e. g., the conversion of Diuron to the normethyl derivative, Fig. 7). The subsequent removal of the second AT-methyl group renders the molecule fully nontoxic [169]. On the other hand, the microbial O-demethylation of Chloroneb creates the non-toxic product 2,5-dichloro-4-methoxyphenol (Fig. 7). 

Chlorination of waters containing two phenylurea-type herbicides, isoproturon and diuron, results in the formation of THMs. The reaction of the phenylurea-type herbicide isoproturon with chlorine produced compounds that still contained the aromatic ring of the herbicide with the urea side-chain unmodified. The formation of chlorinated and brominated derivatives was related to the bromide concentration present in the water [113]. 

Diuron Phenylurea 330-54-1 1.83 -1951 Herbicide A preemergence residual herbicide for total control of weeds and mosses in noncrop areas and woody crops... 

Fig. 7 Chromatograms obtained after the preconcentration of 50 ml of a diluted industrial effluent spiked at 1 pg L 1 with a mixture of triazines and phenylureas through a styrene-divinylbenzene (SDB) SPE cartridge (a) and through the terbutylazine MIP cartridge (b). Compounds (1) deethylatrazine (DEA), (2) monuron, (3) deethylterbutylazine (DET), (4) atrazine, (5) diuron, (6) terbutylazine, (7) neburon. UV detection at 220 nm [46]...

Figure 13.14 LC-diode-array detection (DAD) chromatogram (at 220 nm) obtained after preconcentration of 50 ml of ground water sample spiked with various pollutants at levels of 3 p.g l-1 passed through (a) a PLRP-S cartridge and (b) an anti-isoproturon cartridge. Peak identification is as follows 1, chlortoluron 2, isoproturon plus diuron 3, linuron 4, diben-zuron , water matrix. Reprinted from Journal of Chromatography, A 777, I. Ferrer et al. Automated sample preparation with extraction columns by means of anti-isoproturon immunosorbents for the determination of phenylurea herbicides in water followed by liquid chromatography diode array detection and liquid chromatography-atmospheric pressure chemical ionization mass spectrometry , pp. 91-98, copyright 1997, with permission from Elsevier Science.

Scholthof, K.B.G., Z. Guisheng, and A.E. Karu. 1997. Derivation and properties of recombinant fab antibodies to the phenylurea herbicide diuron. J. Agric. Food Chem. 45 1509-1517. 

Figure 8.9. Separation of four phenylurea herbicides using (a) on-line UV detection at 254 nm and (b) on-line electrochemical detection with 1.35 V oxidation potential. Peaks 1, metoxuran 2, diuron 3, linuron 4, neburon. (Reprinted from Ref. 20 with permission.)...

Vroumsia, T., Steiman, R., Seigle-Murandi, F., Benoit-Guyod, J.-L., Khadrani, A. (1996) Biodegradation of three substituted phenylurea herbicides (chlortolruon, diuron, and isoproturon) by soil fungi. A comparative study. Chemosphere 33, 2045-2056. 

The publication TcVim Chzm icoit recently projected growth of the herbicide market by product group (6 ) (Fig. 11). In 1974, the first column, we find arsenicals with 1% of the market phenoxies with 4.7% phenylureas such as diuron, linuron, and fluometuron with 6.6% benzoics such as chloramben, dicamba, tri-chlorobenzoic acid with 9.5% carbamates such as EPTC, diallate, and chloropropham with 10.2% and the tria-zines such as atrazine, prometryne, and cyanazine with 29.7%. The "others" category with 38.3% includes alachlor, paraquat, trifluralin, and some of the more recent product entries such as bentazon, glyphosate, and metribuzin. 

Diuron or N -(3,4-dichlorophenyl)- , -dimethyurea Phenylurea Inhibits photosynthesis, absorbed mainly by the roots Tbtal control of weeds and mosses on noncrop land and under fruit trees 11-9... 

Fig. 1.23. Top the window diagram (the dependence of the resolution on the concentration of 2-propanol in ri-heptane as the mobile phase) for a mixture of eight phenylurea herbicides on a Separon SGX, 7.5 pm. silica gel column (150 x 3.3 mm i.d.). Bottom the separation with optimised concentration 1953 2-propanol in the mobile phase for maximum resolution. Column plaie number N = 5000. T = 40°C. flow rate 1 ml/min. Sample compounds neburon (/). chlorobromuron (2). 3-chloro-4-methylphenylurea (7). desphenuron (4). isoproturon (5). diuron (6). metoxuron (7). dcschlorometoxuron (S).

Fig. 1.33. Top the resolution window diagram for the gradieni-elulion separation of a mixture of twelve phenylurea herbicides on a Separon SGX Cix. 7.5 nm. column (150 x 3.3 mm i.d.) in dependence on the initial concentration of methanol in water at the start of the gradient, A. with optimum gradient volume Mg = 73 ml. Column plate number N =. 5000.. Sample compounds hydroxymetoxuron (/). desphenuron (2), phenuron (.1). metoxuron (4). monuron (5), monolinuron (6). chlorotoluron (7), metobromuron (X), diuron (9), linuron (/O), chlorobromuron (//). neburon U2). Bottom the separation of the twelve phenylurea herbicides with optimised binary gradient from 24 to l(X)9f methanol in water in 73 min. Flow rate I ml/min.

