Perfluorinated carboxylic acids (PFCAs) represent an important group of persistent perfluorinated organic compounds commonly determined in environmental and biological samples. A reversed-phase HPLC method was developed based on derivatization of the PFCAs with the commercially available fluorescent reagent 3-bromoacetyl coumarin. The method was optimized and this resulted in the efficient separation of PFCAs containing from 3 to 12 carbon atoms in molecule in 25 min run. To improve sensitivity, the preconcentration step has been optimized using Oasis-WAX and C18 sorbents for SPE. A 100-fold preconcentration is achieved by solid-phase extraction with the sorbent C18 Sep-PAK to result in limits of detection in the range from 43 to 75 ppt for the analytes examined, and in the application of the method of water analysis.FigureChromatogram of mixture of perfluorinated carboxylic acids C3-PFCA – C12-PFCA with fluorescence detection after derivatization with 3-bromoacetyl coumarin (b), and blank (a)
We report on the electrophoretic mobility and on the thermal diffusion of lysozyme proteins dissolved in aqueous solutions of a nonionic surfactant (C12E6) at a wide range of concentrations of the surfactant (0-20% by weight). We want to estimate the influence of a dense network of elongated micelles of C12E6 on the effective charge of the proteins as observed in the capillary electrophoresis experiments. The possible mechanism leading to the change in the effective charge of protein could involve the deformation of the cloud of counterions around the protein when it squeezes through the narrow (of the order of a protein diameter) aqueous channels formed in the solution of elongated micelles. The combination of independent measurements of the electrophoretic mobility of a family of modified proteins (lysozyme charge ladder [Colton et al. J. Am. Chem. Soc. 1997, 119, 12701]), of the microviscosity of the solutions of surfactant (obtained via fluorescence correlation spectroscopy), and of the hydrodynamic radius of the proteins (photon correlation spectroscopy) allow us to conclude that the effective charge of the proteins is not affected by the presence of surfactant, even at high concentrations.
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