Phenylureas natural waters

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. 

Gerecke, A. C., Tixier, C., Bartels, T., Schwarzenhach, R. P., and Muller, S. R., Determination of phenylurea herbicides in natural waters at 21 concentrations helow 1 ng/1 using SPE, derivatization, and solid-phase microextraction- gas chromatography-mass spectrometry, J. Chromatogr. A, 930,... 

Corcia, A. D., Costantino, A., Crescenzi, C., and Samperi, R., Quantihcation of phenylurea herbicides and their free and humic acid-associated metabolites in natural waters, J. Chromatogr. A, 852, 465-474, 1999. 

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... 

Isotherms for the adsorption of phenylureas on ethylcellulose are of the C-type (71) (top of Figure 12). The constant partition or C-type isotherm is common when new sites become available as the solute is adsorbed from the solution. For every concentration of a particular chemical that is used, the same proportionate amount is partitioned between the adsorbent surface and the solution phase. The diflFerence in adsorption of one compound vs. another depends upon the structure and properties of the compounds and the preference by the adsorbent of the compounds over that of water molecules. The phenylureas were readily desorbed from ethylcellulose with water showing that the adsorption mechanism was physical in nature. 

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