A new homogeneous liquid-liquid extraction using a fluorocarbon ionic surfactant, Zonyl FSA (FSA), having a diethylthioether group as a spacer between the perfluoroalkyl group and carboxyl group has been developed. In this FSA method, the phase separation phenomena were observed at mild pH (below pH 6). Moreover, by using this extraction method as a preconcentration, a highly sensitive spectrofluorometric determination of chlorophyll a was established. The results for the standard chlorophyll a were as follows. The concentration factor (V-w/V-o) was 200 (water phase, V-w, 20 cm(3), water-immiscible phase, V-o, 100 mu l), the distribution ratio, log D, was 4.85, the extraction percentage, E, was 99.7%, and the procedure time was approximate to 30 min. The calibration curve was linear in the concentration range 2 x 10(-11) - 3 x 10(-7) mol dm(-3) and the detection limit (S/N = 3) was 1 x 10(-11) mol dm(-3). The relative standard deviation was 0.72% for 10(-8) mol dm(-3) (five determinations).