Due to the thermal lability of the urea group, phenylureas are not amenable to GC-MS. They are frequently analysed by LC-MS. The general stmcture is shown below. The phenyl ring is substituted with halogen(s), methoxy, methyl, trifluoromethyl, or 2-propyl substitution. The Rj side chains are methyl groups for most phenylureas, while the Rj side chain can be methyl like in diuron, methoxy like in linuron, butyl like in neburon, or a proton like in monomethylmetoxuron. 

The appearance of ESI mass spectra depends on the solvent conditions, especially on the extent of sodium contamination. Sodiated molecules were observed as the base peak for chlortoluron, isoproturon, diuron, linuron, and diflubenzuron [34], while protonated molecules and only weak sodiated molecules were observed for monuron, diuron, and neburon [14], Some phenylureas can also be analysed in negative-ion ESI, where deprotonated molecules as well as acetate or formate adducts can be observed, depending on the mobile-phase composition [9],... 

Schoket B and Vincze I (1990) Dose-related induction of rat hepatic drug-metabolizing enzymes by diuron and chlorotoluron, two substituted phenylurea herbicides. Toxicology Letters 50 1-7. 

A method for analysis of polar pesticides in wine by the use of automated in-tube SPME coupled with LC/ESI-MS was proposed (Wu et al., 2002). In-tube SPME is a microextraction and preconcentration technique that can be coupled on-line with high-performance liquid chromatography (HPLC), suitable for the analysis of less volatile and/ or thermally labile compounds. This technique uses a coated open tubular capillary as an SPME device and automated extraction. Using a polypyrrole coating, six phenylurea pesticides (diuron, fluometuron, linuron, monuron, neburon, siduron) and six carbamates (barban, car-baryl, chlorpropham, methiocarb, promecarb, propham) were analyzed in wine. Structures of compounds are reported in Fig. 9.4. Due to the high extraction efficiency of the fiber toward polar compounds, benzene compounds, and anionic species, LODs ranging between 0.01 and 1.2pg/L were achieved, even if the sample ethanol content affects the recoveries of analytes. 

Some carbamates (carbosulfan, benfuracarb, carbofuran, pirimicarb, diethofencarb, and diuron) and phenylurea pesticides (monuron and monolinuron) were sampled from different fruit juices by using 50-pm carbowax-templated resin (CW-TPR) and a 60-pm PDMS/DVB SPME fiber (Sagratini et al., 2007). The fiber desorption into the SPME-LC/MS interface chamber previously filled with 70% methanol and 30% water, was performed in static mode. 

Figure 9.4. Phenylurea pesticides and carbamates detected in wine by automated intube SPME and LC/ESI-MS analysis (Wu et al., 2002). (14) monuron, (15) fluome-turon, (16) siduron, (17) diuron, (18) linuron, (19) neburon, (20) propham, (21) chlorpropham, (22) barban, (23) promecarb (structures of carbaryl and methiocarb are reported in Figs. 9.1 and 9.11, respectively).

Some nitrogenous herbicides are derived from urea, such as diuron, and contain an aromatic ring (phenylurea). The corresponding UV spectrum shows an absorption peak at 250 nm (Fig. 54). 

The most important substances of this group are l,l-dimethyl-3-phenylurea (fenuron, 5) 3-(4-chlorophenyl)-1,1-dimethylurea, (monuron, 6) 3-(3,4-dichlorophenyl)-1,1 -dimethylurea (diuron,7) 1,1 -dimethyl-3-(a,a,a-trifluoro-m-tolyl)urea (fluometuron, 8) l,l-dimethyl-3-( ,a,a-trifluoro-p-tolyl)urea (para-fluron, 9) 3-(3-chloro-/j-tolyl)-1,1-dimethylurea (chlortoluron, 10) 3-(3-chloro-4-methoxyphenyl)-l,l-dimethylurea (metoxuron, 11) 3-[(4-chlorophenoxy)phenyl]-... 

FIGURE 25.9 Capillary GC with fused-silica column coated with CP-Sil 5 (analogous to SB 30 and OV-101) of HFB derivatives of 13 phenylureas obtained after extraction of a Bosbaan river water sample spiked at 1 fjig/ level, and direct derivatization with HFB A. Injected amount corresponds to 0.1 ng of each herbicide. Symbol explanation Fm, fluometuron Fe, fenuron Mo, monuron Ml, monolinuron Ip, isoproturon Ct, chlorotoluron Mb, metobromuron Bu, buturon Di, diuron Li, linuron Cb, chlorbromuron Mx, metoxuron Nb, neburon. (From Brinkman, U. A. Th., de Kok, A., and Geerdink, R. E., J. Chromatogr., 283, 113, 1984. With permisssion.)... 

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