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Estrogens have been shown to be present in the water compartment, mainly due to the inefficient removal in wastewater treatment plants (WWTP). The concentrations of these compounds, although very low (low ng/L), are sufficient to induce estrogenic responses and alter the normal reproduction and development of wildlife organisms. The compounds have been determined, by a variety of analytical procedures, in the influents and effluents of WWTP, fresh waters, rivers, and even drinking waters. Determination of natural and synthetic estrogens and progestogens in natural water is, however, a difficult analytical task, because of the very low detection limits required and the complexity of the matrix. Thus, in general, complicated, time-consuming extraction and purification processes, usually based on the application of solid-liquid extraction, are performed before final determination by immunoassay, high-performance liquid chromatography, or gas chromatography, very often coupled with mass spectrometry. This paper reviews the analytical methods so far described for the analysis of estrogens, which are currently important environmental pollutants presented in natural and wastewaters. Discuss of the main steps, from sampling up to analysis, and the techniques most commonly used in the determination is presented.

The chromatographic behavior of some flavonoids was established by RP-HPLC on RP-18 (LiChroCART, LiChrosphere RP-18e), RP-8 (Zorbax, Eclipse XDB-C8), CN (Säulentechnik, LiChrosphere CN100) columns. The mobile phases were mixtures of methanol-water in different volume proportions from 70 to 80% v/v for RP-18 and RP-8, while for the CN column the proportions were between 66 and 70% v/v. The lipophilicity was expressed through different lipophilicity descriptors such as mean of k (mk), mean of log k (mlog k), log k(W), S, f() and scores of k and log k corresponding to the first principal component. The experimental lipophilicity indices are directly correlated with the computed values, via computer software and internet module, at a high analytical level. Furthermore, the results obtained applying principal component analysis to k and/or log k values allow the prediction and explanation of the interaction involved in the retention mechanism which takes place between the compounds and the employed stationary phases during the development.

Silica gel plates impregnated with a variety of oils including vegetable oils (olive, sunflower and corn oil) and synthetic oils (trioctylamine and paraffin oil) were evaluated and compared with the commercially available reversed-phases TLC plates (RP-18, RP-18W, and CN). A series of selected lipophilic vitamins was employed to evaluate the suitability of oils as reversed-phases for TLC and to provide different lipophilicity indices: R M0 , scores corresponding to the first principal component of R F and/or R M, the arithmetic mean of R F and R M values obtained with solvent mixture containing various concentrations of methanol in water. The retention results were excellent (r [ 0.98) and allowed accurate estimation of lipophilicity of selected vitamins and to ranking the lipophilicity of oils when comparing with chemically bonded phases. Concerning the lipophilicity scale of vegetable oils, it is worth noting that corn oil presents the highest lipophilicity, closely followed by the olive and sunflower oils.

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