Urea-type pesticides

The structure of urea type pesticide is similar to carbamate, except the terminal oxygen atom is replaced by a nitrogen atom. 

Applications of this technique are growing and include the analysis of mixtures of pesticides and herbicides, including oiganophosphorus, phenoxyacetic acid, caibamate, urea types, mixtures of various types of organic compounds, alkylbenzene sulphonates, polyethylene glycols, nonylphenyl ethoxylates, dioctadecylmethyl ammonium, ozonisation products and chlorination products. 

Furthermore, urea-type pesticides propanil, linuron, and diuron, which arc the main herbicides used throughout the world, have the ability to bind to AR (Cook et ai, 1993 Bauer et al., 1998). Indeed, linuron is strueturally related to the nonsteroidal antiandrogen flutamidc, and its IC50 for competition at the AR is approximately 3.5 limes that of flutamide. The activity of its metabolite, 3,4-dichloroanilinc, is higher than that of linuron. 

Urea-type pesticides, such as, fenuron, siduron, monuron, or linuron — The structure is similar to carbamate except that the terminal oxygen atom is substituted with a nitrogen atom, as follows ... 

Abstract The soil as an adsorbent has various active sites leading to rather complicated adsorption mechanisms with environmental pollutants, like pesticides. According to earlier results the chloroacetani-lide type herbicides as solutes resulted in two-step isotherms on soils and quartz. This phenomenon has not been observed yet concerning trace compounds in the environment. In this case the so-called distributed reactivity model is used, suggesting that the total sorption is given as the sum of the local adsorption isotherms. The adsorption of isoproturon (urea-type herbicide) and prometryn (5-triazine type herbicide) was studied on quartz at different pH values. 

The reaction of [ CJacetyl chloride and sodium azide forms [ " C]acetyl azide, which upon heating rearranges to give methyl [ " C]isocyanate (34). The latter was used for the carbon-14 labeling of eserine 1351. a potent acetylcholinesterase inhibitor of the carbamate type, and of IBMU (36), a urea type pesticide . 

Carboxyhc acid ester, carbamate, organophosphate, and urea hydrolysis are important acid/base-catalyzed reactions. Typically, pesticides that are susceptible to chemical hydrolysis are also susceptible to biological hydrolysis the products of chemical vs biological hydrolysis are generally identical (see eqs. 8, 11, 13, and 14). Consequentiy, the two types of reactions can only be distinguished based on sterile controls or kinetic studies. As a general rule, carboxyhc acid esters, carbamates, and organophosphates are more susceptible to alkaline hydrolysis (24), whereas sulfonylureas are more susceptible to acid hydrolysis (25). 

Estimated half-lives for chlorinated hydrocarbon pesticides vary widely [16, 22] Aldrin, 1-9 Dieldrin, 3-7 Chlordane, 1-8 Heptachlor, 1-4 and DDT, 3-10 years. Half-lives for PCBs range from one year to 16 years [23]. Other types of pesticides, e.g. organophosphates, triazines, carbamates and ureas, are generally less persistent [16, 24],... 

Hydrolytic Reactions. Many pesticides possess bonds that are susceptible to hydrolytic attack. These reactions are most easily characterized according to the type of bond hydrolyzed carboxjlic acid ester, carbamate, oiganophosphate, urea, or chlorine (hydrodechlorination). In many instances the specific hydrolytic enzymes have been purified and characterized and the genes encoding for the enzymes isolated and cloned. It is commonly observed that there are multiple forms of the enzymes catalyzing a particular hydrolytic reaction, which suggests that these catalytic functions have evolved independendy in different bacteria (19). 

The urea pesticides diuron, fluormeturon, neburon and Hnuron cited as potential groundwater contaminants from US EPA in the National Pesticide Survey were quantitatively determined by APCI-LC-MS(-t) [354]. APCI-LC-MS was also used to test for 46 pesticide compounds in shallow groundwater samples from two sandy and two clay catchment areas. Of the neutral polars observed, isopro-turon belonged to the most frequently found compound [351]. Sphid et al. described an APCI-LC-MS method for the determination of isoproturon and different types of pesticides and their degradation products in ground water samples. Detection Umits, recovery, precision and Hnearity data were reported [350]. 

A study with environmental samples was performed analyzing 26 non-acidic (e.g. organophosphorus, carbamate, triazine, anilide, N-substituted amine and phenylurea type) and 13 acidic (urea and phenoxy acid type) target pesticides simultaneously by ESI-LC-MS with recoveries of about 80% [500]. Drinking, ground and... 

In a study covering a wide range of polar and acidic pesticides deethylatrazine and atrazine besides anilide, phenoxy acid, phenylurea, carbamates and other types of specific pesticides in river water were determined by ESI-LC-MS and MS/MS. Recoveries, depending on preconcentration steps, obtained with different SPE materials (PLRS-S, Hyshere-1, LiChrolut EN and Isolute ENV -i-) and at different pH values were reported [502]. Sixteen of the most widely used pesticides in Southern Italy were monitored in surface water samples taken in the Calabria region. Triazines were determined quantitatively by LC-UV and ESI-LC-MS(-i-) and were confirmed by MS [537]. In another study the simultaneous determination of 26 non-acidic (base and neutral e.g. triazine, carbamate, anilide, N-substituted amine, urea and organophosphorus type) and 13 acidic (sulfuron and phenoxy acid type) pesticides in natural waters was performed using ESI-LC-MS. Recoveries... 

---