Phenylureas linuron

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. 

In 1999 Masabni and Zandstra reported on a mutant of Portulaca oleracea with a resistance pattern to PS II inhibitors that was different to most triazine resistant weeds [28], This mutant was resistant to the phenylureas linuron and diuron, but also cross-resistant to atrazine and other triazines. Sequencing of the D1 protein revealed that in the resistant biotype the serine 264 was replaced by threonine and not by glycine. This was the first report on a serine 264 to threonine mutation on a whole plant level. It was proposed that the serine-to-threonine mutation modified the conformation of the herbicide binding niche at the D1 protein in a way, which resulted in reduced binding of phenylureas and triazines as well. 

Linuron Phenylurea 330-55-2 2.03 -1965 Herbicide A herbicide for the pre- and postemergence control of annual grass and broadleaved weeds... 

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.

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.)...

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. 

Fig. 1.6. Dependence of retention faetors. k. of phenylurea herbicides on the concentration. ( / vol. x 10 -). of 2-propanoI in -heplane on a silica gel Separon SGX. 7 nm. column (150 x 3.3 mm i.d.) at 40"C. Dry solvents were used. Sample compounds / = metoxuron. 2 = deschlorometoxuron.. 3 = desphenuron. 4 = linuron. Points experimental data lines best-lit plots of two-parameter Kq. (1.15).

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],... 

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 . ... 

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. 

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).

C-18 Empore extraction disks were used for the isolation and trace enrichment of linuron in 4 1 of river water. At the 0.25 pg/1 level, recovery of this phenylurea was 94% with 6%... 

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.)... 

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... 

Volmer et al. studied phenylureas and sulfonylureas by TSP-LC-MS after sample concentration by Cjg SPE [175]. 15 phenylurea- and 1 thiourea pesticides besides 112 polar pesticides from other pesticide classes were examined by TSP ionisation, detection limits and TSP mass spectra of these polar compounds were presented [245], Besides other polar pesticides, the phenylurea pesticides isoproturon and diuron were on-line concentrated on a precolumn from several surface and drinking water samples and then determined by TSP-LC-MS [247]. A multi-residue TSP-LC-MS method was published by Moore et al. for the determination of the urea pesticides chlortoluron, diuron, isoproturon, and Unuron in water samples after Cig-SPE [248]. Ci8 Empore disks were applied to concentrate phenylureas from river water and spiked seawater samples prior to TSP-LC-MS. Detection limits of 2-20 (ig L and recoveries between 80 and 125% were observed [239]. TSP-LC-MS (SIM) in the positive mode allowed determination of the urea pesticides chlor-bromuron, diuron, linuron, metobromuron, monuron, neburon in apples, beans, lettuce, peppers, potatoes and tomatoes with detection limits of 0.025-1 ppm [255]. 20 other polar pesticides, linuron, which was under suspicion of being a dietary oncogenic risk (US Natl. Res. Council) was determined by TSP-LC-MS a single rapid procedure in vegetables with detection limits of 0.05-0.10 ppm [270]. TSP-LC-MS and ESI were used in a multi-residue method for determination of the sul-... 

Phenylurea herbicides are also degraded under anaerobic conditions. N-(3,4-Dichlorophenyil)-N -dimethylurea (Diuron) and Linuron have shown to be dechlorinated in anaerobic sediments with elimination of the chlorine atom in the pam position [220, 221]. 

Fig. 5 Top. The resolution window diagram for RP gradient elution separation of phenylurea herbicides on a Separon SGX C18 7.5 p,m column (150 X 3.3 mm I.D.) dependent on the initial concentration of methanol in water at the start of the gradient A with optimum gradient volume Vg — 73 ml. Column plate number N = 5000 sample compounds 1, hydroxymetoxuron 2, desphe-nuron 3, phenuron 4, metoxuron 5, monuron 6, monolinuron 7, chlorotoluron 8, metobromuron 9, diuron 10, linuron 11, chlor-obromuron and 12, neburon. Bottom. The separation with optimized binary gradient from 24% to 100% methanol in water in 73 min. Flow rate = 1 ml/min T = 40°C.

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