DETERMINATION OF IRON IN SEAWATER BY FLOW INJECTION-ANALYSIS USING IN-LINE PRECONCENTRATION AND SPECTROPHOTOMETRIC DETECTION

A highly sensitive flow injection analysis (FIA) method for determinin g the concentration of iron in seawater has been developed. The techni que is a modification of the catalytic batch method previously reporte d by Hirayama and Unohara. By optimising the chemistry for FIA and inc orporating in-line preconcentration of the iron from seawater onto a c olumn of resin-immobilised 8-hydroxyquinoline, the detection limit of the method has been reduced to 0.025 nM. The typical precision of the method for a 0.35 nM Fe sample is 2.5% (n = 6). The method has been us ed at sea in its preconcentration mode to determine iron in open ocean water samples from the equatorial Pacific and the North Atlantic. It has also been used in a direct injection mode for hydrothermal plume s amples from around Loihi Seamount in the Central Pacific.