Phenylureas water

Method 2 (from the free amine). Dissolve 9 - 3 g. (9 1 ml.) of aniline in 10 ml. of glacial acetic acid diluted to 100 ml. contained in a 250 ml. beaker or conical flask, and add with stirring or shaking a solution of 6 5 g. of pure sodium cyanate in 50 ml. of warm water. Allow to stand for 30 minutes, then cool in ice, and allow to stand for a further 30 minutes. Filter at the pump, wash with water and dry in the steam oven. The resulting phenylurea is generally colourless and has a m.p. of 148° (i.e., is pure) the yield is 11 g. If the colour or the m.p. of the product is not quite satisfactory, recrj stallise it from boiling water (10 ml. per gram) as in Method 1. 

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. 

This paper deseribes a rapid and versatile on-line-SPE LC-MS/MS method developed for the determination of various pestieides and tlieir metabolites in water. 28 pestieides, ineluding various triazines, phenylureas, organophosphorous eompounds and other speeies, were seleeted for systematie investigations. 

In a 500-cc. round-bottom flask fitted with a reflux condenser are placed 68 g. of phenylurea (0.5 mole) (Note i) and 120 cc. (i mole) of 42 per cent hydrazine hydrate solution (Note 2). The flask is heated on a steam bath for about twelve hours. The hot mixture is treated with a small amount of decolorizing charcoal (Norite) and filtered. The charcoal is washed with two 15-CC. portions of warm water and the filtrate and washings are then concentrated on a steam bath to about 100 cc. On coolipg in an ice bath a crop of crystals separates and is collected on a filter and washed with two 15-cc. portions of cold water. The filtrate and washings are concentrated to about 25 cc. and another crop of crystals is obtained as before. The total yield of crude compound is 47-52 g. It is white at first but sometimes turns brown on drying. It usually melts below 115° because of some unchanged phenylurea. 

The crude product contains about 9-10 g. of unchanged phenylurea which cannot be satisfactorily removed by crystallization from benzene or water. When the hydrochloride of the phenylsemicarbazide is formed, the phenylurea may be recovered from the alcoholic filtrates. 

Phenylurea herbicides (urons). Dinocap, Dinoseb, Benomyl, Carbendazim and Metamitron in Waters [e.g. determination of phenylurea herbicides by reverse phase HPLC, phenylurea herbicides by dichloromethane extraction, determination by GC/NPD, phenylurea herbicides by thermospray LC-MS, Dinocap by HPLC, Dinoseb water by HPLC, Carbendazim and Benomyl (as Carbendazim) by HPLC], 1994... 

V. Pichon, F. Chen and M.-C. Hennion, On-line preconcenti ation and liquid cliromato-graphic analysis of phenylurea pesticides in environmental water using a silica-based immunosorbent , Aim/. Chim. Acta 311 429-436 (1995). 

V. Pichon, F. Chen, M.-C. Hennion, R. Daniel, A. Martel, F. Fe Goffic, J. Abian and D. Barcelo, Preparation and evaluation of immunosoi bents foi selective rtace enrichment of phenylurea and triazine herbicides in environmental waters . Anal. Chem. 67 2451-2460(1995). 

I. Fener, V. Pichon, M-C. Hennion and D. Barcelo, Automated sample preparation with exti action columns by means of anti-isoproturon immunosorbents foi the determination of phenylurea herbicides in water followed by liquid chi omatography-diode aixay detection and liquid cliromatogi aphy-atmospheric pressure chemical ionization mass spectrometiy , 7. Chromatogr. 777 91-98 (1997). 

If it is heated alone at 160°, ammonia comes off rapidly, the aniline and phenylisocyanate may be detected by their odor but they combine in large part to form 5ym.-diphenyliu ea which crystallizes out from the hot liquid, and cyanic acid may be detected by means of silver nitrate in the water with which the apparatus is washed out after the experiment. When an aqueous solution of phenylurea is distilled, aniline may be detected in the distillate and 5ym.-diphenylurea crystallizes from the boiling liquid. By heating urea with the amine or with its hydrochloride at 160°, or by refluxing urea in aqueous solution with the amine or its hydrochloride, we have prepared sym.-6i-o- and />-tolyl, di-a- andjS-naphthyl, dimethyl, di-w-butyl, di-w- and i5 -amyl and dibenzylureas in satisfactory yield. 

Lord and Pawliszyn" developed a related technique called in-tube SPME in which analytes partition into a polymer coated on the inside of a fused-silica capillary. In automated SPME/HPLC the sample is injected directly into the SPME tube and the analyte is selectively eluted with either the mobile phase or a desorption solution of choice. A mixture of six phenylurea pesticides and eight carbamate pesticides was analyzed using this technique. Lee etal. utilized a novel technique of diazomethane gas-phase methylation post-SPE for the determination of acidic herbicides in water, and Nilsson et al. used SPME post-derivatization to extract benzyl ester herbicides. The successful analysis of volatile analytes indicates a potential for the analysis of fumigant pesticides such as formaldehyde, methyl bromide and phosphine. 

The major metabolite of buprofezin in plants is its p-hydroxy metabolite (p-OH-buprofezin) and that in soil is l-isopropyl-3-phenylurea (BF12). The target analytes are considered to be buprofezin and p-OH-buprofezin in plant materials, buprofezin and BF12 in soils and buprofezin in water samples. 

Pesticides Triazines, phenylureas, OPs, chloroacetanilides, thiocarbamates River water Online SPE... 

Electrospray mass spectrometry has been used to characterise triazine, phenylurea, and other herbicides in estuarine water [391]. 

Analysis of pesticides in water was performed by fully automated online solid-phase extraction-liquid chromatography-tandem mass spectrometry (SPE-LC-MS/ MS) [25, 31]. These pesticides (a total of 22 belonging to the classes of triazines, OP, chloroacetanilides, phenylureas, thiocarbamates, acid herbicides, and anilides) were selected on the basis of previously published studies [20, 25], information gathered from the water authorities, and known use in rice crops. 

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. 

Determination of Phenylurea Compounds in Drinking Water by SPE and HPLC with UV Detection. 

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]. 

In the above directions the concentration is as high as it is safe to make it if less water be used the yield of phenylurea decreases and there is grave danger of loss due to the sudden heating of the mixture by rapid separation of crystals. This phenomenon has been observed with a more concentrated mixture even on heating on the steam bath. 

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