Organic phenylurea

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. 

Spurlock, F.C. and Biggar, J.W. Thermodynamics of organic chemical partition in soils. 2. Nonlinear partition of substituted phenylureas from aqueous solution. Environ. Sci Technol., 28(6) 996-1002, 1994. 

An interesting result found by Canonica and Freiburghaus (2001) for the DOM-sensitized oxidation of electron-rich phenols is that k°sens was more or less proportional to the concentration of the dissolved organic carbon, independent of the source of the DOM. In addition, for some phenylureas, Gerecke et al. (2001)... 

Gerecke, A. C., S. Canonica, S. R. Muller, M. Scharer, and R. P. Schwarzenbach, Quantification of dissolved organic matter (DOM) mediated phototransformation of phenylurea herbicides in lakes , Environ. Sci. Technol., 35, 3915-3928 (2001). 

Pussemier, L., R. DeBorger, P. Cloos, and R. VanBladel. 1989. Relation between the molecular structure and the adsorption of arylcarbamate, phenylurea and anilide pesticides in soil and model organic adsorbents. Chemosphere 18(9/10) 1871-1882. 

Combined exposures have also been documented for surface waters. An example includes the Swiss river Aa, where mixtures of 5 herbicides comprising triazine and phenylureas were found. Seasonal variations in pollution levels were expected to lead to considerable combination effects in aquatic organisms (Chevre et al. 2006). 

Fig. 1.34. The selectiviiy window diagram for ihe optimisaiion of isocratic ternary mobile phases meihanol-acetoniirile-water. The maximum separation factor ri j in reversed-phasc separation of twelve phenylurea herbicides is searched for. X = concentration of acetonitrile related to the concentration sum of the organic. solvents in ternary mobile pha.ses. Column and sample compounds as in Fig. 1.33.

Pussemier, L., De Borger, R., Cloos, P. and Van Bladel, R. (1989). Relation Between the Molecular Structure and the Adsorption of Arylcarbamate, Phenylurea and Anilide Pesticides in Soil and Model Organic Adsorbents. Chemosphere, 18,1871-1882. 

Nonvolatile Organic Compounds Carbamates, Substituted Amides, and Phenylureas in Water and Soil... 

Stocklein WFM, Rohde M, Scharte G et al. Sensitive detection of triazine and phenylurea pesticides in pure organic solvent by enzyme linked immunosorbent assay (ELISA) Stabilities, solubilities and sensitivities. Anal Chim Acta 2000 405 255-265. 

Phenylureas. The phenylureas show extremely weak acidic properties in aqueous systems. Partial ionization occurs in basic (4.2N NaOH) solution (355). Although the phenylureas are too weak to be titrated in aqueous systems, Cluett (355) titrated them in an organic solvent and used the half-neutralization potentials (HNP) as an index of acidity (the larger the HNP, the weaker the acid). The HNP values, along with other properties, for several phenylurea herbicides are given in Table IX. The HNP values decrease as water solubilities decrease and parachors increase. 

Fenuron was mobile in soil systems compared with other phenylurea herbicides (87, 356), Movement was related to the water solubilities of the compounds (87). Fenuron s leachability was also greater in coarse textured soils than in fine textured ones and was related to the organic matter content of the soil. In a recent field experiment fenuron moved substantially in a lateral direction over the soil surface and in a vertical direction into the subsoil (63). Femuron moved into the subsoil much more on coarse textured soils than on fine textured ones, but it moved only when excessive amounts (80-160 pounds per acre) were used (356). 

Herbicidal activity of the phenylureas in soils decreased as the organic matter content of the soils increased 165, 347, 350, 372, 373, 374, 375, 376), Studies showed that adding organic matter to sandy soil greatly reduced the herbicidal activity of fluometuron and fenuron in growth chamber studies with model soil systems (63) and in field experiments on modified soils (121),... 

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