Chlorsulfuron

Urea hydrolysis is frequently observed as the initial reaction for pesticides having urea bonds, such as linuron, diuron, and chlorsulfuron (10) (eq. 14)... 

Extensive use of two more recendy developed classes of herbicides will further dramatically reduce the amount of appHed to control weeds. The sulfonylurea herbicides are extremely active compounds first discovered in the mid-1970s at DuPont they have been discussed extensively (78). Sulfonjiurea herbicides have experienced a rapid and widespread success since thek commercial introduction in 1982 with chlorsulfuron (Table 5). The sulfonylureas are appHed at rates of 2—75 g/ha. The chemistry of the sulfonylurea molecule permits the synthesis of a very large number of useful analogues, consequentiy many new herbicides are anticipated for crop production. As of this writing (1996), over 350 patents have been issued to about 27 agricultural companies covering tens of millions of stmctures known or expected to be herbicidaHy active. 

A multiresidue analytical method based on sohd-phase extraction enrichment combined with ce has been reported to isolate, recover, and quantitate three sulfonylurea herbicides (chlorsulfuron, chlorimuron, and metasulfuron) from soil samples (105). Optimi2ation for ce separation was achieved using an overlapping resolution map scheme. The recovery of each herbicide was >80% and the limit of detection was 10 ppb (see Soil chemistry of pesticides). 

A solvent free, fast and environmentally friendly near infrared-based methodology was developed for the determination and quality control of 11 pesticides in commercially available formulations. This methodology was based on the direct measurement of the diffuse reflectance spectra of solid samples inside glass vials and a multivariate calibration model to determine the active principle concentration in agrochemicals. The proposed PLS model was made using 11 known commercial and 22 doped samples (11 under and 11 over dosed) for calibration and 22 different formulations as the validation set. For Buprofezin, Chlorsulfuron, Cyromazine, Daminozide, Diuron and Iprodione determination, the information in the spectral range between 1618 and 2630 nm of the reflectance spectra was employed. On the other hand, for Bensulfuron, Fenoxycarb, Metalaxyl, Procymidone and Tricyclazole determination, the first order derivative spectra in the range between 1618 and 2630 nm was used. In both cases, a linear remove correction was applied. Mean accuracy errors between 0.5 and 3.1% were obtained for the validation set. 

Sulfonylureas are not directly amenable to gas chromatography (GC) because of their extremely low volatility and thermal instability. GC has been used in conjunction with diazomethane derivatization, pentafluorobenzyl bromide derivatization, and hydrolysis followed by analysis of the aryl sulfonamides. These approaches have not become widely accepted, owing to poor performance for the entire family of sulfonylureas. Capillary electrophoresis (CE) has been evaluated for water analysis and soil analysis. The low injection volumes required in CE may not yield the required sensitivity for certain applications. Enzyme immunoassay has been reported for chlorsulfuron and triasulfuron, with a limit of detection (LOD) ranging from 20 to 100 ng kg (ppt) in soil and water. 

Cereals MEKC UV 0.02-0.04 mg kg- 50mM SDS,25mM sodium phosphate (monobasic), pH 6.15 Metsulfuron-methyl, thifensulfuron-methyl, chlorsulfuron, rimsulfuron, tribenuron-methyl 125... 

Of the compounds listed in Table II, chlorsulfuron and acifluorfen (Figure 2, VI and VII, respectively) look particularly interesting with regard to manipulation of allelochemical production. Both of these compounds can cause large increases in the phenolic titre of plant tissues (e.g. Figures 6 7). Suttle et al. (75) suggested that chlorsulfuron would be an excellent chemical for manipulation of the quality and quantity of secondary phenolic compounds in studies of the role of these potential allelochemics in ecological Interactions. 

Figure 6. Time course of effects of 10 ug chlorsulfuron per seedling on total phenolic content of sunflower hypocotyls expressed as -coumaric acid equivalents. Reproduced with permission from Ref. 75. Copyright 1983, J. Plant Growth Regul.

Several compounds with excellent potential for manipulation of phenolic allelochemic production have been discussed. These include glyphosate, AOPP, chlorsulfuron, and acifluorfen. 

The hydrilla 2-node explants were also sensitive to the herbicides chlorsulfuron. One part per billion chlorsulfuron (ca. 3 X 10 M reduced growth of new shoots by almost 80% but had no effect on new shoot initiation (Table XI). when the herbicide was removed after 14 days, new shoots began to elongate. 

C. J. McNeil, Determination of the herbicide chlorsulfuron by amperometric sensor based on separation-free bienzyme immunoassay. Sens. Actual. B 98, 254—261 (2004). 

The reported dissipation rate of chlorsulfuron in surface soil is 0.024/day (Walker and Brown, 1983). The persistence of chlorsulfuron decreased when soil temperature and moisture were increased (Walker and Brown, 1983 Thirunarayanan et al., 1985). 

Plant Chlorsulfuron is metabolized by plants to hydroxylated, nonphytotoxic compounds including 2-chloro-7V-(((4-methoxy-6-methyl-l,3,5-triazin-2-yl)amino)carbonyl)benzenesulfon-amide (Duke et al., 1991). Devine and Born (1985) and Peterson and Swisher (1985) reported that the uptake of chlorsulfuron in Canada thistle leaves ranged from 23 to 43% after 2 d. The uptake in roots is higher under slightly acidic conditions. Fredrickson and Shea (1986) reported 12% of C-chlorsulfuron was taken up in the roots at soil pH 5.9. 

Photolytic. The reported photolysis half-lives of chlorsulfuron in distilled water, methanol, and natural creek water at 1 >290 nm were 18, 92, and 18 h, respectively. In all cases, 2-chlorobenzenesulfonamide, 2-methoxy-4-methyl-6-amino-l,3,5-triazine, and trace amounts of the tentatively... 

Fredrickson, D.R. and Shea, P.J. Effect of soil pH on degradation, movement, and plant uptake of chlorsulfuron. Weed Scl., 34 328-332, 1986. 

Herrmann, M., Kotzias, D., and Korte, F. Photochemical behavior of chlorsulfuron in water and in adsorbed phase, Chemosphere, 14(l) 3-8, 1985. 

Peterson, RJ. and Swisher, B.A. Absorption, translocation, and metabolism of C-chlorsulfuron in Canada thistle (Cirsium arvensd). Weed Sci., 33 7-11, 1985. 

Walker, A. and Brown, P.A. Measurement and prediction of chlorsulfuron persistence in soil. Bull Environ. Contam. Toxicol, 30(3) 365-372, 1983. 

The DuPont Company has commercialized two of these compounds. The first of these is chlorsulfuron (Fig. 1), formerly DPX-W4189, the active ingredient in Glean weed killer. It is being marketed by DuPont for use in small grains such as wheat and barley. 

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