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Trace organic precursors remaining in water after primary treatment can originate a variety of toxic disinfection by-products during chlorination. Therefore, knowledge of conditions leading to their persistence or transformation in chlorinated media is crucial for human health protection. Using phenol as model compound at trace level (50 ppb), the short term formation and degradation of chlorophenols (CPs) in plain water and buffered water (pH 4.8, 7 and 9) treated with typical chlorine doses (1-5 ppm) was investigated. Total phenol consumption and quantitative degradation of formed CPs occurred in < or =5h with 5 ppm chlorine in plain water and alkaline buffer, and with 1 ppm chlorine in phosphate buffer of pH 7. The enhanced reactivity in this buffer was attributed to high ionic strength (0.18 M). On the contrary, phenol was only slowly transformed to monochlorophenols (MCPs) in acidic media. Analysis of phenol and CPs concentration profiles indicated the coexistence of two competing reaction pathways in neutral and alkaline conditions: 1) successive ortho-para chlorination of aromatic ring up to 2,4,6-trichlorophenol followed by ring cleavage, 2) direct oxidation of MCPs to rapidly degradable oxygenated aromatics (dihydroxybenzenes, benzoquinones). Ionic strength and pH had some influence on preferred pathway but chlorine dose was determinant.

A simple, rapid, and reliable online methodology for the determination of benzidine and 3,3'-dichlorobenzidine (3,3'-DCB) in natural waters is proposed. The analytes are extracted and preconcentrated from aqueous samples in a small stainless steel precolumn packed with a polymeric PLRP-S phase. The precolumn is further online-analyzed by reversed-phase gradient-elution chromatography with a highly sensitive and selective coulometric detection at E = 700 mV. Recoveries greater than 90% and a relative standard deviation of approximately 5% are achieved with samples spiked at low micrograms-per-liter concentration levels. The detection limits of the method in fortified reagent water samples are 100 ng/L for benzidine and 50 ng/L for 3,3'-DCB.

The behavior and main characteristics of a commercial immunosorbent (IS) cartridge for the solid-phase extraction of phenylureas are determined in this work. The measured capacity for the analyte-antigen (isoproturon) in a new cartridge is 215 ng and, after more than 100 adsorption-desorption cycles, the remaining capacity still is approximately 70 ng, demonstrating the good stability of the bonded antibody and the interesting possibility of extensive cartridge reuse. Only isoproturon and diuron are specifically retained in this sorbent. The weak nonspecific retention of other pesticides, including other phenylureas, can be avoided by increasing the sample volume during the loading step. Thus, a very selective and sensitive method for the determination of isoproturon and diuron in natural and potable waters is developed by loading a 50-mL sample adjusted to pH 7.4 in the IS cartridge, eluting with methanol-water (60:40, v/v), and analyzing the eluate by high-performance liquid chromatography with UV detection. The clean chromatograms, low detection limits (approximately 0.1 micro g/L), and good precision (< 5%) obtained with this rapid and simple method demonstrate that immunoaffinity extraction can be an excellent alternative for sample preparation in the environmental monitoring of particular pesticides in water matrices.

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