HOMOGENEOUS LIQUID-LIQUID-EXTRACTION BY PH DEPENDENT PHASE-SEPARATION WITH A FLUOROCARBON IONIC SURFACTANT AND ITS APPLICATION TO THE PRECONCENTRATION OF PORPHYRIN COMPOUNDS

Aqueous perfluorooctanoate (PFOA-) solution of water-miscible organic solvent (SOLV), such as dioxane and acetone, was separated into two immiscible phases reversibly by charge neutralization of PFOA- ion with proton (H+) (pK(a) value of HPFOA was 1.01, at I = 0.1, 20-degrees-C). The transparent heavier phase, in which HPFOA was concentrated quantitatively, consisted of three components in the molar ratio of HPFOA:SOLV:H2O = 1:4.0:6.6 for acetone system, and 1:0.47:1.9 for dioxane system, respectively. This separation provides a new homogeneous liquid-liquid extraction method, which can be successfully applied to the ultra-high preconcentration of water-soluble porphyrin compounds: 10(4)-fold concentration was achieved within 20 min.