A water-soluble polymer, poly(N-isopropylacrylamide), becomes water-insoluble above a lower critical solution temperature (∼32°C) and forms gumlike precipitates (polymer phase) having a very small volume fraction. The features in the polymer precipitation were dependent on the molecular weight of the polymer and/or the concentration of salts or buffer components. Accompanying the formation of the polymer phase, hydrophobic organic compounds including polycyclic aromatic hydrocarbons, alkylphenols, chlorobenzenes, chlorophenols, phthalic esters, pesticides, and steroid hormones in water were efficiently incorporated into the polymer phase. On the other hand, hydrophilic components such as inorganic ions or polysaccharides remained in the bulk aqueous solution. The extractabilities of the compounds increased with increasing hydrophobic properties. The distribution coefficients, based on the volume fractions of their aqueous and polymer phases, between the bulk aqueous and polymer phases were correlated with the water-octanol distribution coefficients. The linear relationship between the two equilibrium coefficients indicated that the hydrophobic interaction is the predominating force for incorporating solutes. The introduction of the concentrated polymer solution into the hygroorganic mobile phase of the reversed-phase HPLC rarely interfered with the chromatographic operation. The application of the polymermediated extraction to HPLC significantly enhanced the peak intensities of the hydrophobic analyte varieties by reducing the interferences of the hydrophobic matrix components.Polycyclic aromatic hydrocarbons, alkylphenols, chlorobenzenes, chlorophenols, phthalic esters, and pesticides are ubiquitous environmental pollutants resulting from automobile exhaust, waste from paper mills, a series of agricultural and industrial chemicals or their starting materials, and the combustion of fossil fuels. 1,2 Because of their hydrophobic properties, these compounds tend to bioaccumulate in the lipid stores of animals and human beings. Additionally, recent studies report their potential for several physiological actions including estrogen-like properties. Methods for determining these compounds at trace levels in matrix components generally include solvent extraction and an extensive sample cleanup procedure prior to the analysis. However, the solvent extraction methods for sample cleanup usually use considerable amounts of organic solvents, which often generate serious problems with respect to human health and ecological systems.Recently, an extraction methodology based on the temperatureinduced phase separation of aqueous micellar solutions of nonionic surfactants (namely cloud point extraction) 3,4 has been developed as another possible selection for the sample treatment of HPLC. [5][6][7][8][9][10][11] Due to the hydrophobic interaction between analytes and surfactant assemblies, hydrophobic analytes can be incorporated into the surfactant-rich phase formed by the phase separation of the micellar solution, while hydroph...

The relative standard deviation of measurements in atomic absorption spectrometry for cadmium determination is predicted by the signal fluctuation model, which is made up of the white noise and Markov process. The standard deviation (SD), w̃, of the white noise and SD, m̃, and autocorrelation parameter, ρ, of the Markov process are determined from the power spectrum of the actual signal fluctuation in the system and in turn are put to use for the uncertainty prediction of measurements in the time space. The confidence intervals of the conventional calibration and standard addition method are calculated from the predicted SD of measurements.

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